"This trend of warmer sea-surface temperatures in the North Atlantic appears to be correlated with dry spells we have seen in the West since the late 1990s," said Veblen. "If the trend continues for the next 60 years or so as it has in the past, the degree of fire occurrence in the West could be unprecedented compared to anything in recent memory."
Although the atmospheric mechanisms relating drought in North America to sea-surface temperatures in the North Atlantic are subject to debate among climatologists, there is a strong statistical association of drought and fire in western North America when the Atlantic sea surface warms, said Veblen. The sea-surface temperature of both the Atlantic and Pacific oceans combine to influence the climate of much of the world through a complex web of atmospheric interconnections, he said.
"The key issue is that the Atlantic Multi-Decadal Oscillation persists on time scales of 60 to 80 years, compared to just one year or a few years for El Nio," he said.
Veblen said warmer temperatures in the West since the 1990s have exacerbated outbreaks of spruce and pine beetle populations, which have decimated millions of acres of coniferous forests in the West. "There is good evidence that warming trends like the one we are now seeing is very favorable for the population growth of these beetles."
Fire suppression activities during the 20th century have increased fuels and fire hazard in some forest types, although forest thinning may help reduce the impact of some severe fires by eliminating potential fuel sources, Veblen said. But the effectiveness of such practices pale in comparison to the potential of climatic factors.
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Contact: Thomas Veblen
Thomas.Veblen@colorado.edu
303-492-8528
University of Colorado at Boulder
26-Dec-2006