As temperatures rise in the western U.S., so does the damage from wildfires.
The years with the most acres burned by wildfires have some of the highest temperatures, an Associated Press analysis of fire and weather data has found. As climate change has warmed the world over the past 35 years, the land consumed by flames has more than doubled.
Experts say the way global warming worsens wildfires comes down to the basic dynamics of fire. Fires need ignition, oxygen and fuel. And what's really changed is the fuel -- the trees, brush and other plants that go up in flames.
"Hotter, drier weather means our fuels are drier, so it's easier for fires to start and spread and burn more intensely," said University of Alberta fire scientist Mike Flannigan.
It's simple, he said: "The warmer it is, the more fire we see."
Federal fire and weather data show that higher air temperatures are turbocharging fire seasons.
The five hottest fire seasons, stretching from April to September, in the West produced years that on average burned more than 13,500 square miles of land, according to data at the National Interagency Fire Center and the National Oceanic and Atmospheric Administration.
That's triple the average for the five coldest fire seasons.
In the West, this summer has been more than 3 degrees Fahrenheit warmer than the 20th-century average. California in July logged its hottest month in 124 years of record-keeping.
A difference of even a degree or two is crucial for fuel. The hotter it is, the more water evaporates from plants.
For every 1.8 degrees Fahrenheit that the air warms, 15 percent more rain is needed to make up for the drying of fuel, Flannigan said.
And low humidity is "the key driver of wildfire spread," according to University of Colorado fire scientist Jennifer Balch, who says the West soon will start to see wildfires of 1 million acres.
Mike Sugaski, a veteran Colorado firefighter, said he used to consider 10,000-acre fires big.
"You kind of keep saying, 'How can they get much worse?' But they do," Sugaski said.
The number of U.S. wildfires hasn't changed much over the past few decades, but the area consumed has soared.
"The year 2000 seemed to be some kind of turning point," said Randy Eardley, the fire center's chief spokesman.
From 1983-99, the United States didn't reach 10,000 square miles burned annually. Since then, 10 years have had more than 10,000 square miles burned, including three in which more than 15,000 square miles burned.
Some people who reject mainstream climate science point to statistics that seem to show that far more acres burned in the 1930s and 1940s. But Eardley said statistics before 1983 are not reliable because fires "may be double-counted, tripled-counted or more."
Nationally, more than 8,900 square miles have burned this year, about 28 percent more than the 10-year average as of mid-August. California is having one of its worst years.
Scientists generally avoid blaming global warming for specific disasters without extensive analysis, but scientists have done those extensive examinations on wildfires.
John Abatzgolou of the University of Idaho looked at forest fires and dry conditions in the Western United States from 1979-2015 and compared that to computer simulations of what would be expected with n0 climate change.
He concluded that global warming had a role in an extra 16,200 square miles of forest-burning since 1984.
One 2015 study said that globally, fire seasons had become about 18.7 percent longer since 1979. Another study that year found that climate change was increasing extreme wildfire risk in California.
Contrary to the views of fire scientists, Interior Secretary Ryan Zinke last week told Breitbart radio that "what's driving" increased wildfires is an increase in fuel. He said the government has "been held hostage by environmental terrorist groups" that oppose clearing dead trees that they say provide wildlife habitat. Zinke, however, has acknowledged that climate change was a factor in worsening wildfires.
A Section on 08/20/2018