Study: Urbanizing Central Valley could add to global warming

MERCED
February 12, 2007 6:27am

Converting farm land in the Central Valley to urban uses could add to global warming, warns a new study from the University of California.

It found that the prevalence of irrigation throughout the Central Valley and the rest of the state might be masking the effects of global warming.

Lara Kueppers, with the School of Natural Sciences at UC Merced, says she and two colleagues from UC Santa Cruz began looking at how irrigation's natural cooling can affect mean temperatures in certain areas.

What they found is that irrigation causes the mean temperature in summer months to drop, even as greenhouse gas emissions drive temperatures upward.

"It gives a false sense of security because the irrigation makes it really difficult to assess the effects of greenhouse gases," Ms. Kueppers says.

The Central Valley is the state's largest irrigated area.

The researchers’ computer model indicates that August's mean temperature in irrigated areas has dropped by about 6.5 degrees Fahrenheit, while greenhouse gas emissions are expected to warm the Earth about the same amount.

"If we don't consider what we're doing to the area by urbanizing, which removes farmland that has a cooling effect, we could very well end up with a much hotter Central Valley," she says.

She and co-authors Mark Snyder and Lisa Sloan of the Climate Change and Impacts Laboratory, Department of Earth and Planetary Sciences at UC Santa Cruz, say more research looking at absolute temperatures -- not using computer models -- is already under way at Lawrence Livermore National Laboratory.

"From what I've seen, their work is coming to similar conclusions as ours," Ms. Kueppers says.