Global warming cutting wheat yields

PALO ALTO, Calif., Jan. 30 (UPI) -- Rising temperatures caused by global warming are cutting wheat yields in India, suggesting difficulties ahead for global food supplies, a researcher said.

On the Ganges plain, the breadbasket of India, winter wheat planted in November is harvested when temperatures rise in spring and the wheat turns from green to brown, a sign the grain is no longer growing.

Researcher David Lobell of Stanford University used nine years of images from an Earth-observation satellite to track when the change from green to brown occurs in the region. He found wheat turned brown earlier in periods of higher average temperatures, with temperatures higher than 93.2 degrees Fahrenheit having a significant effect.

He then predicted yield loss using previous field studies and said current estimates of global warming and its impact on food supplies may have underestimated the problem by a third.

"It surprised me a little how much crop models underestimate the observed effects," Lobell told NewScientist.com.

The crop yield models may have especially underestimated the impact of hot spells, he said, since wheat evolved in cool uplands and has few defenses against heat.