Devastating Wildfire Seasons Could Grow More Frequent

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Colorado wildfires consume 450 homes and kill two people.

A Prescott wildfire grows to 7,000 acres in 24 hours, forcing hundreds to flee their homes.

Still, the region bakes with no hint of the monsoon that would reduce the extreme fire risk.

Well, best get used to it.

Climate projections call for a doubling in the number of wildfires in the West between now and 2050, according to a study published in the journal Forest Ecology and Management.

That study reinforces climate projections coming from NASA, presented at a recent conference of the American Geophysical Union. Those projections say that high-fire years like 2012 historically occurred about once a decade. As average temperatures rise and droughts lengthen, high fire years will come more like 2-4 times per decade.

Last year, more than 6 million acres burned in the U.S. That’s still short of 2011’s record total of 8 million acres — but higher than 12 of the 15 years since NASA began compiling reliable satellite-based data in 1997.

The study found that the average number of acres burned has increased markedly in the past 25 years. As a result, the amount of heat-trapping carbon dioxide released into the atmosphere has increased from an average of 9 million tons annually between 1994 and 1985 to an average of 22 million tons annually between 1996 and 2008 — even before the record setting years of 2011 and 2012.

The researchers noted that controlled burns and agricultural fires accounted for 70 percent of the total.

The Forest Ecology study hinted at the impact of that dramatic rise in the number of fires and the smoke they produce.

Smoke from big fires can readily rise into the upper reaches of the atmosphere, where it can have a marked effect on temperatures. Some particles readily absorb solar radiation, which ought to cool the surface in the immediate area. On the other hand, the carbon dioxide in the smoke also blocks the radiant heat coming off rocks and earth. That has the effect of increasing the temperature over a much wider area.

Moreover, the smoke particles also inhibit the formation of raindrops, temporarily reducing rainfall. The wildfires can then create a feedback loop: Longer, deeper droughts cause more fires, which put out smoke, which reduces rainfall, which extends and deepens droughts.

Soot that eventually settles to earth can have other effects. For instance, soot can settle out over long distances. If it lands on snow packs, it will prompt the snow banks to absorb more heat and melt sooner in the spring.

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