Policy brief: Climate trend and global crop production since 1980

Global warming is likely already taking a toll on world wheat and corn production, according to a new study led by Stanford University researchers. But the United States, Canada and northern Mexico have largely escaped the trend.

"It appears as if farmers in North America got a pass on the first round of global warming," said David Lobell, an assistant professor of environmental Earth system science and center fellow at the Program on Food Security and the Environment at Stanford University. "That was surprising, given how fast we see weather has been changing in agricultural areas around the world as a whole."

Lobell and his colleagues examined temperature and precipitation records since 1980 for major crop-growing countries in the places and times of year when crops are grown. They then used crop models to estimate what worldwide crop yields would have been had temperature and precipitation had typical fluctuations around 1980 levels.

The researchers found that global wheat production was 5.5 percent lower than it would have been had the climate remained stable, and global corn production was lower by almost 4 percent. Global rice and soybean production were not significantly affected.

The United States, which is the world's largest producer of soybeans and corn, accounting for roughly 40 percent of global production, experienced a very slight cooling trend and no significant production impacts.

Outside of North America, most major producing countries were found to have experienced some decline in wheat and corn (or maize) yields related to the rise in global temperature. "Yields in most countries are still going up, but not as fast as we estimate they would be without climate trends," Lobell said.

Lobell is the lead author of the paper, Climate Trends and Global Crop Production Since 1980, published May 5 online in Science Express.

Russia, India and France suffered the greatest drops in wheat production relative to what might have been with no global warming. The largest comparative losses in corn production were seen in China and Brazil.

Total worldwide relative losses of the two crops equal the annual production of corn in Mexico and wheat in France. Together, the four crops in the study constitute approximately 75 percent of the calories that humans worldwide consume, directly or indirectly through livestock, according to research cited in the study.

"Given the relatively small temperature trends in the U.S. Corn Belt, it shouldn't be surprising if complacency or even skepticism about global warming has set in, but this study suggests that would be misguided," Lobell said.

Since 1950, the average global temperature has increased at a rate of roughly 0.13 degrees Celsius per decade. But over the next two to three decades average global temperature is expected to rise approximately 50 percent faster than that, according to the report of the Intergovernmental Panel on Climate Change. With that rate of temperature change, it is unlikely that the crop-growing regions of the United States will continue to escape the rising temperatures, Lobell said.

"The climate science is still unclear about why summers in the Corn Belt haven't been warming. But most explanations suggest that warming in the future is just as likely there as elsewhere in the world," Lobell said.

"In other words, farmers in the Corn Belt seem to have been lucky so far."

This is the first study to come up with a global estimate for the past 30 years of what has been happening, Lobell said.

To develop their estimates, the researchers used publicly available global data sets from the United Nations Food and Agriculture Organization and from the University of Delaware, University of Wisconsin, and McGill University.

The researchers also estimated the economic effects of the changes in crop yield using models of commodity markets.

"We found that since 1980, the effects of climate change on crop yields have caused an increase of approximately 20 percent in global market prices," said Wolfram Schlenker, an economist at Columbia University and a coauthor of the paper in Science.

He said if the beneficial effects of higher carbon dioxide levels on crop growth are factored into the calculation, the increase drops down to 5 percent.

"Five percent sounds small until you realize that at current prices world production of these four crops are together worth nearly $1 trillion per year," Schlenker said. "So a price increase of 5 percent implies roughly $50 billion per year more spent on food."

Rising commodity prices have so far benefited American farmers, Lobell and Schlenker said, because they haven't suffered the relative declines in crop yield that the rest of the world has been experiencing.

"It will be interesting to see what happens over the next decade in North America," Lobell said. "But to me the key message is not necessarily the specifics of each country. I think the real take-home message is that climate change is not just about the future, but that it is affecting agriculture now. Accordingly, efforts to adapt agriculture such as by developing more heat- and drought-tolerant crops will have big payoffs, even today. "

Justin Costa-Roberts, an undergraduate student at Stanford, is also a coauthor of the Science paper. David Lobell is a researcher in Stanford's Program on Food Security and the Environment, a joint program of Stanford's Woods Institute for the Environment and Freeman Spogli Institute for International Studies. Schlenker is an assistant professor at the School of International and Public Affairs and at the Department of Economics at Columbia.

