Extreme Wildfires Became Twice as Frequent and Intense in 20 Years, Study Finds

As measured by satellites, wildfires have markedly increased in boreal and temperate conifer forests, and rising nighttime temperatures allow flames to keep burning intensely after dark

The silhouette of a firefighter at a blaze at the Florida Panther National Wildlife Refuge.
A firefighter stands in a blaze at the Florida Panther National Wildlife Refuge in 2009. USFWS / Josh O'Connor

Accelerated by human-caused climate change, both the frequency and intensity of the world’s most extreme wildfires have more than doubled over the past 20 years, a new study of satellite data suggests.

The burning threatens to kindle a positive feedback loop, in which the carbon dioxide released during these fires contributes further to global warming, which in turn drives hot and dry conditions—making the landscape ripe for more infernos.

Each of the last 12 months, from June 2023 through May 2024, has been the hottest month of its kind on record. And six of the last seven years have been the planet’s most intense for wildfires, the team found. In the study published Monday in the journal Nature Ecology and Evolution, they report that since 2003, the amount of extreme wildfires has increased by a factor of 2.2—and their intensity has risen by a factor of 2.3. Last year topped the charts for the most intense wildfires ever recorded.

“The fingerprints of climate change are all over this rise,” Calum Cunningham, a pyrogeographer at the University of Tasmania in Australia and lead author of the study, tells the Guardian’s Damian Carrington. “We’ve long seen model projections of how fire weather is increasing with climate change. But now we’re at the point where the wildfires themselves, the manifestation of climate change, are occurring in front of our eyes. This is the effect of what we’re doing to the atmosphere, so action is urgent.”

Aerial photo of the 2013 Alder Fire in Yellowstone National Park
The 2013 Alder Fire in Yellowstone National Park NPS

In the study, the scientists analyzed NASA satellite data for the top 0.01 percent of wildfires, ranked by the amount of energy released per day. They arrived at a sample size of about 2,900 of these extreme events between January 2003 and November 2023.

They found that the number of fires occurring in temperate conifer forests, including spruce and pine forests in western North America, has increased 11.1 times over the past two decades.

Boreal forests in northern parts of Russia and North America also experienced a sharp, 7.3-fold increase in the number of wildfires during the study period. In these ecosystems, the thawing of permafrost has also released carbon, contributing to the warming feedback loop that is helping to heat up the Arctic at least twice as quickly as the rest of the world.

The Mediterranean, as well as Oceania and Australia, where the researchers are based, also experienced a disproportionate rise in fires.

While cooler nights can provide a reprieve for firefighting efforts—and a barrier to the fire’s growth—nighttime temperatures have been rising, allowing fires to burn intensely after dark, the study found.

“This kind of confirms what we’ve been observing, that the fire intensity is not dying down at night like we used to depend on,” Bobbie Scopa, an author and retired firefighter who was not involved in the research, tells the Washington Post’s Sarah Raza.

The most intense wildfires are often the smokiest, posing downwind health risks to wildlife and nearby human communities.

All of this smoke—along with clouds—likely obscured some of NASA’s satellite imagery, meaning fire intensity in the research has probably been underreported, Mark Parrington, a senior scientist at the European Union’s Copernicus Atmosphere Monitoring Service who was not involved in the study, tells the Guardian.

According to an April report from the National Bureau of Economic Research, wildfire smoke has contributed to almost 16,000 excess deaths in the United States per year over the past decade. By 2050, this number could rise to nearly 28,000 per year under a high emission scenario.

“Larger and more severe wildfires are one of the most obvious manifestations of a planet that is heating up,” Jennifer R. Marlon, a senior research scientist at the Yale School of the Environment, tells the New York Times Austyn Gaffney. “If we can help people better understand that connection, we may be able to build support for working more quickly to reduce the root causes of the problem—burning fossil fuels.”

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