tag:blogger.com,1999:blog-76980399391580139692024-02-08T09:47:05.949-08:00Climate Change Science of AfricaTenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.comBlogger52125tag:blogger.com,1999:blog-7698039939158013969.post-24382604658496945002022-06-20T12:37:00.001-07:002022-06-20T12:37:33.117-07:00Changes in West African Savanna agriculture in response to growing population and continuing low rainfall doi.org/10.1016/0167-8809(90)90214-X<p><i>Agriculture, Ecosystems & Environment</i>, 31(<i>2</i>) (2022) 115-132; doi.org/10.1016/0167-8809(90)90214-X</p><h1 class="Head u-font-serif u-h2 u-margin-s-ver" id="screen-reader-main-title" style="box-sizing: border-box; color: #505050; font-family: NexusSerif, Georgia, "Times New Roman", Times, STIXGeneral, "Cambria Math", "Lucida Sans Unicode", "Microsoft Sans Serif", "Segoe UI Symbol", "Arial Unicode MS", serif !important; font-size: 1.5rem !important; font-weight: 400 !important; line-height: 1.333 !important; margin-bottom: 16px !important; margin-left: 0px; margin-right: 0px; margin-top: 16px !important; padding: 0px; word-break: break-word;"><span class="title-text" style="box-sizing: border-box; margin: 0px; padding: 0px;">Changes in West African Savanna agriculture in response to growing population and continuing low rainfall</span></h1><div><span class="title-text" style="box-sizing: border-box; margin: 0px; padding: 0px;"><br /></span></div><div><span class="title-text" style="box-sizing: border-box; margin: 0px; padding: 0px;"><span style="font-family: georgia; font-size: medium;">H. I. D. Fierich and W. A. Stoop</span></span></div><div><span class="title-text" style="box-sizing: border-box; margin: 0px; padding: 0px;"><span style="font-size: 14px;"><span style="font-family: georgia;"><i><br /></i></span></span></span></div><div><span class="title-text" style="box-sizing: border-box; margin: 0px; padding: 0px;"><span style="font-size: 14px;"><span style="font-family: georgia;"><i>International Crops Research Institute for the Semi-Arid Tropics ICRISAT/UNDP, P.O. Box 1165, Ouagadougou, Burkina Faso</i></span></span></span></div><div><span class="title-text" style="box-sizing: border-box; margin: 0px; padding: 0px;"><span style="font-size: 14px;"><span style="font-family: georgia;"><br /></span></span></span></div><div><span class="title-text" style="box-sizing: border-box; margin: 0px; padding: 0px;"><span style="font-family: georgia;"><span style="font-size: 14px;">(Accepted 12 September 1989; available online 27 June 2003</span><span style="font-size: 14px;">.)</span></span></span></div><div><span class="title-text" style="box-sizing: border-box; margin: 0px; padding: 0px;"><h2 class="section-title u-h3 u-margin-l-top u-margin-xs-bottom" style="box-sizing: border-box; color: #505050; font-family: NexusSerif, Georgia, "Times New Roman", Times, STIXGeneral, "Cambria Math", "Lucida Sans Unicode", "Microsoft Sans Serif", "Segoe UI Symbol", "Arial Unicode MS", serif; font-size: 1.2rem !important; line-height: 1.333 !important; margin-bottom: 8px !important; margin-left: 0px; margin-right: 0px; margin-top: 32px !important; padding: 0px;">Abstract</h2><div id="aep-abstract-sec-id6" style="box-sizing: border-box; margin: 0px; padding: 0px;"><p style="box-sizing: border-box; color: #2e2e2e; font-family: NexusSerif, Georgia, "Times New Roman", Times, STIXGeneral, "Cambria Math", "Lucida Sans Unicode", "Microsoft Sans Serif", "Segoe UI Symbol", "Arial Unicode MS", serif; font-size: 18px; margin: 0px 0px 16px; padding: 0px; text-align: justify;">Changes in village farming systems brought about by population growth and continuing low rainfall, are described for the three main agro-ecological zones in Burkina Faso. The toposequential land use and cropping patterns were used as the basis for a model, which describes the long-term ecological degradation from declining proportions of fallow land and over-cropping. The implications of these changes for land tenure systems have also been considered. The result provide a human and ecological setting for th current land degradation problem in the West African savanna and thereby indicate possible directions and priorities for future agricultural research.</p><p style="box-sizing: border-box; margin: 0px 0px 16px; padding: 0px;"><span style="color: #2e2e2e; font-family: NexusSerif, Georgia, Times New Roman, Times, STIXGeneral, Cambria Math, Lucida Sans Unicode, Microsoft Sans Serif, Segoe UI Symbol, Arial Unicode MS, serif;"><span style="font-size: 18px;"><a href="https://www.sciencedirect.com/science/article/abs/pii/016788099090214X">https://www.sciencedirect.com/science/article/abs/pii/016788099090214X</a></span></span></p></div></span></div>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-29062018875245627342017-07-14T11:20:00.001-07:002017-07-14T11:20:45.026-07:00Impacts of climate change on hydro-meteorological drought over the Volta Basin, West Africa, by P. G. Oguntunde, B. J. Abiodun & G. Lischeid; https://doi.org/10.1016/j.gloplacha.2017.07.003<span style="font-family: "georgia" , "times new roman" , serif;"><i>Global and Planetary Change</i>, (online July 12, 2017), <a class="S_C_ddDoi" href="https://doi.org/10.1016/j.gloplacha.2017.07.003" id="ddDoi" style="background-color: white; border: 0px; color: #316c9d; margin: 0px; padding: 0px; text-decoration-line: none; vertical-align: baseline;" target="doilink">https://doi.org/10.1016/j.gloplacha.2017.07.003</a></span><br />
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<span style="font-family: "georgia" , "times new roman" , serif; font-size: large;">Impacts of climate change on hydro-meteorological drought over the Volta Basin, West Africa</span></h1>
<span style="font-family: "georgia" , "times new roman" , serif;"><b>Philip G. Oguntunde</b>, <b>Batatunde J. Abiodun</b>, and <b>Gunnar Lischeid</b></span><br />
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<span style="font-family: "georgia" , "times new roman" , serif; font-size: small;">Highlights</span></h2>
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<span style="font-family: "georgia" , "times new roman" , serif; font-size: small;">We examined the past and future characteristics of drought over Volta River Basin.</span></div>
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<span style="font-family: "georgia" , "times new roman" , serif; font-size: small;">We investigated the coupling between drought and streamflow with wavelets analysis.</span></div>
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<span style="font-family: "georgia" , "times new roman" , serif; font-size: small;">A 2–3 month lead time was found between drought indices and stream flow.</span></div>
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<span style="font-family: "georgia" , "times new roman" , serif; font-size: small;">Drought area extent is projected to increase by 24% to 34% in the future.</span></div>
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<span style="font-family: "georgia" , "times new roman" , serif; font-size: small;">This study may guide policy on strategic and adaptive capacity building in the basin.</span></div>
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<span style="font-size: small;">Abstract</span></h2>
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<span style="font-family: "georgia" , "times new roman" , serif;">This study examines the characteristics of drought in the Volta River Basin (VRB), investigates the influence of drought on the streamflow, and projects the impacts of future climate change on the drought. A combination of observation data and regional climate simulations of past and future climates (1970–2013, 2046–2065, and 2081–2100) were analyzed for the study. The Standardized Precipitation Index (SPI) and Standardized Precipitation and Evapotranspiration (SPEI) were used to characterize drought while the Standardized Runoff Index (SRI) were used to quantify runoff. Results of the study show that the historical pattern of drought is generally consistent with previous studies over the Basin and most part of West Africa. RCA ensemble medians (RMED) give realistic simulations of drought characteristics and area extent over the Basin and the sub-catchments in the past climate. Generally, an increase in drought intensity and spatial extent are projected over VRB for SPEI and SPI, but the magnitude of increase is higher with SPEI than with SPI. Drought frequency (events per decade) may be magnified by a factor of 1.2 (2046–2065) to 1.6 (2081–2100) compared to the present day episodes in the basin. The coupling between streamflow and drought episodes was very strong (P < 0.05) for the 1–16-year band before the 1970 but showed strong correlation all through the time series period for the 4–8-years band. Runoff was highly sensitive to precipitation in the VRB and a 2–3 month time lag was found between drought indices and streamflow in the Volta River Basin. Results of this study may guide policymakers in planning how to minimize the negative impacts of future climate change that could have consequences on agriculture, water resources and energy supply.</span></div>
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<span style="color: #2e2e2e; font-family: "georgia" , "times new roman" , serif;"><span style="word-spacing: -1.25977px;"><a href="http://www.sciencedirect.com/science/article/pii/S0921818116305215">http://www.sciencedirect.com/science/article/pii/S0921818116305215</a></span></span></div>
Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-59258238483585801632017-05-07T08:19:00.000-07:002017-05-07T08:19:07.236-07:00Catastrophic mesoscale convective system storms in the western Sahel now three times more likely<span style="font-family: Georgia, Times New Roman, serif;"><strong style="background-color: white;">Climate change brings more Sahel storms<br /><br />Climate change is upsetting rainfall patterns and the frequency of flooding in West Africa as it makes the region's Sahel storms three times likelier.</strong><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">by Tim Radford, </span><em style="background-color: white;">Climate News Network</em><span style="background-color: white;">, May 7, 2017</span><em style="background-color: white;"><br /><br />LONDON </em><span style="background-color: white;">– Climate change has already made a difference to life in the West African Sahel, the arid belt of land stretching from the Atlantic to the Red Sea which separates the Sahara desert from the African savanna. It has made catastrophic storms three times more frequent.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">And, according to a new study in the journal <i>Nature</i>, Sahel storms are among the most powerful on the planet. In 2009, one vast downpour deposited 263 mm of rain over Ouagadougou, the capital of Burkina Faso, claiming 8 lives, flooding half the city and forcing 150,000 people out of their homes.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">Researchers believe the pattern of thunderstorms known as mesoscale convective systems will increase in frequency as global temperatures rise, as a consequence of increasing levels of carbon dioxide in the atmosphere, in turn driven by worldwide use of fossil fuels as sources of energy.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">Mesoscale convective systems are big, bad, and very cold columns of thunderous cloud: up to 16 km high, covering an area of 25,000 square kilometres, and with temperatures at the highest altitude as low as minus 40 °C.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">Between 1986 and 2005, Burkina Faso registered floods at a rate of little more than one a year. In the 11 years between 2006 and 2016, it was hit by 55 flood events.</span><br style="background-color: white;" /><br style="background-color: white;" /><strong style="background-color: white;">Repeated warnings</strong><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">Climate scientists have been warning for three decades that global warming will be accompanied by an increase in “extreme” events: in particular drought, flood, heat wave, and tropical cyclone.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">Global warming has already been observed in the Sahel, and the consequences have not necessarily been bad: overall, precipitation has increased, and farmers have benefited, although in a dryland region south of the Sahara where people have endured a 2,000-year history of periodic drought, famine remains a constant hazard.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">And now, so do massive downpours of rain: the Sahel storms. British and French scientists examined 35 years of satellite data and the rain gauges in the region to identify a rise in extreme daily rainfall totals. They found 85% of extreme rainfall cases coincided with satellite records of a passing mesoscale convection system.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">They also examined the pattern of temperatures over the region and found that although the annual average temperatures have risen, the so-called “wet season” temperatures have remained steady. That is, locally warmer conditions alone have not brought more rainfall.</span><br style="background-color: white;" /><br style="background-color: white;" /><strong style="background-color: white;">“Global warming is expected to produce more intense storms, but we were shocked to see the speed of changes taking place in this region of Africa”</strong><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">Instead, they blame man-made global warming which has changed wind and rain conditions, and this will go on strengthening during this century, “suggesting the Sahel will experience particularly marked increases in extreme rain,” they conclude.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">“Global warming is expected to produce more intense storms, but we were shocked to see the speed of changes taking place in this region of Africa,” said Christopher Taylor, a meteorologist at the UK’s Centre for Ecology and Hydrology, who led the study.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">His co-author Douglas Parker, professor of meteorology at the University of Leeds in the UK, said: “African storms are highly organised meteorological engines, whose currents extract water from the air to produce torrential rain.</span><br style="background-color: white;" /><br style="background-color: white;" /><span style="background-color: white;">“We have seen these engines becoming more efficient over recent decades, with resulting increases in the frequency of hazardous events.” </span></span><br />
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<span style="font-family: Georgia, Times New Roman, serif;"><span style="background-color: white;"><a href="http://climatenewsnetwork.net/climate-change-brings-more-sahel-storms">http://climatenewsnetwork.net/climate-change-brings-more-sahel-storms</a></span></span>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com1tag:blogger.com,1999:blog-7698039939158013969.post-90983055447362191682015-10-30T20:58:00.001-07:002015-10-30T20:58:33.049-07:00Evidence stretching back 40,000 years shows that global warming will increase drying in a region of East Africa where drought already causes humanitarian crises<span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">by Alex Kirby,</span><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;"> <i>Climate News Network</i>, October 10, 2015</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">LONDON – One of Africa’s most volatile regions has become increasingly dry over the last century and faces a future of rising tension if this trend continues, US researchers say.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">They say the rate of drying in the Horn of Africa is both unusual in the context of the last 2,000 years and in step with human-influenced warming. And they think the drying will continue as the region warms.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">“Right now, aid groups are expecting a wetter, greener future for the Horn of Africa, but our findings show that the exact opposite is occurring,” says one of the study’s co-authors, Peter deMenocal, who heads the Center for Climate and Life at Columbia University’s Lamont-Doherty Earth Observatory.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">“The region is drying, and will continue to do so with rising carbon emissions.” The study, published in the journal <i>Science Advances</i>, was based on evidence stretching back for 40,000 years.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;"><b>Sediment core</b></span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">The researchers used a sediment core they had extracted from the Gulf of Aden to infer past changes in temperature and aridity. After matching the core’s record with 20th-century observations, they concluded that drying is likely to continue across Somalia, Djibouti and Ethiopia.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">That contradicts other models, which have suggested that future warming might bring rainier weather patterns that could benefit East Africa.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">“What we see in the paleoclimate record from the last 2,000 years is evidence that the Horn of Africa is drier when there are warm conditions on Earth, and wetter when it is colder,” says lead author Jessica Tierney, associate professor of geosciences at the University of Arizona.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">Global-scale models used to predict future changes as the climate warms suggest that the region should become wetter, primarily during the “short rains” season from September to November.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">However, the new study suggests that those gains may be offset by declining rainfall during the “long rains” season from March to May, on which the region’s rain-fed agriculture relies.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">The authors say the region has been racked with political instability and violence as it has dried. The Horn of Africa has suffered droughts every few years in recent decades − creating humanitarian crises as famine and violence spread.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">In Somalia, as the political situation deteriorated amid the droughts of the 1980s and 1990s, hundreds of thousands of refugees fled the country, and pirates began raiding ships off the coast.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">The 40,000-year-old sediment core has already yielded insights into Africa’s climate. In 2013, Tierney and deMenocal showed that the Sahara, which once used to burst into verdant life with regular rainfall, suddenly dried out over a century or two, during a warm period about 5,000 years ago – not more gradually, as many researchers had thought.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">Their work provided evidence that climate shifts can happen quite suddenly, even if the forces driving them are gradual.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">This latest study uses isotopes from leaf waxes found in the sediment sample to compare rates of drying over the past 2,000 years.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">Plants reflect the environment that sustains them. When the climate is drier, leaf waxes are more enriched with deuterium, or heavy hydrogen isotopes, while leaf waxes from wetter climates reflect the more abundant rainfall through the presence of the normal hydrogen isotopes.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">The researchers found an increasing shift toward heavy hydrogen in the last century as the climate − which had experienced a wet period during the Little Ice Age (1450-1850 AD) − dried out.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;"><b>Climate modelling</b></span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">Their findings suggest that climate modelling, frequently done at a global scale, would benefit from region-specific studies with higher-resolution results in high-impact areas such as the Horn of Africa</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">Tierney says: “If we can simulate rainfall in these arid tropical and subtropical regions better, we can understand the future impact of climate change.”</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">The development agency Oxfam says Ethiopia is facing a major emergency, with 4.5 million people needing food aid because of successive poor rains this year.</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">Oxfam’s representative in Ethiopia describes the situation − attributed to the El Niño periodic climate phenomenon in the Pacific − as “the start of a major emergency, which is expected to be serious and long.”</span><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><br style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;" /><span style="background-color: white; color: #222222; font-family: Georgia, 'Times New Roman', serif;">Meanwhile, parts of West Africa are suffering from the aftermath of severe floods − also attributed to El Niño − that have ruined crops and destroyed homes in Burkina Faso and Niger. </span>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-12357284811796450622015-09-07T15:36:00.001-07:002015-09-07T15:36:59.001-07:00Impact of climate change on staple food crop production in Nigeria, Climatic Change, September 2015; doi: 10.1007/s10584-015-1428-9<span style="font-family: Georgia, Times New Roman, serif;"><i>Climatic Change,</i> <b>132</b>(<i>2</i>) (September 2015) 321-336; doi: <span style="background-color: white; color: #666666; line-height: 15.6px;">10.1007/s10584-015-1428-9</span></span><br />
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<span style="font-family: Georgia, Times New Roman, serif; font-size: large;">Impact of climate change on staple food crop production in Nigeria</span></h1>
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<li style="border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: 1.5; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><span class="AuthorName_container" style="border-bottom-color: rgb(215, 214, 214); border-bottom-style: dotted; border-width: 0px 0px 1px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; position: relative; vertical-align: baseline;"><span class="AuthorName" style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><b>Valentina Mereu</b></span></span></li>
<li style="border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: 1.5; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">, </span><span class="AuthorName_container" style="border-bottom-color: rgb(215, 214, 214); border-bottom-style: dotted; border-width: 0px 0px 1px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; position: relative; vertical-align: baseline;"><span class="AuthorName" style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><b>Gianluca Carboni</b></span></span></li>
<li style="border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: 1.5; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">, </span><span class="AuthorName_container" style="border-bottom-color: rgb(215, 214, 214); border-bottom-style: dotted; border-width: 0px 0px 1px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; position: relative; vertical-align: baseline;"><span class="AuthorName" style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><b>Andrea Gallo</b></span></span></li>
<li style="border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: 1.5; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">, </span><span class="AuthorName_container" style="border-bottom-color: rgb(215, 214, 214); border-bottom-style: dotted; border-width: 0px 0px 1px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; position: relative; vertical-align: baseline;"><span class="AuthorName" style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><b>Raffaello Cervigni</b></span></span></li>
<li style="border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: 1.5; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"> and </span><span class="AuthorName_container" style="border-bottom-color: rgb(215, 214, 214); border-bottom-style: dotted; border-width: 0px 0px 1px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; position: relative; vertical-align: baseline;"><span class="AuthorName" style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; display: inline; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><b>Donatella Spano</b></span></span></li>
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<b><span style="font-family: Georgia, Times New Roman, serif;">Abstract</span></b><br />
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<span style="background-color: white; color: #333333; font-family: Georgia, Times New Roman, serif; line-height: 19.64px;">Climate change impact on the agricultural sector is expected to be significant and extensive in Sub-Saharan Africa, where projected increase in temperature and changes in precipitation patterns could determine sensible reductions in crop yields and concerns for food security achievement. This study presents a multi-model approach to analysing climate change impacts and associated risks for staple food crops in Nigeria. Previous attempts to evaluate climate change impacts in Nigeria had mainly focused on a reduced number of crops, with analysis limited to single experimental fields or specific areas, and in many cases considering only a limited number of climate models. In this work, crop simulation models implemented in the DSSAT-CSM software were used to evaluate climate change impacts on crop production in different Agro-Ecological Zones, considering multiple combinations of soils and climate conditions, varieties and crop management. The climate impact assessment was made using an ensemble of future climate projections, to include uncertainty related to climate projections. Even if precipitations could increase in most parts of Nigeria, this is not likely to offset the crop yield reduction due to the increase in temperatures, particularly over the medium-term period (2050), with yield decreases projected especially for cereals. The short-term effects are more uncertain and yields for cassava and millet might actually increase by 2020. Moreover, yield reductions are only partially mitigated by the direct effect of increased CO<sub>2</sub> atmospheric concentrations enhancing crop yields. In both periods and for all crops, there is a higher risk that crop yields may fall below the actual risk threshold.</span></div>
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<span style="background-color: white; color: #333333; font-family: Georgia, Times New Roman, serif; line-height: 16.64px;"><a href="http://link.springer.com/article/10.1007/s10584-015-1428-9">http://link.springer.com/article/10.1007/s10584-015-1428-9</a></span><br />
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<span style="background-color: white; color: #333333; font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: 13px; line-height: 16.64px;"><br /></span>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-63895432717262173902014-05-05T13:23:00.000-07:002014-05-05T13:23:20.889-07:00NASA Finds Drought May Take Toll on Congo Rainforest<span class="lead_image" style="background-color: white; color: #4b5c68; font-family: Helvetica, Arial, Verdana, sans-serif;"><img alt="A view of the entire African rainforest area (green)" border="0" src="http://www.jpl.nasa.gov/images/earth/africa/20140423/earth20140423-640.jpg" height="350" style="border: 0px; margin-top: 10px;" width="640" /></span><span style="background-color: white; color: #4b5c68; font-family: Helvetica, Arial, Verdana, sans-serif;"></span><span class="photo_caption" style="background-color: white; color: #4b5c68; font-family: Helvetica, Arial, Verdana, sans-serif; font-size: 0.7em; line-height: 1.3em;">A V</span><span class="photo_caption" style="background-color: white; line-height: 1.3em;"><span style="font-family: Georgia, Times New Roman, serif;">iew of the entire African rainforest area (green) transitions into a view of the region included in the Nature study, primarily in the Congo forest (mostly brown). The study area represents intact areas in the Congo rainforest where satellite data are high quality. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio<br /><a href="http://www.jpl.nasa.gov/images/earth/africa/20140423/earth20140423-full.jpg" style="text-decoration: none;">› Larger image</a></span></span><br />
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<span style="font-family: Georgia, Times New Roman, serif;">from NASA's Jet Propulsion Laboratory, April 23, 2014</span><br />
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<span style="font-family: Georgia, Times New Roman, serif;">A new analysis of NASA satellite data shows Africa's Congo rainforest, the second-largest tropical rainforest in the world, has undergone a large-scale decline in greenness over the past decade.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">The study, led by Liming Zhou of University at Albany, State University of New York, shows between 2000 and 2012 the decline affected an increasing amount of forest area and intensified. The research, published Wednesday in <i>Nature</i>, is one of the most comprehensive observational studies to explore the effects of long-term drought on the Congo rainforest using several independent satellite sensors.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">"It's important to understand these changes because most climate models predict tropical forests may be under stress due to increasing severe water shortages in a warmer and drier 21st century climate," Zhou said.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Scientists use the satellite-derived "greenness" of forest regions as one indicator of a forest's health. While this study looks specifically at the impact of a persistent drought in the Congo region since 2000, researchers say that a continued drying trend might alter the composition and structure of the Congo rainforest, affecting its biodiversity and carbon storage.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Previous research used satellite-based measurements of vegetation greenness to investigate changes in the Amazon rainforest, notably the effects of severe short-term droughts in 2005 and 2010. Until now, little attention has been paid to African rainforests, where ground measurements are even sparser than in the Amazon and where droughts are less severe but last longer.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">To clarify the impact of long-term drought on the Congo rainforest, Zhou and colleagues set out to see whether they could detect a trend in a satellite measure of vegetation greenness called the Enhanced Vegetation Index. This measure is developed from data produced by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Terra satellite. The scientists focused their analysis on intact, forested regions in the Congo Basin during the months of April, May and June each year - the first of the area's two peak rainy and growing seasons each year.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">The study found a gradually decreasing trend in Congo rainforest greenness. The decrease, sometimes referred to as "browning," suggests a slow adjustment to the long-term drying trend. This is in contrast to the more immediate response seen in the Amazon, such as large-scale tree mortality, brought about by more episodic drought events.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">The browning of the forest canopy is consistent with observed decreases in the amount of water available to plants, whether that is in the form of rainfall, water stored in the ground, water in near-surface soils, or water within the vegetation.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">These changes in available water were detected in part with NASA satellites including the NASA/JAXA Tropical Rainfall Measuring Mission, NASA's Quick Scatterometer (QuikScat), and NASA's Gravity Recovery and Climate Experiment, a joint mission with the German Aerospace Center. The latter two missions are managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">"Combining measurements from different sensors has given us more confidence in the results of the MODIS data and provided us with insights into the environmental and physiological mechanisms of the browning observed by the MODIS data," said co-author Sassan Saatchi of JPL.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Climate factors known to affect vegetation growth were also in line with the observed browning. Land surface temperatures, for example, were observed to increase over most of the study area. Decreased cloudiness allowed more solar radiation to reach the plants, which typically promotes photosynthesis, but in this case it likely posed an extra stress on the plants from the resulting depletion of soil moisture.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">"Forests of the Congo Basin are known to be resilient to moderate climate change because they have been exposed to dry conditions in the past few hundred years," Saatchi said. "However, the recent climate anomalies as a result of climate change and warming of the Atlantic Ocean have created severe droughts in the tropics, causing major impacts on forests."</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">How the changes affect individual plant species in the area remains to be seen. For example, drier conditions may favor deciduous trees at the expense of evergreen trees.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">"Our assessment is a step toward an improved understanding of how African rainforests respond to increasing drought," Zhou said. "We need to consider the complex range of processes affecting different tropical rainforest species before we can fully assess the future resilience of tropical forests."</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">The other authors for this research include Yuhong Tian at I.M. Systems Group, Inc. at the Center for Satellite Applications and Research, the science arm of National Oceanic and Atmospheric Administration's Satellite and Information Service, College Park, Md.; Ranga Myneni at Boston University in Massachusetts; Philippe Ciais at Laboratoire des Sciences du Climat et de l'Environnement, Gif sur Yvette Cedex, France; Yi Y. Liu at University of New South Wales, Australia; Shilong Piao at Peking University, China; Haishan Chen at Nanjing University of Information Science and Technology, China; Eric Vermote of NASA's Goddard Space Flight Center, Greenbelt, Md.; and Conghe Song and Taehee Hwang at the University of North Carolina at Chapel Hill.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">NASA monitors Earth's vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.</span></div>
