Wildfires Lead to More Warming than Climate Models Predict
Current climate models suggest 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—impact 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 the largest New Mexico fire demonstrates that the above assumption, particularly about smoke impacts on climate, may not be valid. To evaluate the impact of wildfires on climate requires better understanding of 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 from a smoldering fire at La Conchas, NM, the largest in New Mexico’s history. The team found smoke from the fire contained large 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. They also found that organic substances in the smoke almost always coat the soot particles, with 50% of soot particles coated completely by organic substances present in the smoke. The coating acts as lenses that focus and amplify the amount of sunlight the soot particles absorb. The tar balls and coated soot particles in the smoke do not cancel out each other’s effect as climate models assume, but together more than double the amount of warming at the surface. To date, data paucity has resulted in an incomplete, perhaps even inaccurate, understanding of the impact of wildfires on climate. This study shows that understanding aerosol properties is critical in evaluating the impact of wildfires on climate, especially as dry and hot summers lead to an increase in the frequency of these events.
China, S., C. Mazzoleni, K. Gorkowski, A. C. Aiken, and M. K. Dubey. 2013. “Morphology and Mixing State of Individual Freshly Emitted Wildfire Carbonaceous Particles,” Nature Communications, DOI: 10.1038/ncomms3122.