The work was supported by a grant from the Rockefeller Foundation.

Sugarcane - a principal crop for biofuel - reduces the local air temperature compared to pasturelands or fields growing soybeans or maize, according to a new study from researchers at Stanford University and the Carnegie Institution for Science. But sugarcane's effect on temperature is a "double-edged machete," as it increases ambient temperatures compared with natural vegetation.

These small local changes should be taken into consideration in studies of global climate change, the researchers said.

The researchers looked at changes in vegetation in the Brazilian Cerrado - a vast tropical savanna lying south of the Amazon basin - large areas of which have been converted from natural vegetation to agriculture in recent decades.

Increasingly, these existing agricultural areas are now being converted to sugarcane for use in biofuel production. Brazil is now second only to the United States in ethanol production, much of which is used domestically.

What the effect on global climate would be if sugarcane farming were to expand significantly is not yet clear, said David Lobell, an assistant professor in environmental Earth system science at Stanford and center fellow at the Program on Food Security and the Environment.

"The temperature changes are happening locally, where the land-use change is happening," Lobell said. "It does not seem to spill over into other countries, for example, at least as far as we can tell right now."

But Lobell said sugarcane growing in the Cerrado is definitely expanding and given that the region encompasses approximately 1.9 million square kilometers (733,000 square miles) - an area larger than Alaska - the potential exists for a globally significant effect.

Using maps and data from hundreds of satellite images, the researchers calculated the temperature, the amount of water given off and how much light was reflected rather than absorbed for each of the different types of vegetation. They found that compared to land cultivated with other annual crops, sugarcane reduced the local air temperature by an average of 0.93 degrees Celsius (1.67 F).

But compared to the natural vegetation of the Cerrado - mainly grass and shrubs - the sugarcane fields warmed the ambient air by 1.55 C (2.79 F).

Lobell said the bulk of the temperature difference is due to evapotranspiration - the moisture released to the air through the leaves of the plants and the soil. Most of the land put into sugarcane had previously been converted from natural vegetation to pastureland, said Scott Loarie, a postdoctoral researcher at Carnegie. "If someone has a farm that once was natural vegetation, that transition to pasture and annual crops caused local warming," he said. "So now as the farm is going to sugarcane, by comparison it is cooling temperatures locally."

Their research, Direct Impacts on Local Climate of Sugarcane Expansion in Brazil, is described in the current issue of Nature Climate Change.

This local cooling does not necessarily mean that the global climate is cooling as a result. It depends in part on what happens with the agriculture that was displaced by the sugarcane, Loarie said. For example, if cattle used to graze on a tract of land and some Amazon forest is cut down to provide new pasture for them, net carbon emissions will actually increase.

"You might not make any difference as far as cooling the world globally at all; in fact, you might make the world marginally warmer," he said.

"The global implications of these local effects were not a part of this study, and any discussion of mitigating global climate should consider the potential for these land use cascades."

One of the important aspects of the study, Lobell said, is that it demonstrates how satellite data can be used in real time to understand the effects of environmental changes. Most research studying the impact of biofuel use on climate has been done with computer modeling.

"I think the coolest thing about this study is you actually can see these temperature effects happening already," Lobell said. "In terms of the more general point about bio energy, I think it is another good example of why looking only at greenhouse gases is not the full picture."

Another takeaway from the study, Loarie said, is that the temperature findings support the existing rule of thumb that biofuel crops are best located on land that is already used for agriculture. That general guideline stems from the fact that there is less carbon released to the atmosphere by converting land where the existing vegetation contains low amounts of carbon, such as pasture or crops, than by cutting down the dense, carbon-rich forests in the Amazon.

Loarie said that while the study clearly showed that planting sugarcane moves the temperature closer to what it would have been if the natural vegetation had not been removed from the land, that doesn't mean the land is any closer to its natural state in other respects.

"Converting pasture to sugarcane is definitely not ecological restoration," said Chris Field, a professor of biology and of environmental Earth system science, who was involved in the research.