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<span style="line-height: 19.200000762939453px;"><a href="http://www.jpl.nasa.gov/news/news.php?release=2014-124"><span style="font-family: Georgia, Times New Roman, serif;">http://www.jpl.nasa.gov/news/news.php?release=2014-124</span></a></span></div>
Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-11455910339555981772014-04-25T18:23:00.002-07:002014-04-25T18:23:40.023-07:00Congo forest feels bigger climate impact<span style="font-family: Georgia, Times New Roman, serif;"><span style="background-color: white; color: #222222;">by Tim Radford, </span><span style="background-color: white; color: #222222;"><i>Climate News Network</i>, April 25, 2014</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">Researchers say there is increasing evidence that climate change is among the factors causing serious damage to the rainforest of the Congo basin.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">LONDON, 25 April - The Congo – one of the world’s greatest rainforests – is getting steadily less green. The slow change in colour during this century, recorded by a series of US satellites, has been matched by a rise in temperature and lower precipitation. And, researchers think, it could reflect a forest’s response to climate change.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">Scientists from Australia, China, the US and France report in the journal <i>Nature</i> that they examined optical, thermal, microwave and gravity data collected by orbiting sensors between 2000 and 2012.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">They concentrated on intact forested regions during the months of April, May and June each year, which span the peaks of growth and rainfall. They detected an intensification in the forest’s decline. This decline was consistent with lower rainfall, poorer water storage below the canopy and a gradual change in the composition of species.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">“It is important to understand these changes because most climate models predict tropical forests may be under stress due to increasing severe water shortages in a warmer and drier 21st century climate,” said Liming Zhou, of Albany State University of New York. But other factors could accelerate this “browning” of one of the world’s greatest rainforests.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;"><b>Half as hot again</b></span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">A team from the Catholic University of Louvain in Belgium - also known in Belgium’s other language as KU Leuven - predicts in the <i>Journal of Climate</i> that explosive population growth and inefficient agricultural practices are likely to make things a great deal hotter for the region and a great deal worse for the rainforest.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">By 2050, according to their computer models, Central Africa will be on average 1.4 °C hotter than it is today just because of greenhouse gas emissions. And the steady destruction of the forest will add an extra 0.7 °C to that figure.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">Temperature increases on such a scale will harm plant and animal species and even bring about some extinction. Where the forests have been cleared, there will be increased levels of evaporation, and consequent rises in temperature.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">Across the Atlantic, things also look bleak for the Amazon rainforest. Paulo Brando of the Amazon Environmental Research Institute in Brazil and colleagues from the US report in the Proceedings of the National Academy of Sciences that the piecemeal clearing of the rainforest, along with drought, has begun to create “tinderbox” conditions and an ever more destructive cycle of burning.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;"><b>Non-average menace</b></span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">Over the course of 8 years, in one of the longest-running experiments of its kind, the researchers burned 50-hectare plots of forest in the south-eastern Amazon, a region vulnerable to climate change. They compared the tree deaths each year to measure the impact of drought on fire intensity.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">“Drought causes more intense and widespread fires,” said Dr Brando. “Four times more adult trees were killed by fire during a drought year, which means that there was also more carbon dioxide released into the atmosphere, more tree species loss and a greater likelihood of grasses invading the forest.”</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">This research, too, was backed up by satellite observation. In 2007, a year of drought, fires in south-east Amazonia burned 10 times more forest than in an average year - an area equivalent to a million soccer fields, according to Douglas Morton of the US space agency NASA, a co-author.</span><br style="background-color: white; color: #222222;" /><br style="background-color: white; color: #222222;" /><span style="background-color: white; color: #222222;">Climate change is expected to bring shorter, more intense rainy seasons and longer dry seasons in the region. Michael Coe of Woods Hole Research Center, another author, said “We tend to think only about average conditions, but it is the non-average conditions we have to worry about.” </span></span>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-68570651718851909912014-01-28T10:11:00.000-08:002014-01-28T10:11:44.485-08:00Vulnerable to climate change, Cameroon tackles the problem head-on<span style="background-color: white; line-height: 18.17727279663086px;"><span style="font-family: Georgia, Times New Roman, serif;">Though particularly vulnerable to climate change, students in Cameroon are developing innovative technological solutions</span></span><br />
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<span style="font-family: Georgia, Times New Roman, serif;">by John Abraham, "Climate Consensus - The 97%," <i>The Guardian</i>, January 28, 2014</span><br />
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<span style="font-family: Georgia, Times New Roman, serif;"><img alt="A man cycles past furniture for sale at the roadside in Cameroon." data-pin-description="A man rides a bicycle in Cameroon; a country very vulnerable to climate change that it didn't cause, but developing innovative solutions to the problem. Photograph: Peter Treanor/Alamy" height="276" itemprop="contentUrl representativeOfPage" src="http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2010/5/11/1273583142890/A-man-cycles-past-furnitu-007.jpg" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px;" width="460" /></span><div class="caption" itemprop="caption" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px;">
<span style="font-family: Georgia, Times New Roman, serif;"><i>A man rides a bicycle in Cameroon; a country very vulnerable to climate change that it didn't cause, but developing innovative solutions to the problem. Photograph: Peter Treanor/Alamy</i></span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">My research involves not only studying the Earth's climate, but also working to find clean energy solutions that will enable people and regions to have access to reliable electricity without increasing emissions of heat-trapping gases. In support of this effort, I recently traveled to <a href="http://www.theguardian.com/world/cameroon" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;" title="More from the Guardian on Cameroon">Cameroon</a>, which is on the western coast of Africa. There, in a town near the coast called Buea, I spent two weeks with my family and colleagues, working with a new university (<a href="http://cuib-cameroon.com/" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">Catholic University Institute of Buea</a>, or CUIB for short) but more about that later.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">First, readers of this column will note that I take a particular interest in the impacts of <a href="http://www.theguardian.com/environment/climate-change" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;" title="More from the Guardian on Climate change">climate change</a> that are being felt at regional or national levels. In particular, changes to weather patterns and how those changes are being driven by either natural or human causes is something I care deeply about. Fortunately, there is extensive literature available about observed changes or expected changes to climate and weather in and around Cameroon. For instance, <a href="http://www.sciencedirect.com/science/article/pii/S0022169401004450" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">some studies</a> that focus on the impacts of climate change on the water cycle project that increases in rainfall and evaporation from lakes, rivers, oceans, and plants will have impacts that must be considered in future development planning.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;"><a href="http://www.citeulike.org/group/342/article/1306758/" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">Another study</a> focused on the impacts that land-use changes and climate change have on Cameroon's forests; the study found future effects will be profound. Loss of forest lands will lead to loss of animal life in particular. <a href="http://link.springer.com/article/10.1007/s11027-010-9216-3#page-1" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">More recent work</a> confirms the vulnerability of Cameroon's forests to climate change. Those researchers found that while the people in Cameroon expressed a great deal of understanding and appreciation of climate change, the ability of the country to adapt to climate change was limited.<br style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px;" /><br style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px;" />Perhaps the most detailed study regarding Cameroon's susceptibility to climate change was completed <a href="http://www-wds.worldbank.org/servlet/WDSContentServer/IW3P/IB/2007/09/20/000158349_20070920134147/Rendered/PDF/WPS4364.pdf" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">by the World Bank</a>, which related agricultural output to climate change, in particular to changes in temperature and precipitation. The authors reported that since a large majority of the poor of Cameroon (and a significant percentage of the national GDP) work in agriculture, Cameroon as a nation is particularly sensitive to some of the changes we expect to see as the world warms.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">And all of this brings us back to the university CUIB. I traveled there to find out what people on the ground observe. I spoke with the Dean of <a href="http://uidb-cameroon.com/sanr/" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">the School of Agriculture and Natural Resources</a>, Dr. <a href="http://uidb-cameroon.com/offices/ooe/" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">Laetitia Ako Kima</a>. She told me,</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">"Farmers in this region are dependent on rain-fed agriculture and have observed erratic rainfall patterns and intensity which adversely affect agricultural activities and their livelihoods. Effects of this include among others, difficulty in following cropping calendars due to unpredictable and unseasonably long rainy periods, decline in crop yields, high disease incidence and crop losses, increased post-harvest losses and high labour costs, coupled with increasing incidents of HIV/AIDS.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">These adversely affect their livelihoods, exacerbating already entrenched poverty which prevails at the grassroots level. There is therefore an urgent need for alternative coping strategies to mitigate prevailing circumstances."</span></div>
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<span class="inline wide" style="border-collapse: collapse; display: block; float: none; line-height: 17.261037826538086px; margin: 0px; padding: 0px; width: auto;"><span style="font-family: Georgia, Times New Roman, serif;"><img alt=" Outdoor community classrooms at CUIB." data-pin-description="Outdoor community classrooms at CUIB." height="254" src="http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2014/1/28/1390873041018/CUIB.jpg" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 5px 0px 0px;" width="378" /></span><span class="caption" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; display: block; line-height: 1.25; margin: 0px 0px 13px; padding: 0px; width: 378px;"><span style="font-family: Georgia, Times New Roman, serif;"><i>Outdoor community classrooms at CUIB.</i></span></span></span><div style="border-collapse: collapse; line-height: 17.261037826538086px; margin-bottom: 13px; padding: 0px;">
<span style="font-family: Georgia, Times New Roman, serif;">So, how will a country like Cameroon plan for <a href="http://www.theguardian.com/science/scienceofclimatechange" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;" title="More from the Guardian on Climate change">climate change</a> and how do universities like CUIB contribute to those plans? First, we must recognize that climate change is a global problem. Emitted greenhouse gases do not abide by borders, nor do their impacts. In fact, as we've seen elsewhere, Cameroon is another country that has largely <a href="http://skepticalscience.com/graphics.php?g=15" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">not caused the problem but may be impacted more significantly</a> than other nations. The reason for this is threefold. First, since Cameroon's annual temperatures are confined to a small range, the biological systems are less capable of adapting to changes that modify the range. Second, Cameroon is heavily dependent on agriculture, which, in turn, depends on climate. Finally, Cameroon's limited financial resources make adaptation particularly difficult.</span></div>
<span class="inline wide" style="border-collapse: collapse; display: block; float: none; line-height: 17.261037826538086px; margin: 0px; padding: 0px; width: auto;"><span style="font-family: Georgia, Times New Roman, serif;"><img alt="Countries that contribute least to climate change tend to be the most vulnerable to its impacts." data-pin-description="Countries that contribute least to climate change tend to be the most vulnerable to its impacts, according to Samson et al. (2011)." height="338" src="http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2014/1/28/1390873250119/Vulnerable_Countries_450.jpg" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 5px 0px 0px;" width="450" /></span><span class="caption" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; display: block; line-height: 1.25; margin: 0px 0px 13px; padding: 0px; width: 450px;"><span style="font-family: Georgia, Times New Roman, serif;"><i>Countries that contribute least to climate change tend to be the most vulnerable to its impacts, according to Samson et al. (2011).</i></span></span></span><div style="border-collapse: collapse; line-height: 17.261037826538086px; margin-bottom: 13px; padding: 0px;">
<span style="font-family: Georgia, Times New Roman, serif;">Of course, Cameroon can, and will, play their role in reducing greenhouse gas emissions. However with a high unemployment rate and with challenges related to electrical power production and distribution, what can this country realistically achieve?</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">This was one of the questions I asked as I sat down with the <a href="http://uidb-cameroon.com/seng/" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">Dean of the School Engineering</a>, Dr. Asong Zisuh and his students. I quickly learned that innovative ideas from the young and entrepreneur-minded scientists and engineers might serve as a role model for us all. Dr. Asong Zisuh told me,</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">"The mission of CUIB (the entrepreneurial university) is to prepare servant leaders with moral and spiritual values to contribute to the sustainable development of their communities. Students are required to undertake entrepreneurial projects on issues related to sustainable development. Ongoing student projects in the the School of Engineering include: construction of wind turbines to generate clean and renewable electricity; construction of a solar drier to help conserve local farm products; drawing building plans for local housing that incorporate energy conservation practices; developing concepts for sustainable management of solid and liquid waste by local councils; biogas production for small scale use; and production of briquettes from bio-residues."</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">All of these very advanced and innovative ideas have been generated by enthusiastic undergraduate students. The young, it seems, express tremendous courage because they don't know what cannot be done. By this naïveté, they are sometimes able to accomplish what we old folks think is impossible.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">The motivation for these environmental-conservation and climate change projects is not only related to the need to curb greenhouse gas emissions, but also to meet the growing demand for energy amidst huge supply shortages. Cameroon is a tropical country that receives a significant amount of daily sunshine and experiences a high generation rate of bio-residues, especially from agricultural activities. Thus, harnessing these available and inexpensive opportunities is required for the sustainable and economic development of the country.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Retrospectively, for someone like myself who works everyday on climate change, the slow progress can be demoralizing at times. I know that humans have the capacity to solve our climate and energy problems, we only lack the will. When I see what is happening at a small Cameroonian university that almost no one has heard of, I get encouraged. Maybe, just maybe, innovators like I've met at CUIB will be the change agents needed to preserve our future. Let's hope that's the case and let's support their efforts.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;"><span style="line-height: 17.261037826538086px;"><a href="http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/jan/28/cameroon-vulnerable-tackles-climate-change">http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/jan/28/cameroon-vulnerable-tackles-climate-change</a></span></span></div>
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Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-39619231506128547802014-01-13T15:54:00.003-08:002014-01-13T15:54:54.552-08:00John Abraham: Global warming and energy – intertwined problems in Africa<h1 itemprop="name headline " style="background-color: white; background-repeat: no-repeat no-repeat; border-bottom-color: rgb(123, 187, 0); border-collapse: collapse; border-left-color: rgb(123, 187, 0); border-right-color: rgb(123, 187, 0); border-top-width: 0px; font-weight: normal; line-height: 1.154; margin: 0px 0px 2px; padding: 0px; width: 460px;">
<span style="line-height: 1.25;"><span style="font-family: Georgia, Times New Roman, serif; font-size: large;">Kenya is training for tomorrow's technology leaders to deal with today's climate and energy problems</span></span></h1>
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<span style="font-family: Georgia, Times New Roman, serif;">by John Abraham, "Climate Consensus - The 97%," <i>The Guardian</i>, January 12, 2014</span><br />
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<span style="font-family: Georgia, Times New Roman, serif;"><img alt="Kenya drought " data-pin-description="A young girl in northern Kenya digs a hole in a river bed to retrieve water. Parts of Kenya are hit by drought as other areas get excessive rains. Photograph: Christopher Furlong/Getty Images" height="276" itemprop="contentUrl representativeOfPage" src="http://static.guim.co.uk/sys-images/Guardian/About/General/2012/5/25/1337937602096/Kenya-drought--009.jpg" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px;" width="460" /></span><div class="caption" itemprop="caption" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px;">
<span style="font-family: Georgia, Times New Roman, serif;"><i>A young girl in northern Kenya digs a hole in a river bed to retrieve water. Parts of Kenya are hit by drought as other areas get excessive rains. Photograph: Christopher Furlong/Getty Images</i></span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Much of my work involves the design and installation of clean and robust<a href="http://www.theguardian.com/environment/energy" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;" title="More from the Guardian on Energy">energy</a> sources in remote parts of the world. On a recent trip to <a href="http://www.theguardian.com/world/kenya" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;" title="More from the Guardian on Kenya">Kenya</a>, my family had the opportunity to tour the Lake Naivasha region in Kenya. This region contains a treasure of wildlife and was a filming location for the movie "<em style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px;">Out of Africa</em>." During a boat ride, we witnessed the impacts on <a href="http://www.theguardian.com/environment/climate-change" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;" title="More from the Guardian on Climate change">climate change</a> – not through academic journal articles or conference presentations – but through people who see climate change with their own eyes.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">In past years, Lake Naivasha had seen dramatic reductions in water level. The coastline had changed and plants and animals had adapted to a new normal. Recently, however, extreme rains have raised the waters approximately 4 meters according to our guide. The new waterline had submerged and killed beautiful Acacia trees. After conversations with many other Kenyans, it was apparent that the reliable wet-dry weather patterns had become more erratic; you didn't have to witness dying Acacia trees when farmers throughout the country told similar tales. Extreme weather swings were evident here before our eyes.</span></div>
<span class="inline wide" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; display: block; float: none; margin: 0px; padding: 0px; width: auto;"><span style="font-family: Georgia, Times New Roman, serif;"><img alt="Flooding in Western Kenya, submerged buildings and Acacia trees." data-pin-description="Flooding in Western Kenya, submerged buildings and Acacia trees." height="302" src="http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2014/1/9/1389311005582/photo450.JPG" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 5px 0px 0px;" width="450" /></span><span class="caption" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; display: block; line-height: 1.25; margin: 0px 0px 13px; padding: 0px; width: 450px;"><span style="font-family: Georgia, Times New Roman, serif;"><i>Flooding in Western Kenya, submerged buildings and Acacia trees.</i></span></span></span><div style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin-bottom: 13px; padding: 0px;">
<span style="font-family: Georgia, Times New Roman, serif;">Kenyan culture (and much of Africa) is deeply rooted in the patterns of weather and climate; much of their economy depends on agricultural production. That dependency has given them much clearer foresight than others about how to plan for the changed future.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">The entirety of Kenya has awakened to the threats of <a href="http://www.theguardian.com/science/scienceofclimatechange" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;" title="More from the Guardian on Climate change">climate change</a>, including the government, agricultural sectors, energy industries and the educational system. My journey to learn more about Kenya's plans brought me to the beautiful and large <a href="http://www.ku.ac.ke/" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">Kenyatta University</a> campus, just northeast of Nairobi. There, very new and quickly growing programs in <a href="http://www.ku.ac.ke/schools/engineering/departments/mechanical-and-manufacturing-engineering" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">mechanical engineering</a>, <a href="http://www.ku.ac.ke/schools/engineering/departments/energy" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">energy and sustainability</a>, and <a href="http://www.ku.ac.ke/schools/agriculture/" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">agricultural engineering</a> are just a few of the programs training tomorrow's technology leaders to make an impact solving today's problems.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Among the many initiatives are goals to provide clean, renewable, and robust energy for the campus and the country. Some applications they are focusing on are wind-powered water-pumping systems. The plan is to design, manufacture, install, and service small-scale wind power systems that slowly pump water into elevated storage tanks throughout the day and night. Students, faculty, and staff draw the water is drawn down, typically during morning and evening hours. The prototype wind turbine will be adapted to manufacturing techniques used locally, near the university. It is hoped that wide-scale testing of the wind turbine system will occur over the next three years and thereafter, fast market penetration throughout Africa will be inevitable.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Another emerging technology coming from Kenyatta is the use of novel technologies for heating, ventilation, and air-conditioning (HVAC). By using thermochemical sorption technologies, sometimes with solar heating, <a href="http://www.ku.ac.ke/schools/engineering/faculty/profile/97-school-faculty-profiles/225-dr-jeremiah-k-kiplagat" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">Dr. Jeremiah Kiplagat</a> (recent recipient of the African Education Leadership Outstanding Professor Award) and his colleagues are setting the framework for improving the performance of refrigeration systems using these methodologies.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">As a third example, a series of faculty-led student projects have been completed to develop solar concentrating and tracking systems for heat generation and photovoltaic power generation. The research teams have developed effective and simple means of moving reflecting mirrors and parabolic concentrators with the sun throughout the day to increase the amount of absorbed solar energy and increase the efficiency of the overall system.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">While the faculty and staff are at the forefront in technology development projects such as these, much credit must be given to the administration. With implementation of new degrees such as doctoral programs in sustainability and masters programs in mechanical engineering, electrical engineering, engineering hydrology, and biomedical engineering, with a focus on solving the energy and health problems that are prevalent in the East African region, this university, and the country as a whole are destined to remain leaders in their geographical region.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">It is clear from formal academic studies and from anecdotal evidence that developing countries that rely upon agriculture will suffer greatly from climate change in the coming decades. It is hence apparent that the solutions to climate change, such as accelerated implementation of clean and renewable power, must be implemented with great wisdom so that people in these regions are able to access the same low-cost electricity that other nations have enjoyed. In this regard, the climate-energy problem is often thought of as a double-edged sword – solutions to the climate problem make access to low-cost electricity more difficult.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Currently, the major source of energy in Kenya is hydropower. This is why the School of Engineering at Kenyatta University has also partnered with regional and international organizations to promote climate mitigation in water and energy sectors. An example is the research being carried out by <a href="http://www.ku.ac.ke/schools/engineering/faculty/profile?id=219" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">Dr. Luke Olang</a> in collaboration with <a href="http://www.icpac.net/" style="background-repeat: no-repeat no-repeat; border-collapse: collapse; margin: 0px; padding: 0px; text-decoration: none;">IGAD climate center</a> on developing a drought-monitoring tool for the greater horn of Africa in general. The same research team is also actively involved in water management strategies in the vulnerable Mara River Basin, considered a World Heritage site due to the Great Annual Wildebeest Migration.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">What Kenyatta University is showing the world is that it is possible to solve both the energy and the climate problems together. Novel energy solutions using locally available technology and manufacturing techniques can build economies, provide low-cost energy, and preserve the future climate for our children. This type of systematic planning and dedication gives me hope that our future climate and energy problems can be solved.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Perhaps the vision is best expressed by Prof. Chris Shisanya, Dean School of Humanities and Social Sciences who told me,</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">"We at Kenyatta University have decided to prepare our students early enough during their study programmes to confront the challenges posed by climate change. We are now offering such courses as MSc. (Integrated Watershed Management) and MSc. (Climate Change and Sustainable Development), whose main focus is on adaptation to climate change. We believe that by exposing our students to such knowledge, they will be better equipped to help communities in Kenya's rural landscapes enhance their resilience to climate change impacts."</span></div>
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<a href="http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/jan/12/global-warming-energy-intertwined-africa"><span style="color: black; font-family: Georgia, Times New Roman, serif;">http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/jan/12/global-warming-energy-intertwined-africa</span></a>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-60056896847106362202013-04-13T11:58:00.001-07:002013-04-13T11:58:21.967-07:00"Unsustainable fuelwood extraction from South African savannas," by K. J. Wessels et al., ERL 8 (2013); doi: 10.1088/1748-9326/8/1/014007<span style="background-color: white; color: #333333; font-family: Georgia, 'Times New Roman', serif; font-size: 13px; line-height: 20.796875px;"><i>Environmental Research Letters</i>, 8 (2013) 014007; doi: <a href="http://dx.doi.org/10.1088/1748-9326/8/1/014007" style="color: #bf0000; line-height: 16.1875px; text-decoration: none;">10.1088/1748-9326/8/1/014007</a></span><span style="background-color: white; color: #333333; font-family: Georgia, 'Times New Roman', serif; font-size: 13px; line-height: 20.796875px;"><br /></span><span style="background-color: white; color: #333333; font-family: Georgia, serif; font-size: 13px; line-height: 20.796875px;"></span><br />
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<span style="font-family: Georgia, 'Times New Roman', serif; font-size: medium; letter-spacing: 0.2em;">UNSUSTAINABLE FUELWOOD EXTRACTION FROM SOUTH AFRICAN SAVANNAS</span></h2>
<span style="background-color: white; color: #333333; font-family: Georgia, 'Times New Roman', serif; font-size: 13px; line-height: 20.796875px;"><span style="line-height: 16.1875px;">K. J. Wessels</span><sup style="bottom: 0.5em; line-height: 16.1875px; position: relative; vertical-align: baseline;">1,2</sup><span style="line-height: 16.1875px;">, M. S. Colgan</span><sup style="bottom: 0.5em; line-height: 16.1875px; position: relative; vertical-align: baseline;"><span style="font-size: xx-small;">3</span></sup><span style="line-height: 16.1875px;">, B. F. N. Erasmus</span><sup style="bottom: 0.5em; line-height: 16.1875px; position: relative; vertical-align: baseline;">4</sup><span style="line-height: 16.1875px;">, G. P. Asner</span><sup style="bottom: 0.5em; line-height: 16.1875px; position: relative; vertical-align: baseline;">3</sup><span style="line-height: 16.1875px;">, W. C. Twine</span><sup style="bottom: 0.5em; line-height: 16.1875px; position: relative; vertical-align: baseline;">4</sup><span style="line-height: 16.1875px;">, R. Mathieu</span><sup style="bottom: 0.5em; line-height: 16.1875px; position: relative; vertical-align: baseline;">5</sup><span style="line-height: 16.1875px;">, J. A. N. van Aardt</span><sup style="bottom: 0.5em; line-height: 16.1875px; position: relative; vertical-align: baseline;">6</sup><span style="line-height: 16.1875px;">, J. T. Fisher</span><sup style="bottom: 0.5em; line-height: 16.1875px; position: relative; vertical-align: baseline;">4</sup><span style="line-height: 16.1875px;"> and I. P. J. Smit</span><sup style="bottom: 0.5em; line-height: 16.1875px; position: relative; vertical-align: baseline;">7</sup></span><br />
<span style="background-color: white; color: #333333; font-family: Georgia, 'Times New Roman', serif; font-size: 13px; line-height: 20.796875px;"><br /></span><span style="background-color: white; color: #333333; font-family: Georgia, serif; font-size: 13px; line-height: 20.796875px;"></span><b style="background-color: white; color: #333333; font-family: Georgia, 'Times New Roman', serif; font-size: 13px; line-height: 20.796875px;">Abstract</b><br />
<span style="background-color: white; color: #333333; font-family: Georgia, 'Times New Roman', serif; font-size: 13px; line-height: 20.796875px;"><br /></span><span style="background-color: white; color: #333333; font-family: Georgia, serif; font-size: 13px; line-height: 20.796875px;"></span>
