Climate change now main driver of wildfire weather in western US, study finds
LOS ANGELES — A new study adds to a growing body of evidence that climate change is fueling more frequent and intense wildfires in the western U.S.
The study’s researchers report that based on the rate that dry air sucks up moisture, climate change is essentially two-thirds to 88% responsible for the conditions driving the region’s wildfire woes.
And that’s a conservative estimate, said study author Rong Fu, a climate researcher at the University of California, Los Angeles.
“It’s happened so much faster than we previously anticipated,” she added.
The study, published this week in the Proceedings of the National Academy of Sciences, looks at what’s known as the vapor pressure deficit, which basically describes how thirsty the atmosphere is, Fu said. The researchers found this to be the leading meteorological variable that controls how much land burns in the western U.S. during a given fire season. The higher the deficit, the more moisture the atmosphere saps from soil and plants, priming the landscape to burn.
Such findings are driving the conversation this week as world leaders meet in Scotland to discuss how to fight global warming.
Mel Melcon/Los Angeles Times
Burned trees rise above a truck destroyed by the Dixie Fire in the town of Greenville, Calif.
Previous studies have found the atmosphere in the western U.S. has grown thirstier over the last 40 years. Experts have theorized that is due to both natural fluctuations in the weather and because carbon dioxide emissions have caused the planet to warm, and warmer air can hold more moisture.
This team of researchers, which included scientists from UCLA and the Lawrence Livermore National Laboratory, sought to explain exactly how much of each of those factors has driven the increase. They used a machine learning approach to compare recent vapor pressure deficit values with those observed in the past during similar weather patterns.
“Prior to 2000, we can explain this fire weather pretty well just using the weather patterns,” Fu said. “But now we can only explain like 30% of what we see with the fire weather.”
After ruling out other influences like changes in vegetation and cloud cover, the researchers concluded the other 70% is due to greenhouse gases warming the planet, she said, a figure that some climate modeling suggested could be as high as 88%.
The findings have important implications for fire management. If natural weather cycles were driving the increase in fire danger, it could be expected to lessen again at some point. But the planet is expected to continue to warm, meaning the risk will likely only increase, Fu said.
