Climate change main cause of fires in US west: study

A home continues to burn as flames from the LNU Lightning Complex fire spreads in Vacaville, California on August 19, 2020

Climate change caused overwhelmingly by human activity is the primary source of the unprecedented forest fires regularly ravaging the western United States, according to a study published Monday.

Fires destroyed an average of 13,500 square kilometers (5,200 square miles) per year in the American west between 2001 and 2018 -- twice as much as between 1984-2000.

In order to understand what contributed to such a significant deterioration of conditions in such a short time, a team of American researchers led by Fu analyzed various factors at work in the "vapor pressure deficit" (VPD), which indicates how dry the air is.

Scientists have determined that the increase in wildfires in the western United States is closely linked to this deficit during the warm season. Between May and September, the number of days with a high VPD increased 94 percent between 2001 and 2008 compared to the previous period, the study said.

"Prior to 2000, we can explain this fire weather pretty well just using weather patterns," said Fu, a climatologist at the University of California UCLA. "But now we can only explain 30 percent of what we see with fire weather."

In August 2020, when California suffered the largest fire ever recorded in the region -- the August Complex Fire, which alone burned nearly 4,200 square kilometers (1,600 square miles)  -- so-called anthropogenic warming was responsible for about 50 percent of the "unprecedented high" moisture deficit, the study said.

Most of the warming has occurred in the last 50 years.

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Originally published as Climate change main cause of fires in US west: study