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<span style="line-height: 18px;"><span style="font-family: Georgia, 'Times New Roman', serif;">Wood and charcoal supply the majority of sub-Saharan Africa's rural energy needs. The long-term supply of fuelwood is in jeopardy given high consumption rates. Using airborne light detection and ranging (LiDAR), we mapped and investigated savanna above-ground biomass across contrasting land uses, ranging from densely populated communal areas to highly protected areas in the Lowveld savannas of South Africa. We combined the LiDAR observations with socio-economic data, biomass production rates and fuelwood consumption rates in a supply–demand model to predict future fuelwood availability. LiDAR-based biomass maps revealed disturbance gradients around settlements up to 1.5 km, corresponding to the maximum distance walked to collect fuelwood. At current levels of fuelwood consumption (67% of households use fuelwood exclusively, with a 2% annual reduction), we calculate that biomass in the study area will be exhausted within thirteen years. We also show that it will require a 15% annual reduction in consumption for eight years to a level of 20% of households using fuelwood before the reduction in biomass appears to stabilize to sustainable levels. The severity of dwindling fuelwood reserves in African savannas underscores the importance of providing affordable energy for rural economic development.</span></span></div>
<span style="background-color: white; color: #333333; font-family: Georgia, serif; font-size: 13px; line-height: 18px;"><span style="font-family: Georgia, 'Times New Roman', serif;"><br /></span></span><span style="background-color: white; color: #333333; font-family: Georgia, serif; font-size: 13px; line-height: 20.796875px;"></span><span style="background-color: white; color: #333333; font-family: Georgia, 'Times New Roman', serif; font-size: 13px; line-height: 20.796875px;"><span style="line-height: 16.1875px;">Received 4 October 2012, accepted for publication 12 December 2012 </span><br style="line-height: 16.1875px;" /><span style="line-height: 16.1875px;">Published 17 January 2013</span></span><br />
<span style="background-color: white; color: #333333; font-family: Georgia, serif; font-size: 13px; line-height: 18px;"><span style="font-family: Georgia, 'Times New Roman', serif;"><br /></span></span><span style="background-color: white; color: #333333; font-family: Georgia, serif; font-size: 13px; line-height: 20.796875px;"></span><span style="background-color: white; color: #333333; font-family: Georgia, 'Times New Roman', serif; font-size: 13px; line-height: 20.796875px;"><span style="line-height: 18px;">Open access article: </span><a href="http://iopscience.iop.org/1748-9326/8/1/014007/article" style="color: #776644; text-decoration: none;">http://iopscience.iop.org/1748-9326/8/1/014007/article</a></span>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-48982022507662208392013-04-12T13:18:00.005-07:002013-04-12T13:18:44.931-07:00New Map Sharpens View of African Ecosystems<table style="background-color: white; color: #222222; font-family: Georgia, Helvetica, Arial, sans-serif; font-size: 13px; line-height: 18px;"><tbody>
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<span style="color: #555555; font-family: Georgia, Helvetica, Arial, sans-serif; font-size: small; line-height: 18px;">Posted:</span><span style="color: #555555; font-family: Georgia, Helvetica, Arial, sans-serif; font-size: small; line-height: 18px;"> </span><span style="color: #555555; font-family: Georgia, Helvetica, Arial, sans-serif; font-size: small; line-height: 18px;">11 Apr 2013 09:49 AM PDT</span></div>
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<span style="font-size: small;">A team of African and North American scientists led by the U.S. Geological Survey and NatureServe, a conservation non-profit organization, has created a series of continent-wide ecosystem maps that offer the most detailed portrayals of Africa's natural setting yet produced. The new maps and related data on landforms, geology, bioclimates, and vegetation can be used across Africa for conservation planning and resource management, as well as for impact assessments of climate change and changes in land use, such as agriculture, deforestation, and urbanization. </span><br />
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<span style="font-size: small;">"This was a multi-organizational, international collaboration to create new earth science datasets for the entire continent at finer resolutions than ever before," said Matt Larsen, USGS Associate Director for Climate and Land Use Change. "An added benefit is that this information about ecosystem conditions can be put to many different uses. It will have tremendous utility beyond ecosystem assessments." </span><br />
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<span style="font-size: small;">USGS and NatureServe researchers collaborated with the Regional Centre for Mapping of Resources for Development (RCMRD), based in Nairobi, Kenya. RCMRD hosted two workshops where invited experts from many African nations developed a new classification of African ecosystems and provided location data for the newly classified ecosystems.</span><br />
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<span style="font-size: small;">Overall, a total of 37 experts from 18 countries worked together to formulate the ecosystem classifications (126 distinct ecosystems were mapped) and produce the maps at a base resolution of 90 meters. </span><br />
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<span style="font-size: small;">"This much improved baseline of Africa's ecosystem conditions has the potential for more accurate carbon assessment studies in Africa," observed USGS scientist Roger Sayre, lead author of the publication. </span><br />
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<span style="font-size: small;">Determination of biological carbon stocks in ecosystems is an emerging science. Currently, carbon stocks are assessed in general biome categories like forests, grasses, shrublands, wetlands, deserts, and agricultural lands. The increased classification resolution supplied by the new African ecosystems maps will facilitate a more robust assignment of carbon inventories to a greater, more precise number of biological sources. </span><br />
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<span style="font-size: small;">The Association of American Geographers (AAG) provided key support for the final publication. The publication is <a href="http://pubs.er.usgs.gov/publication/70045097" style="color: #1155cc;" target="_blank">available in digital form</a> from the USGS. <em> </em> </span><br />
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<strong><span style="font-size: small;">A new map of standardized terrestrial ecosystems of Africa. </span></strong><span style="font-size: small;">2013. Sayre, Roger; Comer, Patrick; Hak, Jon; Josse, Carmen; Bow, Jacquie; et al., </span><i style="font-size: medium;">African Geographical Review.</i><br />
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<strong><span style="font-size: small;">Learn more: </span></strong><a href="http://rmgsc.cr.usgs.gov/ecosystems/" style="color: #1155cc;" target="_blank"><span style="font-size: small;">USGS Global Ecosystems</span></a></div>
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Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-35468834986599602252012-08-07T17:14:00.000-07:002012-08-07T17:14:02.102-07:00Mapping the future of climate change in Africa<span style="background-color: white; font-family: Arial, Helvetica, Sans; font-size: 12px;">Mapping the future of climate change in Africa</span><br />
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<span style="background-color: white; font-family: Arial, Helvetica, Sans; font-size: 12px;">August 2, 2012</span><br />
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<span style="font-family: Arial, Helvetica, Sans;"><span style="font-size: 12px;">Please see the link at the end of the article in order to see the figures.</span></span><br />
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<span style="background-color: white; font-family: Arial, Helvetica, Sans; font-size: 12px;">The composite picture highlights areas of chronic insecurity where the four sources of vulnerability coalesce. Credit: Joshua Busby et al. </span><br />
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<span style="background-color: white; font-family: Arial, Helvetica, Sans; font-size: 12px;">Our planet's changing climate is devastating communities in Africa through droughts, floods and myriad other disasters.</span><br style="background-color: white; clear: both; font-family: Arial, Helvetica, Sans; font-size: 12px;" /><br style="background-color: white; clear: both; font-family: Arial, Helvetica, Sans; font-size: 12px;" /><span style="background-color: white; font-family: Georgia, 'Times New Roman', serif;">Using detailed regional climate models and geographic information systems, researchers with the Climate Change and African Political Stability (CCAPS) program developed an online mapping tool that analyzes how climate and other forces interact to threaten the security of African communities. The program was piloted by the Robert S. Strauss Center for International Security and Law at The University of Texas at Austin in 2009 after receiving a $7.6 million five-year grant from the Minerva Initiative with the Department of Defense, according to Francis J. Gavin, professor of international affairs and director of the Strauss Center. </span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">"The first goal was to look at whether we could more effectively identify what were the causes and locations of vulnerability in Africa, not just climate, but other kinds of vulnerability," Gavin said. CCAPS comprises nine research teams focusing on various aspects of climate change, their relationship to different types of conflict, the government structures that exist to mitigate them, and the effectiveness of international aid in intervening. Although most CCAPS researchers are based at The University of Texas at Austin, the Strauss Center also works closely with Trinity College Dublin, the College of William and Mary, and the University of North Texas. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">"In the beginning these all began as related, but not intimately connected, topics" Gavin said, "and one of the really impressive things about the project is how all these different streams have come together." Africa is particularly vulnerable to the effects of climate change due to its reliance on rain-fed agriculture and the inability of many of its governments to help communities in times of need. The region is of increasing importance for U.S. national security, according to Gavin, because of the growth of its population, economic strength and resource importance, and also due to concerns about non-state actors, weakening governments and humanitarian disasters.</span></span><br style="background-color: white; clear: both; font-family: Arial, Helvetica, Sans; font-size: 12px;" /><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">Although these issues are too complex to yield a direct causal link between climate change and security concerns, he said, understanding the levels of vulnerability that exist is crucial in comprehending the full effect of this changing paradigm. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">The vulnerability mapping program within CCAPS is led by Joshua Busby, assistant professor at the Lyndon B. Johnson School of Public Affairs. </span></span><br />
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<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">To determine the vulnerability of a given location based on changing climate conditions, Busby and his team looked at four different sources: (1) the degree of physical exposure to climate hazards, (2) population size, (3) household or community resilience, and (4) the quality of governance or presence of political violence. </span></span><br />
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<a href="http://cdn.physorg.com/newman/gfx/news/2012/1-mappingthefu.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="218" src="http://cdn.physorg.com/newman/gfx/news/2012/1-mappingthefu.jpg" width="320" /></a></div>
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<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><i>Climate security vulnerability in Somalia is greatest in and around the capital of Mogadishu and the far north. Insecurity in these areas is driven by all four dimensions of vulnerability but particularly by low resilience and poor governance. Credit: Joshua Busby et al. </i></span></span><br />
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<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">The first source records the different types of climate hazards which could occur in the area, including droughts, floods, wildfires, storms and coastal inundation. However, their presence alone is not enough to qualify a region as vulnerable. </span></span><br />
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<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">The second source—population size—determines the number of people who will be impacted by these climate hazards. More people create more demand for resources, potentially making the entire population more vulnerable. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">The third source looks at how resilient a community is to adverse effects, analyzing the quality of their education and health, as well as whether they have easy access to food, water and health care. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">"If exposure is really bad, it may exceed the capacity of local communities to protect themselves," Busby said, "and then it comes down to whether or not the governments are going to be willing or able to help them." </span></span><br />
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<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">The final source accounts for the effectiveness of a given government, the amount of accountability present, how integrated it is with the international community, how politically stable it is, and whether there is any political violence present. </span></span><br />
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<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">Busby and his team combined the four sources of vulnerability and gave them each equal weight, adding them together to form a composite map. Their scores were then divided into a ranking of five equal parts, or quintiles, going from the 20 percent of regions with the lowest vulnerability to the 20% with the highest. The researchers gathered information for the tool from a variety of sources, including historic models of physical exposure from the United Nations Environment Programme (UNEP), population estimates from LandScan, as well as household surveys and governance assessments from the World Bank's World Development and Worldwide Governance Indicators. This data reflects past and present vulnerability, but to understand which places in Africa would be most vulnerable to future climate change, Busby and his team relied on the regional climate model simulations designed by Edward Vizy and Kerry Cook, both members of the CCAPS team from the Jackson School of Geosciences. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">Enlarge Children in the foothills of Drakensberg mountains in South Africa who still live in traditional rondavels on family homesteads. Credit: Credit: Todd G. Smith, CCAPS Program. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">Vizy and Cook ran three, 20-year nested simulations of the African continent's climate at the regional scales of 90 and 30 kilometers, using a derivation of the Weather Research and Forecasting Model of the National Center for Atmospheric Research. One was a control simulation representative of the years 1989-2008, and the others represented the climate as it may exist in 2041-2060 and 2081-2100. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">"We're adjusting the control simulation's CO2 concentration, model boundary conditions, and sea surface temperatures to increased greenhouse gas forcing scenario conditions derived from atmosphere-ocean global climate models. We re-run the simulation to understand how the climate will operate under a different, warmer state at spatial resolutions needed for regional impact analyses," Vizy said. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">Each simulation took two months to complete on the Ranger supercomputer at the Texas Advanced Computing Center (TACC). "We couldn't run these simulations without the high-performance computing resources at TACC, it would just take too long. If it takes two months running with 200 processors, I can't fathom doing it with one processor," Vizy said. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">Researchers input data from these vulnerability maps into an online mapping tool developed by the CCAPS program to integrate its various lines of climate, conflict and aid research. CCAPS's current mapping tool is based on a prototype developed by the team to assess conflict patterns in Africa with the help of researchers at the TACC/ACES Visualization Laboratory (Vislab), according to Ashley Moran, program manager of CCAPS. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">"The mapping tool is a key part of our effort to produce new research that could support policy making and the work of practitioners and governments in Africa," Moran said. "We want to communicate this research in ways that are of maximum use to policymakers and researchers." </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">The initial prototype of the mapping tool used the ArcGIS platform to project data onto maps. Working with its partner Development Gateway, CCAPS expanded the system to incorporate conflict, vulnerability, governance and aid research data. After completing the first version of their model, Busby and his team carried out the process of ground truthing their maps by visiting local officials and experts in several African countries, such as Kenya and South Africa. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">"The experience of talking with local experts was tremendously gratifying," Busby said. "They gave us confidence that the things we're doing in a computer lab setting in Austin do pick up on some of the ground-level expert opinions." </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">Busby and his team complemented their maps with local perspectives on the kind of impact climate was already having, leading to new insights that could help perfect the model. For example, local experts felt the model did not address areas with chronic water scarcity, an issue the researchers then corrected upon returning home. According to Busby, the vulnerability maps serve as focal points which can give way to further analysis about the issues they illustrate. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">Some of the countries most vulnerable to climate change include Somalia, Sierra Leone, Guinea, Sudan and parts of the Democratic Republic of Congo. Knowing this allows local policymakers to develop security strategies for the future, including early warning systems against floods, investments in drought-resistant agriculture, and alternative livelihoods that might facilitate resource sharing and help prevent future conflicts. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">The next iteration of the online mapping tool to be released later this year will also incorporate the future projections of climate exposure from the models developed by Vizy and Cook. The CCAPS team publishes their research in journals like <i>Climate Dynamics</i> and <i>The International Studies Review</i>, carries out regular consultations with the U.S. government and governments in Africa, and participates in conferences sponsored by concerned organizations, such as the United Nations and the United States Africa Command. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">"What this project has showed us is that many of the real challenges of the 21st century aren't always in traditional state-to-state interactions, but are transnational in nature and require new ways of dealing with," Gavin said. </span></span><br />
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white;"><span style="font-family: Georgia, Times New Roman, serif;">Provided by University of Texas at Austin</span></span><br />
<span style="font-family: Georgia, Times New Roman, serif;"><br /></span>
<span style="font-family: Georgia, Times New Roman, serif;"><a href="http://phys.org/news/2012-08-future-climate-africa.html">http://phys.org/news/2012-08-future-climate-africa.html</a> </span><br style="background-color: white; clear: both; font-family: Arial, Helvetica, Sans; font-size: 12px;" /><br style="background-color: white; clear: both; font-family: Arial, Helvetica, Sans; font-size: 12px;" />Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-63270608779232477832011-06-09T06:35:00.000-07:002011-06-09T06:35:41.781-07:00Said AlSarmi & Richard Washington, J. Geophys. Res., 116 (2011), Recent observed climate change over the Arabian Peninsula<span class="Apple-style-span" style="color: #652c90; line-height: 20px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"></span></span><br />
<div id="runhead" style="color: black; line-height: 1.5em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, D11109, 15 PP., 2011<br />
doi:10.1029/2010JD015459</span></div><div id="title" style="color: black; font-weight: bold; line-height: 1.2em; margin-bottom: 1.5em; margin-left: 0px; margin-right: 0px; margin-top: 1.2em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="Apple-style-span" style="font-size: large;">Recent observed climate change over the Arabian Peninsula</span></span></div><div class="keypoints" id="keypoints" style="border-bottom-color: rgb(153, 153, 153); border-bottom-style: solid; border-bottom-width: 1px; border-top-color: rgb(153, 153, 153); border-top-style: solid; border-top-width: 1px; margin-bottom: 15px; padding-top: 5px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="keypoint" style="color: black; font-weight: bold; line-height: 1.9em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;">Key Points</span><ul style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-top: 0px;"><li style="color: black; line-height: 1.4em; margin-bottom: 8px;">Arabian Peninsula is warming significantly</li>
<li style="color: black; line-height: 1.4em; margin-bottom: 8px;">Many Arabian Peninsula stations reported high warming rates</li>
<li style="color: black; line-height: 1.4em; margin-bottom: 8px;">The warming in minimum temperature is the highest and most spatially coherent</li>
</ul></span></div><div class="author" style="color: black; line-height: 1.2em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><b>Said AlSarmi </b>and<b> Richard Washington</b></span></div><div class="author" style="color: black; font-weight: bold; line-height: 1.2em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><br />
</span></div><div class="affiliation" style="color: black; line-height: 1.2em; margin-bottom: 0.8em; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><i>Climatology Research Group, Oxford University Centre for the Environment, University of Oxford, Oxford, UK</i></span></div><div class="abstract" style="border-top-color: rgb(153, 153, 153); border-top-style: solid; border-top-width: 1px;"><div style="color: black; line-height: 1.5em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><br />
</span></div><div style="color: black; line-height: 1.5em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><b>Abstract</b></span></div><div style="color: black; line-height: 1.5em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><b><br />
</b></span></div><div style="color: black; line-height: 1.5em; text-align: justify;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">We have examined trends in temperature and precipitation parameters for the Arabian Peninsula (AP) during the last 2 to 3 decades. The data set has been carefully quality controlled and checked for homogeneity. Although of low density (21 stations) and relatively short time period, a clear picture of climate change in the region has emerged. The general pattern of the AP mean annual temperature trend is one of warming, with 14 of 21 stations show statistically significant warming at 0.05 level and most at 0.001 level and only one (Seeb) showing statistically significant cooling. The highest statistically significant mean annual warming trends are found in Oman (Sur = 1.03 °C decade<sup style="bottom: 3px; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">−1</sup>) and Emirates (Dubai = 0.81 °C decade<sup style="bottom: 3px; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">−1</sup>). The season of maximum warming in mean temperature is March to April. The highest monthly mean temperature trend in the AP occurs in Sur in May (1.47 °C decade<sup style="bottom: 3px; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">−1</sup>). There is a broad statistically significant increase in mean annual maximum temperature in AP in 12 out of 21 stations, with the highest trends in central and eastern/southeastern AP. Only SW AP and the Gulf of Oman do not show warming. The highest monthly maximum temperature trend in the AP occurs in Bahrain in March (2.27 °C decade<sup style="bottom: 3px; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">−1</sup>). The second highest significant warming trends are reported in Doha in February (1.54 °C decade<sup style="bottom: 3px; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">−1</sup>). For minimum temperature, 16 out of 21 stations show statistically significant warming trends, with the highest annual trends observed in the Emirates (Dubai = 1.24 °C decade<sup style="bottom: 3px; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">−1</sup>), northwest Oman (Sohar = 1.17 °C decade<sup style="bottom: 3px; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">−1</sup>) and Qatar (Doha = 1.13 °C decade<sup style="bottom: 3px; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">−1</sup>). The highest monthly minimum temperature warming rate occurred in October. Both Dubai and Kuwait reported the highest significant rate of 2.00 °C decade<sup style="bottom: 3px; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">−1</sup>. The general mean annual diurnal temperature range trend is negative in the AP, with six out of 21 stations show statistically significant negative trends while three stations show statistically significant positive trends. Trends in mean annual precipitation are significant at only two stations which show a decrease in precipitation.</span></div><div style="color: black; line-height: 1.5em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><br />
</span></div><div style="color: black; line-height: 1.5em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.agu.org/pubs/crossref/2011/2010JD015459.shtml">http://www.agu.org/pubs/crossref/2011/2010JD015459.shtml</a></span></div></div>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-87617395549405848662011-04-23T09:12:00.000-07:002011-04-23T09:12:50.059-07:00Elinor Breman, Lindsey Gillson & Kathy Willis, The Holocene, How fire and climate shaped grass-dominated vegetation and forest mosaics in northern South Africa during past millennia<i>The Holocene</i>, <span class="slug-metadata-note ahead-of-print">published online before print <span class="slug-ahead-of-print-date">April 21, 2011</span>; doi: <span class="slug-doi">10.1177/0959683611400196 </span></span><cite><abbr class="slug-jnl-abbrev" title="The Holocene"></abbr><span class="slug-elocation"> </span></cite><br />
<h1 id="article-title-1">How fire and climate shaped grass-dominated vegetation and forest mosaics in northern South Africa during past millennia</h1><div class="contributors intlv"> <ol class="contributor-list" id="contrib-group-1"><li class="last" id="contrib-1"><span class="name"><a class="name-search" href="http://hol.sagepub.com/search?author1=Elinor+Breman&sortspec=date&submit=Submit">Elinor Breman</a></span><ol class="affiliation-list"><li class="aff"><a href="" id="aff-1" name="aff-1"></a><address>Oxford University, UK</address></li>
</ol></li>
</ol></div><div class="contributors intlv"> <ol class="contributor-list" id="contrib-group-2"><li class="last" id="contrib-2"><span class="name"><a class="name-search" href="http://hol.sagepub.com/search?author1=Lindsey+Gillson&sortspec=date&submit=Submit">Lindsey Gillson</a></span><ol class="affiliation-list"><li class="aff"><a href="" id="aff-2" name="aff-2"></a><address>University of Cape Town, South Africa</address></li>
</ol></li>
</ol></div><div class="contributors intlv"> <ol class="contributor-list" id="contrib-group-3"><li class="last" id="contrib-3"><span class="name"><a class="name-search" href="http://hol.sagepub.com/search?author1=Kathy+Willis&sortspec=date&submit=Submit">Kathy Willis</a></span><ol class="affiliation-list"><li class="aff"><a href="" id="aff-3" name="aff-3"></a><address>University of Oxford, UK</address></li>
</ol></li>
</ol></div><div class="section abstract" id="abstract-1"> <h2><span style="font-size: small;">Abstract</span></h2><div id="p-1" style="text-align: justify;">Grassland and savanna are globally important ecosystems, both ecologically and economically. These grass-dominated systems are at risk from current and future climate change and increasing anthropogenic impact. Key questions for understanding the resilience and variability of grass-dominated ecosystems under current and future environmental conditions include: How have these systems responded to climate change and disturbance in the past? What are the principal driving agents responsible for their present-day composition and distribution? Do the palaeoecological data provide evidence for feedbacks between climate, fire and anthropogenic activities? In this study, the temporal dynamics of grassland, savanna and forest in the summer rainfall region of northern South Africa were reconstructed for the last ∼6500 years. Palaeoecological techniques used include analyses of fossil pollen, charcoal and stable isotopes. Data from two sites located at the present-day grassland-savanna ecotone in Mpumalanga province of South Africa are reported. Results indicate that a mosaic of grassland, savanna and <em>Podocarpus</em> forest occupied the landscape throughout the late Holocene, with grassland and forest dominating higher altitudes, and savanna and forest lower altitudes. <em>Podocarpus</em> forest retreated and grass-dominated vegetation expanded its range around 1800 cal. yr BP at the lower altitude site (Lowveld) and 600 cal. yr BP at the higher altitude site (Highveld), representing a change from a stable state forest savanna/grassland mosaic to an increasingly grass-dominated system. Climatic stress, changes in fire regime and anthropogenic impact led to the vegetation transitions recorded, and resulted in changes in water and nutrient cycles. In an increasingly warm world, with fluctuating water availability and heightened anthropogenic use of natural resources, the future of grass-dominated ecosystems appears far from stable. </div><div id="p-1"><br />
</div><a href="http://hol.sagepub.com/content/early/2011/04/21/0959683611400196.abstract">http://hol.sagepub.com/content/early/2011/04/21/0959683611400196.abstract</a></div>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-44387477939511276452011-03-23T12:56:00.000-07:002011-03-23T12:56:48.477-07:00Climatological determinants of woody cover in Africa, by S. P. Good & K. K. Caylor, PNAS, Vol. 108, No. 12<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="Apple-style-span" style="line-height: 9px;"><abbr class="slug-jnl-abbrev" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;" title="Proceedings of the National Academy of Sciences"><i>PNAS</i></abbr></span><span class="Apple-style-span" style="line-height: 9px;"><span class="slug-pub-date" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"> (March 22, 2011), V</span></span><span class="Apple-style-span" style="line-height: 9px;"><span class="slug-vol" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;">ol. 108, N</span></span><span class="Apple-style-span" style="line-height: 9px;"><span class="slug-issue" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;">o. 12, pp. 4902-4907; </span></span><span class="Apple-style-span" style="line-height: 9px;">doi: </span></span><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; line-height: 9px;">10.1073/pnas.1013100108</span><br />
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<h1 id="article-title-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: Georgia, 'Times New Roman', serif; font-size: 1.8em; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 10px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;">Climatological determinants of woody cover in Africa</h1><div class="contributors" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;"><ol class="contributor-list" id="contrib-group-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: bold; line-height: inherit; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 15px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline; white-space: normal;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">
<li class="contributor" id="contrib-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: inline; font-style: inherit; font-weight: inherit; line-height: 1.7; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline; white-space: normal;"><span class="name" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><a class="name-search" href="http://www.pnas.org/search?author1=Stephen+P.+Good&sortspec=date&submit=Submit" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0px; white-space: nowrap;">Stephen P. Good</a></span><a class="xref-corresp" href="http://www.pnas.org/content/108/12/4902.abstract?etoc#corresp-1" id="xref-corresp-1-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0.2em;"><sup style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: inherit; line-height: 0; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: super;">1</sup></a> and </li>
<li class="last" id="contrib-2" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: inline; font-style: inherit; font-weight: inherit; line-height: 1.7; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline; white-space: normal;"><span class="name" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><a class="name-search" href="http://www.pnas.org/search?author1=Kelly+K.+Caylor&sortspec=date&submit=Submit" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0px; white-space: nowrap;">Kelly K. Caylor</a></span></li>