"Still, the direct effect on climate is potentially important enough to play a role in future decisions about land use and land management in large parts of the tropics," he said.

The study was funded by the Stanford University Global Climate and Energy Project.

Greg Asner, a professor, by courtesy, of environmental Earth system science, is a coauthor of the paper. Lobell is also a center fellow at both the Freeman Spogli Institute for International Studies and the Woods Institute for the Environment. Field is also a senior fellow at the Precourt Institute for Energy and at the Woods Institute, and director of the Department of Global Ecology at the Carnegie Institution.

To begin his talk, Archon Fung poses the following question: why is there no "killer" ICT platform in politics? After all, there are highly disruptive platforms in social media, commerce and other realms. These so-called "killer" platforms tend to be characterized by three features: notably that many users adopt the ICT platform and abandon the old way of doing something; the new platform improves users' experience by changing how they do some activity; and the organizations using new killer platforms displace those that do not use them.

Fung proceeds to present explanations for this puzzle, following a brief clarification of the scope of his question. When Fung refers to politics, he is not referring to aspects like partisan mobilization, e-government or the public sphere; instead, he examines the potential for ICT platforms in the realms of decision-making, problem solving and accountability. While the typical level of resolution for discussion is on the macro effects of ICT as a social force, Fung's analysis stems from his narrowing in on ICT platforms (such as Facebook, Wikipedia, Ushahidi, and others) themselves.

The first argument Fung presents in answer to his initial question is that both the suppliers and the demanders are different in politics than in other areas (e.g. commerce). Politics is aggregative, characterized by collective action and results, not focused on "individual benefits and gratification" like commerce and social interaction might be.

Second, while it is possible to have parallel, collaborative production in some types of platforms (e.g. Wikipedia), production in politics is characterized by strategic action. Various examples can help illustrate that there are key differences between commerce and politics on the supply side. In commerce, Amazon's customers want books and Amazon wants to sell books. While citizens want influence in the public sphere, however, politicians and officials typically do not want to give citizens power to influence the public sphere. Although there are counterexamples, as in some cities (such as Belo Horizonte) in Brazil, where 10% of the electorate directly influences public spending online through the Participatory Budgeting process, these cases are few and far between.

Another important factor is that there are much more ambiguous benefits in politics than in other spheres. While it is well understood that amassing more Facebook, Amazon or Google users will result in more money or fame, it is less well know what the benefits of more public deliberation or accountability might be. Since the factors that explain platform success in other areas don't translate to politics, Fung concludes, there is less innovation in the supply side.

In order to understand cases in which ICT platforms have nevertheless become important on the local level, Fung and his colleagues carried out a large case study analysis of specific examples from Brazil, Chile, Kenya, India, and Slovakia. Through analyzing these cases, which include such examples as São Paolo's Cidade Democrática, Santiago's Reclamos, Nairobi's Budget Tracking Tool and others, the researchers arrive at three key conclusions.

1. ICT platforms that have had success within the realm of politics that Fung is interested in have been characterized by the predominance of professionals and organizations among their users. The main users of Cidade Democratica, for example, are organizations and professionals.
2. Second, ICTs do not necessarily act independently. Instead, journalism and media play an important role, and even make up the main base of users for platforms like Bratislava's Fair Play Alliance and Mumbai Votes. After all, ICT can help journalists reduce research costs and represents a neutral and credible source.
3. ICT's do not go around or undermine traditional NGOs and government. Instead, at least in the cases examined, they are typically effective because they operate through these existing organizations. Kiirti in Bangalore is one example.

The bottom line from Fung's case study analysis is that getting context right can be more important for an ICT platform's success than getting the technology right. Typically, the uptake of a platform only occurs once all other pieces are in place.

In the final part of his talk, Fung addressed audience questions, many of which related to Fung's chosen standards for a killer platform. One audience member asked why Facebook could not be considered a killer platform, given its many uses for political purposes. After all, Facebook enables a kind of action to occur that would have occurred before, since it can often be accessed even in countries where public gatherings may be restricted. Another questioned why Wikileaks was not considered a killer platform. Fung replied that while Wikileaks does bring together people and information better, a killer platform would need to transform the nature of politics from group to individuals, which no existing platform has yet achieved.

