Global warning: Disaster for crop yields?

RALEIGH, N.C., Aug. 25 (UPI) -- A study predicts yields of three of the most important U.S. crops -- corn, soybeans and cotton -- will plummet if temperatures rise due to climate change.

North Carolina State University Assistant Professor of agricultural and resource economist Michael Roberts and Columbia University Assistant Professor of economics Wolfram Schlenker predict U.S. crop yields could decrease by 30 percent to 46 percent during the next century under slow global warming scenarios and by 63 percent to 82 percent under the most rapid global warming scenarios.

The study shows crop yields increase gradually between roughly 50 to 86 degrees Fahrenheit. But when temperature levels exceed 84.2 degrees Fahrenheit for corn, 86 degrees Fahrenheit for soybeans and 89.6 degrees Fahrenheit for cotton, yields fall steeply.

"While crop yields depend on a variety of factors, extreme heat is the best predictor of yields," Roberts said. "There hasn't been much research on what happens to crop yields over certain temperature thresholds, but this study shows that temperature extremes are not good."

Roberts said the study examined only U.S. crop yields under warming scenarios, but the research has important implications for the entire world since the United States produces 41 percent of the Earth's corn and 38 percent of its soybeans.

The study is reported in the early online edition of the Proceedings of the National Academy of Sciences.