</span></ol><ol class="affiliation-list hideaffil" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: normal; left: -9999px; line-height: inherit; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 1em; margin-left: 27px; margin-right: 27px; margin-top: 1em; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; text-align: inherit; vertical-align: baseline; width: 5000px;"><li class="aff" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: list-item; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.blogger.com/post-edit.g?blogID=7698039939158013969&postID=4438747793951127645" id="aff-1" name="aff-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0.2em;"></a><address style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; display: inline; font-style: normal; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;">Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544</address></span></li>
</ol><ol class="fn-track" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: inherit; line-height: inherit; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;"><li class="fn-edited-by" id="fn-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 5px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;"><div id="p-1" style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: inherit; line-height: 1.5; margin-bottom: 15px; margin-left: 0px; margin-right: 0px; margin-top: 15px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Edited* by Ignacio Rodriguez-Iturbe, Princeton University, Princeton, NJ 08544, and approved January 28, 2011 (received for review September 3, 2010)</span></div></li>
</ol></div><div class="section abstract" id="abstract-1" style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; clear: both; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><h2 style="border-bottom-color: rgb(153, 153, 153); border-bottom-style: dotted; border-bottom-width: 2px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 10px; margin-left: 0px; margin-right: 0px; margin-top: 10px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: small;">Abstract</span></h2><div id="p-3" style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: inherit; line-height: 1.5; margin-bottom: 15px; margin-left: 0px; margin-right: 0px; margin-top: 15px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: justify; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Determining the factors that influence the distribution of woody vegetation cover and resolving the sensitivity of woody vegetation cover to shifts in environmental forcing are critical steps necessary to predict continental-scale responses of dryland ecosystems to climate change. We use a 6-year satellite data record of fractional woody vegetation cover and an 11-year daily precipitation record to investigate the climatological controls on woody vegetation cover across the African continent. We find that—as opposed to a relationship with only mean annual rainfall—the upper limit of fractional woody vegetation cover is strongly influenced by both the quantity and intensity of rainfall events. Using a set of statistics derived from the seasonal distribution of rainfall, we show that areas with similar seasonal rainfall totals have higher fractional woody cover if the local rainfall climatology consists of frequent, less intense precipitation events. Based on these observations, we develop a generalized response surface between rainfall climatology and maximum woody vegetation cover across the African continent. The normalized local gradient of this response surface is used as an estimator of ecosystem vegetation sensitivity to climatological variation. A comparison between predicted climate sensitivity patterns and observed shifts in both rainfall and vegetation during 2009 reveals both the importance of rainfall climatology in governing how ecosystems respond to interannual fluctuations in climate and the utility of our framework as a means to forecast continental-scale patterns of vegetation shifts in response to future climate change.</span></div><div id="p-3" style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; font-style: inherit; font-weight: inherit; line-height: 1.5; margin-bottom: 15px; margin-left: 0px; margin-right: 0px; margin-top: 15px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: justify; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.pnas.org/content/108/12/4902.abstract">http://www.pnas.org/content/108/12/4902.abstract</a></span></div></div>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-1594281931767076742011-03-15T09:34:00.000-07:002011-03-15T09:34:34.096-07:00M. Auffhammer, Nature Climate Change (March 15, 2011), Agriculture: Weather dilemma for African maize<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><i>Nature Climate Change</i> (March 15, 2011)</span><br />
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<header><h1 class="article-heading" style="color: #222222; font-family: arial, helvetica, clean, sans-serif; font-size: 26px; font-weight: normal; letter-spacing: -0.5px; line-height: 1.173; margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Agriculture: Weather dilemma for African maize</span></h1><ul class="authors citation-authors" style="font-weight: bold; margin-bottom: 10px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><li class="vcard c1" style="display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a class="name" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#auth-1" style="color: #216a9d; font-weight: bold; text-decoration: none;"><span class="fn">Maximilian Auffhammer</span></a></span></li>
</ul><dl class="citation" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><dd class="journal-title" style="display: inline; font-style: italic; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px; text-transform: capitalize;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Nature Climate Change</span></dd><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"> <dd style="display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px;">(2011)</dd> <dd class="doi" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bg_pipe.gif); background-origin: initial; background-position: 0px 0.4ex; background-repeat: no-repeat no-repeat; display: inline; margin-bottom: 0px; margin-left: 4px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 10px; padding-right: 3px; padding-top: 0px;">doi:10.1038/nclimate1061</dd></span></dl><dl class="citation dates" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><dt class="published-online first" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: none !important; background-origin: initial; background-position: 0px 0.4ex; background-repeat: no-repeat no-repeat; display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Published online</span></dt>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"> <dd style="display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px;"><time datetime="2011-03-13" pubdate="pubdate">13 March 2011</time></dd></span></dl></header><section><div class="section first no-nav no-title first-no-nav" style="clear: both; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><div class="content" style="border-top-color: rgb(255, 255, 255); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 20px; zoom: 1;"><div class="standfirst" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The impact of climate change on food production remains uncertain, particularly in the tropics. Research that exploits the results of historical crop trials indicates that Africa's maize crop could be at risk of significant yield losses.</span></div></div></div></div></section><section><div class="section second no-nav no-title" style="clear: both; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><div class="content" style="border-top-color: rgb(255, 255, 255); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; zoom: 1;"><aside><div class="article-tools" style="float: right; margin-bottom: 20px; margin-left: 10px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><h2 class="hidden" style="color: #111111; font-weight: bold; height: 1px; left: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; overflow-x: hidden; overflow-y: hidden; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; top: -500px; width: 1px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="Apple-style-span" style="font-size: small;">Article tools</span></span></h2><ul class="box" style="border-bottom-color: rgb(231, 231, 231); border-bottom-style: solid; border-bottom-width: 1px; border-left-color: rgb(231, 231, 231); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(231, 231, 231); border-right-style: solid; border-right-width: 1px; border-top-color: rgb(231, 231, 231); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 5px; padding-left: 5px; padding-right: 5px; padding-top: 10px;"><li class="print" style="display: block; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><br />
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</ul></div></aside><div class="illustration illustration-right" style="clear: right; float: right; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 10px; padding-left: 10px; padding-right: 0px; padding-top: 10px; width: auto;"><div class="box" style="background-attachment: initial; background-clip: initial; background-color: #f5f6f7; background-image: initial; background-origin: initial; background-position: initial initial; background-repeat: initial initial; border-bottom-color: rgb(231, 231, 231); border-bottom-style: solid; border-bottom-width: 1px; border-left-color: rgb(231, 231, 231); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(231, 231, 231); border-right-style: solid; border-right-width: 1px; border-top-color: rgb(231, 231, 231); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; width: 200px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><img alt="" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/images/nclimate1061-i1.jpg" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: block; height: 133px; width: 200px;" /><div class="credit" style="color: #909090; font-style: italic; line-height: 1.4em; margin-bottom: 10px; margin-left: 0px; margin-right: 0px; margin-top: 5px; padding-bottom: 0px; padding-left: 10px; padding-right: 10px; padding-top: 0px; text-align: right;">© MARSHALL BURKE, STANFORD UNIVERSITY</div><div class="description" style="background-attachment: initial; background-clip: initial; background-color: #f5f6f7; background-image: initial; background-origin: initial; background-position: initial initial; background-repeat: initial initial; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><div style="color: #666666; line-height: 1.5em; margin-bottom: 10px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 10px; padding-right: 10px; padding-top: 0px;">Maize in a farmer's field in Kenya. Millions of people depend on maize for food and their livelihoods, so understanding the potential impacts of climate change on the crop is highly important. Using data from historical crop trials in Africa, Lobell and colleagues<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#ref1" id="ref-link-5" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Lobell, D. B., Banziger, M., Magorokosho, C. & Vivek, B. Nature Clim. Change 10.1038/nclimate1043 (2011).">1</a></sup> show that yields of tropical maize are sensitive to exposure to very hot days and that drought stress significantly increases their sensitivity to warming — results that could help farmers adapt to climate change on the continent and elsewhere.</div></div></span></div></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The growing global demand for calories — caused by an expanding population and a rise in average wealth — is one reason for the current peak in food prices. Coupled to this have been decreases in food supply caused by extreme weather events, such as last year's Russian heatwave. Regardless of where extreme weather occurs, the effects on food availability and price are disproportionately felt by the world's poor. Moreover, crop failures due to extreme weather not only affect those buying and selling in the global marketplace, but also have a direct impact on subsistence farmers. Understanding how such extreme weather events — which are predicted to become more frequent under climate change — affect both yields and total production of the world's staple food crops is thus an issue of both scientific and societal importance. Writing in <i style="font-style: italic;">Nature Climate Change</i>, David Lobell and colleagues<sup style="line-height: 0; margin-left: 0.15em; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#ref1" id="ref-link-6" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Lobell, D. B., Banziger, M., Magorokosho, C. & Vivek, B. Nature Clim. Change 10.1038/nclimate1043 (2011).">1</a></sup> present results that further our understanding of how maize yields — a crop on which millions depend for food and their livelihoods — respond to hotter days under both drought and non-drought conditions.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Global food markets have become increasingly volatile in recent years. Both supply and demand have contributed to this instability: rising incomes, growing populations and biofuel policies are upping the productivity required from a limited amount of agricultural land, and an almost incomprehensibly intricate set of agricultural support and trade policies within and across countries have historically made the economics of food supply extremely complicated.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Extreme weather events have also played a role. Wheat production in Russia decreased by almost a third last year<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#ref2" id="ref-link-7" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="http://faostat.fao.org/ (accessed 10 February 2011).">2</a></sup>, largely due to the summer heatwave, and the unusually high rainfall in Australia this past summer meant that a significant share of the nation's 2010–2011 wheat crop had to be downgraded to 'animal feed' quality. In the near term, the prospects for other major markets look equally pessimistic — the US Department of Agriculture and the United Nations Food and Agricultural Organization have both warned of a significant decrease in yields of Chinese winter wheat this year owing to drought<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#ref3" id="ref-link-8" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="http://www.pecad.fas.usda.gov/highlights/2011/01/China/ (accessed 10 February 2011).">3</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#ref4" id="ref-link-9" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="United Nations Food and Agriculture Organization Special Alert 330 (8 February 2011); available at http://www.fao.org/giews/english/alert/index.htm.">4</a></sup>; a change that could result in the emerging superpower becoming a buyer of wheat on world markets.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Lobell and colleagues<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#ref1" id="ref-link-10" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Lobell, D. B., Banziger, M., Magorokosho, C. & Vivek, B. Nature Clim. Change 10.1038/nclimate1043 (2011).">1</a></sup> exploit historical data from over 20,000 field trials of maize conducted in Africa over the past decade or so. The trials were originally conducted to test the resilience of the crop to different environmental conditions and involved varieties that are either currently in use or intended for planting by African farmers. Using daily weather records, the authors matched the yield results for each trial to the daily weather experienced by the plants while growing. They controlled for other factors that might affect the results at each site (such as soil quality) and during each season (such as changing global carbon dioxide concentrations) indirectly in a statistical model. This analysis allowed them to extract the effects of temperature and rainfall on yields.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The results show that each 'degree day' that the crop spends above 30 °C (a unit that reflects both the amount and duration of heat experienced by the plant) depresses yields by 1% if the plants are receiving sufficient water. This sensitivity is similar to that observed for temperate maize varieties in the United States<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#ref5" id="ref-link-11" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Roberts, M. Proc. Natl Acad. Sci. USA 106, 15594-15598 (2009).">5</a></sup>. However, Lobell and co-workers also show that water availability has an important effect on the sensitivity, with yields decreasing by 1.7% for each degree day spent over 30 °C under drought conditions.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">To put these numbers in perspective, they indicate that under non-drought conditions 65% of the area in Africa that is under maize cultivation at present would experience yield losses from a uniform 1 °C warming. Under drought conditions, 100% of the present cultivated area would experience yield losses, with 75% of this area suffering yield losses of at least 20%.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">What is most concerning about these results is the empirical confirmation that drought stress significantly amplifies the effects of heat stress. The authors are careful to caution that the field trials on which their results are based use fairly high levels of nitrogen fertilizers, which is not the case in many areas of Africa. Plants under nitrogen stress may react less strongly to temperature stress, suggesting that their results may be an upper bound for what one could expect in actual field settings. However, the close match with the field-based results for temperate maize in the United States<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#ref5" id="ref-link-12" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Roberts, M. Proc. Natl Acad. Sci. USA 106, 15594-15598 (2009).">5</a></sup> indicates that this effect is probably minor.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The study raises several issues related to how best to deal with the impacts of climate change on agriculture. It suggests that maize planted in a future Africa characterized by a drier and hotter climate will need to be able to withstand the joint stress imposed by heat and drought, which poses a challenge for the development of new varieties of the crop. But maize is not the only crop available to farmers, so they will most probably shift to growing other crops if maize yields are depressed to the extent that it is no longer profitable. Understanding the heat sensitivity of substitute crops is of prime importance for establishing the optimal sequence of crops that farmers could move to as temperatures rise.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">One of the most important aspects of the work by Lobell and colleagues<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html#ref1" id="ref-link-13" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Lobell, D. B., Banziger, M., Magorokosho, C. & Vivek, B. Nature Clim. Change 10.1038/nclimate1043 (2011).">1</a></sup> is that it offers a new way of obtaining this information from a widely available source of data. Data repositories hold the results of field trials for a variety of crops and locations, and should be exploited in the same fashion to establish an 'atlas of climate sensitivities' for multiple crops in different regions. Finally, social scientists can help crop scientists understand how farmers' decisions may change with climate. Farmers mitigate the effect of a changing climate by adjusting the mix of crops they plant and inputs they use, but these factors are normally held fixed in experimental field trials and computer-based simulation models. Additional interdisciplinary research that takes the human response to changing weather patterns into account will be key to obtaining reliable impact estimates and therefore to designing optimal policy responses.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html">http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1061.html</a></span></div></div></div></section>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-80507850716008334302011-03-15T09:31:00.000-07:002011-03-15T09:31:41.317-07:00David B. Lobell et al., Nature Climate Change (March 15, 2011), Nonlinear heat effects on African maize as evidenced by historical yield trials<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><i>Nature Climate Change</i> (March 15, 2011)</span><br />
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<header style="font-family: arial, helvetica, clean, sans-serif; font-size: 13px;"><h1 class="article-heading" style="color: #222222; font-size: 26px; font-weight: normal; letter-spacing: -0.5px; line-height: 1.173; margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Nonlinear heat effects on African maize as evidenced by historical yield trials</span></h1><ul class="authors citation-authors" style="font-weight: bold; margin-bottom: 10px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><li class="vcard c1" style="display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a class="name" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#auth-1" style="color: #216a9d; font-weight: bold; text-decoration: none;"><span class="fn">David B. Lobell</span></a><span class="comma">,</span> </span></li>
<li class="vcard" style="display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a class="name" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#auth-2" style="color: #216a9d; font-weight: bold; text-decoration: none;"><span class="fn">Marianne Bänziger</span></a><span class="comma">,</span> </span></li>
<li class="vcard no-comma" style="display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a class="name" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#auth-3" style="color: #216a9d; font-weight: bold; text-decoration: none;"><span class="fn">Cosmos Magorokosho</span></a> </span></li>
<li class="vcard last-author no-comma" style="display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">& <a class="name" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#auth-4" style="color: #216a9d; font-weight: bold; text-decoration: none;"><span class="fn">Bindiganavile Vivek</span></a></span></li>
</ul><ul class="cleared" id="author-links" style="display: block; margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><li class="first" style="background-attachment: scroll; background-clip: initial; background-color: initial; background-image: none; background-origin: initial; background-position: 0px 0.6ex; background-repeat: no-repeat no-repeat; float: left; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0.5em; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#affil-auth" style="color: #216a9d; font-weight: bold; text-decoration: none;">Affiliations</a></span></li>
<li style="background-attachment: scroll; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bg_pipe.gif); background-origin: initial; background-position: 0px 0.6ex; background-repeat: no-repeat no-repeat; float: left; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0.5em; padding-right: 0.5em; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#contrib-auth" style="color: #216a9d; font-weight: bold; text-decoration: none;">Contributions</a></span></li>
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</ul><dl class="citation" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><dd class="journal-title" style="display: inline; font-style: italic; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px; text-transform: capitalize;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Nature Climate Change</span></dd><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"> <dd style="display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px;">(2011)</dd> <dd class="doi" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bg_pipe.gif); background-origin: initial; background-position: 0px 0.4ex; background-repeat: no-repeat no-repeat; display: inline; margin-bottom: 0px; margin-left: 4px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 10px; padding-right: 3px; padding-top: 0px;">doi:10.1038/nclimate1043</dd></span></dl><dl class="citation dates" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><dt class="received first" style="background-image: none !important; display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Received</span></dt>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"> <dd style="display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px;"><time datetime="2010-10-27">27 October 2010</time></dd>
<dt class="accepted" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bg_pipe.gif); background-origin: initial; background-position: 0px 0.4ex; background-repeat: no-repeat no-repeat; display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 8px; padding-right: 3px; padding-top: 0px;">Accepted</dt>
<dd style="display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px;"><time datetime="2011-02-04">04 February 2011</time></dd>
<dt class="published-online" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bg_pipe.gif); background-origin: initial; background-position: 0px 0.4ex; background-repeat: no-repeat no-repeat; display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 8px; padding-right: 3px; padding-top: 0px;">Published online</dt>
<dd style="display: inline; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 3px; padding-top: 0px;"><time datetime="2011-03-13" pubdate="pubdate">13 March 2011</time></dd></span></dl></header><section><div class="section first no-nav no-title first-no-nav" style="clear: both; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><div class="content" style="border-top-color: rgb(255, 255, 255); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 20px; zoom: 1;"><aside><div class="article-tools" style="float: right; margin-bottom: 20px; margin-left: 10px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><h2 class="hidden" style="color: #111111; font-family: arial, helvetica, clean, sans-serif; font-size: 13px; font-weight: bold; height: 1px; left: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; overflow-x: hidden; overflow-y: hidden; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; top: -500px; width: 1px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Article tools</span></h2><ul class="box" style="border-bottom-color: rgb(231, 231, 231); border-bottom-style: solid; border-bottom-width: 1px; border-left-color: rgb(231, 231, 231); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(231, 231, 231); border-right-style: solid; border-right-width: 1px; border-top-color: rgb(231, 231, 231); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 5px; padding-left: 5px; padding-right: 5px; padding-top: 10px;"><li class="print" style="display: block; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><br />
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</ul></div></aside><div class="first-paragraph" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: justify;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">New approaches are needed to accelerate understanding of climate impacts on crop yields, particularly in tropical regions. Past studies have relied mainly on crop-simulation models<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref1" id="ref-link-1" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; text-decoration: none;" title="Jones, P. G. & Thornton, P. K. The potential impacts of climate change on maize production in Africa and Latin America in 2055. Glob. Environ. Chang. 13, 51-59 (2003).">1</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref2" id="ref-link-2" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; text-decoration: none;" title="Fischer, G., Shah, M. N., Tubiello, F. & van Velhuizen, H. Socio-economic and climate change impacts on agriculture: an integrated assessment, 1990-2080. Phil. Trans. Biol. Sci. 360, 2067-2083 (2005).">2</a></sup> or statistical analyses based on reported harvest data<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref3" id="ref-link-3" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; text-decoration: none;" title="Lobell, D. B. et al. Prioritizing climate change adaptation needs for food security in 2030. Science 319, 607-610 (2008).">3</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref4" id="ref-link-4" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; text-decoration: none;" title="Schlenker, W. & Lobell, D. B. Robust negative impacts of climate change on African agriculture. Environ. Res. Lett. 5, 014010 (2010).">4</a></sup>, each with considerable uncertainties and limited applicability to tropical systems. However, a wealth of historical crop-trial data exists in the tropics that has been previously untapped for climate research. Using a data set of more than 20,000 historical maize trials in Africa, combined with daily weather data, we show a nonlinear relationship between warming and yields. Each degree day spent above 30<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C reduced the final yield by 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> under optimal rain-fed conditions, and by 1.7<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> under drought conditions. These results are consistent with studies of temperate maize germplasm in other regions, and indicate the key role of moisture in maize’s ability to cope with heat. Roughly 65<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> of present maize-growing areas in Africa would experience yield losses for 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C of warming under optimal rain-fed management, with 100<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> of areas harmed by warming under drought conditions. The results indicate that data generated by international networks of crop experimenters represent a potential boon to research aimed at quantifying climate impacts and prioritizing adaptation responses, especially in regions such as Africa that are typically thought to be data-poor.</span></div></div><div class="figures-at-a-glance" style="clear: both; margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 20px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><h2 style="color: #111111; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="Apple-style-span" style="font-size: small; font-weight: normal;">Figures at a glance</span></span></h2><div class="figure-browser" style="background-attachment: initial; background-clip: initial; background-color: #e1e4e9; background-image: initial; background-origin: initial; background-position: initial initial; background-repeat: initial initial; height: 120px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; overflow-x: hidden; overflow-y: hidden; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: relative;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a class="nav left inactive" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/figure_browser_left.gif); background-origin: initial; background-position: 0px 50%; background-repeat: no-repeat no-repeat; border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; cursor: default; display: block; font-weight: bold; height: 100px; left: 0px; opacity: 0.2; position: absolute; text-decoration: none; top: 10px; width: 25px; z-index: 3;" tabindex="-1"><span style="display: block; height: 1px; overflow-x: hidden; overflow-y: hidden; width: 1px;">left</span></a><div class="thumbs masking" style="height: 120px; left: 30px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; overflow-x: hidden; overflow-y: hidden; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; top: 0px; width: 566px;"><ol style="left: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; top: 0px; visibility: visible;"><li style="left: 0px; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; top: 10px;"><figure><figcaption></figcaption><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;"><img alt="" class="fig" id="figure-browser-thumb-nclimate1043-f1" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/carousel/nclimate1043-f1.jpg" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: block; height: 100px; width: 114px;" title="Figure 1: The study region in Africa." /></a></figure></li>
<li style="left: 124px; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; top: 10px;"><figure><figcaption></figcaption><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;"><img alt="" class="fig" id="figure-browser-thumb-nclimate1043-f2" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/carousel/nclimate1043-f2.jpg" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: block; height: 100px; width: 87px;" title="Figure 2: The effect of heat on maize yields." /></a></figure></li>
<li style="left: 221px; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; top: 10px;"><figure><figcaption></figcaption><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;"><img alt="" class="fig" id="figure-browser-thumb-nclimate1043-f3" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/carousel/nclimate1043-f3.jpg" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: block; height: 100px; width: 174px;" title="Figure 3: Model estimates of maize yield changes for 1[thinsp][deg]C warming." /></a></figure></li>
</ol></div><a class="nav right inactive" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/figure_browser_right.gif); background-origin: initial; background-position: 0px 50%; background-repeat: no-repeat no-repeat; border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; cursor: default; display: block; font-weight: bold; height: 100px; opacity: 0.2; position: absolute; right: 0px; text-decoration: none; top: 10px; width: 25px; z-index: 3;" tabindex="-1"><span style="display: block; height: 1px; overflow-x: hidden; overflow-y: hidden; width: 1px;">right</span></a></span></div></div></div></div></section><section><div class="section expanded" id="main" style="clear: both; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><h1 class="section-heading toggle" style="color: #444444; font-weight: bold; letter-spacing: -0.5px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 18px; padding-bottom: 2px; padding-left: 0px; padding-right: 0px; padding-top: 2px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/collapse.gif); background-origin: initial; background-position: 0px 50%; background-repeat: no-repeat no-repeat; color: #444444; font-weight: bold; padding-bottom: 0px; padding-left: 23px; padding-right: 0px; padding-top: 0px; text-decoration: none;" title="Main"><span class="Apple-style-span" style="font-size: small;">Main</span></a></span></h1><div class="content" style="border-top-color: rgb(231, 231, 231); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; zoom: 1;"><nav><ul class="section-nav cleared" style="color: #a2a7ab; display: block; margin-bottom: 0px; margin-left: -4px; margin-right: 0px; margin-top: 0px; padding-bottom: 14px; padding-left: 0px; padding-right: 0px; padding-top: 5px;"><li class="current first" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span>Main</span></span></li>
