WASHINGTON California wildfires pumped nearly 8
million metric tons of climate-warming carbon dioxide into the
atmosphere in just a week, about one-quarter as much as fossil
fuels do in that state in a month, scientists said on
The release of carbon dioxide in wildfires is part of the
natural cycle in which burning plays an important role, the
scientists reported in the online journal Carbon Balance and
Management. And the ebb and flow of carbon that is alternately
sucked up and emitted by plants is different from that spewed
by fossil-fueled factories and vehicles.
Overall, the study estimates that fires in the contiguous
United States and Alaska release about 290 million tons of
carbon dioxide a year, equivalent to 4 to 6 percent of U.S.
emissions from the burning of fossil fuels like coal and oil.
These figures are hard to pin down because of the challenge
of figuring out how much carbon was tied up in the plants that
burned, and what percentage of the plants actually went up in
flames in different kinds of fires, said Jason Neff of the
University of Colorado at Boulder, a co-author of the study.
The estimates carry a 50 percent margin of error, but that
still means U.S. wildfires emission are equivalent to between 2
and 8 percent of emissions from fossil fuel burning, which Neff
noted is a considerable fraction.
Fires contribute a higher proportion of carbon dioxide in
several western and southeastern states, especially Alaska,
Idaho, Oregon, Montana, Washington, Arkansas, Mississippi and
Arizona, the study said.
HEAVY CARBON FOOTPRINT
Big fires like the ones that destroyed more than 2,000
homes in California this month can have a particularly heavy
carbon footprint, the researchers wrote.
"A striking implication of very large wildfires is that a
severe fire season lasting only one or two months can release
as much carbon as the annual emissions from the entire
transportation or energy sector of an individual state," the
Because planetary climate change is expected to bring more
frequent and widespread wildfires, these could release more
carbon dioxide into the atmosphere as the planet warms, in what
scientists call a positive feedback loop -- a cycle that feeds
on itself, spurring global warming.
Neff and Christine Wiedinmyer of the National Center for
Atmospheric Research drew a distinction between carbon dioxide
released by periodic wildfires and that released by fossil fuel
Carbon emitted by fires will eventually be absorbed by
plants as forests and grasslands regenerate after the blaze.
But modern trends to suppress fires can have an unintended
effect of giving the next fire more plant life to feed upon,
since forests have the time to grow more densely.
Carbon emitted by fossil fuel burning is carbon that was
locked underground for hundreds of millions of years, and after
it is released, it will not be reabsorbed by the ecosystem on
any human timetable. This is a large release of climate-warming
gas, Neff said.