Forest Fires Largely Overlooked by Climate-Change Modelers

  Forest Fires Largely Overlooked by Climate-Change Modelers

24 April 2009

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Global — Forest fires worsen global warming and make it harder for societies to adapt to drought and higher temperatures, scientists said.

Trees and brush set ablaze, by accident or through slash- and-burn farming in the tropics, fuel hotter weather, said Jennifer Balch, a researcher at the National Center for Ecological Analysis and Synthesis in Santa Barbara, California. That’s because smoke adds more carbon dioxide to the atmosphere.

“We don’t think about fire correctly,” Balch said. “It’s very intrinsic to the planet when you consider the oxygen level, the vegetation and that large parts of earth are dry and hot.”

The emissions of carbon dioxide, a greenhouse gas adding to global warming, are about equal to half the output from burning fossil fuels such as coal, Balch and colleagues wrote in a study published yesterday in the journal Science on the role of fire in the climate system.

Even so, the effect of fires are rarely figured into models that predict future global warming.

Scientists are still looking for ways to properly quantify the influence of fires on the earth’s climate system, Balch said in an interview.

Almost one-third of the planet experiences frequent fires, according to research by Emilio Chuvieco, a geographer at the University of Alcala, Spain, and colleagues. The frequency of fires is increasing as regions such as western North America become warmer and drier, said Balch.

‘Huge Task to Accomplish’

“It’s a huge task to accomplish to integrate dynamic vegetation models into the climate models, and it needs more time and careful work,” said Kirsten Thonicke, a researcher in geoecology at the Potsdam Institute for Climate Impact Research in Germany.

“If you want to do projections 50 or 100 years from now or even further, you want to know if your biosphere is still able to provide you with the fuel you need to burn,” Thonicke said.

It’s clear that fires occur systematically when there is wood to burn, lightning strikes or humans set blazes amid hot and dry climate conditions, Balch said.

Fires in Southeast Asia in 1997 and 1998 related to the El Nino effect cost the region’s economy about $9 billion, including $1 billion in health-related expenses because of smoke inhalation. As much as $15 billion in damage resulted from fires in South America the same year.

Old-growth forests once studded with pine and firs from California to British Columbia are being consumed more regularly by fire as temperatures have risen as much as 0.5 degrees Celsius (0.9 degrees Fahrenheit) a decade since the 1970s, U.S. Geological Survey researcher Phillip van Mantgem said.

The earth in general is a flammable planet with carbon-rich vegetation, periodic dry seasons, lightning and volcanic eruptions, Balch and colleagues wrote in the study. Even normally moist rain forests can become combustible if invasive species take hold or as a result of human-induced burning.

Increased frequency of fires also will have an impact on carbon markets if negotiators at United Nations climate talks include forest preservation in a new climate-protection treaty, Balch said.

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