A hidden trove of historical crop yield data from Africa shows that corn - long believed to tolerate hot temperatures - is a likely victim of global warming.

Stanford agricultural scientist David Lobell and researchers at the International Maize and Wheat Improvement Center (CIMMYT) report in the inaugural issue of Nature Climate Change next week that a clear negative effect of warming on maize - or corn - production was evident in experimental crop trial data conducted in Africa by the organization and its partners from 1999 to 2007.

Led by Lobell, the researchers combined data from 20,000 trials in sub-Saharan Africa with weather data recorded at stations scattered across the region. They found that a temperature rise of a single degree Celsius would cause yield losses for 65 percent of the present maize-growing region in Africa - provided the crops received the optimal amount of rainfall. Under drought conditions, the entire maize-growing region would suffer yield losses, with more than 75 percent of areas predicted to decline by at least 20 percent for 1 degree Celsius of warming.

"The pronounced effect of heat on maize was surprising because we assumed maize to be among the more heat-tolerant crops," said Marianne Banziger, co-author of the study and deputy director general for research at CIMMYT."

"Essentially, the longer a maize crop is exposed to temperatures above 30 C, or 86 F, the more the yield declines," she said. "The effect is even larger if drought and heat come together, which is expected to happen more frequently with climate change in Africa, Asia or Central America, and will pose an added challenge to meeting the increasing demand for staple crops on our planet."

Similar sources of information elsewhere in the developing world could improve crop forecasting for other vast regions where data has been lacking, according to Lobell, who is lead author of the paper describing the study.

"Projections of climate change impacts on food production have been hampered by not knowing exactly how crops fair when it gets hot," Lobell said. "This study helps to clear that issue up, at least for one important crop."

While the crop trials have been run for many years throughout Africa, to identify promising varieties for release to farmers, nobody had previously examined the weather at the trial sites and studied the effect of weather on the yields, said Lobell, who is an assistant professor of environmental earth system science and fellow at Stanford's Program on Food Security and the Environment.

"These trials were organized for completely different purposes than studying the effect of climate change on the crops," he said. "They had a much shorter term goal, which was to get the overall best-performing strains into the hands of farmers growing maize under a broad range of conditions."

The data recorded at the yield testing sites did not include weather information. Instead, the researchers used data gathered from weather stations all over sub-Saharan Africa. Although the stations were operated by different organizations, all data collection was organized by the World Meteorological Organization, so the methods used were consistent.

Lobell then took the available weather data and interpolated between recording stations to infer what the weather would have been like at the test sites. By merging the weather and crop data, the researchers could examine climate impacts.

"It was like sending two friends on a blind date - we weren't sure how it would go, but they really hit it off," Lobell said.

Previously, most research on climate change impacts on agriculture has had to rely on crop data from studies in the temperate regions of North America and Europe, which has been a problem.

"When you take a model that has been developed with data from one kind of environment, such as a temperate climate, and apply it to the rest of the world, there are lots of things that can go wrong" Lobell said, noting that much of the developing world lies in tropical or subtropical climates.

But he said many of the larger countries in the developing world, such as India, China and Brazil, which encompass a wide range of climates, are running yield testing programs that could be a source of comparable data. Private agribusiness companies are also increasingly doing crop testing in the tropics.

"We're hoping that with this clear demonstration of the value of this kind of data for assessing climate impacts on crops that others will either share or take a closer look themselves at their data for various crops," Lobell said.

"I think we may just be scratching the surface of what can be achieved by combining existing knowledge and data from the climate and agriculture communities. Hopefully this will help catalyze some more effort in this area."

Lobell is a Center Fellow at the Program on Food Security and the Environment, a joint program of Stanford's Woods Institute for the Environment and Freeman Spogli Institute for International Studies.

The work was funded by the Rockefeller Foundation

President Obama's vision of a "world free of nuclear weapons" -- first enunciated in Prague in April 2009 -- has been derided by his critics as a utopian fantasy that will have no influence on the nuclear strategies of other nations.

