10.23.2007 12:00 AM

California Wildfires and Global Warming

Wildfires are More Frequent and Intense Due to Climate Change

The wildfires consuming Southern California are extraordinary: Extraordinary because they have claimed so many homes. extraordinary because they started so quickly and have burned so intensely. Extraordinary because they are exhausting the formidable firefighting resources in a region used to wildfire.

But in the years to come, they may become ordinary.

Scientists have already tied increased frequency and intensity of wildfires to the changing climate, and scientists are confident that the conditions that will be brought on by global warming will only make conditions more ripe for wildfire. Forest management practices -- like the fire-suppression techniques that left tinder-dry brush and wood littered across the Western landscape.

In a scientific paper published a year ago co-authored by Tom Swetnam of the University of Arizona's Laboratory of Tree-Ring Research, and Anthony Westerling, of the University of California-San Diego's Scripps Institution of Oceanography, scientists concluded that the changing climate was a greater influence on wildfire activity and intensity than forest management.

There were four times as many major wildfires between 1986 and 2004 as there were from 1970 to 1986, and a six-fold increase in the area of forest burned in the Western United States.

(Not included in the report were the three most recent years, all of which had intense fire seasons, including record-setting 2006, when more acreage burned than ever before recorded. So far this year (as of Monday) 76,451 large fires have burned 8,251,275 acres. That puts 2007 on a pace to rival the record-setting 2006 fire season.)

The active wildfire season has increased by more than two months, and individual fires are burning longer -- up from barely a week on average to more than five.

As spring and summer temperature has increased, snowpacks in the mountains has melted earlier -- between one week and one month earlier, on average, than 50 years ago. Since snow melt is responsible for 75% of annual stream flow, the decrease in snowpack drains regional streams and rivers, leading in turn to a drop in humidity.

So while no one event can be attributed to climate change -- no one can say that global warming caused these fires in California -- we can say that fires like these may well become more likely as global warming changes conditions on the ground.

It still takes a spark to start a fire -- whether it comes in the form of lightning, an illegal campfire or arson -- but the warmer climate sets the stage.

Find this article at: http://www.thedailygreen.com/environmental-news/latest/Global-Warming-California-Wildfire-47102305