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<li style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#methods" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;"></a><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#methods" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">Methods</a></li>
<li style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#references" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">References</a></li>
<li style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#acknowledgments" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">Acknowledgements</a></li>
<li style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#author-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">Author information</a></li>
<li class="last" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: none; background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">Supplementary information</a></li>
</span></ul></nav><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Effective adaptation of agriculture to climate change in the developing world will require at least two pieces of information: the relative risks posed by climate change across different locations and cropping systems, which is useful for prioritizing the use of scarce resources devoted to adaptation, and the likely mechanisms of potential damage from climate change, to prioritize among different types of possible solution. For example, a main strategy will probably be breeding for improved abiotic stress, but the particular traits that present the largest opportunities for progress are often unclear<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref5" id="ref-link-6" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Araus, J. L., Slafer, G., Royo, C. & Serret, M. D. Breeding for yield potential and stress adaptation in cereals. Crit. Rev. Plant Sci. 27, 377-412 (2008).">5</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref6" id="ref-link-7" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Barnabas, B. A. T., Jager, K. & Feher, A. The effect of drought and heat stress on reproductive processes in cereals. Plant Cell Environ. 31, 11-38 (2008).">6</a></sup>.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Present approaches to addressing both of these needs are limited, especially in developing countries. For example, simulation models have been calibrated mainly in temperate systems, do not include all potentially relevant processes, and are dependent on inputs that prescribe cultivar characteristics, management practices, soil properties and initial conditions, all of which are imperfectly known<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref7" id="ref-link-8" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Thornton, P. K., Jones, P. G., Alagarswamy, G. & Andresen, J. Spatial variation of crop yield response to climate change in East Africa. Glob. Environ. Change 19, 54-65 (2009).">7</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref8" id="ref-link-9" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Gijsman, A. J., Jagtap, S. S. & Jones, J. W. Wading through a swamp of complete confusion: How to choose a method for estimating soil water retention parameters for crop models. Eur. J. Agron. 18, 75-105 (2002).">8</a></sup>. Statistical approaches are frequently limited by the quantity and quality of data used to train them, which results in fairly large uncertainties<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref4" id="ref-link-10" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Lobell, D. B. Robust negative impacts of climate change on African agriculture. Environ. Res. Lett. 5, 014010 (2010).">4</a></sup>, although the data sets available for statistical approaches are improving<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref9" id="ref-link-11" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Peng, S. et al. Rice yields decline with higher night temperature from global warming. Proc. Natl Acad. Sci. USA 101, 9971-9975 (2004).">9</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref10" id="ref-link-12" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Welch, J. R. et al. Rice yields in tropical/subtropical Asia exhibit large but opposing sensitivities to minimum and maximum temperatures. Proc. Natl Acad. Sci. USA 107, 14562 (2010).">10</a></sup>.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Here we introduce an empirical approach that relies on newly available data from a network of cropping trials. In this case, we focus on field trials for tropical maize conducted in Africa in 1999–2007 on a network of 123 research stations managed by the International Maize and Wheat Improvement Center (CIMMYT), National Agricultural Research Programs and private seed companies<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref11" id="ref-link-13" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Banziger, M., Setimela, P. S., Hodson, D. & Vivek, B. Breeding for improved abiotic stress tolerance in maize adapted to southern Africa. Agr. Water Manage. 80, 212-224 (2006).">11</a></sup> (<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f1" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Fig. 1</a>). The original purpose of these trials was to test new varieties across a range of environmental conditions, to identify robust lines for release to farmers. Most trials were carried out under ‘optimal’ management, that is, rain-fed conditions using site-specific agronomic treatments to minimize nutrient, water, disease and other stresses. The second most common treatment was managed drought stress, where the varieties were irrigated in a rain-free period until plants were established, and then irrigation was cut off to induce moisture stress during flowering and grain-filling<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref11" id="ref-link-14" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Banziger, M., Setimela, P. S., Hodson, D. & Vivek, B. Breeding for improved abiotic stress tolerance in maize adapted to southern Africa. Agr. Water Manage. 80, 212-224 (2006).">11</a></sup>. The varieties included in this data set are grown or intended for farmers’ fields throughout Africa, nearly all of which are rain-fed. We refer to each combination of maize variety, station, year and management regime as a single trial.</span></div><div class="figure cleared" id="f1" style="clear: both; display: block; margin-bottom: 19px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><figure><figcaption><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="legend" style="color: #111111; display: block; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: -3px; padding-bottom: 3px; padding-left: 0px; padding-right: 0px; padding-top: 3px;">Figure 1: The study region in Africa.</span></span></figcaption><div class="figure-content box" style="border-bottom-color: initial; border-bottom-style: initial; border-bottom-width: 0px; border-left-color: rgb(231, 231, 231); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(231, 231, 231); border-right-style: solid; border-right-width: 1px; border-top-color: rgb(231, 231, 231); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 20px; padding-left: 10px; padding-right: 10px; padding-top: 17px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a class="fig-link" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1043_F1.html" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;"><img alt="The study region in Africa." class="fig" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/images_article/nclimate1043-f1.jpg" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: block; height: 526px; width: 600px;" /></a><div class="description" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><div style="line-height: 1.507em; margin-bottom: 18px; margin-left: 0px; margin-right: 0px; margin-top: 18px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;">The circles show locations of crop trials, with the size of the circle indicating the number of trials per site (ranging from 20 to 1,249). Weather stations with daily data for at least some portion of the study period 1999–2007 are marked as crosses. The background map shows elevation, with higher altitudes appearing darker.</div></div><ul class="resources" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><li class="full" style="clear: both; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1043_F1.html" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/icon_full_figure.gif); background-origin: initial; background-position: 2px 0px; background-repeat: no-repeat no-repeat; border-bottom-color: initial; border-bottom-style: initial; border-bottom-width: 0px; color: #216a9d; font-weight: normal; padding-bottom: 0px; padding-left: 25px; padding-right: 0px; padding-top: 0px; text-decoration: none;">Full size image (266 KB)</a></li>
</ul></span></div><nav><ul class="figure-nav cleared" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bg_light_grad.gif); background-origin: initial; background-position: 0px 0px; background-repeat: repeat no-repeat; border-bottom-color: rgb(231, 231, 231); border-bottom-style: solid; border-bottom-width: 1px; border-left-color: rgb(231, 231, 231); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(231, 231, 231); border-right-style: solid; border-right-width: 1px; border-top-color: initial; border-top-style: initial; border-top-width: 0px; display: block; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 20px; padding-right: 20px; padding-top: 0px; position: relative;"><li class="index" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: auto; margin-right: auto; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: center;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1043_ft.html" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; display: inline; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-top: 0px; text-align: center; text-decoration: none;">Figures index</a></span></li>
<li class="next down-arrow" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: auto; margin-right: auto; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; right: 10px; top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f2" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/arrow_small_down.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-color: rgb(234, 234, 236); border-left-style: solid; border-left-width: 1px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; display: block; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 20px; padding-right: 12px; padding-top: 0px; text-align: right; text-decoration: none;" title="The effect of heat on maize yields.">Next figure</a></span></li>
</ul></nav></figure></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">For each trial, we recreated the daily temperature and precipitation using thin-plate spline interpolation of daily records from nearby weather stations (see <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#methods" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Methods</a>). Various summary statistics of the growing season weather were then computed, including growing degree sums, averages for critical development phases and time spent above critical temperature thresholds. In total, 17,713 trials with optimal management and 3,244 with managed drought stress for the period 1999–2007 were used. The effect of weather on yields was modelled using a linear fixed-effects model, with three weather variables:</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><img alt="" class="align-middle" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/images/nclimate1043-m1.gif" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; vertical-align: middle;" /></span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">where <i style="font-style: italic;">Y</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;"><i style="font-style: italic;">i</i>,<i style="font-style: italic;">s</i>,<i style="font-style: italic;">t</i></sub> is the natural logarithm of reported yield (log(yield)) for the <i style="font-style: italic;">i</i>th trial at station <i style="font-style: italic;">s</i> in year <i style="font-style: italic;">t</i>, <i style="font-style: italic;">X</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;"><i style="font-style: italic;">i</i>,<i style="font-style: italic;">s</i>,<i style="font-style: italic;">t</i></sub> is a vector of climate variables for that trial, <b style="font-weight: bold;">a</b> is a vector of coefficients, <b style="font-weight: bold;">b</b><sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;"><i style="font-style: italic;">s</i></sub> represents an intercept associated with station <i style="font-style: italic;">s</i>, <b style="font-weight: bold;">c</b><sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;"><i style="font-style: italic;">t</i></sub> represents an intercept for year <i style="font-style: italic;">t</i> and <i style="font-style: italic;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">ε</span></i> is an error term. The weather variables in <i style="font-style: italic;">X</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;"><i style="font-style: italic;">i</i>,<i style="font-style: italic;">s</i>,<i style="font-style: italic;">t</i></sub> in our initial model included three terms: GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">8,30</sub>, the sum of growing degree days between 8<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C and 30<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C for the growing season (defined as the interval from sowing to 150 days after sowing for each trial), GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub>, the sum of growing degree days above 30<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C, and prec<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">anth</sub>, total precipitation for the 21-day period centred on anthesis. GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">8,30</sub> represents a typical measure used to predict maize development rates<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref12" id="ref-link-15" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Kiniry, J. R. & Bonhomme, R. in Predicting Crop Phenology (ed. Hodges, T.) 115-131 (CRC Press, 1991).">12</a></sup>, and is closely related to average growing-season temperature (<i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">avg</sub>), with a correlation over 0.98 in our sample. GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub> is a measure of exposure to temperatures above a threshold at which warming can be quite harmful to growth and reproductive processes<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref13" id="ref-link-16" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Roberts, M. J. Nonlinear temperature effects indicate severe damages to US crop yields under climate change. Proc. Natl Acad. Sci. USA 106, 15594-15598 (2009).">13</a></sup>, and is only weakly correlated with <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">avg</sub> (<i style="font-style: italic;">r</i>=0.49) and GDD<sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">8,30</sub> (<i style="font-style: italic;">r</i>=0.45;<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Supplementary Fig. S1</a>). Precipitation around anthesis is used because maize plants are particularly susceptible to drought stress at this stage<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref6" id="ref-link-17" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Barnabas, B. A. T., Jager, K. & Feher, A. The effect of drought and heat stress on reproductive processes in cereals. Plant Cell Environ. 31, 11-38 (2008).">6</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref14" id="ref-link-18" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Grant, R. F., Jackson, B. S., Kiniry, J. R. & Arkin, G. F. Water deficit timing effects on yield components in maize. Agron. J. 81, 61 (1989).">14</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref15" id="ref-link-19" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Bolanos, J. & Edmeades, G. O. The importance of the anthesis-silking interval in breeding for drought tolerance in tropical maize. Field Crop. Res. 48, 65-80 (1996).">15</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref16" id="ref-link-20" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Claassen, M. M. & Shaw, R. H. Water deficit effects on corn. I. Grain components. Agron. J. 62, 652-655 (1970).">16</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref17" id="ref-link-21" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Banziger, M., Edmeades, G. O., Beck, D. & Bellon, M. Breeding for Drought and Nitrogen Stress Tolerance in Maize: From Theory to Practice (CIMMYT, 2000).">17</a></sup>. Alternative formulations were tested, with similar results as described in the <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Supplementary Information</a>. Inclusion of the coefficients <b style="font-weight: bold;">b</b><sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;"><i style="font-style: italic;">s</i></sub> and <b style="font-weight: bold;">c</b><sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;"><i style="font-style: italic;">t</i></sub> in equation (1) helps to ensure that any perceived effect of weather is not due to differences between sites or years that may arise from omitted variables. Within sites, omitted variables such as use of fertilizers, herbicides or labour are likely to be uniform, and any variations are assumed orthogonal to weather because the locations of trials were randomized within the experiment station.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">We find a highly significant (<i style="font-style: italic;">P</i><0.01) effect of temperature on maize yields, with clear differences between optimal and drought conditions (<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f2" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Fig. 2</a>a). Both management systems show fairly modest and statistically insignificant (<i style="font-style: italic;">P</i>>0.05) sensitivities to increased degree days between 8<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C and 30<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C. In contrast GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub>exhibits a marked negative effect on yields, with the effect larger under drought conditions. As the units of yields are in log, a coefficient of −0.01 (or −0.017) indicates that each additional degree day above 30<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C reduces the final yield by 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> (or 1.7<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span>) under optimal (or drought) conditions.</span></div><div class="figure cleared" id="f2" style="clear: both; display: block; margin-bottom: 19px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><figure><figcaption><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="legend" style="color: #111111; display: block; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: -3px; padding-bottom: 3px; padding-left: 0px; padding-right: 0px; padding-top: 3px;">Figure 2: The effect of heat on maize yields.</span></span></figcaption><div class="figure-content box" style="border-bottom-color: initial; border-bottom-style: initial; border-bottom-width: 0px; border-left-color: rgb(231, 231, 231); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(231, 231, 231); border-right-style: solid; border-right-width: 1px; border-top-color: rgb(231, 231, 231); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 20px; padding-left: 10px; padding-right: 10px; padding-top: 17px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a class="fig-link" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1043_F2.html" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;"><img alt="The effect of heat on maize yields." class="fig" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/images_article/nclimate1043-f2.jpg" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: block; height: 689px; width: 600px;" /></a><div class="description" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><div style="line-height: 1.507em; margin-bottom: 18px; margin-left: 0px; margin-right: 0px; margin-top: 18px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><b style="font-weight: bold;">a</b>, Regression estimates of the effects of an increase of GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">8,30</sub> and GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub> by 1 degree day, using data from trials managed for optimal (<i style="font-style: italic;">n</i>=17,713) or drought (<i style="font-style: italic;">n</i>=3,244) conditions. Error bars indicate 95<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> confidence interval using robust standard errors clustered by site–year.<b style="font-weight: bold;">b</b>, Model estimate of yield impact of 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C warming for trials at different average growing-season temperatures, using regression equations for trials with optimal or drought management. The lines are the best fits to the mean impact at each temperature level, and the shaded areas show an estimate of the 95<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> confidence interval using robust standard errors.</div></div><ul class="resources" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><li class="full" style="clear: both; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1043_F2.html" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/icon_full_figure.gif); background-origin: initial; background-position: 2px 0px; background-repeat: no-repeat no-repeat; border-bottom-color: initial; border-bottom-style: initial; border-bottom-width: 0px; color: #216a9d; font-weight: normal; padding-bottom: 0px; padding-left: 25px; padding-right: 0px; padding-top: 0px; text-decoration: none;">Full size image (163 KB)</a></li>
</ul></span></div><nav><ul class="figure-nav cleared" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bg_light_grad.gif); background-origin: initial; background-position: 0px 0px; background-repeat: repeat no-repeat; border-bottom-color: rgb(231, 231, 231); border-bottom-style: solid; border-bottom-width: 1px; border-left-color: rgb(231, 231, 231); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(231, 231, 231); border-right-style: solid; border-right-width: 1px; border-top-color: initial; border-top-style: initial; border-top-width: 0px; display: block; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 20px; padding-right: 20px; padding-top: 0px; position: relative;"><li class="prev up-arrow" style="left: 10px; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: auto; margin-right: auto; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f1" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/arrow_small_up.gif); background-origin: initial; background-position: 0px 50%; background-repeat: no-repeat no-repeat; border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-color: rgb(234, 234, 236); border-right-style: solid; border-right-width: 1px; border-top-style: none; border-top-width: 0px; color: #216a9d; display: block; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 12px; padding-right: 20px; padding-top: 0px; text-align: left; text-decoration: none;" title="The study region in Africa.">Previous figure</a></span></li>
<li class="index" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: auto; margin-right: auto; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: center;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1043_ft.html" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; display: inline; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-top: 0px; text-align: center; text-decoration: none;">Figures index</a></span></li>
<li class="next down-arrow" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: auto; margin-right: auto; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; right: 10px; top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f3" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/arrow_small_down.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-color: rgb(234, 234, 236); border-left-style: solid; border-left-width: 1px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; display: block; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 20px; padding-right: 12px; padding-top: 0px; text-align: right; text-decoration: none;" title="Model estimates of maize yield changes for 1[thinsp][deg]C warming.">Next figure</a></span></li>
</ul></nav></figure></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The importance of GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub> is consistent with the only previous study to our knowledge with a comparable sample size, which focused on temperate maize in the US (ref. <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref13" id="ref-link-22" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Roberts, M. J. Nonlinear temperature effects indicate severe damages to US crop yields under climate change. Proc. Natl Acad. Sci. USA 106, 15594-15598 (2009).">13</a>). As in the optimal management case here, they found that increases in GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">8,30</sub> improved yields but each additional GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub> reduced yields by about 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span>. In our drought management case, yields are reduced by roughly 1.7<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> for each additional GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub>. This demonstrates the importance of moisture status in the response to heat, an insight that is not possible from evaluating data from a single or, as in ref. <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref13" id="ref-link-23" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Roberts, M. J. Nonlinear temperature effects indicate severe damages to US crop yields under climate change. Proc. Natl Acad. Sci. USA 106, 15594-15598 (2009).">13</a>, unknown mixture of management regimes. The interaction between moisture and heat could indicate that the main mechanism of heat damage is by reducing soil moisture and increasing the severity of drought, that the ability of maize to cope with direct effects of heat on cellular processes is dependent on plant water availability status, or both. For example, evaporative cooling is an important mechanism for coping with heat, but can occur only with ample soil moisture<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref18" id="ref-link-24" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Reynolds, M. P., Balota, M., Delgado, M. I. B., Amani, I. & Fischer, R. A. Physiological and morphological traits associated with spring wheat yield under hot, irrigated conditions. Aust. J. Plant Physiol. 21, 717-730 (1994).">18</a></sup>.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The negative impact of GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub> found here and elsewhere indicates that daytime warming is more harmful to maize than night-time warming. To corroborate this, we carried out a regression with linear and quadratic terms for growing-season average daily maximum and minimum temperature. The results confirmed that warming is more harmful during the day, and under optimal management warming at night can even be beneficial (<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Supplementary Fig. S2</a>). This result is probably crop dependent; for instance, recent analysis of rice indicates that night-time warming is more harmful than daytime warming<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref10" id="ref-link-25" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Welch, J. R. et al. Rice yields in tropical/subtropical Asia exhibit large but opposing sensitivities to minimum and maximum temperatures. Proc. Natl Acad. Sci. USA 107, 14562 (2010).">10</a></sup>.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">One mechanism of yield loss from daytime heat and moisture stress is damage to reproductive organs. To evaluate this further, a regression with GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">8,30</sub> and GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub> split across three stages of the growing season was carried out. The results supported an important role for processes related to flowering, as sensitivity to GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub> was highest under optimal management for the 21 days around silking, and under drought management for pre-silking and silking stages (<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Supplementary Fig. S3</a>).</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The net effect of warming on yields was computed for each trial by artificially raising observed temperatures on each day by 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C, recomputing temperature indices such as GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">8,30</sub>, and using the regression equations to predict the new yield. Results were summarized as averages for all trials at a given baseline temperature to assess the nonlinearity of warming effects (<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f2" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Fig. 2</a>b). For optimal management, at present, maize growing below ~23<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C in average growing-season temperature tends to gain from warming, owing to positive effects of GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">8,30</sub>, whereas yields of maize grown in areas above this baseline temperature tend to decline with warming. Sites above 25<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C in average temperature decline quite rapidly, albeit with considerable uncertainty, because of frequent exposure to temperatures above 30<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C, with more than 10<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> yield loss per °C of warming.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Under drought conditions, even the coolest trials are harmed by 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C warming, with losses exceeding 40<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> at the hottest sites. Again, this emphasizes the importance of moisture in the ability of maize to cope with heat. Similarly, studies for maize in the US have shown much greater sensitivity to hot days for eastern, rain-fed states than in the western states, where irrigation is much more common<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref13" id="ref-link-26" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Roberts, M. J. Nonlinear temperature effects indicate severe damages to US crop yields under climate change. Proc. Natl Acad. Sci. USA 106, 15594-15598 (2009).">13</a></sup>.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The relationships derived from trial data were used to map potential impacts for maize under optimal or drought management across sub-Saharan Africa (<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f3" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Fig. 3</a>). Under optimal management, negative yield impacts were projected for roughly 65<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> of the area where maize is harvested at present in Africa. All maize areas were projected to exhibit yield declines under drought management, with more than 75<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> of areas predicted to decline by at least 20<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span> for 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C warming.</span></div><div class="figure cleared" id="f3" style="clear: both; display: block; margin-bottom: 19px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><figure><figcaption><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="legend" style="color: #111111; display: block; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: -3px; padding-bottom: 3px; padding-left: 0px; padding-right: 0px; padding-top: 3px;">Figure 3: Model estimates of maize yield changes for 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C warming.</span></span></figcaption><div class="figure-content box" style="border-bottom-color: initial; border-bottom-style: initial; border-bottom-width: 0px; border-left-color: rgb(231, 231, 231); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(231, 231, 231); border-right-style: solid; border-right-width: 1px; border-top-color: rgb(231, 231, 231); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 20px; padding-left: 10px; padding-right: 10px; padding-top: 17px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a class="fig-link" href="http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1043_F3.html" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;"><img alt="Model estimates of maize yield changes for 1[thinsp][deg]C warming." class="fig" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/images_article/nclimate1043-f3.jpg" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: block; height: 345px; width: 600px;" /></a><div class="description" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><div style="line-height: 1.507em; margin-bottom: 18px; margin-left: 0px; margin-right: 0px; margin-top: 18px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><b style="font-weight: bold;">a</b>–<b style="font-weight: bold;">c</b>, Present growing-season average temperature (<b style="font-weight: bold;">a</b>) and estimated impacts of 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C warming for all areas for optimal (<b style="font-weight: bold;">b</b>) and drought (<b style="font-weight: bold;">c</b>) management. <b style="font-weight: bold;">d</b>–<b style="font-weight: bold;">f</b>, Present maize-growing area (fraction of grid cell; ref. <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref23" id="ref-link-5" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Monfreda, C., Ramankutty, N. & Foley, J. A. Farming the planet: 2. Geographic distribution of crop areas, yields, physiological types, and net primary production in the year 2000. Glob. Biogeochem. Cycles 22, GB1022 (2008).">23</a>; <b style="font-weight: bold;">d</b>) and estimated impacts of 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C warming for areas with at least 1<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">%</span>of maize (<b style="font-weight: bold;">e</b>,<b style="font-weight: bold;">f</b>).</div></div><ul class="resources" style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><li class="full" style="clear: both; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1043_F3.html" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/icon_full_figure.gif); background-origin: initial; background-position: 2px 0px; background-repeat: no-repeat no-repeat; border-bottom-color: initial; border-bottom-style: initial; border-bottom-width: 0px; color: #216a9d; font-weight: normal; padding-bottom: 0px; padding-left: 25px; padding-right: 0px; padding-top: 0px; text-decoration: none;">Full size image (297 KB)</a></li>
