[asa] Crop Yields Face Non-Linear Effects Due to Climate Change

http://www.physorg.com/news170350697.html

In a paper published online this week in Proceedings of the National Academy
of Sciences, North Carolina State University agriculture and resource
economist Dr. Michael Roberts and Dr. Wolfram Schlenker, an assistant
professor of economics at Columbia University, predict that U.S. crop yields
could decrease by 30 to 46 percent over the next century under slow global
warming scenarios, and by a devastating 63 to 82 percent under the most
rapid global warming scenarios. The warming scenarios used in the study -
called Hadley III models - were devised by the United Kingdom's weather
service.

The study shows that crop yields tick up gradually between roughly 10 and 30
degrees Celsius, or about 50 to 86 degrees Farenheit. But when temperature
levels go over 29 degrees Celsius (84.2 degrees Farenheit) for corn, 30
degrees Celsius (86 degrees Farenheit) for soybeans and 32 degrees Celsius
(89.6 degrees Farenheit) for cotton, yields fall steeply.

"While crop yields depend on a variety of factors, extreme heat is the best
predictor of yields," Roberts says. "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 adds that while the study examined only U.S. crop yields under
warming scenarios, the crop commodity market's global reach makes the
implications important for the entire world, as the United States produces
41 percent of the world's corn and 38 percent of the world's soybeans.

"Effects of climate change on U.S. crop production will surely be felt
around the globe, especially in developing countries," he says.

More information: "Nonlinear temperature effects indicate severe damages to
U.S. crop yields under climate change" Wolfram Schlenker, Columbia
University and Michael Roberts, North Carolina State University; Published:
Aug. 24, 2009, in the online version of Proceedings of the National Academy
of Sciences.

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Received on Thu Aug 27 22:41:44 2009