Climate change producing more, hotter wildfires

July 1, 1993

Wildfires in Western forests are getting hotter and lasting longer as a result of global warming, according to a new study by the Climate Research Division of the Scripps Institution of Oceanography.

Researchers said the new findings, published in the journal Science, indicate climate change, not firefighting policies and forest fuel buildup, is the primary driver of recent increases in large forest fires.

The analysis, prepared by Anthony Westerling, Hugo Hidalgo and Dan Cayan of Scripps, and Tom Swetnam of the University of Arizona, was developed from a database they built that looked at large Western wildfires from 1970 onward and compared that data with climate and land surface information from the region involved. It showed large wildfires multiplied “suddenly and dramatically” in the 1980s, according to the Scripps Web site.

It quotes Cayan on the topic: “The increase in large wildfires appears to be another part of a chain of reactions to climate warming. The recent ramp-up is likely, in part, caused by natural fluctuations, but evidence is mounting that anthropogenic effects have been contributing to warmer winters and springs in recent decades.” Cayan is director of the institution’s Climate Research Division and a co-author of the study.

The scientists examined 1,166 forest fires of at least 1,000 acres between 1970 and 2003, using data from U.S. Forest Service and National Park Service lands. They compared the times of the fires with the timing of snowmelt and spring and summer temperatures for the 34-year period.

Westerling commented: “At higher elevations, what really drives the fire season is the temperature. When you have a warm spring and early summer, you get earlier snowmelt. With the snowmelt coming out a month earlier, areas then get drier earlier overall, and there is a longer season in which a fire can be started—there’s more opportunity for ignition.”

The study found the greatest increases in wildfires happened in the northern Rockies, where the forest ecosystems were found to be highly susceptible to temperature increases. Other significant rises in the number of wildfires were in the Sierra Nevada, the southern Cascades and the coastal ranges of northern California and southern Oregon.

For Tom Swetnam, director of the Laboratory of Tree-ring Research at the University of Arizona in Tucson, the findings confirm the reality of global warming, the Scripps Institution reported.

“I see this as one of the first big indicators of climate change impacts in the continental United States,” he said. “We’re showing warming and earlier springs tying in with large forest fire frequencies. Lots of people think climate change and the ecological responses are 50 to 100 years away. But it’s not 50 to 100 years away—it’s happening right now in forest ecosystems through fire.” Dryness has been a factor in more than 50,000 fires in the first half of this year.

And while the temperatures in the West continue to soar, the current heat wave in our part of the country draws only annoyed responses to the old saw: “Hot enough for you?”

Past history shows heat waves are more lethal than hurricanes or tornadoes, according to an article on www.livescience.com. That site says studies have shown that extreme heat for extended periods will be more common in the future. The article reported that studies by NASA showed urban areas areespecially vulnerable because asphalt and rooftops soak up more solar radiation than open country, boosting nighttime readings as much as 5 degrees.

Temperatures are as much as 30 degrees higher than the seasonal average in the past few decades, according to Laurence Kalkstein, senior research fellow at the University of Delaware’s Center for Climatic Research. The summer of 2003 in Europe was one of the hottest in hundreds of years. The summer of 2005 set a new record for the hottest average global temperature, according to the www.livescience.com report.

Top computer models are showing continued global heating for the next several decades, no matter if greenhouse gases are curbed. No good plans to halt the rise have been proposed, according to www.livescience.com.

Researchers developed some scenarios of what extreme heat might do in the United States. “We tried to take the Paris heat wave in 2003 and transpose it onto the climate of five different cities,” Kalkstein said. The cities were New York, Detroit, Philadelphia, St. Louis, and Washington, D.C., according to an article by Sara Goudonzi on www.livescience.com.

In the simulations, Washington had 11 days of temperatures above 105 degrees, and St. Louis hit 116 degrees. New York and Philadelphia set all-time highs for four days. Detroit set new records twice in that period, the article said.

Worse, simulated deaths were five times the historical summer average, Kalkstein said. New York and St. Louis had the most. “New York is much bigger and clearly will have more deaths than cities like Washington and Detroit,” he said. “The second thing is that [a place such as] New York is a very sensitive city with a lot of high-rises and buildings that are sensitive to extreme heat,” the article said.

Kalkstein told www.livescience.com that improved planning and changes in architecture could save many lives during times of excessive heat. But the outlook is not encouraging. The Web site reported scientists have announced the first half of this year has seen temperatures the highest ever recorded in this country.

www.livescience.com reported temperatures for January through June were 3.4 degrees Fahrenheit more than the 20th-Century average. The states of Texas, Oklahoma, Kansas, Nebraska and Missouri saw record heat for the period, and no state had cooler-than-average temperatures, according to scientists at NOAA’s National Climatic Data Center in Asheville, N.C. We had the second-warmest June on record since 1895, according to the Web site.

Less-than-average rainfall brought moderate to extreme drought in nearly 45 percent of the country. What that portends for food production if the trend continues remains to be seen. One study said the amount of land damaged by drought has more than doubled in the last 30 years. Mother Nature is striking back.

From the July 19-25, 2006, issue

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