for National Geographic News
The rapidly warming Arctic may be given a brief annual reprieve by smoke from North American wildfires, which cools the surface for weeks or months at a time, a new study found.
The smoke creates a veil of aerosols—tiny liquid and solid particles suspended in air—that reduces the amount of sunlight, temporarily lowering surface air temperatures.
The effect may last weeks to months during late spring through autumn if smoke is widely dispersed, potentially offsetting some of the warming caused by greenhouse gases, researchers say.
(Learn how the greenhouse effect works.)
When wildfires raged through Alaska and Canada in the summer of 2004, study lead author Robert Stone, from the University of Colorado and the National Oceanic and Atmospheric Administration (NOAA), and colleagues analyzed the fires' impacts on the amount of the sun's energy reaching Earth's surface.
The team used data collected at a NOAA climate observatory near Barrow, Alaska.
"That particular summer, the smoke from those fires drifted directly over Barrow, creating a natural laboratory to study this event ," Stone said.
The smoke layer was so thick that the total absorption and scattering of the sun's energy rose a hundredfold above typical summer values.
Stone's study is detailed this week in the Journal of Geophysical Research—Atmospheres.
Dark vs. Light
Like clouds, smoke cover can impact how much sunlight surfaces absorb.
Dark surfaces, such as land or open ocean, absorb most of the sunlight that reaches the surface. This process can make surface air temperatures warmer over dark regions.
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