Recent fire seasons have fueled intense speculation regarding the effect of anthropogenic climate change on wildfire in western North America and especially in California. During 1972–2018, California experienced a fivefold increase in annual burned area, mainly due to more than an eightfold increase in summer forest‐fire extent. Increased summer forest‐fire area very likely occurred due to increased atmospheric aridity caused by warming. Since the early 1970s, warm‐season days warmed by approximately 1.4 °C as part of a centennial warming trend, significantly increasing the atmospheric vapor pressure deficit (VPD). These trends are consistent with anthropogenic trends simulated by climate models. The response of summer forest‐fire area to VPD is exponential, meaning that warming has grown increasingly impactful. Robust interannual relationships between VPD and summer forest‐fire area strongly suggest that nearly all of the increase in summer forest‐fire area during 1972–2018 was driven by increased VPD. Climate change effects on summer wildfire were less evident in nonforested lands. In fall, wind events and delayed onset of winter precipitation are the dominant promoters of wildfire. While these variables did not change much over the past century, background warming and consequent fuel drying is increasingly enhancing the potential for large fall wildfires. Among the many processes important to California’s diverse fire regimes, warming‐driven fuel drying is the clearest link between anthropogenic climate change and increased California wildfire activity to date.
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Winds fuel wildfires in California as blazes rage across US west
Region sees amber skies while Washington state faces more acres burned in a day than typically burn in a year
Large, fast-moving fires raged on across the American west on Wednesday, destroying hundreds of homes in the Pacific north-west and sending a dense plume of smoke that turned skies amber across parts of the region.
More than 85 significant wildfires are burning across the west. In California, high, dry winds stoked dozens of out-of-control blazes that have forced helicopter rescues and evacuations. In Washington, more acres burned in a single day than firefighters usually see all year, and the fires scorched farming town of Malden. Fires also forced people to flee in Oregon and Idaho.
“The geographic scale and intensity of what is transpiring is truly jarring,” wrote Daniel Swain, a climate scientist at the University of California, Los Angeles.
“What’s remarkable is that there’s so many fires,” said Chris Field, who directs the Stanford Woods Institute for the Environment. “Even as someone whose job is to understand what’s happening, it’s really hard to keep up.”
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