Wednesday, June 18, 2008

Global Warming to Spark Increase in US Wildfires


TODAY much of the north-western US wilderness is already a tinderbox, but thanks to global warming, wildfires will be scorching even more land every year by the end of the century.

Because warmer oceans encourage warmer weather, emergency planners in the US Southwest have long monitored temperatures in the equatorial Pacific to forecast wildfire activity. But a warm Pacific can spark fires in the north-west as well, says Yongqiang Liu of the US Department of Agriculture's Forest Service in Athens, Georgia. Warmer-than-average ocean temperatures in the North Pacific create more low-pressure weather systems than cooler waters do, pushing jet stream circulation north into Canada. This leaves room for high-pressure systems to move in from the south, bringing drier and hotter air to the north-west.

Liu plugged US fire and ocean temperature data from 1980 to 2002 into two major climate models, which predicted that average ocean surface temperatures in the northern Pacific will warm by least 0.6 °C by 2080. Liu's calculations show the amount of land burned annually in the north-west will grow from under a million hectares in 2002 to nearly 2 million hectares by 2080. He presented the work in May at an American Geophysical Union meeting in Fort Lauderdale, Florida.

From issue 2661 of New Scientist magazine, 18 June 2008, page 22

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