Global Warming and Agriculture

From Tuesday's House hearing on the proposed bill to strip EPA of the authority to regulate greenhouse gases (h/t Balloon Juice):

One witness, Christopher B. Field, director of global ecology at the Carnegie Institution for Science, piqued the interest of members on both sides of the aisle by detailing new research on the adverse effects of rising temperatures on agriculture. Dr. Field said crops had certain temperature thresholds above which yields dropped sharply. For corn, he said, that temperature is 84 degrees, and a single day of 104 degrees causes a 7 percent drop in yield. Dr. Field said that extreme warming could reduce crop yields by more than 60 percent. “This new information is quite striking,” he said. “Major food crops and cotton show little sensitivity to rising temperatures until you reach a threshold. That’s why people are generally not aware of these sensitivities."

Over at Balloon Juice, John discards what the skeptics say.