Study: Irrigation affecting global warming

NEW YORK, Sept. 8 (UPI) -- Expanding irrigation is helping feed the world's billions of people and may even mask global warming, but the future could bring problems, scientists say.

Columbia University researchers say some major groundwater aquifers, a source of irrigation water, will dry up in the future hitting people with the double blow of food shortages and higher temperatures, an article in the journal Geophysical Research says.

"Irrigation can have a significant cooling effect on regional temperatures, where people live," Michael Puma, a university hydrologist, says. "An important question for the future is what happens to the climate if the water goes dry and the cooling disappears? How much warming is being hidden by irrigation?"

Pumping huge amounts of heat-absorbing water onto crops, researchers say, is lowering temperatures in some regions -- for now.

Globally, irrigation's effect on climate is small, about 0.2 degree F. But regionally, the cooling can match or exceed the impacts of greenhouse gases, say the scientists.

Irrigation has increased because it boosts crop yields, supporting many millions of small farmers. But concern is growing that groundwater supplies in places like India and China may not keep up.

"Near term and future climate predictions are essential for anticipating climate shocks and improving food security," Upmanu Lall, head of the Columbia Water Center at the Earth Institute, said.

"The study points to the importance of including irrigation in regional and global climate models so that we can anticipate precipitation and temperature impacts, and better manage our land, water and food," he said.