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.

A year has passed since the South Korean warship Cheonan sank into the depths of the Yellow Sea, an event attributed to an attack from North Korea and one that rekindled afresh the ongoing tensions between South and North. In that time, Pyongyang has transmitted confusing signals to the world about the strength of its leadership and its intentions toward South Korea, including publishing photos of a steely but frail-looking Kim Jong Il alongside his young heir apparent Kim Jong Un and unexpectedly attacking Yeonpyong Island in late November. It is clear that the Kim Jong Il regime still maintains strong control over its citizens and that the country's nuclear program continues to grow. Nevertheless, there are hints of instability and signs of information from the outside world trickling into North Korea that point to coming change.

During an April 21 television interview, visiting fellow Sang-Hun Choe, an International Herald Tribune journalist with many years of experience reporting on North Korea, addressed the complexity of the country's current political situation, noting the lack of firsthand information and the mixture of fear and genuine belief motivating adherence to the longstanding official party line. Choe emphasized the importance for the countries most closely tied to North Korean political developments—especially South Korea, the United States, and China—to consider the key questions regarding the future of North Korea, including what shape a transfer of power or a regime collapse could take.

Media coverage of North Korea

Reporting on North Korea is no simple matter, due in large part to the government's tight control on the flow of information in and out of the country. "North Korea is so closed that it is almost impossible for journalists to gather firsthand information," stresses Choe. Television and radio broadcasts and the internet are closely monitored in North Korea, and there is a recent move to confiscate mobile phones as they are smuggled into the country.

Choe suggests that a journalist's own interests and the political agenda of his or her country often shape the angle of their coverage of North Korea. For example, the U.S. media tends to focus on North Korean nuclear developments and the resumption of the Six Party Talks, a reflection of the official U.S. defense agenda. Reporting in South Korea is not quite as straightforward. "South Korea's relationship with North Korea is very complex," Choe states. While there is deep resentment toward North Korean attacks on the South, there is also a sense of shared Korean identity that influences South Korean news coverage of North Korea, he says.

Juche and the Kim family dynasty

Tapping into the deeply rooted sense of nationalism that emerged in Korea as a result of great power competition over the peninsula, North Korea's founder Kim Il Sung masterfully applied the principle of juche to found his family's political dynasty. "It [‘juche'] is very difficult to translate," says Choe. "One of the most common English translations is ‘self reliance,' but that does not really explain everything. It is more like ‘in our own way of living' or ‘in charge of our own fate.'"

North Korean citizens do not mindlessly follow the official party ideology, stresses Choe. Some people are motivated by fear of punishment, while others firmly believe in juche. "We have to take these two elements into account when we try to understand North Korea," he says. "There is fear, but there is also pride in their system. Whether you call it ‘brainwashing' or not, it is the reality."

Kim Jong Il's apparently failing health and heir Kim Jong Un's youth and lack of experience weigh heavily on the minds of political analysts. Photos suggest that Kim Jong Il is recovering from a stroke, a fact confirmed several months ago by the South Korean government. According to Choe, the key question now is how long Kim Jong Il will live. "[He] did not expect that he would have a stroke," he says, "so the transition [of power] is being prepared in a hurry." Kim Jong Il's own rise to power was gradual and he held numerous political positions over the years. Despite being made a military general in September, Kim Jong Un's political experience is comparatively limited.

Future concerns and possible scenarios

Despite uncertainties about the transfer of power in North Korea, recent reports suggest that the country continues to develop its nuclear program. In addition to the regional security concerns this poses, the nuclear accident in Japan this March raises environmental safety questions. For example, how would North Korea prepare for or respond to damage to a nuclear facility caused by a natural disaster? "Despite being a very technologically advanced country, Japan has still had a lot of difficulties dealing with its nuclear disaster," Choe emphasizes.

While North Korea's juche ideology continues to legitimize the Kim family dynasty, Choe suggests that the current system cannot last forever, especially with the country's ongoing food shortages and the significant regional economic and political developments of the past few decades. "If you look at Northeast Asia, all of the other former communist countries are more or less thriving by adopting market reforms/economies, and North Korea is left alone," he says. "It is a very poor, isolated country in a very well-to-do neighborhood of the world—it cannot last forever."

Choe downplays the possibility of an Egypt-style revolution in North Korea, but suggests that China, South Korea, and the United States should consider the potential scenarios for the future of North Korean politics. "The big question is when and how change will come," he states. "If the regime collapses, will there be some kind of power struggle between factions? Is China going to intervene?"

China does not necessarily support North Korea's political decisions, including its nuclear program and economic policies, Choe suggests, but the collapse of North Korea could lead to a mass exodus of refugees into its northeastern provinces. Furthermore, he says, "Another concern for China is what will happen on the Korean Peninsula if North Korea collapses. Is South Korea going to take over the northern half of the peninsula and create one unified Korea, or is America? China might not be happy to have a small, but well-to-do pro-America unified Korea right on its border . . . That explains its attitude seemingly ambiguous [toward North Korea.]"

It is certain that the current North Korean political situation is a very puzzling and complex one, with apparently more questions than answers at this time. As Choe suggests, it is most important now for the world—especially China, South Korea, and the United States—to examine the possible future issues and scenarios facing North Korea, and to identify the related key questions in an effort to prepare for the inevitable change that will one day come.

A full recording of Choe's interview is available online at the KEMS TV website (Korean language).