The Arctic may get some temporary relief from global warming if the annual North American wildfire season intensifies, according to a new study by researchers at the University of Colorado and NOAA. The study, which appears this week in the Journal of Geophysical Research, argues that smoke transported to the Arctic from northern forest fires may cool the surface for several weeks to months at a time.
Ironic, isn't it?
According to the lead author of the paper, atmospheric scientist Robert Stone:
"Smoke in the atmosphere temporarily reduces the amount of solar radiation reaching the surface. This transitory effect could partly offset some of the warming caused by the buildup of greenhouse gases and other pollutants."
Stone and his research colleagues analyzed the short-term climate impact of numerous wildfires that swept through Alaska and western Canada in 2004. That summer, fires burned a record 10,000 square miles of Alaska's interior and another 12,000 square miles in western Canada.
Smoke in the atmosphere tends to cool the snow-free tundra while warming the smoke layer itself, the authors found. Smoke has an even greater cooling effect over the darker, ice-free ocean and less over bright snow.
"The heating of the smoke layer and cooling of the surface can lead to increased atmospheric stability, which in turn may keep clouds from forming," said Stone. "We think that this influence of smoke aerosol on clouds further affects the balance of radiation reaching the surface in the Arctic."
To conduct their analysis, Stone and colleagues looked at how a range of smoky conditions might change the amount of solar radiation reaching the Earth’s surface. Models showed that the cooling caused by future forest fires would depend on the severity of the fire season and on the geographic dispersion of smoke.
The authors cautioned, however, that the full climate impact of Arctic aerosols, including smoke particles, is still not entirely clear. For one thing, smoke particles captured within clouds or deposited on snow may change the brightness of these objects, further affecting the amount of solar radiation absorbed by the surface.
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Photo Credit: California wildfires taken from the International Space Station (NASA)