World agriculture may suffer under global warming

Though recent winter temperatures might make global warming seem a distant and apocalyptic scenario, the phenomenon is alive and well — and if a guest lecturer at the University is right, it will have an unprecedented impact on global agriculture.

Yale students and faculty gathered at Luce Hall yesterday to hear William Cline, senior fellow at both the Peterson Institute for International Economics and the Center for Global Development, lead a discussion on a controversial aspect of the global warming debate.

Guest lecturer William Cline spoke yesterday to students and faculty on the potential effects of global warming on the world’s agriculture.
Amy Ly
Guest lecturer William Cline spoke yesterday to students and faculty on the potential effects of global warming on the world’s agriculture.

“World agriculture is the most basic economic resource,” Cline said. “Hot, dry conditions and prolonged droughts … such as those predicted by global warming … could be potentially devastating to agriculture. This is a strong reason for concern.”

Cline’s analysis, which is based on six existing models of climate effects on agriculture as well as several past studies, concluded that the financial cost to agriculture from climate change will amount to 0.3 percent of U.S. gross domestic product, which translates into a loss of roughly $40 billion per year.

Cline said his estimate is significantly higher than many past predictions, some of which have even suggested that the U.S. will benefit financially. Much of this previous research is overly optimistic, he said, due to the tendency of climate analysts to factor in “risky assumptions.”

For instance, past research may overestimate the mitigating effects of carbon fertilization, a phenomenon in which increased carbon dioxide levels enhance photosynthesis and thereby increase agricultural yield. Cline said his analysis placed the gain from carbon fertilization at 15 percent in overall productivity — a figure lower than past predictions — which takes into account the fact that, while some plants respond positively to increased carbon dioxide, others do not respond at all.

Cline said one of the greatest challenges — a point of overlap between his analysis and existing literature — is that global warming’s effects on agriculture will be distributed inequitably. Developing countries will experience greater agricultural damage because they currently have higher temperatures on average, while some colder, industrial nations may come out unaffected or even advantaged.

Cline’s research predicts that developing nations will experience a 10 to 20 percent reduction in agricultural output, even factoring in the unconfirmed mitigating effect of carbon fertilization. He said he found it especially worrying because many developing nations have agriculture-based economies.

“There will be sharp losses in developing countries … Latin America and Africa in particular,” Cline said. “These could be potentially serious if nothing is done to stop it.”

This pattern should motivate developing countries to step up their participation in international attempts to cut carbon dioxide emissions, Cline said, given that many currently evade such global protocols.

“Developing nations should think twice,” Cline said. “They could end up injuring themselves, if they were to stay in that mode.”

Robert Mendelsohn, a professor at the School of Forestry whose research Cline used heavily in his analysis, said he disagrees with Cline on two points: his assessments of how much global temperatures will increase and the role of carbon fertilization.

“Dr. Cline has his own slant [on the issue],” Mendelsohn said. “He predicts very low carbon fertilization effects and scenarios that are more pessimistic overall. You have to look at the experiments. The bulk [of them] say that carbon fertilization is going to be a large factor.”

Mendelsohn added that Cline based his calculations on the “highest end” of the prediction range for global temperature increase, which spans from 2 to 4.5 degrees Celsius. If the same relationships are investigated assuming only a two-degree rise in temperature, Mendelsohn argued, warming’s effects on agriculture become beneficial.

Nicholas Olsen ’09 said that although he found the lecture intriguing, the results of Cline’s analysis did not come as a surprise. He added that he wishes more students recognized the immediacy of global warming.

“I think the fact that we’re not going to see the climate change with our own eyes, the fact that it will happen over hundreds of years, makes people think it’s going to be less of an issue,” he said. “People think, if it won’t affect me directly, why should I care?”

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