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Study Finds Damage, Pollution from Western Wildfires Could Surge With Moderate Global Warming

By 2055, wildfires in the western United States could scorch about 50% more land than they do now, causing a sharp decline in the region’s air quality, according to a new study by atmospheric researchers at Harvard. This potential leap in destructiveness and pollution—mainly from an increase in wildfire frequency—is forecast by computer models calculating impacts of moderate global warming on western US wildfire patterns and atmospheric chemistry.

The models show the greatest future increases in area burned (75 to 175%) in the forests of the Pacific Northwest and the Rocky Mountains. And, because of extra burning throughout the western US, one important type of smoke particle—organic carbon aerosols—would increase, on average, by about 40% during the roughly half-century period, they add.

Logan 1   Logan2
Percent increase in area burned by wildfires, from the present-day to the 2050s, for the May-October fire season. The model follows a scenario of moderately increasing emissions of greenhouse gas emissions and leads to average global warming of 1.6 °C by 2050. Most of the calculated increase in area burned is due to warmer temperatures in the West, which leads to dryer conditions and more serious wildfires. Source: Spracklen et al. Click to enlarge. Percent increase in organic carbon particles at the surface, from the present-day to the 2050s. The increase is due mainly to the simulated rise in wildfire frequency in the future, warmer climate. Source: Spracklen et al. Click to enlarge.

Previous studies by other researchers have probed the links between climate change and fire severity in the West and elsewhere. However, the Harvard study represents the first attempt to quantify the impact of future wildfires on the air we breathe, says Jennifer Logan of Harvard’s School of Engineering and Applied Sciences (SEAS), who led the research. A report on the results has been accepted for publication in the Journal of Geophysical Research - Atmospheres, a journal of the American Geophysical Union (AGU).

Warmer temperatures can dry out underbrush, leading to a more serious conflagration once a fire is started by lightning or human activity. Because smoke and other particles from fires adversely affect air quality, an increase in wildfires could have large impacts on human health.

—Jennifer Logan

To conduct the research, the team first examined a 25-year record of observed meteorology and fire statistics to identify those meteorological factors that could best predict area burned for each ecosystem in the western United States. To see how these meteorological factors would change in the future, the researchers then next ran a global climate model out to 2055, following a scenario of future greenhouse gas emissions known as A1B.

This scenario, one of several devised by the United Nations Intergovernmental Panel on Climate Change, describes a future world with rapid economic growth and balanced energy generation from fossil and alternative fuels. Relative to the other scenarios, it leads to a moderate warming of the earth’s average surface temperature, about 1.6 degrees Celsius (3 degrees Fahrenheit) by 2050.

By hypothesizing that the same relationships between meteorology and area burned still hold in the future, we then could predict wildfire activity and emissions from 2000 to the 2050s.

—Jennifer Logan

As a last step, the researchers used an atmospheric chemistry model to understand how the change in wildfire activity would affect air quality. This model, combining their predictions of areas burned with projected 2050s meteorology data, shows the quantities of emissions and the fates of smoke and other particles released by the future wildfires. The resulting diminished air quality could lead to smoggier skies and adversely affect those suffering from lung and heart conditions such as asthma and chronic bronchitis.

Such consequences are a climate penalty that diminishes the effectiveness of efforts to reduce air pollution across the United States, the researchers say. Their new work could help policymakers gauge how severe that penalty might become. In addition, the study underscores the need for a vigorous fire management plan.

The team next plans to focus on future wildfires and air quality over the densely populated areas in California and in the southwest United States.

Logan’s collaborators include Research Associate Loretta Mickley and former postdocs Dominick Spracklen and Rynda Hudman, all at SEAS. Grants from the STAR (Science to Achieve Results) program of the National Center for Environmental Research of the US Environmental Protection Agency and from NASA supported this research.


  • D. V. Spracklen, L. J. Mickley, J. A. Logan. R. C. Hudman, R. Yevich, M. D. Flannigan, and A. L. Westerling (2009) Impacts of climate change from 2000 to 2050 on wildfire activity and carbonaceous aerosol concentrations in the western United States, J. Geophys. Res., In press



People familiar with combustion should understand well the effect of dry, hot air and oxidation rate.
Once the fuel reaches flash point it takes less energy to instigate and the rate of propogation over the minimum threshold rapidly increases both likelihood and intensity. Siilar to stoimetrich ratio of combussion.
If we saw the background percentage of promotants increase, the effect will not be linear.

Eualyptus trees expell more volatile oils in warmer wether/ dry hot etc and the forest fires favours thier expansion. One study showed that they also are able to take advantage of increased CO2 with reduced water levels so we can say these (and other fire tolerant plants) will gain range.

I dont think most people are aware how sensitive (or large) this sytem is.


The fire season in California starts earlier and ends later every year now. Soon we may have a perpetual fire season that never ends, which will require huge resources to combat. If we can not afford the resources, then it will burn and millions of acres will be lost.

Scott Miller

Instead of merely citing the potential impact of "global warming" (a disputed thesis) on wildfires, I would like to see a trend line study of the greenhouse gas, NOx, SOx, and PM10 emissions from the accelerating growth of wildfires in the U.S. (in general) and my home state of California (in particular).

I have documented studies by Tom Bonnicksen at my BIOstock Blog ( ) which draw the connection between wildfires and GHG emissions and suggests that the way to combat this trend is to: 1) reduce the size of fires by managing our forests better with fuelwood and underbrush thinning operations (which, incidentally, has been funded by the U.S. Congress but poorly implemented), 2) salvage the dead, decaying, CH4 emitting tree carcasses from wildfires (which retain 75% of the live tree's carbon), and 3) immediately reforest the afflicted areas.

If aggressively implemented on public lands the way that it is on private lands, the salvage and reforestation projects would render a net negative carbon impact from the wildfires because growing trees sequester carbon faster than grown trees. If not implemented, the greenhouse gas consequences as well as the permanent destruction of forests and wildlife habitats ( ) will continue to be devastating.

Of course, the would require the political support of "environmental" NGOs and an end to their obstructive lawsuits against the Forest Service ( ).

It would also require growth in the forest products industry because it is the only way the harvested biomass can be safely disposed of and expanded forest management self-funded.


More than a decade ago, the federal government put out a bid request for clearing the the forests of dead trees and brush, NO one bid. Preactive thinking says pay to clear the bush before a fire starts, but it is SO labor intensive that there were no bidders for the contract.

If we can develop biomass gasification like Range Fuels has in North Carolina that can be brought closer to the site, then we might convert forest waste to fuel. If we can find automated machinery to go in and get the dead trees, then we might do this more cost effectively.

I am more for solutions that we can use now rather than studies and discussions that go on for decades. Every cycle we face losing another Yellowstone to fire. We need to have a plan now and put it into place so that we avert any possible fire catastrophe that may threaten our forests.

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