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.

Martha Crenshaw has been researching terrorist organizations since the late 1960s. In the wake of the U.S. military’s successful mission against Osama bin Laden, she comments on what happens to Al Qaeda now, and the challenges that remain.

CISAC: What does the death of Osama bin Laden mean for the world?

Crenshaw: The killing of bin Laden brings closure to a pursuit that began well before the 9/11 attacks. The successful raid demonstrated American tenacity as well as a somewhat surprising ability to keep a secret over the past several months as American intelligence agencies zeroed in on bin Laden's fortified compound in Abbottabad. Although most of the world thought he was hiding in the mountainous and inaccessible border regions of Pakistan, sheltered by local tribes, he was actually centrally located in a city not too far from Islamabad. It is often said that terrorism cannot be deterred because terrorists have no return address, but it turned out that bin Laden did. After years of patient intelligence work the U.S. finally found it. 

CISAC: What happens to Al Qaeda now?

Crenshaw: There are differing opinions. One is that bin Laden is a unique figure and that there's no other leader of a terrorist organization that has the kind of aura he has. People who joined Al Qaeda swore personal allegiance to him. He had this kind of bearing, and they respected his personal piety. It's hard to replace a leader like that. At the same time, that part of the organization affiliated with bin Laden is still a major actor. A lot of attacks, like the London bombing, are traced back toward them. A lot of the failed and foiled attacks in the U.S. were traced back there, too, suggesting he played an operational role as well as an inspirational role.

On the other side, even if Al Qaeda disappeared, other affiliates like Al Qaeda in the Arabian Peninsula are still extremely dangerous and capable. They can trade on his reputation and inspire others to join. They might make demands for revenge. There are also those who could replace bin Laden, not so much as an inspirational leader but in terms of operations. The central organization's more visible second in command, Ayman Al-Zawahiri, is free although he will be under intense pressure. There is also a second-tier leadership whose abilities and appeal are largely unknown. Local affiliates such as Al Qaeda in the Arabian Peninsula have often overshadowed AQ central, and in fact AQAP is currently considered to be the most serious threat to US security. 

CISAC: It sounds like there is likely to be jockeying for power.

Crenshaw: There certainly will be. Will Zawahiri necessarily step into the No. 1 role now? Or will he be challenged? It's possible. You can kind of see how little we know and how hard it is for the U.S. to piece it together by how long it has taken to find bin Laden. The U.S. has been looking for him since 1998.

CISAC: Does that make things more or less dangerous?

Crenshaw: There's a theory that the more fragmentation you have, the higher the level of violence. The way you get more resources and support is to be more audacious than your rivals. You could have violence from one faction against another. There's also the idea that you attack your enemy to show how dangerous you really are. Nobody wants to be seen as weak, so they feel that they have to do what the other side is doing. 

More: An interview with Fundación para las Relaciones Internacionales y el Diálogo Exterior, a European think tank based in Madrid. 

CISAC's Nuclear Security Fellow, Gaurav Kampani, discusses the question of nuclear stability in South Asia.

Twenty-eight rising leaders from emerging democracies around the world have been named to the 2011 class of Draper Hills Summer Fellows on Democracy and Development at CDDRL.

This group represents the seventh class of Draper Hills Summer Fellows and is composed of democracy activists, development practitioners, academics, policymakers, journalists, and entrepreneurs representing societies where democracy is most threatened. The finalists were selected from a competitive pool of over 200 applicants and represent a dynamic cohort of mid-career professionals who are committed to improving or establishing democratic governance, economic growth, and rule of law in their home countries.

The program is funded by generous support from Bill and Phyllis Draper and Ingrid von Mangoldt Hills.

Some interesting statistics to illustrate the diverse nature of this class are as follows; 50 are women, the average age is 37 years, almost half hold graduate degrees, and Africa and the Middle East represent the largest geographical proportion of the incoming class.

Together, the Draper Hills Summer Fellows are helping to accelerate social and political change by developing multiparty democracy in Ghana, fighting for minority rights in Nepal, promoting good governance in Zimbabwe, training political parties in Iraq, and advocating for constitutional reform in Venezuela.

This group will convene at Stanford University July 25-August 12, for a three-week intensive executive education program led by an interdisciplinary team of leading faculty affiliated with CDDRL. During this time, the Draper Hills Summer Fellows will hear from distinguished speakers, engage in peer learning, and meet with executives of leading Silicon Valley companies and non-profit organizations to share best practices and expand their professional networks.

This high-impact program helps to create a broader community of global activists and practitioners, intent on sharing experiences to bring positive change to some of the world's most troubled regions.

An analysis of India's evolving approach to ballistic missile defense and the militarization of space.

In a wide-ranging interview, CISAC co-director Scott Sagan discusses his career in political science, and his interests in nuclear deterrence, nonproliferation, South Asia, and more.