November 2, 2007

Fires Contribute to Global Warming?

The recent wildfires in California have certainly provided an opportunity for the greenhouse crusade to further claim that global warming is already increasing fire frequency, duration, and intensity all over the planet. In the midst of the disaster in California, Nevada Democrat and Senate Majority Leader Harry Reid told reporters that “One reason why we have the fires in California is global warming.” However, when pressed by astonished reporters on whether he really believed global warming caused the fires, he appeared to back away from his comments, saying there are many factors that contributed to the disaster. Since then, literally hundreds of newspaper articles appeared throughout the country reinforcing the idea that emissions of greenhouse gases have warmed the earth, dried the forests, and made fires a lot worse.

An Associated Press story entitled “Global Warming Could Worsen California Wildfires” carried in USA Today and elsewhere contained the following pessimistic quotes about the future:

“Fires that charred nearly three-quarters of a million acres could presage increasingly severe fire danger as global warming weakens more forests through disease and drought, experts warn.”

“Warmer, windier weather and longer, drier summers would mean higher firefighting costs and greater loss of lives and property, according to researchers at the Lawrence Berkeley National Laboratory and the U.S. Forest Service.”

“Both the number of out-of-control fires and the acreage burned are likely to increase — more than doubling losses in some regions”

“The researchers say the projections use conservative forecasts that don’t take into account expected factors like increased lightning strikes and the spread of volatile grasslands into areas now dominated by less flammable fuel. Even potentially wetter winters simply mean more growth, providing additional fuel for summer fires.”

“Fires may be hotter, move faster, and be more difficult to contain under future climate conditions”

“Extreme temperatures compound the fire risk when other conditions, such as dry fuel and wind, are present.”

We have covered the issue of wildfires and global warming many times in the past, and to say the least, and as noted by Harry Reid, there is a lot more to the story than these simplistic statements that sprung up during the California fires (see here, for example). However, a very interesting article entitled “Estimates of CO2 from Fires in the United States: Implications for Carbon Management” is forthcoming in the relatively new journal called Carbon Balance and Management. The article is written by two scientists at the National Center for Atmospheric Research in Boulder, Colorado and the University of Colorado, also in Boulder. Unlike the mound of material on global warming causing an increase in fire activity, Wiedinmyer and Neff turn the question around and explore how much CO2 is generated by these fires, and the results are surprising and have significant implications to policies aimed at reducing greenhouse gas emissions.

The scientists begin their article noting that “A changing climate and a century of policies that encourage fire suppression, has increased the recent extent and frequency of Western US fires” and that “The amount of CO2 emitted from fires in the US is equivalent to 4-6% of anthropogenic emissions at the continental scale and, at the state-level, fire emissions of CO2 can, in some cases, exceed annual emissions of CO2 from fossil fuel usage.” Also, “A striking implication of very large wildfires is that a severe fire season lasting only one or two months can release as much carbon as the annual emissions from the entire transportation or energy sector of an individual state.” They note with respect to our neighbors to the north that “In a study of emissions in Canada, wildfires contribute the equivalent of 18% of emissions from the energy sector of the country with a year to year range in emissions that varies from 2 to 75%.”

Wiedinmyer and Neff produced the graphic below (Figure 1) comparing CO2 emissions from fires to CO2 emissions from anthropogenic activities (e.g., fossil fuel consumption), and among other findings, we see states like Alaska where CO2 emissions from fires nearly equal or exceed the anthropogenic emissions. The authors go on to show that most of the CO2 from fires comes from needleleaf forests, with small contributions from grasslands (<5%) and crops (<3%).

Figure 1. Annually-averaged anthropogenic emissions (2000-2003) of CO2 and annually-averaged CO2 emissions (2002-2006) from fires for states where average fire emissions greater than 5% of the states’ anthropogenic emissions. The error bars associated with the fire emission estimates represent the standard deviation of the monthly emissions for 2002-2006 (from Wiedinmyer and Neff, 2007).

There are several particularly interesting implications from this work. First, if a state or groups of states are interested in stabilizing or even reducing CO2 emissions by a few percent (and many states have moved in this direction), fire suppression must be in the discussion. However, as noted in the Wiedinmyer and Neff article, fire suppression leads quickly to increased fuel in the forest making the next fire even larger than if no suppression had been implemented. Basically, fire suppression only delays the inevitable release of the carbon back to the atmosphere (a point often lost by the ever-growing “carbon offsets” crowd). Furthermore, a state could expend considerable funds to lower the CO2 emission on the anthropogenic side of the equation, but one lightning strike, one careless camper, or one kid with one match could start a forest fire that wipes out any gains, at least in the short term, from the reduction program. The costs of the emission reduction program would literally go up in smoke!

It would be another case of all pain, no gain.


Wiedinmyer, C., and J.C. Neff. 2007. Estimates of CO2 from Fires in the United States: Implications for Carbon Management. Carbon Balance and Management, in press.

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