The number of wildfires in California and the western U.S. this summer may represent a "new normal."
Nationally, wildfires have burned at least 6.5 million acres in 2015. Federal fire managers say that's a 38 percent increase over the 10-year average to this point in the year.
UC Berkeley professor Scott Stephens is co-director of the Center for Fire Research and Outreach. He says some of the increase in fire frequency is likely due in part to climate change.
"But there's no doubt, just the increasing temperatures and less snow on the ground, longer periods for fuels to dry in a Mediterranean climate," says Stephens. "The physics of that just tell us the fire is going to be able to move more frequently and possibly even higher intensity."
Stephens says warmer temperatures are causing fires to grow overnight too, and the Rocky and Jerusalem fires are prime examples.
"We're not having the recovery at night, we're not seeing as much recovery in terms of temperatures -- they're not going down," says Stephens. "Humidities are not coming up at night, so we're seeing more active burning at night, and that happened in both of the recent fires that occurred in Lake County, with burning in the chaparral."
Stephens says more thinning and prescribed fires in the forest areas of California would help limit the severity and size of future wildfires, even with impacts from drought and climate change.
"There are still restoration activities we could do today that really would make a huge difference in the mitigation of kind of some of the impacts we don't want to see - large area mortality and lots of smoke emissions," says Stephens.
'We need to coexist with fire'
In previous reports for the U.N. Intergovernmental Panel on Climate Change, researchers showed that wildfires in the western U.S. would be more frequent and severe.
"Drought index projections and climate change regional models show increases in wildfire risk during the summer and fall on the southeast Pacific coast, Northern Plains and the Rocky Mountains," according to an IPCC summary of a 2014 report. "In places like the Sierra Nevada, mixed conifer forests, which have a natural cycle of small, non-crown fires, are projected to have massive crown-fires."
A 2012 study by UC Berkeley researchers showed climate change will bring about major shifts in worldwide fire patterns.
The study, "Climate change and disruptions to global fire activity" showed that by the end of the century, almost all of North America, and most of Europe, would see an increase in the frequency of wildfires, primarily because of increasing temperature trends. It concluded that the western United States would see more fire.
"We need to learn how to coexist with fire," said study lead author Max Moritz, a fire specialist in UC Cooperative Extension.
Moritz said if there is a new angle to the 2012 study in 2015, it could be that the on-going drought is having "big impacts on the plants, and thus fires, this year ... almost the entire landscape is basically parched and much drier than it normally would be."