<div><span><span><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/abstract/1128834v1?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=westerling+forest+fires&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT" target="_blank">
http://www.sciencemag.org/cgi/content/abstract/1128834v1?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=westerling+forest+fires&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT</a></span></span></div>
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<p>Published Online July 6, 2006<br><em>Science</em> DOI: 10.1126/science.1128834</p></td>
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<h2>Research Articles</h2>
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<p><font size="-1">Submitted on April 17, 2006</font><br><font size="-1">Accepted on June 28, 2006</font><br><br>
<h2>Warming and Earlier Spring Increases Western U.S. <span>Forest</span> Wildfire Activity </h2><strong>Anthony Leroy <span>Westerling</span> <sup>1</sup><sup>*</sup>, Hugo G. Hidalgo <sup>2</sup>, Daniel R. Cayan <sup>
3</sup>, Thomas W. Swetnam <sup>4</sup> </strong>
<p><sup>1</sup> Scripps Institution of Oceanography, La Jolla, CA 92093, USA; University of California, Merced, CA 95344, USA.<br><sup>2</sup> Scripps Institution of Oceanography, La Jolla, CA 92093, USA.<br><sup>3</sup>
Scripps Institution of Oceanography, La Jolla, CA 92093, USA; US Geological Survey, La Jolla, CA 92093, USA.<br><sup>4</sup> Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721, USA.<br></p>
<p><sup>*</sup> To whom correspondence should be addressed.<br>Anthony Leroy <span>Westerling</span> , E-mail: <span><a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:awesterl@ucsd.edu" target="_blank">
<font color="#53859f">awesterl@ucsd.edu</font></a></span><span> </span><br>
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<p>Western United States <span>forest</span> wildfire activity is widely thought<sup> </sup>to have increased in recent decades, but surprisingly, the extent<sup> </sup>of recent changes has never been systematically documented.
<sup></sup>Nor has it been established to what degree climate may be driving<sup> </sup>regional changes in wildfire. Much of the public and scientific<sup> </sup>discussion of changes in western United States wildfire has
<sup></sup>focused rather on the effects of 19th and 20th century land-use<sup> </sup>history. We compiled a comprehensive database of large wild<span>fires</span><sup> </sup>in western United States <span>forest</span>s since 1970 and compared it
<sup></sup>to hydro-climatic and land-surface data. Here, we show that<sup> </sup>large wildfire activity increased suddenly and dramatically<sup> </sup>in the mid-1980s, with higher large-wildfire frequency, longer<sup>
</sup>wildfire durations, and longer wildfire seasons. The greatest<sup> </sup>increases occurred in mid-elevation, Northern Rockies <span>forest</span>s,<sup> </sup>where land-use histories have relatively little effect on fire
<sup></sup>risks, and are strongly associated with increased spring and<sup> </sup>summer temperatures and an earlier spring snowmelt.</p>
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<div><span><span><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.usatoday.com/weather/climate/2006-07-06-climate-fires_x.htm" target="_blank">http://www.usatoday.com/weather/climate/2006-07-06-climate-fires_x.htm
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<div><span><span><font size="4">Study links extended wildfire seasons to global warming</font></span></span></div>
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<div><span>Updated 7/7/2006 9:10 AM ET</span> </div>
<div>By Patrick O'Driscoll, USA TODAY</div>
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<div>DENVER — The number and size of large forest fires in the West have grown "suddenly and dramatically" in the past two decades in part because of global warming, a study released Thursday says. </div>
<p>The scientific paper, posted online by the journal <i>Science</i>, says wildfire season in Western states has grown up to 2½ months longer since 1987 because of warmer spring temperatures and earlier, faster melting of mountain snow. The timing of that annual snowmelt, a key source of the West's water, also helps gauge the severity of wildfire season.
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<p>The study by scientists at the University of California-San Diego and the University of Arizona does not address the cause of climate warming, only the effect it has had on forest fires here. Climate change is caused by gases that trap heat in the Earth's atmosphere. Scientists and politicians debate how much of that heating is made worse by humans and the burning of fossil fuels.
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<p>"We didn't set out to make a climate-change argument," says co-author Anthony Westerling, a researcher at UC-San Diego's Scripps Institution of Oceanography. "But it's easier to see how a further (rise) in temperature under climate change would result in more frequent (wildfires) in these severe years. You get early snowmelt, the soil and vegetation dry out sooner, and you get a lot more fires, burning longer and getting bigger."
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<p>The paper analyzes 1,166 large forest fires (at least 1,000 acres each) from 1970 to 2004 on national forest and park land in the West. In the second half of that period, 1987-2004, there were four times as many forest fires, and 61/2 times as much land burned.
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<p>Co-author Tom Swetnam of Arizona's Laboratory of Tree-Ring Research says the key shift was after 1987. Infrequent large fires that lasted a week or so gave way to more frequent infernos that averaged five weeks. One of the worst years was 1988, when almost one-third of Yellowstone National Park burned until autumn. The climate effect is most dramatic in the northern Rockies, which includes Yellowstone. The number of large fires in Idaho, Montana and Wyoming has risen 60% since 1987.
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<div>Climate is the principal reason, Swetnam says. Forests in the northern Rockies have not been as heavily managed to stop fires as most other places in the West. Putting out more fires can lead to worse fires by leaving unburned debris and unthinned groves. So human intervention is a factor, along with warming, in the worsening of wildfires in many areas. But the rising temperatures and dryness due to warming are the main factor in the northern Rockies, Swetnam says.
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<div>Vision2020 Post by Ted Moffett</div>