Are Larger Fires Due to Global Warming?

There were more than 50 wildfires burning across the United States as of June 25, 2008.

Photo: Forest Service

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The number 800 has stuck out in the news coverage of wildfires in California recently. That's the estimated number of fires started by lightning strike over the weekend, and it's an extraordinarily large number. It's certainly news, and it makes a good headline. Today, officials say 500 homes in Big Sur are threatened by fire, and air quality is being damaged by smoke.

But the number of large fires tells a different story, one that speaks to longer-term trends rather than short-term storm damage.

More than 50 wildfires were burning 342,332 acres across the United States, with California so crowded with fires that national fire maps are too cluttered to read.

As of Wednesday, the National Interagency Fire Center had tallied 52 large wildfires in seven states, 33 of them in California.

(Note that the Forest Service map of fires uses a different tally than the Interagency Fire Center; it puts the total at 61 fires across the nation, and 34 in California.)

Buffeted by drought and fed by lightning and wind, the wildfire season has already exceeded the 10-year average by a significant margin. So far in 2008, 34,548 have burned 1.94 million acres, about 23% more than the average acreage to date.

That larger acreage has been burned with 14% fewer fires, demonstrating the influence of the largest of the fires.

California is facing the most fires by far:

NASA Earth Observatory

Besides the 33 fires in California, six other states were battling fires:

• Arizona (6)
• New Mexico (4)
• North Carolina (1)
• Texas (6)
• Virginia (2)
• Florida (1)

Robust just a couple of months ago, California's mountain snowpack had dwindled to just two-thirds of its normal level by the time the wildfire season started. Runoff to reservoirs and farm irrigation ponds was expected to drop by 35-45% from normal.

Drought across the nation has set the stage for a bad wildfire season. The U.S. Drought Monitor's latest weekly report showed worsening conditions across the West and South.

No weather event can be said to have been caused by global warming. There's no scientific way to prove that. But these conflagrations are consistent with what scientists have told us we should expect from climate change.

Scientists have documented an increase in wildfires attributed to climate change. They have predicted that global warming will produce more frequent and intense wildfires, in large part because mountain snowpacks are expected to dwindle. With less runoff, valley conditions will be drier throughout the season, leaving any dry wood more prone to ignition. (Certainly, forest management also plays an important role, as the buildup of dead wood over years or even decades has contributed to the conflagration.) Even the Bush Administration's science advisers recently endorsed these conclusions in a sweeping report that predicts more bouts of extreme weather in the United States and across North America.

Give that, the burning West is something we can expect more of in the years and decades to come.

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