Deborah Zabarenko, PlanetArk 24 Apr 09;
WASHINGTON - In a vicious cycle made worse by humans, scientists now believe fires spur climate change, which in turn makes blazes bigger, more frequent and more damaging to the environment.
Climate experts have known that a warmer world would spawn more fires, but in research published on Thursday in the journal Science, scientists reported that fires -- especially those set by humans to clear forests -- influence climate change.
Smoke particles sent into the atmosphere by fires inhibit rainfall, which makes the land drier and encourages more fires to start, said study co-author Jennifer Balch of the University of Santa Barbara in California.
On a global scale, burning releases vast amounts of heat-trapping greenhouse gases like carbon dioxide, making fires more likely in a warming world, Balch said in a video news briefing.
The report's authors estimate that greenhouse emissions from the world's fires equal about 50 percent of emissions that come from the burning of fossil fuels.
Deforestation fires, like those set to clear forest for pasture in tropical areas like the Amazon, are part of an unintentional "extreme experiment," Balch said: "We're testing how burning forests will influence the climate system."
"THE SCARY BIT"
These deliberately set forest fires contributed up to one-fifth of all human-generated warming in industrial times, she said.
The climate-fire cycle works like this: plants store the climate-warming gas carbon dioxide; when they burn, they release the gas into the atmosphere, which contributes to global warming.
The more fires, the more carbon dioxide is released, which in turn causes more warming in a cycle scientists call positive feedback.
"The scary bit is that, because of the feedbacks and other uncertainties, we could be way underestimating the role of fire in driving future climate change," said co-author Thomas Swetnam of the University of Arizona in Tucson.
This important piece of the climate change puzzle has not previously been emphasized, said co-author David Bowman of the University of Tasmania in Hobart, Australia.
Most climate scientists considered fire to be a natural disturbance that was not a crucial force that should be considered in creating models of how the planet's climate will change, Bowman said.
"Humans and fire have a complex and ancient relationship," Bowman said. "The relationship means that we can manage fire but we can also start fires. A citizen can't create hurricanes, but a citizen (who sets a fire) can create a mass disaster."
The report's 22 authors called on the U.N. Intergovernmental Panel on Climate Change to take the role of fire into account when making future climate models.
Fires Fuel for Climate Change
A warmer climate mean more fires, and more fires mean more greenhouse gases, says new report
Katherine Harmon, Scientific American 23 Apr 09;
The wildfires blazing through North Myrtle Beach, S.C., today are hardly an anomaly in a warming world. According to a landmark report that will be published tomorrow in Science, fires are not just a result of a changing climate, they're also contributing to the overall warming trend much more than imagined, the authors report. As vegetation burns, it releases stored-up carbon into the atmosphere, speeding global warming and thereby exacerbating conditions that may generate a greater incidence of wildfires in the coming years.
Because fires have been part of the global environment for hundreds of millions of years—since the first land plants emerged—as well as a tool for humans for more than 50,000 years, they're largely assumed to be a natural and negligible part of the carbon and climactic cycles. As people use fire on a massive scale as a cheap and efficient way to clear forests for agriculture or development, however, it is having a much greater impact than many scientists realized. In fact, deforestation fires alone have contributed 20 percent of the total greenhouse gases humans have contributed to the atmosphere since industrialization.
The report brought together 22 scientists from a range of disciplines and countries in an effort to better understand the global impact of fire. "This is a critical move away from the thinking that fires are just a disaster," says David Bowman, a professor of forest ecology at the University of Tasmania in Hobart, Australia, and a lead author of the report. Taken in isolation, each conflagration can cause massive human, economic and natural devastation, but as a broader force fire wields a much larger power, according to the report. "Fire is a feature of our planet…. High levels of fire activity have the capacity to change climate," he says.
But across the globe, fires have been getting larger and stronger. "We are witnessing an increasing instance of these megafires," says Thomas Swetnam, director of the Laboratory of Tree-Ring Research at the University of Arizona. This year alone has seen an increase in both the magnitude and deadliness of conflagrations sweeping Australia and the U.S. Southwest. In the past 20 years, the area scorched by fire in the western U.S. was six times greater than in the two decades that preceded it. These infernos are in large part a result of longer, drier summers, which are only poised to get worse with climate change, Swetnam explains.
"The real originality of this work is that we've been able to say something so obvious," Bowman says. He noted that the challenge now will be integrating fire into the large-scale climate models, and that will take further research and understanding.
"What we're calling for," said Bowman of the report, "is inclusion [of fire] in the next [Intergovernmental Panel on Climate Change] models." Not only is the fire of a broader concern for climate stability and human well-being, but large-scale events also pose a risk of upsetting new carbon trading schemes, notes Jennifer Balch, a postdoctoral fellow at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara, because they can release huge amounts of carbon dioxide into the atmosphere with one fell poof.
For more, visit our In-Depth Report on fires and climate change.
