CORVALLIS, Ore. Wildfire, insect outbreaks and hurricanes destroy huge amounts of forest every year and increase the amount of carbon dioxide entering the atmosphere, but scientists are now learning more about another force that can significantly affect their climate impact.
Researchers conclude in a new study that the albedo effect, which controls the amount of energy reflected back into space, is important in the climatic significance of several types of major forest disturbances.
In some cases mostly in boreal forests with significant snow cover increases in reflectivity can provide cooling. If the area disturbed by fire or insects is large, this cooling can substantially offset the increase in global warming that would otherwise be caused by these forest disturbances and the release of greenhouse gases. In other cases where the ground itself is unusually dark, albedo decreases can magnify concerns about warming.
Wildfires are not the only disturbance that significantly alters surface albedo, this study concluded. Insect outbreaks and defoliation by hurricanes can also change surface reflectivity, with effects on climate as great as those caused by carbon dioxide release from the disturbed area.
"On a global scale, warming caused by increased carbon dioxide still trumps everything else," said Beverly Law, a professor in the Department of Forest Ecosystems and Society at Oregon State University. "On a smaller or local scale, however, changes in albedo can be fairly important, especially in areas with significant amounts of snow, such as high latitudes or higher elevations."
Albedo is a measure of radiation reflected by a surface, in this case the surface of the planet. Lighter colors such as snow reflect more light and heat back into space than the dark colors of a full forest and tree canopy.
"This decreased absorption of heat by the land surface is a local atmospheric cooling effect," said Tom O'Hallo
|Contact: Beverly Law|
Oregon State University