An American research report to the National Academy of Sciences says predicted temperature increases due to climate change would have a huge impact on the corn and soybean crops in the U.S. Midwest.

At ambient temperatures up to 29 C for corn and 30 C for soybeans, yields would actually rise with a warmer climate. Above those levels, however, the effect on yields is likely to be devastating.

The calculations, reported in “Nonlinear temperature effects indicate severe damages to U.S. crop yields under climate change,” by Dr Michael Roberts of North Carolina State University and Dr Wolfram Schlenker at Columbia University, indicate a continuation of greenhouse gas emissions at current rates would cut US yields of maize, soybeans and cotton by 63-82%. Even if united action succeeded in cutting emissions down to 50% of 1991 levels by 2050, there would still be warming enough to reduce crop yields across the U.S. by between 30% and 46%.

The scientists emphasized they looked at crops in the U.S. alone. But since American farms have been producing more than 40% of all corn worldwide and 38% of soybeans, they continued, there would be implications for global grain supplies.