Image courtesy of John Fowler (via Wikimedia Commons) under a Creative Commons license.
Aerosol observations from the 2011 Las Conchas fire in New Mexico (seen here) are helping researchers gain a better understanding of wildfire effects on climate.
Current climate models suggest that wildfires may have little to no impact on Earth’s climate because they assume that the two most conspicuous products of biomass-burning events—soot and smoke—affect climate in opposite ways. Soot particles are assumed to absorb sunlight and warm Earth’s climate, whereas smoke reflects sunlight and cools surface temperatures.
An observation-based study of aerosols in smoke emitted from a New Mexico fire demonstrates that the above assumptions, particularly about the effects of smoke on climate, may not be valid. This study shows that understanding aerosol properties is critical in evaluating the impact of wildfires on climate, especially as dry and hot summers increase the frequency of these events.
Evaluating wildfire effects on climate requires better understanding the properties of aerosols emitted during burning events. Using high-precision instruments, a research team from Michigan Technological University and Los Alamos National Laboratory analyzed aerosol samples collected over 10 days in Las Conchas, New Mexico, from a smoldering fire that was the largest in state history. The team found that smoke from the fire contained significant quantities (10 times more than previously thought) of a special type of spherical carbon-rich aerosol known as “tar balls” that strongly absorb sunlight and cause warming. Researchers also found that organic substances in the smoke almost always coat soot particles, 50% of which were coated completely in this particular study. The coating acts as a lens that focuses and amplifies the amount of sunlight a soot particle absorbs. Contrary to climate model assumptions, tar balls and coated soot particles in smoke do not cancel out each other’s effect, but together more than double the amount of warming at the surface. Paucity of relevant data so far has resulted in an incomplete, perhaps even inaccurate, understanding of the impact of wildfires on climate.
Atmospheric Sciences Program, Michigan Technological University, Houghton, Michigan
This work was partially supported by Michigan Technological University start-up funds, National Science Foundation award AGS-1028998, and U.S. Department of Energy (DOE) award DE-SC0006941. Los Alamos National Laboratory work was funded by DOE’s Atmospheric System Research program (project F265, KP1701).
China, S., et al. “Morphology and mixing state of individual freshly emitted wildfire carbonaceous particles,” Nat. Commun. 4, 2122 (2013). [DOI:10.1038/nc comms3122].
University, DOE Laboratory