Residents in the Pacific Northwest and parts of Northern California could see particle pollution from wildfires increase more than 50% by the middle of the century, compared with recent decades, and triple by century's end, new research shows.
The troubling scenarios, published Monday by scientists at Princeton University and the National Oceanic and Atmospheric Administration, up the ante on a sobering trend identified in past research and mark a future in which smoky skies make late summer and early fall practically unbearable.
Already, many in California have had a taste of what might become more commonplace. Weeks of filthy air, and sometimes burnt orange skies, blanketed the state during such recent blazes as the Caldor, Dixie and August Complex fires. Some residents have cited the smoke as a reason for moving away.
The new study is based on modeling of particle pollution that, unlike previous research, incorporates not only how climate change is boosting fire frequency but how some of the intricacies of climate change are playing out: for example, how burned landscapes are causing ground temperatures to rise and further elevate fire risk. The modeling also incorporates how climate change is driving weather conditions conducive to dirty air, for example, increasing air stagnation and smoke transport.
These compounding climate events account for the more dire results.
"We were surprised by both the absolute increase of particle pollution and the difference between our projections and the projections in the [previous] Earth-system models," said Yuanyu Xie, the study's lead author and a postdoctoral research associate at Princeton University.
The work of Xie and her colleagues was published in the journal Proceedings of the National Academy of Sciences.
The paper is just the latest in a slew of new research focused on wildfire smoke. The studies increasingly show that the tiny liquid and solid particles suspended in smoke, known as particle pollution, have increased the risk of experiencing a vast array of previously unconnected health issues, from cardiovascular failure to birth defects to COVID-19.
Some studies have suggested that particle pollution from smoke is even more harmful than particles emitted from cars and power plants.
The problems start when the material is inhaled and enters the lungs and bloodstream. The ensuing mechanics and medical ramifications are still not fully understood.
The new study, like earlier research, shows that particle pollution from wildfire smoke is likely to worsen as the climate continues to warm, but even small bumps in temperature — which could come if effective climate policies are put in place — result in much dirtier air, the models show.
Under what the researchers call a "strong-mitigation" scenario, in which temperatures stabilize this century, the amount of PM 2.5 — particulate matter that is 2.5 micrometers or smaller — would increase 50% by 2050 in August and September in Oregon, Washington and the most northerly parts of California, compared with emissions between 1990 and 2010.
Conversely, if temperatures aren't stabilized before 2100, PM 2.5 emissions would continue to grow in these places, doubling or tripling by the end of the century during August and September, compared with the recent decades.
Under this more dire scenario, the probability that air quality in late summer and early fall would exceed the daily national standard for PM 2.5 would rise to 70% by 2080 in the Pacific Northwest and the northernmost part of California, according to the modeling. The standard is 35 micrograms per cubic meter.
Many days would see PM 2.5 levels well above the daily standard, according to the models, pushing to thresholds that popular air quality sites, such as AirNow and PurpleAir, would flag as very unhealthy.
Marshall Burke, an associate professor of earth system science at Stanford University who wasn't affiliated with the new study but has researched wildfire smoke, said there's no doubt that particle pollution from smoke is on the rise.
A study published last year by Burke found that wildfires have recently accounted for up to half of the PM 2.5 pollution observed across parts of the West, and that amount could very well grow.
State and federal environmental laws have made inroads on curbing particle pollution from vehicles and industry but not wildfire smoke.
"The frustrating thing here is that through a lot of investment and policy change over the past few decades we've made a lot of improvement in air quality," Burke said. "Unless something changes, with wildfires, a lot of that progress is going to be reversed. It would be sad to lose this progress that has had benefits for so many people."
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