But in a special issue of The Nonproliferation Review, entitled Arms, Disarmament, and Influence: International Responses to the 2010 Nuclear Posture Review, 13 prominent researchers from around the world examined foreign governments' policy responses to Obama's 2010 Nuclear Posture Review (NPR), the landmark document published a year and a day after his Prague speech.

They found that many nations, though not all, had been "strongly influenced by Washington's post-Prague policy and nuclear posture developments," which reduced the role of nuclear weapons in U.S. national strategy, and assured non-nuclear nations that the U.S. would never use nuclear arms against them provided they remained in compliance with their obligations under the Nuclear Non-Proliferation Treaty.

Indeed, the 11 case studies presented "demonstrate that U.S. pronouncements and actions influenced bureaucratic infighting and domestic debates inside a number of important foreign governments, and that some of these governments have adjusted their own policies and actions accordingly."

Read the full report here.

See a presentation about the report here, or listen to a different one here.

Read CISAC co-director Scott Sagan's essay on "Obama's Disarming Influence" in the Bulletin of the Atomic Scientists.  

Read Thomas Fingar's essay on "How China Views U.S. Policy" in the Bulletin of the Atomic Scientists. 

Highlights:

* Russia adopted a nuclear doctrine that was considerably more moderated than it would have been had the United States not pushed ahead with its own policy changes. In the run up to the April 2010 publication of the NPR, Washington "reset" relations with Russia, ended the deployment of missile defense components in Poland and the Czech Republic, and resumed the disarmament negotiations that ultimately led to the ratification of the New START treaty. As a result of this process, and continuous consultation with Russia about the NPR, Moscow narrowed the role of nuclear weapons in its policy and the range of circumstances in which it would consider using them. (page 39)

* "The most important short-term success of Obama's nuclear weapons policy," along with the "Prague Spirit," has been to halt the erosion of the NPT. "Obama's policies helped extract a minimum positive result from the 2010 NPT Review Conference, a favorable outcome compared to the chaos that his predecessor's representatives had created at the 2005 conference." The Obama policy was welcomed as a positive development, which allowed "key players, such as Egypt and Brazil, to strive for compromise, and others, such as Russia and China, not to block it." (page 219)

* The U.S. effort to encourage other governments to reduce the role of nuclear weapons in their policy was successful in the United Kingdom, which adopted a nuclear posture that was very similar to that to the U.S. (page 238)

* Due in large part to the Obama policy, some of the non-nuclear weapons states in NATO began to push for the removal of sub-strategic nuclear weapons from Europe. At the November 2010 NATO summit, members agreed to a new Strategic Concept that called for negotiations with Russia and a linkage between the reduction and eventual elimination of nuclear weapons in NATO Europe to comparable reductions in western Russia. (page 238)

* Obama's new nuclear doctrine was a driving force behind a May 2010 agreement among 189 nations at the Nonproliferation Review Conference to a set of disarmament objectives and steps to reinforce the nuclear non-proliferation regime. (page 238)

* The Obama disarmament initiatives encouraged Indonesia's decision to begin the process of ratifying the Comprehensive Test Ban Treaty. (page 238)

* China continues to view Washington's nuclear doctrine with suspicion. Although Beijing viewed the 2010 NPR favorably compared to its 2001 predecessor, it still found serious cause for concern. This is partly the result of timing: the NPR came out amid a period of rising tension between U.S. and China. It also reflected a tendency among Chinese leaders to view virtually all U.S. doctrine and actions as part of a concerted effort to constrain its rise. In this view, the NPR would foster comparisons between nuclear decreases in Russia and the U.S., and increases in China, and be used as leverage to force Beijing to engage in an expensive conventional arms race. In keeping with this China-centric view, Chinese officials were also concerned about the U.S. military's continued development of missile defense capabilities. (page 243)