</ul></span></div><nav><ul class="figure-nav cleared" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bg_light_grad.gif); background-origin: initial; background-position: 0px 0px; background-repeat: repeat no-repeat; border-bottom-color: rgb(231, 231, 231); border-bottom-style: solid; border-bottom-width: 1px; border-left-color: rgb(231, 231, 231); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(231, 231, 231); border-right-style: solid; border-right-width: 1px; border-top-color: initial; border-top-style: initial; border-top-width: 0px; display: block; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 20px; padding-right: 20px; padding-top: 0px; position: relative;"><li class="prev up-arrow" style="left: 10px; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: auto; margin-right: auto; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f2" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/arrow_small_up.gif); background-origin: initial; background-position: 0px 50%; background-repeat: no-repeat no-repeat; border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-color: rgb(234, 234, 236); border-right-style: solid; border-right-width: 1px; border-top-style: none; border-top-width: 0px; color: #216a9d; display: block; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 12px; padding-right: 20px; padding-top: 0px; text-align: left; text-decoration: none;" title="The effect of heat on maize yields.">Previous figure</a></span></li>
<li class="index" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: auto; margin-right: auto; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: center;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1043_ft.html" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; display: inline; font-weight: bold; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-top: 0px; text-align: center; text-decoration: none;">Figures index</a></span></li>
</ul></nav></figure></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">It is difficult to relate the management conditions in these trials to those in actual farmers’ fields. One clear difference is that these particular trials use fairly high rates of fertilizer to avoid nitrogen (N) stress, whereas most farmers outside South Africa and Zimbabwe have historically applied little N fertilizer. Nitrogen stress tends to mute the response to other stresses, such as moisture or heat<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref4" id="ref-link-27" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Lobell, D. B. Robust negative impacts of climate change on African agriculture. Environ. Res. Lett. 5, 014010 (2010).">4</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref19" id="ref-link-28" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Heisey, P. W. & Edmeades, G. O. World Maize Facts and Trends 1997/98 (CIMMYT, 1998).">19</a></sup>; thus, the maps in <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f3" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Fig. 3</a> would exaggerate the impacts on actual farmers under present conditions. However, there are widespread efforts to increase fertilizer rates in Africa to raise average yields<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref20" id="ref-link-29" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Denning, G. et al. Input subsidies to improve smallholder maize productivity in Malawi: Toward an African Green Revolution. PLoS Biol. 7, e1000023 (2009).">20</a></sup>, and this would tend to bring fields closer to the types of heat sensitivity estimated here. For example, previously estimated responses to warming using country-level data in southern Africa<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref4" id="ref-link-30" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Lobell, D. B. Robust negative impacts of climate change on African agriculture. Environ. Res. Lett. 5, 014010 (2010).">4</a></sup>, where fertilizer rates are higher, lie between the estimates for optimal and drought conditions estimated here (<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Supplementary Fig. S4</a>).</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Not all maize varieties will respond similarly to climate change, and indeed shifting varieties represents a key potential means of adaptation. The large data set used here affords the opportunity to examine varietal differences (<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Supplementary Fig. S5</a>), indicating a potentially important role for variety switching as an adaptive response to climate change, although the appropriate switch depends on moisture conditions.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Overall, our results indicate two important conclusions. First, maize yields in Africa may gain from warming at relatively cool sites, but are significantly hurt in areas where temperatures commonly exceed 30<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C. This roughly corresponds to areas with growing season <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">avg</sub> of 23<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C or <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">max</sub> of 28<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C. These conclusions are in line with previous results from process-based models<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref7" id="ref-link-31" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Thornton, P. K., Jones, P. G., Alagarswamy, G. & Andresen, J. Spatial variation of crop yield response to climate change in East Africa. Glob. Environ. Change 19, 54-65 (2009).">7</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref21" id="ref-link-32" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Lobell, D. B. & Burke, M. B. On the use of statistical models to predict crop yield responses to climate change. Agric. Forest Meteorol. 150, 1443-1452 (2010).">21</a></sup> or statistical models in Africa that relied on United Nations Food and Agriculture Organization data<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref4" id="ref-link-33" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Schlenker, W. & Lobell, D. B. Robust negative impacts of climate change on African agriculture. Environ. Res. Lett. 5, 014010 (2010).">4</a></sup>, which showed heterogeneous impacts of climate change that, on average, are quite negative. However, the present study offers more precision than previous studies because of the large sample sizes.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Second, sensitivity to heat is clearly exacerbated in drought conditions, with even the coolest sites hurt by warming in the absence of adequate soil moisture. These results indicate that agronomic measures to improve soil moisture and breeding efforts to produce drought-tolerant crops are not only beneficial for managing present and future risks of drought, but are also probably important strategies to deal with future warming. Conversely, improvements in heat tolerance may limit losses during droughts. Although these conclusions cannot be directly extrapolated to other regions or crops, we believe the approach introduced here has wide applicability in other settings, and for a range of questions that extend beyond the present focus on temperature. For example, international public research organizations, national breeding programmes, and multinational companies possess similar data for many crops and regions.</span></div></div></div></section><section><div class="section expanded" id="methods" style="clear: both; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><h1 class="section-heading toggle" style="color: #444444; font-weight: bold; letter-spacing: -0.5px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 18px; padding-bottom: 2px; padding-left: 0px; padding-right: 0px; padding-top: 2px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="Apple-style-span" style="font-size: small;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/collapse.gif); background-origin: initial; background-position: 0px 50%; background-repeat: no-repeat no-repeat; color: #444444; font-weight: bold; padding-bottom: 0px; padding-left: 23px; padding-right: 0px; padding-top: 0px; text-decoration: none;" title="Methods"></a><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#methods" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/collapse.gif); background-origin: initial; background-position: 0px 50%; background-repeat: no-repeat no-repeat; color: #444444; font-weight: bold; padding-bottom: 0px; padding-left: 23px; padding-right: 0px; padding-top: 0px; text-decoration: none;">Methods</a></span></span></h1><div class="content" style="border-top-color: rgb(231, 231, 231); border-top-style: solid; border-top-width: 1px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; zoom: 1;"><nav><ul class="section-nav cleared" style="color: #a2a7ab; display: block; margin-bottom: 0px; margin-left: -4px; margin-right: 0px; margin-top: 0px; padding-bottom: 14px; padding-left: 0px; padding-right: 0px; padding-top: 5px;"><li class="first" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#main" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">Main</a></span></li>
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">
<li class="current" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><span><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#methods" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">Methods</a></span></li>
<li style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#references" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">References</a></li>
<li style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#acknowledgments" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">Acknowledgements</a></li>
<li style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: url(http://www.nature.com/view/images/bullet_small.gif); background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#author-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">Author information</a></li>
<li class="last" style="background-attachment: initial; background-clip: initial; background-color: initial; background-image: none; background-origin: initial; background-position: 100% 50%; background-repeat: no-repeat no-repeat; display: inline; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 4px; padding-right: 7px; padding-top: 0px; white-space: nowrap;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: none; border-bottom-width: 0px; border-color: initial; border-left-style: none; border-left-width: 0px; border-right-style: none; border-right-width: 0px; border-top-style: none; border-top-width: 0px; color: #216a9d; font-weight: bold; text-decoration: none;">Supplementary information</a></li>
</span></ul></nav><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Daily minimum and maximum temperatures and precipitation for each trial were estimated by interpolation of daily measurements made in the World Meteorological Organization, World Weather Watch Program (obtained from <a href="ftp://ftp.ncdc.noaa.gov/pub/data/gsod" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">ftp://ftp.ncdc.noaa.gov/pub/data/gsod</a>). The locations of stations with data are shown in <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f1" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Fig. 1</a>, although many stations have incomplete records over the study period (1999–2007). For each day, a thin-plate spline using latitude (in degrees), longitude (in degrees) and elevation (in kilometres) as predictors was fitted to the available data. Root mean square errors of the model at the World Meteorological Organization sites averaged 1.3<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C for mean temperature and 2.7<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>mm<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>day<sup style="line-height: 0; vertical-align: super;">−1</sup> for precipitation, with cross-validated errors of 1.9<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>°C and 4.8<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>mm<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>day<sup style="line-height: 0; vertical-align: super;">−1</sup>, respectively.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Growing degree days were estimated from daily <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">min</sub> and <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">max</sub> at each site as:</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><img alt="" class="align-middle" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/images/nclimate1043-m2.gif" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; vertical-align: middle;" /></span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">where <i style="font-style: italic;">t</i> is an individual time step (hour) within the growing season, <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;"><i style="font-style: italic;">t</i></sub> is the average temperature during this time step (determined by interpolating between <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">min</sub> and <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">max</sub> with a sin curve) and <i style="font-style: italic;">N</i> is the number of hours between sowing and maturity. Only a small subset of sites reported maturity date, and therefore we could not use trial-specific growing season lengths without omitting a large fraction of the data. The average length to maturity for reporting sites (150 days or 3,600<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span>h) was therefore used for all sites. GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">8,30</sub> corresponds to equation (2) with <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">base</sub>=8<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span><sup style="line-height: 0; vertical-align: super;">°</sup>C, and <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">opt</sub>=30<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span><sup style="line-height: 0; vertical-align: super;">°</sup>C, which is based on established values for maize<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref12" id="ref-link-34" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Kiniry, J. R. & Bonhomme, R. in Predicting Crop Phenology (ed. Hodges, T.) 115-131 (CRC Press, 1991).">12</a></sup>, whereas GDD<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">30+</sub> corresponds to equation (2) with <i style="font-style: italic;">T</i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;">base</sub>=30<span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;"> </span></span><sup style="line-height: 0; vertical-align: super;">°</sup>C, and <img alt="" class="align-middle" src="http://www.nature.com/nclimate/journal/vaop/ncurrent/images/nclimate1043-m3.gif" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; vertical-align: middle;" /> . Daily errors in <i style="font-style: italic;">T</i> estimates will largely cancel when aggregating to growing-season sums, but any residual error will tend to attenuate the regression coefficients toward zero.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Several proxies for soil moisture availability were tested, including precipitation for the 21 days around anthesis (a period commonly viewed as critical to maize<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref17" id="ref-link-35" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Banziger, M., Edmeades, G. O., Beck, D. & Bellon, M. Breeding for Drought and Nitrogen Stress Tolerance in Maize: From Theory to Practice (CIMMYT, 2000).">17</a></sup>), precipitation before anthesis, the difference between precipitation and total potential evapotranspiration before anthesis, and precipitation for the entire growing season. All gave similar results for temperature sensitivity, as did a model without any precipitation term, as well as a model with the measured anthesis–silking interval for the trial, which is a good indicator of moisture stress and a strong predictor of final yield<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref15" id="ref-link-36" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Bolanos, J. & Edmeades, G. O. The importance of the anthesis-silking interval in breeding for drought tolerance in tropical maize. Field Crop. Res. 48, 65-80 (1996).">15</a>, <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref19" id="ref-link-37" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Heisey, P. W. & Edmeades, G. O. World Maize Facts and Trends 1997/98 (CIMMYT, 1998).">19</a></sup> (see <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Supplementary Fig. S6</a>).</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">In the linear mixed model in equation (1), the coefficients <b style="font-weight: bold;">b</b><sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;"><i style="font-style: italic;">s</i></sub> and <b style="font-weight: bold;">c</b><sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;"><i style="font-style: italic;">t</i></sub> can be treated as either fixed effects, where each site and year has its own independent intercept, or random effects, where the effects are viewed as derived from a Gaussian distribution (that is, <b style="font-weight: bold;">b</b><sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;"><i style="font-style: italic;">s</i></sub>~<i style="font-style: italic;">N</i>(0,<i style="font-style: italic;"><span class="mb" style="background-attachment: initial !important; background-clip: initial !important; background-color: transparent !important; background-image: none !important; background-origin: initial !important; display: inline !important; font-weight: inherit !important; line-height: inherit !important; padding-bottom: 0px !important; padding-left: 0px !important; padding-right: 0px !important; padding-top: 0px !important; visibility: visible !important;">σ</span></i><sub style="bottom: -0.6ex; line-height: 0; margin-left: 0.15em; position: relative; vertical-align: baseline;"><i style="font-style: italic;">b</i></sub><sup style="line-height: 0; vertical-align: super;">2</sup>)). We use the more conservative fixed-effects approach, but results were nearly identical when using random effects. Results were also similar when using actual yields instead of log-transformed yields. Log yields were used to account for the skewed distribution of yields (<a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#supplementary-information" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Supplementary Fig. S1</a>), as commonly done and supported in this case by a theta parameter of 0.5 for the Box–Cox power transformation.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">A potential problem when using standard regression is that, if model errors are not independent, the inferred confidence intervals can be overly optimistic. In this context, it is likely that trials conducted for a particular year in a particular station were all affected by the same omitted variables, and therefore errors will not be independent. To account for this, we clustered standard errors by site–year, and use these more conservative estimates of standard errors throughout.</span></div><div style="margin-bottom: 20px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Finally, we note that none of the regression models or impacts shown in <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#f3" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;">Fig. 3</a> considers fertilization effects of elevated carbon dioxide levels. These effects are expected to be small for C<sub style="bottom: -0.6ex; line-height: 0; position: relative; vertical-align: baseline;">4</sub> crops such as maize, for which photosynthesis rates do not respond to higher ambient carbon dioxide<sup style="line-height: 0; vertical-align: super;"><a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1043.html#ref22" id="ref-link-38" style="border-bottom-color: rgb(56, 119, 130); border-bottom-style: dotted; border-bottom-width: 1px; color: #216a9d; font-weight: normal; text-decoration: none;" title="Leakey, A. D. B. Rising atmospheric carbon dioxide concentration and the future of C4 crops for food and fuel. Proc. R. Soc. B 276, 2333-2343 (2009).">22</a></sup>, but may be important under drought conditions when all crops show improved water-use efficiency with elevated carbon dioxide.</span></div></div></div></section>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-40817615483067897612011-03-01T12:05:00.000-08:002011-03-01T12:05:15.641-08:00Christoph Müller et al., PNAS (2011), Climate change risks for African agriculture<span class="slug-metadata-note ahead-of-print" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333300; display: block; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 3px; outline-style: none; padding-bottom: 3px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;">PNAS, published online before print <span class="slug-ahead-of-print-date" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;">February 28, 2011</span>, doi:<span class="slug-doi" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;" title="10.1073/pnas.1015078108">10.1073/pnas.1015078108</span></span><br />
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<h1 id="article-title-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: Georgia, 'Times New Roman', serif; font-size: 1.8em; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 10px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;">Climate change risks for African agriculture</h1><div class="contributors" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;"><ol class="contributor-list" id="contrib-group-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: bold; line-height: inherit; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 15px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline; white-space: normal;"><li class="contributor" id="contrib-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: inline; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: 1.7; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline; white-space: normal;"><span class="name" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><a class="name-search" href="http://www.pnas.org/search?author1=Christoph+M%C3%BCller&sortspec=date&submit=Submit" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0px; white-space: nowrap;">Christoph Müller</a></span><a class="xref-aff" href="http://www.pnas.org/content/early/2011/02/23/1015078108.abstract?etoc#aff-1" id="xref-aff-1-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0.2em;"><sup style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.85em; font-style: inherit; font-weight: inherit; line-height: 0; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: super;">a</sup></a>, </li>
<li class="contributor" id="contrib-2" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: inline; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: 1.7; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline; white-space: normal;"><span class="name" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><a class="name-search" href="http://www.pnas.org/search?author1=Wolfgang+Cramer&sortspec=date&submit=Submit" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0px; white-space: nowrap;">Wolfgang Cramer</a></span><a class="xref-aff" href="http://www.pnas.org/content/early/2011/02/23/1015078108.abstract?etoc#aff-1" id="xref-aff-1-2" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0.2em;"><sup style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.85em; font-style: inherit; font-weight: inherit; line-height: 0; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: super;">a</sup></a>, </li>
<li class="contributor" id="contrib-3" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: inline; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: 1.7; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline; white-space: normal;"><span class="name" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><a class="name-search" href="http://www.pnas.org/search?author1=William+L.+Hare&sortspec=date&submit=Submit" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0px; white-space: nowrap;">William L. Hare</a></span><a class="xref-aff" href="http://www.pnas.org/content/early/2011/02/23/1015078108.abstract?etoc#aff-1" id="xref-aff-1-3" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0.2em;"><sup style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.85em; font-style: inherit; font-weight: inherit; line-height: 0; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: super;">a</sup></a><span class="xref-sep" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: 0.33em;">,</span><a class="xref-aff" href="http://www.pnas.org/content/early/2011/02/23/1015078108.abstract?etoc#aff-2" id="xref-aff-2-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0.2em;"><sup style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.85em; font-style: inherit; font-weight: inherit; line-height: 0; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: super;">b</sup></a>, and</li>
<li class="last" id="contrib-4" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: inline; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: 1.7; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline; white-space: normal;"><span class="name" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><a class="name-search" href="http://www.pnas.org/search?author1=Hermann+Lotze-Campen&sortspec=date&submit=Submit" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0px; white-space: nowrap;">Hermann Lotze-Campen</a></span><a class="xref-aff" href="http://www.pnas.org/content/early/2011/02/23/1015078108.abstract?etoc#aff-1" id="xref-aff-1-4" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0.2em;"><sup style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.85em; font-style: inherit; font-weight: inherit; line-height: 0; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: super;">a</sup></a></li>
</ol><div class="affiliation-list-reveal" style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5; margin-bottom: 15px; margin-left: 0px; margin-right: 0px; margin-top: 15px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><a class="view-more" href="http://www.pnas.org/content/early/2011/02/23/1015078108.abstract?etoc#" style="background-color: white; border-bottom-color: rgb(220, 220, 220); border-bottom-style: solid; border-bottom-width: 1px; border-color: initial; border-left-color: rgb(220, 220, 220); border-left-style: solid; border-left-width: 1px; border-right-color: rgb(220, 220, 220); border-right-style: solid; border-right-width: 1px; border-style: initial; border-top-color: rgb(220, 220, 220); border-top-style: solid; border-top-width: 1px; color: #333333; cursor: pointer; display: block; float: left; font-family: inherit; font-size: 0.833em; font-style: inherit; font-weight: bold; height: 0.9em; line-height: inherit; margin-bottom: 0px; margin-left: -2px; margin-right: 5px; margin-top: 0px; outline-style: none; padding-bottom: 0.4em; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: center; text-decoration: none; vertical-align: baseline; width: 1.3em;">+</a>Author Affiliations</div><ol class="affiliation-list hideaffil" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; left: -9999px; line-height: inherit; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 1em; margin-left: 27px; margin-right: 27px; margin-top: 1em; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; position: absolute; text-align: inherit; vertical-align: baseline; width: 5000px;"><li class="aff" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: list-item; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><a href="" id="aff-1" name="aff-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0.2em;"></a><address style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; display: inline; font-family: inherit; font-size: inherit; font-style: normal; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><sup style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.85em; font-style: inherit; font-weight: inherit; line-height: 0; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: super;">a</sup>Earth System Analysis, Potsdam Institute for Climate Impact Research, D-14412 Potsdam, Germany; and</address></li>
<li class="aff" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; display: list-item; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><a href="" id="aff-2" name="aff-2" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0.2em;"></a><address style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; display: inline; font-family: inherit; font-size: inherit; font-style: normal; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><sup style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.85em; font-style: inherit; font-weight: inherit; line-height: 0; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: super;">b</sup>Climate Analytics GmbH, D-14467 Potsdam, Germany</address></li>
</ol><ol class="fn-track" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.833em; font-style: inherit; font-weight: inherit; line-height: inherit; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;"><li class="fn-edited-by" id="fn-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 5px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;"><div id="p-1" style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5; margin-bottom: 15px; margin-left: 0px; margin-right: 0px; margin-top: 15px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;">Edited by Robert W. Kates, Independent Scholar, Trenton, ME, and approved February 8, 2011 (received for review October 9, 2010)</div></li>
</ol><ul class="pnas-footnotes" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.833em; font-style: inherit; font-weight: inherit; line-height: inherit; list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;"><li class="corresp" id="corresp-1" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 5px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;"><sup style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: inherit; font-size: 0.7em; font-style: inherit; font-weight: inherit; line-height: 0; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: super;">1</sup>To whom correspondence should be addressed. E-mail: <a href="mailto:christoph.mueller@pik-potsdam.de" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #333333; font-family: inherit; font-size: inherit; font-style: inherit; font-weight: normal; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; text-decoration: none; vertical-align: 0em;">christoph.mueller@pik-potsdam.de</a></li>
</ul></div><div class="section abstract" id="abstract-1" style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; clear: both; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><h2 style="border-bottom-color: rgb(153, 153, 153); border-bottom-style: dotted; border-bottom-width: 2px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; font-family: Georgia, 'Times New Roman', serif; font-size: 16px; font-style: inherit; font-weight: bold; line-height: inherit; margin-bottom: 10px; margin-left: 0px; margin-right: 0px; margin-top: 10px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; vertical-align: baseline;">Abstract</h2><div id="p-3" style="border-bottom-width: 0px; border-color: initial; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-style: initial; border-top-width: 0px; font-size: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5; margin-bottom: 15px; margin-left: 0px; margin-right: 0px; margin-top: 15px; outline-style: none; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: inherit; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">The Intergovernmental Panel on Climate Change (IPCC) assessment of major risks for African agriculture and food security caused by climate change during coming decades is confirmed by a review of more recent climate change impact assessments (14 quantitative, six qualitative). Projected impacts relative to current production levels range from −100% to +168% in econometric, from −84% to +62% in process-based, and from −57% to +30% in statistical assessments. Despite large uncertainty, there are several robust conclusions from published literature for policy makers and research agendas: agriculture everywhere in Africa runs some risk to be negatively affected by climate change; existing cropping systems and infrastructure will have to change to meet future demand. With respect to growing population and the threat of negative climate change impacts, science will now have to show if and how agricultural production in Africa can be significantly improved.</span></div></div>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-33323689936089643722011-02-23T13:38:00.000-08:002011-02-23T13:38:22.488-08:00Pascal Oettli et al., Environ. Res. Lett. 6 (January-March 2011), Are regional climate models relevant for crop yield prediction in West Africa?<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="sml" style="line-height: 1.35em;"><i>Environ. Res. Lett</i>. <b>6</b> (January-March 2011) 014008; </span><span class="sml" style="line-height: 1.35em;">doi: 10.1088/1748-9326/6/1/014008</span></span><br />
