Wildfire smoke particles can affect climate for days, not hours, UC Davis study finds

On top of their risk to human health and the environment, emissions from wildfire smoke can also alter the climate — even “hundreds of hours” after the smoke has plumed, according to a recent study led by researchers from University of California, Davis.

A research team traveled in summer 2019 to the Mount Bachelor Observatory in Oregon to gain a “better understanding of the aging of biomass burning organic aerosols,” which are particles that result from fires that burn biomass such as trees, grasses and shrubs, the study’s abstract explains.

Environmental chemists and toxicology researchers conducted measurements of aerosol concentrations linked to fire events.

Working from the Oregon observatory, which sits atop a volcanic mountain, researchers found wildfire plumes with “transport times” varying from about 10 hours to 10 days or longer, according to the study.

The exact effect of wildfire aerosols on the climate can vary, from influencing temperature to seeding rain- or snow-producing clouds, depending on location and numerous other factors, according to a UC Davis news release accompanying the study.

“These parameters are really useful for atmospheric and chemical models,” Qi Zhang, the study’s lead author and an environmental toxicology professor at UC Davis, said in the university news release. “It’s a really important component to solving the effects on climate. To capture those characteristics is super critical.”

It is already well-established that some of the largest, most intense wildfires can create their own weather systems. Multiple “firenadoes” have been confirmed in California in recent wildfire seasons.

But previous academic study of wildfire aerosols and pollution focused mostly on the early hours of smoke plumes. A better understanding of how those aerosols linger and behave in the longer term will be essential to modeling and addressing climate change, according to Zhang’s team.

The new research could help in particular in modeling wildfires’ impacts on climate in “rural or pristine areas with relatively clean air,” university officials wrote.

The plumes’ aerosols traveled a wide range of distances, as well. Some came from Northern California, which had a relatively calm fire year in 2019 compared to surrounding years. One plume was tracked all the way from the Russian province of Siberia.

The study, titled “Persistent Influence of Wildfire Emissions in the Western United States and Characteristics of Aged Biomass Burning Organic Aerosols under Clean Air Conditions,” was published in the March 1 edition of the journal Environmental Science and Technology.