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CLIMATE SCIENCE

America’s Fire Future

16 Climate Models Say A Warming World Means More Wildfires

SOURCE: AP Photo/Gaylon Wampler A helicopter tries to put out fire on the Waldo Canyon wildfire as it moved into subdivisions and destroyed homes in Colorado Springs.

(2012 heat waves via NASA)

When Colorado Gov. John Hickenlooper (D) flew over the blaze engulfing thousands of acres of his state, he said, “It was like looking at the worst movie set you could imagine. It’s almost surreal. You look at that, and it’s like nothing I’ve seen before.”

More than 200m00 acres have been burned in Colorado this year. That’s the equivalent of burning 200 Central Parks. The largest fire—High Park Fireaccounts for more than half the acreage.

The fires in Colorado have drawn national attention.  President Barack Obama even flew to Colorado to take in the situation and extend condolences to residents. Unfortunately, the crisis may be just a preview of long-term changes in fire patterns in the Southwest United States.

(Largest fires by state and year)

Higher temperatures associated with global warming correlate with the worst fires in American history. In March 2012 heat records outnumbered cold 12-to-1. In June more than 3,000 heat records were broken. And global warming projections indicate temperatures will continue to rise. As the table shows, the United States has witnessed its largest fires in these recent years of high temperatures.

The increase in massive wildfires prompted seven scientists to analyze 16 global climate models to forecast the probability of fires around the world. The study, published in the peer-reviewed journal Ecosphere, says 80 percent of the terrestrial world will be disrupted by fires by the end of the century. While tropical areas will see fewer fires, the mid-latitudes of the northern hemisphere, which already possess a lot of biomass and are predicted to get hotter, will see further increases in fires.

The study used six independent variables describing different components of climate to predict changes in fire frequencies around the world in two 30-year time spans: a near-term timespan of 2010 to 2039, and a longer-run projection of 2070 to 2099. The 16 climate models used in the study reached a consensus that much of the mid-northern hemisphere would see increases in fires in the next 28 years, and showed even greater convergence in the longer-term model.

A study of 16 global climate models forecasts that 80 percent of the terrestrial world will be disrupted by fires by the end of the century.

Fires are complicated phenomena; each fire is unique. They spring to life in different conditions, and may grow to enormous sizes or remain small and controllable based on random factors, such as the direction and strength of the wind. Each fire results from an interplay between atmospheric conditions, ignitions (e.g. lightning or human causes), and fuel, and is thus difficult to predict.

The fluctuations in California over recent years demonstrate the difficulty of making fire predictions. In 2010 only 500,000 acres of land burned, a paltry figure compared to the 3 million acres from 2007 to 2008. It is only over a decadal scale that long-term changes become clearer, as is shown by the difference in the area burned from 2000 to 2010 in this interactive map of California.

Given the difficulty in accurately predicting when fires will occur, the researchers’ short-term model based on the 16 climate models only agrees on what will occur on 38 percent of the terrestrial world in the near-term scenario. This area of agreement, however, is concentrated in mid-latitudes and is thus pertinent to the United States. In the long-term model, the consensus was much higher with a 90 percent agreement. It is predicted that 62 percent of land on earth will witness an increases in fires and 20.2 percent will witness decreases.

While it may seem surprising that almost a quarter of the world will see decreases in fires in the next century, consider the number of factors that cause and sustain fires. A particular combination of biomass, climate, and other factors leads to more fires. Without biomass, there is no fuel, and without the right level of dryness, there can be no spark. The study predicts a decrease in the regions of the world with the most concentrated biomass and lots of moisture—tropical rainforests. On the other hand, looser soil in the tundra will support more biomass and therefore support fires.

(Predicted global changes in fire probability for the two time periods in the study)

North America will directly feel the impact of the increase in temperatures on the mid-north latitudes: There is 60 percent to 90 percent agreement that in the next 28 years, the entire Southwest will see an increase in fires. From 2070 to 2099 the models predict with higher degrees of certainty increases between 10 percent and 25 percent in fires in the Midwest and Southwest United States. While these percentages may not seem overwhelming, a 10 percent increase in the number of fires in 2011 would mean more than 7,000 more fires.

This study is the latest and among the most comprehensive projections of the future of fires based on climate change. The authors note if the activity of fire rapidly fluctuates around the world, species of flora and fauna unable to adapt to changes may perish. Humans will also have to pay a price: Fires have large and complex economic impacts on regions.

The state and federal partnership entitled the Western Forestry Leadership Coalition reports that fires lead to flooding and erosion, air and water quality damage, and property damage—all of which have economic consequences. Air pollution caused by fires may lead to increased health care expenditures because of increased rates of respiratory problems. The coalition estimates the total cost of the 2003 Old, Grand Prix, and Padua fire complex in California cost about $1.3 billion and the 2000 Cerro Grande Fire in New Mexico cost about $1 billion.

Just in the Colorado Springs area, fires this year drove 30,000 people from their homes. Colorado’s 2012 fire-fighting expenditures total about $200 million with more than two-hundred thousand acres having been burned, but these expenses do not include indirect economic costs. Loss of workdays; business, restaurant, and hotel closures; and declines in tourism will bring the total economic cost much higher. The Western Forestry Leadership Coalition estimates true costs of these and other indirect factors range from 2 to 30 times the costs reported to the public. That brings the price tag for the 2012 Colorado fires up to a maximum of $6 billion.

What the Ecosphere study makes clear is that in a warming world, we can look forward to more of the devastating megafires like the ones ravaging Colorado. One wonders whether the study would have seen a drop in the fires in the Southwest had it forecasted into the 22nd century. In the 2100s, will there be enough biomass left in the Southwest to burn? Of course, by then, much of the United States might be underwater anyway.

Introducing Sam Finegold, Science Progress’s newest intern and a student a Harvard College.

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