According to researchers who published a recent paper in the International Journal of Wildland Fire (Volume 18 2009), climate change will increase the number and burn severity of fires in Yosemite National Park. Using fire records, weather data, and satellite imagery they analyzed the fires in the park that occurred between 1984 and 2005. Comparing snowfall records with fire severity, they determined that during those years, decreased spring snowpack exponentially increased the number of lightning-ignited fires and the proportion of the landscape that burned at higher severities.
The researchers then made some predictions:
Using one snowpack forecast, we project that the number of lightning-ignited fires will increase 19.1% by 2020 to 2049 and the annual area burned at high severity will increase 21.9%. Climate-induced decreases in snowpack and the concomitant increase in fire severity suggest that existing assumptions may be understated – fires may become more frequent and more severe.
Here is the way this is supposed to work. There is some evidence to suggest that increasing levels of carbon dioxide in the atmosphere will lead to more lightning strikes. With less snow, the lightning strikes are more likely to ignite fires. The dryer fuels will result in the fires burning more intensely.
UPDATE, November 5, 2009: