Global warming is worsening the effects of California's historic drought, according to a study published in the journal Geophysical Research Letters this week.

"A lot of people think that the amount of rain that falls out the sky is the only thing that matters," lead author A. Park Williams, a bioclimatologist at Columbia University's Lamont-Doherty Earth Observatory , 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."

Scientists analyzed data on rainfall, temperature, humidity and other climate factors from 1901 to 2014. The researchers found that while there wasn't a long-term precipitation trend, temperatures rose approximately 2.5 degrees over that time. That increase, combined with the lack of rainfall in California over the last few years, quickened the moisture loss in already dry soil and trees.

Williams said warming trends are likely responsible for 15 percent to 20 percent of the drought.

"New scientific reports now make it crystal clear that climate change is already affecting California and the Southwest in the form of higher temperatures and a more devastating drought," California Gov. Jerry Brown (D) said in a Thursday statement about the study. "Its time for Republicans , foot-dragging corporations and other deniers to wake up and take sensible action before its too late."