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A firefighter saves an American flag as flames consume a home during the Dixie Fire in Greenville, California, on Aug. 4. Photo: Josh Edelson/AFP via Getty Images

Human-caused climate change is the main driver behind increased wildfire risk in the U.S. West, according to a study published Monday.

Why it matters: Researchers hadn't expected human-caused global warming to take over from natural climate variability as the main contributor to fire weather until much later this century, around 2080, per the Los Angeles Times.

By the numbers: Wildfires razed an average of 5,200 square miles of land per year in the Western U.S. from 2001 to 2018 — nearly double the area burned when compared with the period from 1984 to 2000, per the study, published in the Proceedings of the National Academy of Sciences.

  • Researchers found global warming was 68%-88% likely the driving factor for atmospheric conditions fueling increasingly destructive wildfires.

The big picture: The team from UCLA and the Lawrence Livermore National Laboratory analyzed factors behind the "vapor pressure deficit" (VPD), the leading climate variable predicting wildfire risk which indicates how dry the air is.

  • As part of the study, researchers analyzed the role of human-caused climate change in last year's August Complex Fire — California's biggest wildfire event on record, which saw some 1,600 square miles razed.
  • "In the case of the August Complex Gigafire in 2020, the results suggest that anthropogenic warming [originating from human activity] explains 50% of the anomalously high VPD observed during that month," per a statement accompanying the study.

Of note: A UN report published last August warned of the "unequivocal" connection between human-caused global warming and extreme weather and climate events.

The bottom line: The new findings, combined with previous research, show that further global warming will likely continue to intensify "conditions that create record or near-record fuel aridity conditions on the landscape," said Noah Diffenbaugh, a climate scientist at Stanford University to the L.A. Times.

  • "It means a higher risk of more severe fire conditions, simultaneously, in multiple areas of the region," added Diffenbaugh, who wasn't involved in the study.

Go deeper ...

Go deeper

Stuck jet stream brings blowtorch December in Lower 48, frigid Alaska

Short-term climate outlook for Dec. 13-19, 2021, from the Climate Prediction Center at NOAA. (NOAA/CPC)

The Lower 48 states have seen record-shattering warmth so far this December, with temperatures running as high as 35°F above average for this time of year. The warmth has been so pronounced that during the weekend, brush fires broke out in a snowless, unusually mild Denver metro area.

The big picture: The jet stream, which is a river of air that rides at about 30,000 feet along the temperature contrast between air masses, steering storms as it goes, has been stuck in a position well north of the contiguous U.S., keeping storms and cold weather at bay.

Philadelphia's autumn is getting warmer

Expand chart
Data: Climate Central; Chart: Jared Whalen/Axios

It's not your imagination. Autumn in Philadelphia is getting warmer.

Why it matters: Climate change is driving the increases, and the warmer weather can lead to additional cooling costs and longer allergy seasons.

California father and son accused of "reckless arson" in Calder Fire

Firefighters at the Caldor Fire along Highway 89 west of Lake Tahoe, California, in September. Photo: Wally Skalij/Los Angeles Times via Getty Images

California officials said they arrested a father and son Wednesday on suspicion of starting the Caldor Fire, which threatened the Lake Tahoe area as it burned for over two months earlier this year. They deny any wrongdoing.

Why it matters: The wildfire was the 15th-biggest ever recorded in California, razing more than 1,000 structures, forcing thousands to evacuate and injuring five people as it burned across nearly 222,000 acres of land in El Dorado, Amador and Alpine counties.