By Michael Kahn

LONDON, Jan 15 (Reuters) - Farmers could help produce cooler temperatures and limit global warming if they grow crop varieties that reflect more sunlight into space, British researchers said on Thursday.

Using a global climate model, they found this strategy could cool much of Europe, North America and parts of North Asia by up to one degree Celsius during the summer growing season, enough to make a difference in easing heat waves and drought.

It would also translate into a 20 percent reduction in a predicted five degree Celsius temperature rise for the region by the end of the century, Andy Ridgwell and colleagues said in the journal Current Biology.

"We found that different varieties of most food crops do differ in how much solar energy is reflected back to space," Ridgwell, who led the study, said in a telephone interview.

"The more energy you reflect back to space the cooler the air temperatures will be."

Governments and researchers across the world are exploring ways to try to slow rising temperatures that experts say will bring heatwaves, droughts, more powerful storms, lead to species extinctions and raise sea levels.

Previous research has shown that wheat, maize, barley and sorghum reflect solar energy differently, depending on either how waxy a plant's surface is, how the leaves are arranged or how hairy they are.

Because the same likely holds true of all food crops, the new findings point to a low-cost strategy that could provide big returns when it comes to global warming, Ridgwell said.

The plan is also very different from biofuels because there is no need to disrupt food production either in terms of yield or the types of crops grown, he added.

"The idea is you could continue to grow maize, for example, but you could grow a variety that has a bigger climate benefit," Ridgwell said. "You are not replacing food crops with something you turn into energy."

The effect would occur mainly in Europe, North America and Northern Asia where most of the world's croplands are located, he added.

The reduction would be equivalent to an annual global cooling of over 0.1 degree Celsius, about 20 percent of the 0.6 rise since the Industrial Revolution.

The findings also raise the possibility farmers could receive carbon credits to encourage them to grow climate-friendly varieties and Ridgwell said selective breeding could ensure such crops remain robust.

"You could use selective breeding for climate characteristics," he said. "This seems very doable without spending lots of money." (Reporting by Michael Kahn; Editing by Diana Abdallah)

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