A Climate for Change

Atmospheric scientist Ethan Coffel is studying the link between climate change and crop production.

As New York state farmers embark on another growing season, they are likely to feel the heat of global warming, says Ethan Coffel, assistant professor of geography and the environment at the Maxwell School.

Coffel is principal investigator on a threeyear National Science Foundation grant project exploring the link between climate and agricultural change—a process known as the crop-climate feedback cycle. He says that while staple food crops may see sharp declines in yields from global warming, agricultural adaptations, like moving crops to cooler latitudes, may reduce some of the damage. “Precipitation and temperature have huge impacts on crop growth,” he explains. “Some places have much lower yields because they’re too dry, wet or hot.”

Coffel studies how crop growth affects local climate, which impacts crop production.

“Research shows that crop growth actually cools the local climate in some of the world’s most agriculturally productive regions,” says Coffel, who also teaches in the College of Arts and Sciences. “This mitigates the effects of hot temperatures and boosts crop yields.”

Coffel and his co-principal investigator, Justin Mankin, are focusing on the upper midwestern United States, eastern Europe, northern China and southern Africa and Asia. “We’re especially interested in the central U.S.—Iowa and Illinois as well as parts of Indiana, Wisconsin, Minnesota and Nebraska— because it has not seen significant increases in maximum temperatures,” says Coffel. “The rest of the world, however, has gotten hotter over the past 40 years.”

Mankin, assistant professor of geography at Dartmouth, was Coffel’s postdoctoral advisor. Their research hinges on large-scale evaporation. “We know that water vapor transpired by plants cools the air around them,” says Mankin. “If crops are productive enough, their transpiration can reduce the number of extremely hot days that they experience.” In fact, he explains, the vast acreage of corn and soybeans in the central United States cools the climate enough to create favorable weather conditions—and contribute to bountiful harvests.

“There is a point at which global warming increases enough, even in the Upper Midwest, so that crops can no longer shed heat to keep apace,” adds Mankin. “When this happens, we might expect a reduction in crop yields and an increase in extreme heat.”

Scientists agree that the Industrial Revolution kickstarted modern global warming. Since the 1830s, carbon-rich deposits of coal, oil and natural gas have been burned for heat energy, pumping a staggering amount of the greenhouse gas carbon dioxide into the environment. The effects of climate change on agriculture include drought, severe weather, livestock shortages and a growing number of pests, to name a few.

In New York, the annual average temperature has risen more than two and a half degrees since 1970, prompting drought, flooding and unseasonably hot and cold temperatures. “It’s getting to the point where Syracuse’s climate is similar to what it used to be in southern New York or New Jersey,” says Coffel.

To stem the tide of global warming, he encourages small, easy lifestyle changes— from shifting toward plant-based diets to swapping cars for bikes to taking fewer flights. “Choices we make today will affect our children and our children’s children,” he says.

— Rob Enslin Assistant