NCAR - Scientists Suspect Beetle-Killed Forests Provide Further Boost To Warming Surface Temperature

[hatrack]

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NCAR researchers are about a year into a four-year study to gauge and assess such effects. The research centers in large part on the ability of living trees to cool the air when they evaporate moisture through their leaves – a process called transpiration – and what happens to climate conditions when large numbers of trees die. Trees also help control surface temperatures by absorbing and reflecting heat from the sun.

Disrupting these basic functions by destroying wide swaths of trees across the West appears to spike surface temperatures. Already the researchers have completed computer modeling studies indicating that if the millions of acres of pine trees in Colorado were to die, that could raise temperatures statewide nearly 4 degrees Fahrenheit, said Christine Wiedinmyer, a NCAR scientist in Boulder and, with Harley, one of the principal investigators on the project. "It's still highly uncertain. People have not gone out and measured the impacts of dead forests," Wiedinmyer said. "But it looks like it can change the temperatures on the ground."

NCAR researchers believe these disruptions could reduce rainfall amounts in the arid West by severing the interaction between tiny airborne particles from plants that rise up into the atmosphere and seed clouds with water droplets, possibly decreasing the availability of particles to form clouds.

A four-degree temperature rise in the West could be particularly calamitous to a region already feeling the stress of limited water supplies. A study by the U.S. Global Change Research Program released earlier this year found the drought, wildfire and invasive species invasions accompanying rising temperatures will reshape the landscape, threatening the region's biodiversity, water supplies, and agriculture and tourism industries. "The most likely future for the Southwest is a substantially drier one," the report's authors noted. "The combined effects of natural climate variability and
human-induced climate change could turn out to be a devastating 'one-two punch' for the region."

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http://wwwp.dailyclimate.org/tdc-newsroom/2009/10/forests-death-brings-higher-temps