December 27, 2006 - By Jeff Barnard, Associated Press
GRANTS PASS, Ore. - Using fire scars on nearly 5,000 tree stumps dating back
450 years, scientists have found that extended periods of major wildfires in
the West occurred when the North Atlantic Ocean was going through periodic
With the North Atlantic at the start of a recurring warming period that
typically lasts 20 to 60 years, the West could be in for an extended period
of multiple fires on the scale of those seen in 2002 and 2006, said Thomas
W. Swetnam. He's the director of the Laboratory of Tree Ring Research at the
University of Arizona and a co-author of the study published in the Dec. 26
issue of the Proceedings of the National Academy of Sciences.
"This study and others have demonstrated that there is an underlying
climatic influence on fuels and then on the weather conditions that promote
fires," said Dan Cayan, climate researcher at the Scripps Institution of
Oceanography, who did not take part in the study.
Ron Neilson, a U.S. Forest Service scientist who has developed models that
predict wildfire danger based on climate models, agreed with the study's
conclusions, and noted all the oceans are affected by global warming. And
that in turn could exacerbate the wildfire cycle.
Scientists have long seen a relationship between weather in the United
States and El Nino, a warming of water in the South Pacific.
When El Nino is strong, the Northwest typically has drought and severe fire
seasons, and the Southwest has rain. When the cycle reverses, known as La
Nina, the South Pacific cools, the Northwest has more rain, and the
Southwest has drought and fires.
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