Report: Deadly ‘Smoke Waves’ Will Inundate the West as Wildfires Grow
As wildfires ravage California and other parts of the American West, a new study warns that choking “smoke waves” from fires will become more frequent, severe, and long lasting as climate change warms the atmosphere.
The study includes an interactive map of 561 Western counties that allows the public, scientists, and policy makers to view recent and projected smoke waves—defined as two or more consecutive days with high levels of particulate matter 2.5 micrometers in diameter (PM2.5)—in each county.
The research, led by scientists at Harvard and Yale universities, was published in the latest issue of the journal Climatic Change.
“I believe it is the first study to estimate a county-level smoke exposure in the future and estimate the size of the population that is likely to be exposed by high pollution episodes from wildfires,” lead author Jia Coco Liu, a recent Ph.D. graduate of the Yale School of Forestry and Environmental Studies, wrote in an email.
The researchers analyzed smoke wave activity in the 561 counties between 2004 and 2009 and, using future models of weather patterns, fire risks, and population densities, estimated how often smoke waves will occur and how many people they will affect between 2046 and 2051.
They found that 312 counties will experience more intense smoke waves with higher amounts of PM2.5.
“Under climate change, the average wildfire-specific PM2.5 level for the years 2046–2051 was estimated to increase approximately 160 percent, and the maximum...by [more than] 400 percent,” the paper said.
The total number of people affected will rise from 57 million to 82 million, including 7 million more children and 5.7 million more elderly people.
Smoke waves will become more frequent, with the current average of 0.98 waves per county each year increasing to 1.53 waves in the 2050s, an increase of 64 percent, the paper said. Smoke intensity is expected to increase an average of 30.8 percent, and smoke wave seasons will grow by 15 days.
Northern California, the Pacific Northwest, and forests in the northern Rocky Mountains have experienced and will experience the greatest smoke waves, which can travel for hundreds of miles through the air.
Some of the worst smoke waves will be felt in heavily populated counties such as San Francisco County, Alameda County, and Contra Costa County in California and King County in Washington state.
The new estimates can help at-risk communities with “public health programs and evacuation plans in response to climate change,” the paper said. The smoke wave projections can also help forest management programs, climate change adaptation plans, and community preparedness.
Janice Nolen, assistant vice president of national policy at the American Lung Association, said the findings, while alarming, were not surprising.
“Most of the major reports I’ve seen identified wildfire smoke as one of the areas that are likely to increase with climate change, and we are already seeing that in the world,” she said.
Nolen, who produces the association’s annual State of the Air report, said smoke waves have almost certainly gotten worse since the 2004–2009 study period.
“The numbers are up in some places in the last few years,” she said. “Some had the highest numbers of unhealthy air days that we have tracked since 2004, and that’s unusual because, generally speaking, particle pollution has been reduced” because of stricter emissions controls on vehicle exhaust, power plants, and other sources.
The association’s 2016 report found that 12 of the 25 most polluted U.S. metropolitan areas saw extreme spikes in short-term particle pollution, suggesting wildfires played a role. Fires were prevalent in the West, “where continuing drought and heat may have increased the dust, grass and wild fires.”
Seven cities had their highest number of unhealthy days on average ever reported.
“It has some of the same toxic emissions as car exhaust,” Nolen said, “including carcinogens like formaldehyde and benzene, and nitrogen oxides, which are highly irritating pollutants that can harm the lungs.”
Particulate matter is especially worrisome, Nolen said.
“Soot and ash kill people—they cause asthma attacks, heart attacks, strokes, and send people to the hospital for care,” she said. “Wildfire smoke is a pretty toxic substance. It’s not as benign as people think when they’re just wiping off soot from their window.”