California is likely to continue to experience larger and more destructive wildfires as the nation's most populated state gets hotter and drier.
"Since the early 1970s, California's annual wildfire extent increased fivefold, punctuated by extremely large and destructive wildfires in 2017 and 2018," the researchers wrote. "This trend was mainly due to an eightfold increase in summertime forest‐fire area and was very likely driven by drying of fuels promoted by human‐induced warming."
Over the past decade, average temperatures there have risen over 2 degrees Fahrenheit, but the moisture deficit — the difference between the amount of water actually in the atmosphere and the amount of water it can hold — has not caught up. Lower relative humidity causes brush to dry out faster, creating more kindling to burn when a fire starts.
"It's not likely to get better as we continue to warm the climate," CBS News climate and weather contributor Jeff Berardelli said. "This will only get worse in the future."
He points out that fire season is about two to three months longer now than it was in 1970.
"Climate change — warmer climate and drier climate — [is] making a huge difference," Berardelli said. "It is a tipping point. It is the straw that breaks the camel's back and makes these, you know, generally controllable fires uncontrollable."
The six most destructive fire seasons in state history have occurred in the last 10 years, and 15 of the 20 largest California fires took place since 2000.
Extreme fire seasons are also affected by other factors, such as the fact that humans are encroaching further into previously rural areas.
For almost a month, millions of Californians have been subject to temporary electricity shut-offs as utilities try to prevent power lines from sparking fires during high wind conditions. Hundreds of thousands have been forced to evacuate their homes and tens of millions of people are under "red flag" warnings.