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Global Climate Change: Ill Wind for California Wildfires

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December 4, 1998

By Lynn Yarris,

BERKELEY  --  Against the backdrop of concerns raised in the aftermath of this year’s El Niņo weather anomaly, researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have released the first-ever analysis of the potential effect of global climate change on wildfires and the ability to suppress them.

"In most cases, climate change would lead to dramatic increases in both the annual area burned by California wildfires and the number of potentially catastrophic fires -- doubling these losses in some regions," the researchers conclude. "These changes would occur despite deployment of fire suppression resources at the highest current levels, implying that climatic change could precipitate an increase in both fire suppression costs and economic losses due to wildfires."

Commenting on the study, U.S. Energy Secretary Bill Richardson said, "This study is indicative of the mounting evidence that the potential effects of climate change can be wide-ranging and very costly."

Other parts of the country might be just as vulnerable as California, according to Margaret Torn of Berkeley Lab’s Earth Sciences Division, one of the three scientists who conducted the study. "Our analysis shows how big an impact climate change can have, and suggests that future climatic conditions in other parts of the United States warrant concern and study," she said.

The other scientists who conducted this study were Evan Mills, with Berkeley Lab's Environmental Energy Technologies Division, and Jeremy Fried, an associate professor of forestry at Michigan State University. The study was sponsored by the U.S. Environmental Protection Agency.

Nearly 85-percent of all catastrophe-related insurance payouts result from natural disasters, with claims averaging about $10 billion per year worldwide over the past decade. Wildfires are among the most pervasive of all the natural disasters, especially for California. According to studies by insurance agencies, of the 38 costliest U.S. wildfires between 1825-1995, 22 were in California. The state also ranks number one in terms of economic losses due to wildfire.

"These insurance exposures are increasing precipitously as human developments encroach further and further into the urban/wildland interface," Says Mills. "The $2 billion Berkeley/Oakland hills fire of 1991 -- the third most costly fire in U.S. history -- is a notable example."

Fire danger has long been linked to climate, with hot, dry spells creating the highest risk. Concerns over the consequences of global warming were rekindled this year by the impacts of El Niņo. Droughts linked to El Niņo were followed by widespread, devastating fires in Florida, Indonesia, and elsewhere.

"The latest predictions suggest that global warming may also create conditions that intensify wildfire danger, by warming and drying out vegetation, and by stirring the winds that spread fires," the Berkeley Lab researchers say in a report on their analysis. "Faster fires are much harder to contain, and thus are more likely to expand into residential neighborhoods, incurring substantial damage to insured property."

To evaluate the potential effects of global climate change on wildfire damage in California, the research team of Torn, Mills, and Fried combined local weather and fire data, validated fire and fire suppression models, and state-of-the-art general global climate models.

"We tested the case in which atmospheric concentrations of the most important greenhouse gas, carbon dioxide, double their current levels," says Torn.

Three regions in Northern California were examined  --  Santa Clara, the Sierra foothills, and Humboldt. Each features a distinct climate, and, together, harbor most of the vegetation types found in the American west, including grass, chaparral (scrub or brush), oak savanna, and mixed conifer and redwood forests.

Taking a conservative approach, the researchers only reported the results based on the climate change model that, out of two tested, predicted the least impact on wildfire. This model, from the Goddard Institute for Space Sciences, provides standard scenarios for climate change impact assessments used by government and university scientists around the world.

"Climate change would cause fires to spread faster and burn more intensely in most vegetation types," the researchers concluded in their report. These faster, hotter fires could be expected to escape containment more frequently, despite increased fire suppression efforts. This would result in many more acres being burned than under the current climate.

"The biggest impacts were seen in grass vegetation, where the fastest spread rates already occur," says Fried. "In forests, where fires move much more slowly, projected impacts were less severe."

In their modeling, Torn, Mills, and Fried found that the most severe effects of global climate change were inflicted on the Sierra foothills where the predicted number of potentially catastrophic fires increased by 143-percent in grassland and 121-percent in chaparral.

"With the number of escaped wildfires more than doubling, climatic change could lead to a significant jump in fire damage in this region," the researchers reported.

In the Santa Clara region, the predicted number of escaped wildfires increased by 53- and 21-percent respectively in grassland and chaparral. Only in Humboldt, the third region examined, which is characterized by redwood forests growing in moist, foggy areas, was there little change in wildfire damage as a result of climate change.

Results of this analysis are being shared with the California Department of Forestry which has been cooperating with the Berkeley Lab researchers throughout.

Says Torn, "The CDF provided us with all of the fire and analysis-zone data we used and kept us informed about model updates. They are carefully following developments on this topic."

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.

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