As of Tuesday, there were 36 large fire complexes in the United States, burning nearly 730,000 acres in 11 states. That's 1,100 square miles, an area about three-quarters the size of Rhode Island. Flare-ups in Washington have come just as firefighters gain ground on the raging fires in California that have dominated the nation's attention.
So far in 2008, 3.2 million acres have burned (15.5% more than the 10-year average, but actually 7.8% less than the five-year average), many millions of dollars have been spent, dozens of homes have been reduced to ash, and nearly 20,000 firefighters continue to put their lives at risk every day to battle the blazes.
And it's likely to get worse, according to a new study.
The reason? As the climate warms, snow is likely to melt off mountains faster than earlier predicted, according to new research out of Purdue University, Loyola Marymount University and North Carolina at Wilmington. Paid for by the National Science Foundation, the research will be published in Geophysical Research Letters, a peer-reviewed scientific journal.
The key finding is that the loss of snow will increase the heat absorbed by the darker land uncovered. The more bare land area exposed, the warmer the area and the harder it is for snow to accumulate, leading to a feedback loop that inhibits snow and favors open land. While that phenomenon was known, these researchers say they've created a better model for predicting how it plays out in the complex topography of the mountainous West.
"Because snow is more reflective than the ground or vegetation beneath it, it keeps the surface temperatures lower by reflecting energy from the sun," said Sara A. Rauscher, visiting scientist at the Abdus Salam International Centre for Theoretical Physics in Trieste, Italy, and lead author on the paper. "When snow melts or does not accumulate in the first place, more solar energy is absorbed by the ground, warming the surface. A feedback loop is created because the warmer ground then makes it more difficult for snow to accumulate and perpetuates the effect."
If mountains shed their snow earlier in the season, it means moisture levels in the valleys will drop faster and drier conditions will set in earlier. That means fire season will start earlier. California Gov. Arnold Schwarzenegger has already stated that the old notion of a fire "season" has given way to round-the-calendar risk.
Of course, early snowmelt also will have important impacts on drinking water supplies, agriculture and wildlife. But with wildfires taxing the West, fire risk is paramount on the minds of many concerned about climate change. Scientists have said that increased wildfire risk is among the predictions they are most confident about when looking at global warming data. Reduced runoff from the mountains, coupled with greater heat and evaporation, and infestations of new insects that will weaken trees, has already led to bigger and more intense fires, according to some studies.
The figure shows projected future changes in the timing of runoff in snow-dominated areas of the western United States. The timing of runoff shifts earlier in almost all areas as greenhouse gas concentrations increase. These snow-dominated areas currently act as natural reservoirs, with melting in the spring and summer providing critical fresh water throughout the western United States. A shift to earlier runoff could pose challenges for human consumption, agriculture, wildfire management and sensitive ecosystems.
Credit: Purdue University/Diffenbaugh Laboratory
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