* Many non-nuclear weapons states--such as Egypt, Brazil, and South Africa--emphasize their opposition to any constraints being placed on their right to enjoy the benefits of civilian nuclear energy. Some of their opposition is "due to post-colonial sensitivity about any apparent inequality in the terms of international agreements that divide the world into 'haves' and 'have-nots.'" Others are engaged in bargaining, waiting to see what nuclear-weapons states will do regarding disarmament before offering to accept more constraints on nuclear technology development. Some governments also appear to be engaged in "hedging behavior--protecting their ability to enrich uranium or reprocess plutonium" to be closer to acquiring nuclear weapons in the future, should they choose to do so. This may be disappointing for Washington policymakers, but it should not be surprising. After all, the U.S. employs a similar "hedging strategy" in its management of its own nuclear stockpile. As a result, it is imperative to begin discussions of how to reduce the danger of both kinds of nuclear hedging behavior. (page 255)

* The Obama administration must continue "to ensure there is consistency and discipline in the messages" emanating from the military and the government bureaucracy. Some foreign governments viewed the NPR's guarantees as mere rhetoric. "Such a skeptical view is encouraged whenever a senior US military officer makes statements that reflect a lack of understanding or lack of discipline regarding nuclear use policy." Even after the NPR was released, a top U.S. general insisted that the United States had not altered its "calculated ambiguity" policy. (page 258)

The special issue of the Nonproliferation Review was coordinated by Scott D. Sagan, co-director of the Center for International Security and Cooperation at Stanford University, and Jane Vaynman, a PhD candidate at the Department of Government at Harvard University, and a National Security Studies Fellow at the Weatherhead Center for International Affairs. The journal is published by the James Martin Center for Nonproliferation Studies at the Monterey Institute of International Studies, and it is edited by Stephen Schwartz.

Authors:

Irma Argüello is founder and chair of the NPSGlobal Foundation, a private nonprofit initiative that focuses on improving global security and reducing risks stemming from WMD proliferation.

Ralph A. Cossa is President of the Pacific Forum CSIS in Honolulu. He is senior editor of the Forum's quarterly electronic journal, Comparative Connections. 

Ambassador Nabil Fahmy is the founding Dean of the School of Global Affairs and Public Policy at the American University in Cairo. He is also the Chair of the James Martin Center for Nonproliferation Studies' Middle East Project.

Thomas Fingar is the Oksenberg-Rohlen Distinguished Fellow and Senior Scholar in the Freeman Spogli Institute for International Studies at Stanford University.

Brad Glosserman is Executive Director of the Pacific Forum CSIS in Honolulu. Mr. Glosserman is co-editor of Comparative Connections, the Pacific Forum's quarterly electronic journal, and writes, along with Ralph Cossa, the regional review.

S. Paul Kapur is associate professor in the Department of National Security Affairs at the U.S. Naval Postgraduate School and a faculty affiliate at Stanford University's Center for International Security and Cooperation.

Mustafa Kibaroglu is an Assistant Professor at Bilkent University.

Michael Krepon is the co-founder of the Stimson Center, a Washington-based think tank specializing in national and international security problems. 

Harald Müller is executive director of Peace Research Institute Frankfurt and Professor at International Relations at Goethe University Frankfurt.

Pavel Podvig is an independent analyst based in Geneva, Switzerland, where he manages the research project Russian Nuclear Forces.

Scott D. Sagan is the Caroline S.G. Munro Professor of Political Science, co-director of Stanford's Center for International Security and Cooperation, and a Senior Fellow at the Freeman Spogli Institute. He also serves as the co-chair of the American Academy of Arts and Science's Global Nuclear Future Initiative.

Scott Snyder is Director of the Center for U.S.-Korea Policy at The Asia Foundation, Senior Associate at Pacific Forum CSIS, and Adjunct Senior Fellow for Korean Studies at the Council on Foreign Relations.

Jane Vaynman is a PhD candidate at the Department of Government at Harvard University and a National Security Studies Fellow at the Weatherhead Center for International Affairs.

^{The Center for International Security and Cooperation (CISAC), part of the Freeman Spogli Institute for International Studies (FSI), is an interdisciplinary university-based research and training center addressing some of the world's most difficult security problems with policy-relevant solutions. The Center is committed to scholarly research and to giving independent advice to governments and international organizations.}