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Climate change fuels more ‘fire-prone’ days beyond U.S. West coast

by David Sherfinski | @dsherfinski | Thomson Reuters Foundation
Wednesday, 25 August 2021 14:00 GMT

Rosevelt Hotshot crew members hose off backfires in Pollock Pines, California, U.S., August 23, 2021. REUTERS/Fred Greaves

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California and the Pacific Northwest have attracted much of the attention during the 2021 wildfire season, but climate change-fueled fire risk is encroaching much farther east, researchers say

* "Fire weather" days spike in U.S. beyond regular hot spots

* Climate change seen as key driver of fire-prone conditions

* Increases seen in states like Oklahoma, Kansas

By David Sherfinski

WASHINGTON, Aug 25 (Thomson Reuters Foundation) - Climate change is fueling conditions for more rapid growth of wildfires in the western United States - including in some places, from Oklahoma to Nebraska, that may not expect them, researchers said Wednesday.

Wildfires are already devastating broad swaths of the West coast but other western states are also seeing spikes in fire-prone days, suggesting safe havens from the deadly blazes will continue to decline without greater efforts to curb climate change.

"(In) most of these communities, it's not a matter of if - it's a matter of when," said Kaitlyn Weber, a data analyst for Climate Central, the research group that released a new report on fire risks.

Weber, who grew up near where the Caldor fire has burned through more than 100,000 acres of land outside of Sacramento this month, said parts of California dominated the places most fire-prone, as expected.

What was more surprising was the growing number of days in which heat, wind and low humidity were boosting fire risks in other states, she said.

"Going into Oklahoma and parts of Kansas… even parts of Nebraska – it is changing," she said. "The weather is setting the stage more often for these serious fires."

The San Joaquin and Sacramento drainage regions of California ranked second and seventh respectively in their percentage increase in "fire weather" days between 1973 and 2020, according to the analysis, which looked at federal climate zones across 17 states.

A fire-prone day is considered one where temperatures hit at least 45-55 degrees Fahrenheit (7-12 degrees Celsius) depending on the season, wind speeds top 15 miles per hour and relative humidity approaches thresholds the federal government uses to define elevated fire risk - 15% humidity in many parts of the west.

"Climate change is causing an increase in temperatures, and that increase in temperatures is causing a serious drying trend out in the west," Weber said. "It's greatly increasing the risk of more severe wildfires."

California accounted for nearly 40% of the total acreage burned by wildfires in 2020 in the United States, according to the Congressional Research Service. But other states also showed rising fire risk.

Two regions in Nevada, which encompass Las Vegas and the south-central part of the state, had the highest average number of "fire weather" days per year between 1973 and 2020, with 94 and 93 respectively.

In 2020, Nevada saw more than 250,000 acres burned in wildfires, according to the National Interagency Fire Center, ranking near the top of all U.S. states.

Areas of New Mexico, California, and Texas saw the biggest total increases in fire days since 1973, with about two additional months of "fire weather" now compared to 1973, the analysis found.

Parts of southern Texas, California, Oregon and Washington, meanwhile, saw the biggest percentage increase in fire weather days since the early 1970s, with such days more than doubled, it found.

Southwest Oklahoma, which borders Texas, saw a 169% jump in fire weather.

HEADING EAST?

Climate scientist Michael Wehner said such increases in fire risk haven't been limited to the western United States, with countries such as Greece, Turkey, Spain and France now seeing consecutive damaging fire seasons.

U.S. states further east may also find themselves at growing risk, said Wehner, one of the lead authors of an August report from the Intergovernmental Panel on Climate Change.

The Greenwood fire burning in northern Minnesota, for instance, has charred nearly 20,000 acres over the past 10 days.

"I would expect that there's an increase for fire risk throughout the mid-latitudes," Wehner said. "The dry climates are always more at risk for these types of things, but you can have forest fires in the eastern United States."

Weber, of Climate Central, said that as climate change drives hotter temperatures in many states, fires are also becoming a risk in more places.

The report is "kind of a warning sign that we really need to pay attention to that", she said.

Weber cautioned that weather is only one factor in wildfire risk, which also depends on the brush and other fuel available to burn and a region's topography.

She said the Bootleg fire, which has burned more than 400,000 acres in Oregon starting last month, happened in the state's south central region, which was outside the report's most high-risk zones.

What's clear is that higher temperatures and drier soil are helping fuel fires, said Wehner, a senior staff scientist at Lawrence Berkeley National Laboratory in California.

"Because it's hotter, regardless of what happens to the humidity, the soils are drier and plants are drier. And so, hence, it's more flammable," said Wehner.

The Climate Central analysis found that some parts of North Dakota and South Dakota, as well as pockets of Kansas and Nebraska, saw a decline in the frequency of fire weather days since 1973 amid relatively cooler spring and summer temperatures.

That cooling, however, was expected to be temporary and may have been influenced by changes in land use and crop irrigation as well as natural variation, it found.

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("Reporting by David Sherfinski. Editing by Laurie Goering. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers the lives of people around the world who struggle to live freely or fairly. Visit http://news.trust.org)

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