Wildfire shifts could dump more ice-melting soot in Arctic

Raging wildfires could burn away efforts to reduce Arctic-damaging soot emissions. Soot produced by burning fossil fuels and plants, also called black carbon, can cause respiratory diseases and greenhouse warming, and can accelerate the melting of ice.

Rising temperatures and changing weather patterns will shift where and how fiercely wildfires burn and spew soot, new simulations show. Outside of the tropics, fire seasons will last on average one to three months longer during the 2090s than they do currently, researchers report online April 8 in the Journal of Geophysical Research: Atmospheres. Soot emissions from wildfires will as much as double in regions that border the Arctic and counteract projected reductions in soot from human activities, the researchers predict.
“Humankind would do well to proactively develop adequate land and fire management strategies to have at least some control on future wildfire emissions,” says study coauthor Andreas Veira, an earth system scientist at the Max Planck Institute for Meteorology in Hamburg.

Predicting the future of fires is difficult because many factors — from weather to vegetation — influence wildfires. Veira and colleagues strung together three different computer simulations that projected the impact of climate change on wildfires (SN Online: 7/15/15). The first predicted future changes in global vegetation, which fed into the second, a wildfire simulation called SPITFIRE. Finally, the researchers plugged their predicted fires into a climate simulation.

If carbon emissions aren’t cut, overall soot emissions from wildfires will stay fairly steady but shift in location. Outside of the tropics, wildfire soot emissions will increase 49 percent by the end of the century as fire seasons get longer, the researchers predict. In the tropics, changing land usage and fewer human-caused ignitions due to urbanization will help decrease emissions there by 37 percent.

A northward shift in wildfires will push more soot emissions toward the Arctic, the researchers warn. Fallen soot darkens ice and snow, accelerating melting (SN: 10/5/13, p. 26). A 2009 study estimated that soot was responsible for more than a third of Arctic warming between 1976 and 2007. The new simulations show that about 53 percent more soot will fall on the Arctic at the end of the century, even if humans cut their own soot emissions in half.

Many factors that could influence future wildfires remain uncertain, says atmospheric scientist Shane Murphy of the University of Wyoming in Laramie. “We shouldn’t take the absolute numbers to mean too much, just to inform us that there’s the potential for severe consequences.”