Potent Mix of Record Heat and Dryness Fuels Wildfires Across the West

I have said that the fossil fuel executives who spread global warming denialism for the sake of their pocketbooks, and the politicians and news media who help them for the sake of money, are morally the same as drug lords. Actually, they are far worse.

https://insideclimatenews.org/news/05092017/west-wildfires-california-canada-forests-record-heat-climate-change

By Georgina Gustin
Sept. 5, 2017

Wildfires burned across hundreds of thousands of acres in the American and Canadian West this week, fueled by scorching temperatures that are breaking heat and fire records across the region.

In California, while temperatures have eased, at least 15 cities have seen record-breaking heat, and the state has experienced its hottest summer on record. San Francisco hit 106 degrees over the weekend, breaking its previous high by 3 degrees. Stoked by unusually high temperatures, fires burned on thousands of acres just outside Los Angeles, while firefighters in Washington, Oregon and Montana battled dozens of blazes across those states.

By the end of the day Tuesday, at least 81 large fires were blazing across 1.5 million acres of the U.S. West, from Colorado to California and north to Washington. Over the Canadian border, British Columbia has already had a record-breaking fire season—and it's not over yet. Cities including Seattle were shrouded in a smoky fog. In satellite pictures, the smoke could be seen traveling the jet stream and reaching the East Coast.

As firefighters battled the blazes, climate researchers pointed to studies finding that a warmed global atmosphere, with increasingly clear human fingerprints, will continue driving a potent mix of heat and dryness that's projected to escalate in the West.

"These unprecedented extreme events, on the daily to the seasonal scale, are exactly the types of events that are more likely due to the global warming that's already occurred," said Daniel Swain, a climate scientist at UCLA. "That's not so much a future projection, but an observational reality, and that's something we expect to increase in the future. When we get these extremes, there's a human fingerprint."

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Swain co-authored a study led by Stanford researcher Noah Diffenbaugh published earlier this year that found human-caused greenhouse gas emissions have increased the chances of extreme heat across more than 80 percent of the globe's surface area.

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Nine of the 10 worst fire seasons in the past 50 years have all happened since 2000, and 2015 was the worst fire season in U.S. history, surpassing 10 million acres for the first time on record. So far this year, wildfires in the U.S. have burned 7.8 million acres, but the fire season is far from over. (In 2015, 8.4 million acres had burned by early September.) The average fire season is 78 days longer than it was in the 1970s—now nearly seven months—beginning and extending beyond the typical heat of summer. By April of this year, wildfires had scorched more than 2 million acres in the U.S.—nearly the average consumed in entire fire seasons during the 1980s.

Last fall, researchers published the results of a study that found human-induced climate change accounted for about half the observed increase in fuel aridity, or forest dryness, in the western U.S. since 1979 and had nearly doubled the area of the U.S. West affected by forest fires since 1984.

During that same time period, temperatures across the West have risen. Temperatures are projected to rise further—and along with them, the tinderbox conditions that fuel wildfires.

"We know that global warming has already increased the probability of unprecedented high temperatures in the western U.S., including in California," Diffenbaugh said. "And we know, with high confidence, that continued global warming will continue to intensify those increases."