<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><span class="sml"></span><span class="Apple-style-span" style="line-height: 21px;"><br />
</span></span><br />
<div style="line-height: 1.35em; width: 61em;"><b class="h2" style="color: #556088; line-height: 1.35em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: large;">Are regional climate models relevant for crop yield </span></b></div><div style="line-height: 1.35em; width: 61em;"><b class="h2" style="color: #556088; line-height: 1.35em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: large;">prediction in West Africa?</span></b></div><div style="line-height: 1.35em; width: 61em;"><b class="h2" style="color: #556088; line-height: 1.35em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><br />
</span></b></div><div style="line-height: 1.35em; width: 61em;"></div><div class="all_authors"><div class="authors"><span class="lrg" style="font-family: Georgia, 'Times New Roman', serif; line-height: 1.35em;"><b>Pascal Oettli</b><sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">1,2</sup>, <b>Benjamin Sultan</b><sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">1</sup><sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">,5</sup>, <b>Christian Baron</b><sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">3</sup> and <b>Mathieu Vrac</b><sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">4</sup></span></div><div class="affils"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><br />
<sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">1</sup> IPSL—LOCEAN, Paris, France<br />
<sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">2</sup> University of Tokyo, Tokyo, Japan<br />
<sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">3</sup> CIRAD UPR AIVA, Montpellier, France<br />
<sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">4</sup> IPSL—LSCE, Gif-sur-Yvette, France</span><div style="line-height: 1.35em; width: 61em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><sup style="bottom: 0.8ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">5</sup> Address for correspondence: LOCEAN, Boite 100, T45/55, 4 Place Jussieu, 75252 Paris </span></div><div style="line-height: 1.35em; width: 61em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">cedex 05, France</span></div><div style="line-height: 1.35em; width: 61em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">E-mail: <a href="mailto:benjamin.sultan@locean-ipsl.upmc.fr" style="color: #006eb2; font-weight: bold; text-decoration: none;">benjamin.sultan@locean-ipsl.upmc.fr</a></span></div><div style="line-height: 1.35em; width: 61em;"><br />
</div></div></div><div style="line-height: 1.35em; width: 61em;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Received 18 October 2010; Accepted 17 January 2011; Published 1 February 2011</span></div><div style="line-height: 1.35em; width: 61em;"></div><table bgcolor="#ffffcc" style="font-family: Arial, Helvetica, Verdana, sans-serif; font-size: 1.2em; line-height: 1.35em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;"><tbody>
<tr><td style="padding-bottom: 10px; padding-left: 8px; padding-right: 8px; padding-top: 10px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: small;"><span class="sanserif"><b>Abstract. </b></span>This study assesses the accuracy of state-of-the-art regional climate models <br />
for agriculture applications in West Africa. A set of nine regional configurations with eight <br />
regional models from the ENSEMBLES project is evaluated. Although they are all based <br />
on similar large-scale conditions, the performances of regional models in reproducing the <br />
most crucial variables for crop production are extremely variable. This therefore leads to <br />
a large dispersion in crop yield prediction when using regional models in a climate/crop <br />
modelling system. This dispersion comes from the different physics in each regional model <br />
and also the choice of parametrizations for a single regional model. Indeed, two configurations of the same regional model are sometimes more distinct than two different regional models. Promising <br />
results are obtained when applying a bias correction technique to climate model outputs. <br />
Simulated yields with bias corrected climate variables show much more realistic means and <br />
standard deviations. However, such a bias correction technique is not able to improve the <br />
reproduction of the year-to-year variations of simulated yields.</span><div style="line-height: 1.35em; width: 748px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: small;">This study confirms the importance of the multi-model approach for quantifying uncer-</span></div><div style="line-height: 1.35em; width: 748px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: small;">tainties for impact studies and also stresses the benefits of combining both regional and </span></div><div style="line-height: 1.35em; width: 748px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: small;">statistical downscaling techniques. Finally, it indicates the urgent need to address the main </span></div><div style="line-height: 1.35em; width: 748px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: small;">uncertainties in atmospheric processes controlling the monsoon system and to contribute </span></div><div style="line-height: 1.35em; width: 748px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: small;">to the evaluation and improvement of climate and weather forecasting models in that respect.</span></div><div style="line-height: 1.35em; width: 748px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: small;"><br />
</span></div><div style="line-height: 1.35em; width: 748px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif; font-size: small;"><a href="http://iopscience.iop.org/1748-9326/6/1/014008/fulltext">http://iopscience.iop.org/1748-9326/6/1/014008/fulltext</a></span></div></td></tr>
</tbody></table>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-23183712132179122882011-02-16T06:13:00.000-08:002011-02-16T06:13:52.749-08:00Zambia is burning: Insights From a Honeymoon in Zambia<h1 class="entry-title" style="color: black; font-family: nyt-cheltenham-hinted-1, nyt-cheltenham-hinted-2, georgia, 'times new roman', times, serif; font-size: 25px; font-weight: normal; line-height: 1.083em; margin-bottom: 2px; margin-left: 0px; margin-right: 0px; margin-top: 5px;">Insights From a Honeymoon in Zambia</h1><div><br />
</div><address class="byline author vcard" style="color: grey; font-family: arial, helvetica, sans-serif; font-size: 1.1em; font-style: normal; line-height: 1.2em; margin-bottom: 2px; margin-top: 2px;">By <a class="url fn" href="http://kristof.blogs.nytimes.com/author/daniel-and-sindiso-mnisi-weeks/" style="color: #00325b; text-decoration: none; text-transform: uppercase;" title="See all posts by DANIEL AND SINDISO MNISI WEEKS">DANIEL AND SINDISO MNISI WEEKS</a>, New York Times, February 16, 2011</address><div class="entry-content" style="color: #333333; font-family: georgia, 'times new roman', times, serif; line-height: 15px; margin-top: 15px;"><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">Zambia is burning.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">Its fires are not of the ethnic conflict-civil war variety we are used to seeing in the occasional reports on Africa that surface in western media. Its flames do not stir the imaginations or pull at the heartstrings of western readers like child soldiering or Janjaweed militias.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">No, this burning is of fire and ash. Its cause, while less dramatic than ethnic conflict, is devastating in its longterm effects.</div><div class="w151 right" style="clear: right; float: right; margin-bottom: 1em; margin-left: 12px; margin-right: 0px; margin-top: 5px; overflow-x: hidden; overflow-y: hidden; width: 151px;"><img alt="A roadside vendor in Zambia, where drought and desertification is a constant threat." height="220" id="100000000557803" src="http://graphics8.nytimes.com/images/2011/01/14/opinion/zambia/zambia-blogSmallInline.jpg" width="151" /><span class="credit" style="color: #909090; display: block; font-family: arial, helvetica, sans-serif; line-height: 1.223em; margin-bottom: 2px; margin-left: 0px; margin-right: 0px; margin-top: 2px; text-align: right;">Daniel Weeks</span><span class="caption" style="color: #666666; display: block; font-family: arial, helvetica, sans-serif; line-height: 1.2727em; margin-bottom: 3px; margin-left: 2px; margin-right: 2px; margin-top: 3px;">A roadside vendor in Zambia, where drought and desertification is a constant threat.</span></div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">Tucked in the middle of southern Africa, Zambia is burning because life south of the equator is becoming dangerously hot and dry. That is in large part because since the Second Industrial Revolution of the middle 19th century, the West has been pumping billions of tons of climate-changing carbon into the atmosphere with impunity, leaving Africa hotter and drier than at any time since our earliest ancestors found their feet and began to walk away.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">We walk away still. At least that’s what the two of us newlyweds were doing when we drove the main road that connects Livingstone in the southwest with the capitol Lusaka in the middle at the end of our honeymoon, and discovered the otherwise pitch-black and pot-holed central artery lit up by incessant bush fires along the way.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;"><span id="more-7741"></span></div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">We didn’t mean to drive the road at night, but car troubles at the Zimbabwean border put us back five hours on the eve of our departing flight (it takes a village to fix a car: a mechanic, an electrician, and a dozen or so of their helpers to be precise). By the time we hit the bumpy road, we were admittedly fairly desperate to reach the airport the following morning and be gone.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">Zambia is a peculiar honeymoon destination, as not a few friends observed. For us, it was firstly a welcome escape from the flurry of planning three weddings in three cities on two continents: a nod to Sindiso’s Swati culture in Johannesburg, our shared Christian identity in Cape Town, and Dan’s Waspy heritage in northern New Hampshire.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">We came to Zambia hoping for cheap prices, the wild bush, and a bit more exposure to the everyday realities of life in the Global South than one gets at a Cancun resort (In our more aspirational moments, we think that being challenged by more than each other is good for marital bliss and a sense of purpose longterm).</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">We didn’t find much in the way of cheap prices, a hardship we genuinely lamented until we considered the missing zeros between our incomes and those of the people around us. As for the wild bush and human suffering, those we found in abundance. Only the bush was brown and burning, which made the human suffering–in what is already the world’s twelfth-poorest country–all the more extreme.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">But we digress. Back to our nighttime drive, what surprised us even more than the burning itself was the fact that we were alone in our surprise. Locals lugging heavy loads of coal or corn as much as thirty miles to the nearest town (sometimes aided by a bicycle, cart or donkey, sometimes not) breathed in the heavy smoke unfazed. Mothers and children would cross the street if the heat on one side got too bad, but otherwise continue their pre-dawn chores without a thought.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">There wasn’t a fire truck or helicopter in sight…small wonder in a country where the average individual earns $850 per year and it costs nearly $100 to fill up a tank of gas. Even if Zambians could afford the trucks and choppers to fight the fires, where would they find enough water to fill the other tank? Victoria Falls is a majestic fount indeed, but that water feeds Lake Kariba and the mighty Kariba Dam. The dam, in turn, was built to light the cities of Zambia and neighboring Zimbabwe, such as they are.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">When Zambia burns by fire it burns by poverty too. And one cause, at least, is shared by both. The rise in concentration of atmospheric carbon from 284 parts per million by volume (ppmv) 150 years ago to nearly 400 ppmv today is hastening drought and desertification in sub-Saharan Africa to a shocking degree. It’s a cause which cannot be addressed by improving governments or building schools or staffing clinics on the ground, desirable as those things might be. Rather, it’s a cause for which we in the industrialized West must take a large share of the blame.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">As we were pained to see, global climate change is turning once-fertile fields from green to brown, turning soil into dust, turning water into a gold that cannot be extracted from even the richest African mine. It is undermining economic growth and foreign exchange, and denying some one billion of the world’s poorest citizens even a toehold on the ladder of industrialization and wealth.</div><div style="line-height: 1.5em; margin-bottom: 1em; margin-left: 0px; margin-right: 0px; margin-top: 0px;">No, we did not meet happy Africans on our honeymoon. Kind and courteous, yes, but also hot and thirsty and mostly poor, and having not much reason to hope that things will change before they die. At the end of the week, we boarded our plane and walked away. God willing, not for good.</div><div style="line-height: 1.5em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;"><em>Daniel Weeks is the president of <a href="http://www.acrreform.org/" style="color: #00325b; text-decoration: underline;">Americans for Campaign Reform</a>, and Dr. Sindiso Mnisi Weeks serves on the <a href="http://www.lrg.uct.ac.za/" style="color: #00325b; text-decoration: underline;">Law Faculty of the University of Cape Town</a> (specializing in women’s rights and customary law). They divide their time between Concord, NH and Cape Town. They met in 2007 while studying at Oxford as Marshall and Rhodes Scholars, respectively.</em></div></div>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-72248492942458157572011-01-29T07:24:00.000-08:002011-01-29T07:24:06.063-08:00A. Park Williams & Chris Funk, Climate Dynamics (2011), A westward extension of the warm pool leads to a westward extension of the Walker circulation, drying eastern Africa<span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><i>Climate Dynamics</i>, <span class="Apple-style-span" style="line-height: 16px;"><span class="label" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">DOI:</span></span><span class="Apple-style-span" style="line-height: 16px;"> </span><span class="Apple-style-span" style="line-height: 16px;"><span class="value" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">10.1007/s00382-010-0984-y</span></span></span><br />
<span class="Apple-style-span" style="color: #999999; font-family: Myriad, 'Trebuchet MS', sans-serif; font-size: 16.8px; line-height: 16px;"><span class="value" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; background-position: initial initial; background-repeat: initial initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-size: 12px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;"><br />
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<span class="Apple-style-span" style="line-height: 16px;"><span class="value" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;"><span class="Apple-style-span" style="line-height: 17px;"></span></span></span><br />
<h1 class="title" lang="en" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: Minion, Garamond, serif; font-size: 1.5em; font-weight: 400; line-height: 1.2em; margin-bottom: 0.4em; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">A westward extension of the warm pool leads to a westward extension of the Walker circulation, drying eastern Africa</h1><div class="authors" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0.5em; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;"><br />
</div><div class="authors" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0.5em; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><a href="http://www.springerlink.com/content/?Author=A.+Park+Williams" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-decoration: none; vertical-align: baseline;" title="View content where Author is A. Park Williams">A. Park Williams</a> and <a href="http://www.springerlink.com/content/?Author=Chris+Funk" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-decoration: none; vertical-align: baseline;" title="View content where Author is Chris Funk">Chris Funk</a></span></div><div class="authors" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0.5em; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><br />
</span></div><div class="authors" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0.5em; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><b>Abstract</b></span></div><div class="authors" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0.5em; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;"><br />
</span></div><div class="authors" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0.5em; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: justify; vertical-align: baseline;"><span class="Apple-style-span" style="line-height: 20px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Observations and simulations link anthropogenic greenhouse and aerosol emissions with rapidly increasing Indian Ocean sea surface temperatures (SSTs). Over the past 60 years, the Indian Ocean warmed two to three times faster than the central tropical Pacific, extending the tropical warm pool to the west by ~40° longitude (>4,000 km). This propensity toward rapid warming in the Indian Ocean has been the dominant mode of interannual variability among SSTs throughout the tropical Indian and Pacific Oceans (55° E–140° W) since at least 1948, explaining more variance than anomalies associated with the El Niño-Southern Oscillation (ENSO). In the atmosphere, the primary mode of variability has been a corresponding trend toward greatly increased convection and precipitation over the tropical Indian Ocean. The temperature and rainfall increases in this region have produced a westward extension of the western, ascending branch of the atmospheric Walker circulation. Diabatic heating due to increased mid-tropospheric water vapor condensation elicits a westward atmospheric response that sends an easterly flow of dry air aloft toward eastern Africa. In recent decades (1980–2009), this response has suppressed convection over tropical eastern Africa, decreasing precipitation during the ‘long-rains’ season of March–June. This trend toward drought contrasts with projections of increased rainfall in eastern Africa and more ‘El Niño-like’ conditions globally by the Intergovernmental Panel on Climate Change. Increased Indian Ocean SSTs appear likely to continue to strongly modulate the Warm Pool circulation, reducing precipitation in eastern Africa, regardless of whether the projected trend in ENSO is realized. These results have important food security implications, informing agricultural development, environmental conservation, and water resource planning.</span></span></div><div class="authors" style="background-attachment: initial; background-clip: initial; background-color: transparent; background-image: initial; background-origin: initial; border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; margin-bottom: 0.5em; margin-left: 0px; margin-right: 0px; margin-top: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: justify; vertical-align: baseline;"><span class="Apple-style-span" style="line-height: 20px;"><span class="Apple-style-span" style="font-family: Georgia, 'Times New Roman', serif;">Link: </span></span><span class="Apple-style-span" style="line-height: normal;"><a href="http://www.springerlink.com/content/u0352236x6n868n2/">http://www.springerlink.com/content/u0352236x6n868n2/</a></span></div>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-74098026094808140832011-01-29T07:20:00.000-08:002011-01-29T07:20:40.805-08:00More Frequent Drought Likely in Eastern Africa<h1 style="border-collapse: collapse; font-family: arial, sans-serif; font-size: 15.6px;">More Frequent Drought Likely in Eastern Africa</h1><div style="border-collapse: collapse; font-family: arial, sans-serif; font-size: 15.6px;"><a href="http://www.addthis.com/bookmark.php?v=250&pub=oc_web&url=http%3A%2F%2Fwww.usgs.gov%2Fnewsroom%2Farticle.asp%3FID%3D2690&title=" style="color: #5c4520;" target="_blank" title="Bookmark and Share"><img alt="Bookmark and Share" height="16" src="http://s7.addthis.com/static/btn/sm-share-en.gif" style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px;" width="83" /></a></div><div style="border-collapse: collapse; font-family: arial, sans-serif;"><div style="font-size: 15.6px;">The increased frequency of drought observed in eastern Africa over the last 20 years is likely to continue as long as global temperatures continue to rise, according to new research published in <em>Climate Dynamics</em>.</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">This poses increased risk to the estimated 17.5 million people in the Greater Horn of Africa who currently face potential food shortages.</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">Scientists from the U.S. Geological Survey and the University of California, Santa Barbara, determined that warming of the Indian Ocean, which causes decreased rainfall in eastern Africa, is linked to global warming. These new projections of continued drought contradict previous scenarios by the Intergovernmental Panel on Climate Change predicting increased rainfall in eastern Africa.</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">This new research supports efforts by the USGS and the U.S. Agency for International Development to identify areas of potential drought and famine in order to target food aid and help inform agricultural development, environmental conservation, and water resources planning.</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">“Global temperatures are predicted to continue increasing, and we anticipate that average precipitation totals in Kenya and Ethiopia will continue decreasing or remain below the historical average,” said USGS scientist Chris Funk. “The decreased rainfall in eastern Africa is most pronounced in the March to June season, when substantial rainfall usually occurs. </div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">Although drought is one reason for food shortages, it is exacerbated by stagnating agricultural development and continued population growth.”</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">As the globe has warmed over the last century, the Indian Ocean has warmed especially fast. The resulting warmer air and increased humidity over the Indian Ocean produce more frequent rainfall in that region. The air then rises, loses its moisture during rainfall, and then flows westward and descends over Africa, causing drought conditions in Ethiopia and Kenya.</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">“Forecasting precipitation variability from year to year is very difficult, and research on the links between global change and precipitation in specific regions is ongoing so that more accurate projections of future precipitation can be developed,” said University of California, Santa Barbara, scientist Park Williams. “It is also important to note that while sea-surface temperatures are expected to continue to increase in the Indian Ocean and cause an average decrease in rainfall in eastern Africa, there will still occasionally be very wet years because there are many factors that influence precipitation.”</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">Scientists compiled existing datasets on temperature, wind speed and precipitation to see what was driving climate variations in the tropical Indian and Pacific Ocean region. Most of the Indian Ocean warming is linked to human activities, particularly greenhouse gas and aerosol emissions. The Indian Ocean has warmed especially fast because it is quickly being encroached upon by the Tropical Warm Pool, which is an area with the warmest ocean surface temperatures of anywhere on earth.</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">This research supports efforts by the USGS and the U.S. Agency for International Development through the Famine Early Warning Systems Network. FEWS NET is a decision support system that helps target more than two billion dollars of food aid to more than 40 countries each year. Through this system, scientists are helping with early identification of agricultural drought that might trigger food insecurity. For more information, visit <a href="http://www.fews.net/" style="color: #5c4520;" target="_blank">http://www.fews.net</a>.</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;">The article, “A westward extension of the warm pool intensifies the walker circulation, drying eastern Africa,” was published in <em>Climate Dynamics</em> and can be found at:</div><div style="font-size: 15.6px;"><br />
</div><div style="font-size: 15.6px;"><a href="http://www.springerlink.com/content/u0352236x6n868n2/" style="color: #5c4520;" target="_blank">http://www.springerlink.com/<wbr></wbr>content/u0352236x6n868n2/</a>.</div><div style="font-size: 15.6px;"></div><h2><span class="Apple-style-span" style="font-size: small;">Photos for this release:</span></h2>Visit:<span class="Apple-style-span" style="font-size: 15.6px;"> </span><a href="http://gallery.usgs.gov/tags/NR2011_01_28" style="color: #5c4520; font-size: 15.6px;" target="_blank">http://gallery.usgs.gov/tags/<wbr></wbr>NR2011_01_28</a><span class="Apple-style-span" style="font-size: 15.6px;"> for all available photos.</span></div><div><br />
</div>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-656176502101279512010-12-13T07:28:00.000-08:002010-12-13T07:28:52.166-08:005 links to more articles on climate change and Africa<span class="Apple-style-span" style="font-size: large;">Richard Rood's blog (December 9, 2010, entry: </span><a href="http://www.wunderground.com/blog/RickyRood/comment.html?entrynum=178">http://www.wunderground.com/blog/RickyRood/comment.html?entrynum=178</a><span class="Apple-style-span" style="font-size: large;">) at wunderground contained the following links to information on climate change and Africa:</span><br />
<span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><a href="http://hdl.handle.net/10568/2665c" rel="nofollow" target="_blank">Climate variability and climate change: Impacts on Kenyan agriculture</a></span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><a href="http://www.ilri.org/aggregator/sources/2" rel="nofollow" target="_blank">A wonderful collection of stories on agriculture and climate change in Africa</a></span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><a href="http://www.ilri.org/ilrinews/index.php/archives/4025?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+ilrinews+%28ILRI+News%29" rel="nofollow" target="_blank">Climate change as opportunity in Africa</a></span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><a href="http://www.voanews.com/english/news/africa/decapua-africa-climate-change-29nov10-110960904.html" rel="nofollow" target="_blank">Voice of America Coverage of African Climate Adaptation</a></span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><a href="http://www.pbs.org/frontlineworld/stories/africa705/history/africa.html" rel="nofollow" target="_blank">Africa’s Growing Water Crisis</a></span><span class="Apple-style-span" style="font-family: Arial, sans-serif; font-size: 14.4px;"><br />
</span>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-37226621999448702022010-11-22T04:15:00.000-08:002010-11-22T04:15:28.577-08:0012 Million Egyptians to be Affected by Climate Change<h2> 12 Million Egyptians to be Affected by Climate Change </h2><small>by Mohamed Abdel Salam, January 2, 2010 </small><br />
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<small><a href="http://bikyamasr.com/wordpress/?cat=1" rel="category" title="View all posts in News"></a> </small> <br />
Cairo: A study conducted by the Center for Remote Sensing at Boston University, commissioned by the Arab Forum for Environment and Development, warned that Egypt would be one of the Arab countries most affected by climate change. The study analyzed a variety of scenarios of climate change impact, particularly on coastal areas, based on satellite images of the region, and showed that Egypt would be the most affected Arab country due to a rise in sea levels. The study stated that, “at least 12 million Egyptians will be forced to migrate from their area of residence in parts of the Nile Delta and that with a rise in sea level of 5 meters, almost one third of the total affected Arab population would be Egyptian."<br />
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The study was prepared by Dr. Eman Ghoneim, a research professor at the Center for Remote Sensing, and devoted a large portion of its findings to the impact of rising sea levels in the Nile Delta. The study warned, “under the scenarios of rising sea levels, much of the Nile Delta would be lost forever, and the analysis by the remote sensing and geographic information system classified some areas in the Nile Delta at risk if sea levels rise by one meter.” The report estimated that a rise of only one meter could engulf much of the Nile Delta. With about one third of the Delta area underwater, some of its coastal cities, such as Alexandria, Edco, Port Said and Damietta, would be in great danger. Under this scenario, it is estimated that about 8.5% of the country’s population (7 million) would be forced to migrate to other areas.<br />
The study added, “In the extreme case scenario of a 5-meter sea level rise, more than half of the Nile Delta (58%) will face devastating effects and 10 major cities would be threatened, including Alexandria, Damanhur, Kafr El-Sheikh, Damietta, Mansoura and Port Said. Rising water would drown productive plots of agricultural land and force about 14% of the country’s population (11.5 million) to move to areas of the more densely populated areas south of the Nile Delta region.”<br />
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The study went on to say that “the Nile Delta, which covers about 24,900 square kilometers, and accounts for about 65% of agricultural land in Egypt, was once the largest site for sediment deposits in the basin of the Mediterranean Sea. It is an extreme example of low, flat land located in an area that is very vulnerable to rising sea levels.” The Delta is threatened due to accelerated erosion of the coastline and the establishment of the Aswan High Dam in 1962, which subsequently sequestered large amounts of sediment behind the dam in Lake Nasser.<br />
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The study showed that coastal erosion of the Delta as a result of natural causes and the extraction of groundwater can be seen in satellite images, especially near the coastal cities of Rosetta and Damietta. The analysis of satellite images shows that the Ras Rashid “Rosetta” lost almost 9.5 square kilometers of area. Likewise, the coastline retreated 3 km in the last 30 years (1972-2003), meaning that this part of the Delta declined at the alarming rate of about 100 meters per year.<br />
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Study also discussed the consequences of climate change on the Arab region as a whole, including the impact of rising sea levels and its effects on the growth of cities, stating that the southern part of the Nile Delta is now suffering from uncontrolled population growth in the city of Cairo. The results also showed a loss of about 12% (62 square kilometers) of the agricultural areas adjacent to Cairo between 1984 and 2002.<br />
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Link: http://bikyamasr.com/wordpress/?p=7325Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0tag:blogger.com,1999:blog-7698039939158013969.post-55376896361472427742010-09-02T11:07:00.000-07:002010-09-02T11:07:49.610-07:00Hydro-climatic trends and water resource management implications based on multi-scale data for the Lake Victoria region, Kenya<i>Environ. Res. Lett.</i> <b>5</b> (July-September 2010) 034005; doi:10.1088/1748-9326/5/3/034005<br />
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<b class="h2" style="color: #556088; font-size: 1.6em; line-height: 1.35em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;">Hydro-climatic trends and water resource management implications based on multi-scale data for the Lake Victoria region, Kenya</b><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"></div><div class="all_authors"><div class="authors"><span class="lrg" style="font-family: Helvetica, Arial, sans-serif; font-size: 1.4em !important; line-height: 1.35em;"><br />
</span></div><div class="authors"><span class="lrg" style="font-family: Helvetica, Arial, sans-serif; font-size: 1.4em !important; line-height: 1.35em;">A. J. Koutsouris, G. Destouni, J. Jarsjö and S. W. Lyon</span><span class="lrg" style="font-family: Helvetica, Arial, sans-serif;"><span class="Apple-style-span" style="font-size: small;"><span class="Apple-style-span" style="font-size: 12px; line-height: 11px;">*</span></span></span></div><br />
<div class="affils"><i>Bert Bolin Centre for Climatic Research, Department of Physical Geography and Quaternary Geology, Stockholm University, 106 91 Stockholm, Sweden</i></div><div class="affils"><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">*Correspondence e-mail: <a href="mailto:steve.lyon@natgeo.su.se" style="color: #006eb2; font-weight: bold; text-decoration: none;">steve.lyon@natgeo.su.se</a></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><br />
</div></div></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Received 4 June 2010, accepted 23 July 2010, published 6 August 2010<br />
<br />
