By Alex Dobuzinskis
LOS ANGELES, Aug 20 (Reuters) - Climate change has aggravated California's devastating drought, causing between 8 and 27 percent of the dry conditions afflicting the nation's most populous state, a study released on Thursday has found.
The study, published this week in Geophysical Research Letters, is the first paper to estimate how much climate change has exacerbated the state's drought by sending moisture from plants and soils into the air, according to Columbia University, where the lead author works.
Researchers examined monthly weather data, including rainfall and temperatures, going back 114 years to isolate the proportion of the drought they concluded was due to climate change, as opposed to natural weather variations that have heated up the state, according to Columbia University.
The paper estimated between 8 and 27 percent of the drought is likely attributable to climate change, the university said.
But A. Park Williams, a Columbia research professor of biology and paleo environment who was lead author of the paper, said the most likely estimate is somewhere in the middle, probably between 15 and 20 percent.
"A lot of people think that the amount of rain that falls out of the sky is the only thing that matters," Williams said in a statement. "But warming changes the baseline amount of water that's available to us, because it sends water back into the sky."
In fact, the researchers did not find climate change altered the amount of rainfall in California, which varies widely from year to year.
Nevertheless, when rainfall declined in California in 2012, moisture evaporated at an unusually intense rate from soil, trees and crops, the study found.
While heavy rainfall will return to California, perhaps as soon as this winter, the study said increased moisture evaporation in the state will over the long run play a larger role than the sporadic boon of precipitation.
The ongoing drought, now in its fourth year, will cost the California economy about $2.7 billion in 2015, according to a study released this week by economists at the University of California, Davis.
Firefighters in California also are battling a fierce wildfire season that officials say has turned wilder and more dangerous because of bone-dry conditions from the drought.
California Governor Jerry Brown, a Democrat, has said global warming caused by human activity plays a significant role in the drought and has challenged Republican presidential candidates to discuss their plans on climate change. (Reporting by Alex Dobuzinskis; Editing by Eric Beech)