Aerosols in wildfire smoke can affect the climate for days

A new study led by the University of California, Davis has found that aerosols – suspended liquid or particles that are key to cloud formation – carried within wildfire smoke plumes which are hundreds of hours old can still have a significant impact on the climate.

These findings could help fill a scientific knowledge gap and can inform predictions about the climate and atmospheric effects of wildfire over the lifetime of aerosols, especially in rural areas or other regions with relatively clean air.

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

In 2019, Professor Zhang and her colleagues spent time at the Mount Bachelor Observatory, located on top of a volcanic mountain in Oregon. Although that year was relatively calm in terms of wildfires, smoke plumes and aerosols could still be detected. Some of these were at least 10 days old and came from as close as Northern California and as far as Siberia in Russia.

Due to their chemical composition and properties, aerosols can scatter or absorb solar radiation affecting temperatures, seed clouds that produce rain or snow, or change cloud reflectivity. All of these processes can have a marked impact on the climate.

The analysis of samples from Mount Bachelor revealed low particulate matter concentrations, but significant traces of oxidized organic aerosols from burning trees, shrubs, or grasses. These aerosols – with a life cycle of two weeks – were larger in aged samples compared to those detected immediately after wildfires start.

“The properties of the smoke determine the effects on the climate,” Professor Zhang explained. “The really aged aerosols can behave very differently than the fresh ones. You want to capture these aerosols over the lifetime to properly account for the effects.” 

Further research is needed to investigate the ways in which these aerosols affect the climate, particularly since biomass burning has become increasingly frequent.

The study is published in the journal Environmental Science & Technology.    

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By Andrei Ionescu, Earth.com Staff Writer