Unreliable rainfall may be a main cause of poverty in rural areas, such as the Kisumu district by Lake Victoria in Kenya. Climate change may further increase the negative effects of rainfall uncertainty. These effects could be mitigated to some extent through improved and adaptive water resource management and planning, which relies on our interpretations and projections of the coupled hydro-climatic system behaviour and its development trends. In order to identify and quantify the main differences and consistencies among such hydro-climatic assessments, this study investigates trends and exemplifies their use for important water management decisions for the Lake Victoria drainage basin (LVDB), based on local scale data for the Orongo village in the Kisumu district, and regional scale data for the whole LVDB. Results show low correlation between locally and regionally observed hydro-climatic trends, and large differences, which in turn affects assessments of important water resource management parameters. However, both data scales converge in indicating that observed local and regional hydrological discharge trends are primarily driven by local and regional water use and land use changes.<br />
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<div style="font-size: 12px; line-height: 1.35em; width: 748px;"><b>Keywords:</b> Lake Victoria, Kenya, hydrology, water resource management, irrigation, climate change, hydro-climatic interaction</div><br />
<span class="Apple-style-span" style="font-size: 23px; line-height: 31px;"><b>1. </b><b>Introduction</b></span><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Climatic changes are likely to threaten the Earth's already scarce water supply. Currently, about 40%, or 2.8 billion people, of the world population live in river basins with water scarcity. Improved water resource management is needed to help mitigate the potential influence of climatic changes and better utilize current water supplies. For example, about 1.6 billion people live in areas where the water scarcity has resource, developmental or economic reasons (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib27" style="color: #006eb2; font-weight: bold; text-decoration: none;">UN 2008</a>). Economic water scarcity occurs when a lack of financial, human or institutional capital causes incapacity to utilize better otherwise sufficient water resources. Lack of water produces negative effects on food security, health, gender equality and education making it both directly and indirectly connected with many of the United Nations' millennium development goals. As lack of financial capital also limits the capacity to import virtual water, which could otherwise compensate for physical water scarcity, water scarcity is thus primarily a crisis of the poor (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib26" style="color: #006eb2; font-weight: bold; text-decoration: none;">UN 2006</a>) that will be exacerbated under climatic changes.</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><br />
</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">For example, Kenya currently uses only 9% of its available water resources (e.g., water resources that would be exploitable if no financial constraints were present) while approximately 50% of the total population is below the national poverty line (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib28" style="color: #006eb2; font-weight: bold; text-decoration: none;">UNDP 2008</a>,<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib23" style="color: #006eb2; font-weight: bold; text-decoration: none;">Swallow <i>et al.</i> 2007</a>). In addition, physical water scarcity often occurs seasonally in Kenya due to unevenly distributed rainfall throughout the year. This creates local water scarcity in many regions of Kenya due to a combination of economical and physical water scarcity. In the Kisumu district, located by Lake Victoria, 53% of the people live below the poverty line with an unreliable rainfall pattern identified as one of the main causes through its effects on food security (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib14" style="color: #006eb2; font-weight: bold; text-decoration: none;">NCAPD 2005</a>). Though the mechanisms behind the poverty levels in rural Kenya are more complex than a cause-and-effect relationship between rainfall and poverty, rainfall patterns may exacerbate existing poverty due to the simple fact that many in rural Kenya are dependent on rain-fed agriculture. In the Kisumu district, approximately 90% of the population is dependent on agriculture for both food and income, causing a large part of the population to be affected directly by droughts and floods. Taken together with the strong seasonality in rainfall, the water resources in Kenya and the Kisumu district are quite sensitive to climatic trends. This is exemplified in Orongo village (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig1" style="color: #006eb2; font-weight: bold; text-decoration: none;">1</a>) located in the Kisumu district. It is a typical rural, lowland floodplain area in Kenya and as such it is sensitive to the effects of rainfall variability and water management (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib23" style="color: #006eb2; font-weight: bold; text-decoration: none;">Swallow <i>et al.</i> 2007</a>). This makes Orongo village a focal point for the efforts of international assistance agencies (e.g., Engineers Without Borders) whose goals are to provide reliable and sustained water resources to the local population.</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866fig1" style="color: #006eb2; font-weight: bold; text-decoration: none;"><img alt="Figure 1" src="http://ej.iop.org/images/1748-9326/5/3/034005/Full/5886601.jpg" style="border-bottom-style: none; border-color: initial; border-left-style: none; border-right-style: none; border-top-style: none; border-width: initial;" /></a></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"></div><table bgcolor="#ffffcc" style="font-size: 1.2em; line-height: 1.35em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;"><tbody>
<tr><td align="left" style="padding-bottom: 10px; padding-left: 8px; padding-right: 8px; padding-top: 10px;"><strong>Figure 1.</strong> Site map showing the location of Lake Victoria and the spatial extent of the Lake Victoria drainage basin in Africa. The location of Orongo village near Kisumu is also indicated.</td></tr>
</tbody></table><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Climatic change may increase the negative effects of rainfall uncertainty, and both current and future effects of this uncertainty could be mitigated to some extent through improved and adaptive water resource management and planning. Planning for improved and more secure water availability relies on our interpretations and projections of the coupled hydro-climatic system behaviour. Better scientific understanding of hydrological and climatic links, conditions and changes is thus a key issue for effective water resource management and its climate adaptation, in Orongo village as in other parts of the Lake Victoria region (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib24" style="color: #006eb2; font-weight: bold; text-decoration: none;">Swallow <i>et al</i> 2008</a>) and other regions of the world.</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Our understanding of the coupled hydro-climatic system may be greatly hindered by limitations in data availability and quality. For instance, trends identified on a local scale may differ significantly from trends based on regional scale data (see, e.g., <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib18" style="color: #006eb2; font-weight: bold; text-decoration: none;">Pielke <i>et al</i>2002</a> considering temperature in eastern Colorado, USA). This study compares such trend results and exemplifies their water management implications on the basis of local scale data from the Orongo village and regional scale data from the whole Lake Victoria drainage basin (LVDB). The main aims of this analysis are to further investigate the prevalence of hydro-climatic trend differences on the basis of data with differing resolution and on different scales, and the propagation of such differences to important water management parameters, such as water storage requirements. In addition to such differences, this study also aims to investigate potential important consistencies in hydro-climatic system trend assessments, which are robust against the use of differently resolved and quantified data on different scales.</div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s2" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><b>2. </b><b>The study area and data set descriptions</b></span></div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s2.1" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><i>2.1. Regional scale: the Lake Victoria drainage basin</i></span></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Lake Victoria is located in East Africa, southwest of Africa's horn (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig1" style="color: #006eb2; font-weight: bold; text-decoration: none;">1</a>), from 31°39 'E to 34°53 'E longitude and 0°20 'N to 3°00 'S latitude. The lake is close to rectangular in shape with an area of around 67 000 km<sup style="bottom: 1ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">2</sup>. The shoreline of the lake is divided between Uganda, Kenya and Tanzania. The water surface level is typically 1140 m above sea level and the lake has a mean depth of 40 m with a maximum depth of around 80–90 m. The LVDB has a land area of about 194 000 km<sup style="bottom: 1ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">2</sup> (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib25" style="color: #006eb2; font-weight: bold; text-decoration: none;">Tate <i>et al</i> 2004</a>) and is inhabited by one of the densest and poorest rural populations of the world (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib29" style="color: #006eb2; font-weight: bold; text-decoration: none;">UNESCO 2006</a>), where many are subsistence farmers depending on rain-fed agriculture (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib2" style="color: #006eb2; font-weight: bold; text-decoration: none;">Anyah <i>et al</i> 2008</a>).</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">The climate in LVDB can be classified as equatorial with hot and humid conditions where the main climate drivers are easterly monsoons and the bimodal passing of the inter-tropical convergence zone (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib1" style="color: #006eb2; font-weight: bold; text-decoration: none;">Anyah and Semazzi 2007</a>). Mean annual precipitation is 1780 mm and mean annual evapotranspiration is 1537 mm (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib15" style="color: #006eb2; font-weight: bold; text-decoration: none;">Nicholson <i>et al</i> 2000</a>). Rainfall occurs mainly during two periods: the long rains in March, April and May; and the short rains in September, October and November. Severe droughts occur approximately every 3–4 years during the short rains, every 7–8 years during the hot dry season (December, January, and February), and every 5–8 years during the long rainy season (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib3" style="color: #006eb2; font-weight: bold; text-decoration: none;">Awange <i>et al</i> 2008</a>). Lake Victoria is mainly rain-fed with direct precipitation accounting for approximately 80% of the water inflow to the lake (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib22" style="color: #006eb2; font-weight: bold; text-decoration: none;">Sutcliffe and Petersen 2007</a>), and about 10% coming from five main tributaries, with the Kagera River being the main contributor. The remaining 10% comes from various small tributaries. The only significant outlet is the White Nile (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib21" style="color: #006eb2; font-weight: bold; text-decoration: none;">Song <i>et al</i> 2004</a>), where the outlet is regulated near Jinja pass (0°25 '21 ' 'N, 33°11 '45 ' 'E). Since 1954, discharge and lake levels have been regulated by the Nalubaale dam (formerly known as the Owen Falls dam).</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Data series of temperature and precipitation values at the regional scale of the LVDB were compiled from the spatially distributed CRU TS 2.1 Global Climate Data Set (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib13" style="color: #006eb2; font-weight: bold; text-decoration: none;">Mitchell and Jones 2005</a>). Temperature and precipitation data were available for monthly time steps from 1901 to 2002. The spatial extent of LVDB was delineated in ArcGIS 9.3<sup style="bottom: 1ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">®</sup> using the hydrology toolbox and the SRTM 90 digital terrain model (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib7" style="color: #006eb2; font-weight: bold; text-decoration: none;">Jarvis <i>et al</i> 2008</a>). Regional scale, basin averages of the annual time series of spatially distributed temperature and precipitation data were calculated for the entire LVDB. The temperature time series was then used to estimate annual actual evapotranspiration from the LVDB area (see the supplementary data available at <a href="http://stacks.iop.org/ERL/5/034005/mmedia" style="color: #006eb2; font-weight: bold; text-decoration: none;">stacks.iop.org/ERL/5/034005/mmedia</a>). Annual discharge data for Lake Victoria at Jinja pass were obtained from the Global hydro-climatic data network data set (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib6" style="color: #006eb2; font-weight: bold; text-decoration: none;">Dettinger and Diaz 2000</a>).</div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s2.2" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><i>2.2. Local scale: Orongo village</i></span></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Orongo village is located near the coast of Lake Victoria within Kenyan territory (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig1" style="color: #006eb2; font-weight: bold; text-decoration: none;">1</a>). It is located east of the Winam Gulf and 6 km southeast of Kisumu, the third largest city in Kenya. Orongo village is characterized by pastures, homesteads and subsistence farming. The village has about 3000 inhabitants and an effective population density of 600 people per km<sup style="bottom: 1ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">2</sup> (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib8" style="color: #006eb2; font-weight: bold; text-decoration: none;">Levicki 2005</a>). Two rivers flank Orongo village: Luanda River in the southeast and Nyamasaria River in the northwest. These rivers have their origin in the Nandi Escarpments which serve as the main recharge area for the region, having elevations up to approximately 1900 m. The lower parts of this region make up a part of the Kano Plains. Elevation in this lower section, a characteristically lowland floodplain with flat topography and minimal slope, ranges between 1140 and 1300 m. The principal soil types in the Kano Plains are histosols and vertisols (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib17" style="color: #006eb2; font-weight: bold; text-decoration: none;">Onyango <i>et al</i> 2005</a>). The land cover in this area is dominated by marshlands and subsistence agriculture (with maize and millet as the main crops).</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Water Resources Management Affairs, Kenya (WRMA), have conducted stream flow observations approximately 30 km northeast from Orongo village. This neighbouring watershed, called the Little Oroba watershed, is the closest reliable stream gauge for Orongo village. The outlet of the 54 km<sup style="bottom: 1ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">2</sup> Little Oroba watershed is located at 34°58 '15 ' 'E, 0°01 '40 ' 'N. Continuous stream flow data are available for daily intervals from 1932 to 1999. These observations were used to calculate a time series of the local scale average annual stream flow from 1932 to 1999. In addition, daily observations of pan evaporation and precipitation measurements are made near Kisumu by WRMA. Pan evaporation data were used to estimate actual evapotranspiration at this local scale (see the supplementary data available at <a href="http://stacks.iop.org/ERL/5/034005/mmedia" style="color: #006eb2; font-weight: bold; text-decoration: none;">stacks.iop.org/ERL/5/034005/mmedia</a>). These time series were averaged to obtain average annual time series of evapotranspiration and precipitation over the periods of record. Note that the temperature data are collected by Kenya meteorological department at Kisumu, but that this data set was not available for consideration in this study.</div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s3" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><b>3. </b><b>Methods</b></span></div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s3.1" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><i>3.1. Hydro-climatic trend analysis</i></span></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Simple linear regression was used to analyse the trends in the time series of hydro-climatic data collected at both the local scale and the regional scale. These data include observed precipitation and river discharge, and estimated actual evapotranspiration, which in turn depends on temperature, based on two different methods for the local scale and the regional scale assessments (see the supplementary data available at <a href="http://stacks.iop.org/ERL/5/034005/mmedia" style="color: #006eb2; font-weight: bold; text-decoration: none;">stacks.iop.org/ERL/5/034005/mmedia</a>).</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">To allow for direct comparison between the different time series, linear regressions were applied to all the data and time series for the period 1968–1995. During this period, all hydro-climatic data have overlapping observation records at both the local scale and the regional scale. The present analysis thus facilitates a direct trend comparison between the local scale and the regional scale hydro-climatic observations and calculations.</div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s3.2" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><i>3.2. Use of trend analysis for water management</i></span></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">In order to exemplify the trend analysis use for concrete water management purposes, we estimated the minimum water storage requirement for an average farmer in the region using both regional scale and local scale data. Minimum storage requirement is defined here as the crop water required under standard climatic conditions. The method used to estimate minimum storage requirement was a sequent peak algorithm (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib4" style="color: #006eb2; font-weight: bold; text-decoration: none;">Bouver 1978</a>). The sequent peak algorithm is a graphical method based on the cumulative sum of precipitation surplus (PS) defined as inflow minus outflow and demand. Assuming that inflow is due primarily to direct precipitation, outflow is the water lost due to evaporation, and demand is the water transpired by crops (i.e., losses due to leakage and irrigation inefficiency are assumed relatively small and negligible), the cumulative sum of precipitation surplus PS can be estimated as</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866eqn1" style="color: #006eb2; font-weight: bold; text-decoration: none;"><img alt="Equation (1)" src="http://ej.iop.org/images/1748-9326/5/3/034005/Full/erl358866eqn1.gif" style="border-bottom-style: none; border-color: initial; border-left-style: none; border-right-style: none; border-top-style: none; border-width: initial;" /></a></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">where <i>P</i> is precipitation and <i>ET</i><sub style="height: 0px; line-height: 1; position: relative; top: 0.5ex; vertical-align: baseline;">a</sub> is the actual evapotranspiration (evaporation plus transpiration by crops) for each time step <i>t</i> over a record of observation that is <i>n</i> time steps in length. Note that as the demand and outflow may be larger than the inflow, <i>P</i> – <i>ET</i><sub style="height: 0px; line-height: 1; position: relative; top: 0.5ex; vertical-align: baseline;">a</sub> may be negative.</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">The sequent peak algorithm is applied to create a time series of cumulative PS. By plotting such a time series, the first peak and the following sequent peak that is higher than the first peak can be identified. The difference between the first-peak value and the minimum value before the sequent peak in time is the water storage requirement for that particular period. This procedure is carried out for the whole record of data at all peaks, and the largest difference found is then the minimum storage required to ensure sufficient water availability. While fairly basic, the sequent peak algorithm provides at least a first-order estimate of water storage requirements, which is compared here between the different scale data for the example of the average farmer of the Orongo village of the Kisumu district.</div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s4" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><b>4. </b><b>Results</b></span></div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s4.1" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><i>4.1. Hydro-climatic trends</i></span></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Considering the precipitation data at the regional scale (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig2" style="color: #006eb2; font-weight: bold; text-decoration: none;">2</a>(A)) and local scale (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig2" style="color: #006eb2; font-weight: bold; text-decoration: none;">2</a>(B)), neither time series indicates any significant linear trend for the period 1968–1995. If the entire record of data available at both spatial scales is considered, this result holds and neither time series indicates any significant linear trends. Similar to precipitation records, estimated actual evapotranspiration at the regional scale (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig2" style="color: #006eb2; font-weight: bold; text-decoration: none;">2</a>(C)) and that at the local scale (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig2" style="color: #006eb2; font-weight: bold; text-decoration: none;">2</a>(D)) show no significant linear trend during the period 1968–1995. Again this lack of significant linear trend holds when considering the entire length of record at both scales.</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866fig2" style="color: #006eb2; font-weight: bold; text-decoration: none;"><img alt="Figure 2" src="http://ej.iop.org/images/1748-9326/5/3/034005/Full/5886602.jpg" style="border-bottom-style: none; border-color: initial; border-left-style: none; border-right-style: none; border-top-style: none; border-width: initial;" /></a></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"></div><table bgcolor="#ffffcc" style="font-size: 1.2em; line-height: 1.35em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;"><tbody>
<tr><td align="left" style="padding-bottom: 10px; padding-left: 8px; padding-right: 8px; padding-top: 10px;"><strong>Figure 2.</strong> Time series of annual regional scale precipitation (A), actual evapotranspiration (C), and discharge (E) data, and local scale precipitation (B), actual evapotranspiration (D), and discharge (F) data considered in this study. Trend lines shown are fitted for the period 1968–1995, over which all hydro-climatic data are available at both spatial scales.</td></tr>
</tbody></table><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">With regard to regional discharge, however, there is a significant (<i>p</i> < 0.05) negative linear trend over the period 1968–1995, following a period of increasing discharge at the outlet of Lake Victoria from 1959 to 1964 (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig2" style="color: #006eb2; font-weight: bold; text-decoration: none;">2</a>E). In 1964 the discharge peaks and shifts to the significant negative trend. This shift excludes the application of a meaningful single linear regression analysis over the entire period of discharge observation. These results are consistent with previous studies of Lake Victoria's lake levels, showing a water level increase that peaks in the early 1960s (see e.g. <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib19" style="color: #006eb2; font-weight: bold; text-decoration: none;">Piper <i>et al</i> 1986</a>, <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib12" style="color: #006eb2; font-weight: bold; text-decoration: none;">Mistry & Conway 2003</a>) and then a decrease through to 2005 (see e.g., <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib11" style="color: #006eb2; font-weight: bold; text-decoration: none;">Mangeni 2006</a>, <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib3" style="color: #006eb2; font-weight: bold; text-decoration: none;">Awange <i>et al</i> 2008</a>).</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">Furthermore, while the regional scale discharge data show a significant negative linear trend from 1968 to 1995, the local scale discharge data (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig2" style="color: #006eb2; font-weight: bold; text-decoration: none;">2</a>(F)) at the Little Oroba gauging station indicate a significant (<i>p</i> < 0.05) positive linear trend in discharge during the 1968–1995 period. This trend is also seen when considering the entire length of record.<br />
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</div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s4.2" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><i>4.2. Water storage requirements</i></span></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">The largest water deficit estimate using the sequent peak algorithm based on the regional scale data occurs during the period 1999–2001 (figure <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866fig3" style="color: #006eb2; font-weight: bold; text-decoration: none;">3</a>). From this deficit, the estimated minimum storage requirement for an average farmer in the region is 205 mm. Using local scale data within the sequent peak algorithm, the largest water deficit occurs during the period 1989–1994, with a minimum storage requirement of 592 mm. That is, an estimated water storage requirement based on local scale data nearly three times as large as that based on regional scale data.</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866fig3" style="color: #006eb2; font-weight: bold; text-decoration: none;"><img alt="Figure 3" src="http://ej.iop.org/images/1748-9326/5/3/034005/Full/5886603.jpg" style="border-bottom-style: none; border-color: initial; border-left-style: none; border-right-style: none; border-top-style: none; border-width: initial;" /></a></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"></div><table bgcolor="#ffffcc" style="font-size: 1.2em; line-height: 1.35em; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;"><tbody>
<tr><td align="left" style="padding-bottom: 10px; padding-left: 8px; padding-right: 8px; padding-top: 10px;"><strong>Figure 3.</strong> Results from the sequent peak algorithm using an annual time step. The difference between the two sets of paired dashed lines shows the difference in estimated storage requirement based on regional scale and local scale data.</td></tr>
</tbody></table><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">These minimum storage assessments can further be used to estimate the number of irrigation ponds needed to meet the storage requirements of the average farmer in the Orongo village. For example, Engineers Without Borders assumes that a typical irrigation pond in this region should have the dimensions of 15 m × 20 m × 2 m or about 600 m<sup style="bottom: 1ex; height: 0px; line-height: 1; position: relative; vertical-align: baseline;">3</sup> of storage (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib9" style="color: #006eb2; font-weight: bold; text-decoration: none;">Levicki 2009</a>). Using this design recommendation, the regional scale estimate of minimum storage translates into a requirement of about two irrigation ponds per acre of agricultural land. Using the local scale data, however, four irrigation ponds per acre of agricultural land are needed. There is, thus, a large influence of the choice of spatial hydro-climatic data resolution on the practical water resource management and planning for the example of Orongo village in the Kisumu district.<br />
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</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">The large difference in estimated storage requirements may be partly due to the use of two different methods for estimating actual evapotranspiration at the local scale and the regional scale (see the supplementary data available at<a href="http://stacks.iop.org/ERL/5/034005/mmedia" style="color: #006eb2; font-weight: bold; text-decoration: none;">stacks.iop.org/ERL/5/034005/mmedia</a>). The use of different methods, however, is not an independent choice, but a necessity due to differences in data resolution and availability at the two scales. It is often the case that available data dictate which methods can be used to determine unobserved hydro-climatic parameters such as evapotranspiration for use in estimates of water storage requirements.</div><a href="http://www.blogger.com/post-create.g?blogID=7698039939158013969" name="erl358866s5" style="color: #006eb2; font-weight: bold; text-decoration: none;"></a><br />
<div style="font-size: 1.2em; line-height: 1.35em; width: 61em;"><span class="sanserif"><b>5. </b><b>Discussion and conclusion</b></span></div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">There is clear disparity between discharge observations at the regional and local scales considered in this study, leading to different hydrological trend assessments based on the data from the different scales. The present results further exemplify and quantify how this disparity leads to large differences in the essential parameter of water storage requirement for provision of reliable and sustained water resources.</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">The inherent influence of data resolution and scale on the choices of quantification methods for water resource management assessments, as discussed above for the evapotranspiration quantification, is not often considered. This is probably because real-world water resource managers must often make decisions regardless of data availability limitations. Still, it is important to consider the effects of these limitations and associated implicit assumptions and generalizations, when managers are confronted with serious water management and climate-adaptation problems. These effects may be significant for resulting decisions and designs of water resource management options, particularly in hydro-climatically sensitive regions.</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">In the present results, however, we have also seen one important consistent aspect of regional scale and local scale discharge data implications: during the period of significant trends in inter-annual hydrological discharge (even though the trends are opposite on the different data scales), there are no significant trends evident in the climate variables precipitation and evapotranspiration, with the latter in turn depending on temperature. This aspect indicates that neither the regional nor the local trends in the inter-annual discharge changes are currently climate driven. Rather, the current observed discharge trends are most probably connected to local and regional water use and land use changes. This is consistent with the major land use changes, such as deforestation and agricultural expansion, and population growth observed in Lake Victoria drainage basin (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib16" style="color: #006eb2; font-weight: bold; text-decoration: none;">Odada <i>et al</i> 2009</a>, <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib10" style="color: #006eb2; font-weight: bold; text-decoration: none;">Lung and Schaab 2010</a>). This development is not homogeneous within the drainage basin and is mainly seen along rivers and in coastal areas (agricultural expansion and population growth) and in the tropical forest (deforestation). This supports the disconnection between climate trends and discharge trends due to local and regional water use and land use changes.<br />
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</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">For example, the recent negative regional discharge trend may be an effect of water regulation and management practices at the Nalubaale dam. Direct quantification of the effects of dams and other local/regional water management practices are outside the scope of the present study. However, such effects have been investigated in detail and led to similar conclusions for other hydro-climatically sensitive parts of the world, such as the Central Asian region of the Aral Sea drainage basin (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib20" style="color: #006eb2; font-weight: bold; text-decoration: none;">Shibuo <i>et al</i> 2007</a>). In addition, locally driven changes in discharge, in the absence of observable changes in climatic variables, have also been observed in other hydrological catchments in eastern Africa, for instance in Ethiopia (<a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext#erl358866bib5" style="color: #006eb2; font-weight: bold; text-decoration: none;">Collick <i>et al</i> 2009</a>).</div><div style="font-size: 1.2em; line-height: 1.35em; width: 61em;">While the current climatic trends show little direct influence on discharge trends (regardless of data resolution and scale), there is potential for future climate change to influence water availability in this region. Relevant identification of such large scale climate change effects must then be based on realistic assessments also of the water cycling effects of local/regional water use and land use, in hydrological catchments of scales that are consistent with the specific water management problems and decisions.<br />
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Link to rest of paper: <a href="http://iopscience.iop.org/1748-9326/5/3/034005/fulltext">http://iopscience.iop.org/1748-9326/5/3/034005/fulltext</a></div></div>Tenney Naumerhttp://www.blogger.com/profile/11843130378338023902noreply@blogger.com0