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02 September 2009
As California fire fighters battle a huge wildfire near Los Angeles,
scientists are warning of an increasing danger of wildfires due to
global warming. While a single wildfire cannot be linked to global
warming, many scientists speculate that in a warming world the
likelihood of wildfires is higher. Part of the issue is heat-induced
drought. "Fires clearly depend on weather," says Senior Harvard
researcher Jennifer Logan.
Logan and her colleagues are investigating
the consequences of climate change on wildfires, and the impact on U.S.
air quality. She says their research indicates the warming of the earth's
atmosphere "definitely" is linked to a longer summer and shorter
winter, which results in less snow and ice run off.
Hot Weather, Dry Vegetation
Wild
fires tend to get more severe when the weather is very hot, and very
dry for a long time where fuels can age. So far this year, more than
68,000 wildfires have burned about 2.2 million hectares of U.S. land,
which is not far off from the 10-year average (between 1999 and 2008)
of about 2.3 million hectares burned annually, according to the National
Interagency Fire Center.
As the climate warms in the coming
decades, however, Logan and her team of atmospheric scientists at
Harvard's School of Engineering and Applied Sciences (SEAS) expect that
the frequency of wildfires will increase in many regions. Their
research, published in the Journal of Geophysical Research, suggests
that the area of forest burnt by wildfires in the United States will
increase by more than 50 percent by 2050. Temperature was the primary
factor impacting the wildfire surge, though dry vegetation also played
a role.
Increased Wildfires and Increased Pollution
Tropical forests may be particularly affected by soaring
greenhouse gas emissions, noted scientist Chris Field of the Carnegie
Institute. "Tropical forests are essentially inflammable. You couldn't
get a fire to burn there if you tried. But if they dry out just a
little, the result can be very large and destructive," Field said.
The
Harvard study also represents the first attempt to quantify the impact
of future wildfires on the air we breathe. Its findings are ominous.
"Because smoke and other particles from fires adversely affect air
quality, an increase in wildfires could have large impacts on human
health," said Logan.
The researchers predict that an increase of more
than 50 percent in the burn area in the western United States by 2050
would result in a near doubling of carbon-based aerosols into the
atmosphere and "important consequences" for western U.S. air quality
and visibility.
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