Global warming increases wildfires

The trend has occurred in step with rising average temperatures in the region.

Rising temperatures and earlier snowmelts have intensified forest fires.

"Climate change in the West is a reality," says Thomas Swetnam of the University of Arizona in Tucson. "Now, we're starting to see the effects."

Earlier spring snowmelts, which kick off longer fire seasons, account for the trend, he says. The melt's timing influences how parched—and therefore how vulnerable to fire—the landscape gets later in the year.