Oct 11, 2017
Study casts doubt on warming implications of brown carbon aerosol from wildfires
By Beth Miller
As devastating wildfires continue to rage in the western U.S. and Canada, a team of environmental engineers at Washington University in St. Louis have discovered that light-absorbing organic particulate matter, also known as brown carbon aerosol, in wildfire smoke loses its ability to absorb sunlight the longer it remains in the atmosphere.
Rajan Chakrabarty, assistant professor, and Brent Williams, the Raymond R. Tucker Distinguished InCEES Career Development Associate Professor, both aerosol scientists in the Department of Energy, Environmental & Chemical Engineering in the School of Engineering & Applied Science, and their labs found that brown carbon aerosol changes its properties from light-absorbing to light-scattering the longer it remains in the atmosphere. When it is first emitted, the smoke is brown and has a warming effect on the atmosphere. But over several days in the atmosphere, the smoke gradually turns white and has a significantly reduced warming effect. The resulting white smoke roughly contributes to roughly a 46 percent reduction in light absorption compared with the brown smoke.
“Our study casts doubts on the warming implications of brown carbon,” Chakrabarty said. “If this life cycle analysis is not taken into account, climate models could very well give rise to overestimated values of warming due to these aerosols.”
Results of the research were published in early online publication in “Environmental Science & Technology Letters” Sept. 21.
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