Wildfire Smoke May Worsen Extreme Blazes Near Some Coasts, According to New Research

Apart from clouding skies, irritating eyes, clogging respiratory systems and warming the climate, smoke from huge wildfires may actually help fires grow in some coastal areas, according to recently released research. The acrid smoke billowing from a megafire can drive a feedback loop impacting surface winds and humidity to help a fire spread, scientists said.  

“Wildfire is not just a passive responder or consequence of climate warming or extreme weather conditions,” said Xin Huang, an associate professor of atmospheric sciences at Nanjing University and one of the paper’s authors. “It’s also an active and very important participant in the extreme event.”

Firefighters and scientists have long understood that wildfires can create their own weather, with large blazes spawning stormy plumes of clouds that can drive strong, erratic winds that fan flames or strike the ground with lightning. But the new research suggests the smoke from large wildfires may also affect the weather and the fires they drive. 

The team demonstrated “unexpectedly strong feedback between wildfire and weather” in extreme fires in two different coastal regions on opposite sides of the world from one another—the Mediterranean climate of the U.S. West Coast and the monsoon-influenced climate of Southeast Asia. The results could add another datapoint to land managers’ complex calculations for how to cope with wildfire.

In 2020, fires in the Cascade Mountains in Oregon created smoke so thick that it blocked sunlight from reaching the ground, trapping cool air underneath, “like a lid that prevents the smoke from going anywhere,” said Steven Davis, another of the report’s authors and an associate professor of earth system science at the University of California, Irvine.

That’s a phenomenon that scientists have observed in numerous fires, said Diana Bernstein, a climate scientist at the University of Southern Mississippi who was not involved in the research. But that has usually resulted in less severe fires as temperatures drop near the ground and wind patterns change when smoke blots out the sun. Past research focused on years of fires in a mountain range spanning Northern California and Southern Oregon suggested that when smoke creates temperature “inversions”—when the cap of warm air covers cooler air—it reduces winds and increases humidity near the ground, dampening fire severity in lower elevations.

But in their assessment of the extreme fire events in Oregon, researchers found something different: a gap in air density made dry, cool air below the smoke “lid” rush down the West side of the mountains, pushing back breezes coming in from the Pacific Ocean that may have otherwise carried in enough humidity to dampen the flames. The dry winds and low humidity that remained increased the fire’s potential to burn intensely and produce more smoke, researchers said.

“This feedback is driving a circulation that we previously maybe didn’t appreciate completely,” said John Abatzoglou, a climatologist at University of California, Merced, who was not involved in the paper. “That circulation modifies the near-surface winds, which is one of the key ingredients, from a fire behavior perspective.”

Scientists have drawn a clear connection between climate change and worsening wildfires. And researchers have already shown some ways in which fires can interact with the atmosphere. In addition to their influence on ground temperature, wildfires can reduce the height of the “planetary boundary layer,” the band of the atmosphere closest to earth, which then holds smoke closer to the ground and worsens air quality.

Davis said the researchers wanted to fill in gaps in that knowledge. He believes this is the first study to show a feedback between smoke generated by a fire and the severity of the fire itself, with smoke increasing the intensity of the fire, which then produces more smoke.   

Still, a wildfire’s interactions with the atmosphere and the environment are complex, with terrain, vegetation, elevation and regional weather also contributing to the way a blaze develops. More research is needed to understand whether the smoke and fire feedback occurs in other areas.

“Let’s do more science,” said Abatzoglou. “Evaluating how this feedback works across a broader geography would be relevant.”

How fires interact with the weather of a specific, local area is an emerging area of research, according to Tim Brown, director of the Western Regional Climate Center at the Desert Research Institute, an environmental research center in Nevada. The goal is to be able to model fire behavior to predict how a fire could act and where smoke will travel.

“All that is actually quite complex to try and model,” he said.

If integrated with fire management, Davis said the research could inform the complicated calculus of how to allocate scarce firefighting resources. At the beginning of last year, the U.S. Forest Service unveiled a new “Wildfire Crisis Strategy” to direct its firefighting in the next decade.  

“The science is moving forward to understand which fires are going to be worse, so that we can prioritize our prevention and firefighting efforts,” said Davis. “We need more research on this to really try to understand which areas are most at risk.”

Emma Foehringer Merchant

Contributor

Emma Foehringer Merchant is a journalist who has covered environmental issues ranging from disasters to wonky energy regulations to air pollution. She’s reported on the environment and energy for publications including The Boston Globe Magazine, The New Republic, Vice News, and Grist. Most recently, Emma covered clean energy as a staff writer for Greentech Media and helped alums of that organization form a new publication called Canary Media. She’s attending MIT’s Graduate Program in Science Writing and holds a bachelor’s degree in environmental analysis from Pomona College, where she lived through a California drought while studying how climate change is impacting the state’s environment and people.

• [email protected]