June 25, 2014 | California will likely experience more large fires in forested areas this century because of rising temperatures and changes in precipitation along with development patterns, new research finds. The resulting increase in wildfire activity could increase some types of fire-generated air pollution by more than half.

The computer modeling study, led by Matthew Hurteau of Pennsylvania State University with co-authors including NCAR scientist Christine Wiedinmyer, used several development and climate scenarios to project where burned areas are likely to occur based on changes in hydrology, human population, and land-surface characteristics. The authors then estimated the emissions, which can have a significant impact on air pollution.

The work was published earlier this year in Environmental Science & Technology.

A smoky future

To estimate the potential impacts on air pollution, the researchers turned to a computer model known as Fire Inventory from NCAR, or FINN. The model enabled the team to simulate emissions of greenhouse gases (carbon dioxide and methane) and fine particulate matter from the amount of burned plant materials. They also used FINN to estimate emissions of non-methane organic compounds that, when combined with nitrogen oxides (NOx), can react to form ground-level ozone, a pollutant that harms plants and causes airway and lung irritation.

The results for a climate scenario projecting a medium-high increase in temperature suggest that, by 2050, total California wildfire emissions would increase by a median value of 24 percent over 1961–1990 values. The median value reaches 56 percent by the year 2085, with a range from 19 to about 100 percent, depending on how development and population evolve. The largest increases come from projected fires in the national forests of northern California.

The team also examined the amount of carbon dioxide stored in plants that would be emitted to the atmosphere by burning wildfires each year. They found that, by the year 2085, half of the modeled scenarios projected emissions within a range of 16.5 to 19.6 teragrams of CO2 per year, compared to 10.7–12.2 Tg per year in 1970. Emissions of particulates, NOx, and non-methane organic compounds were found to increase in all emission scenarios modeled, and they would be likely to significantly affect California’s air quality.

“Based on what we know now, the probability of having increased fires in California is pretty high. That’s going to lead to a lot more air pollution from fire, which could have big impacts on air quality,” Wiedinmyer said. “Moving forward, these wildfire effects need to be considered in air quality management plans.”

The group is now working on modeling future wildfire and the resulting air pollution for the entire western United States.

Matthew D. Hurteau, Anthony L. Westerling, Christine Wiedinmyer , and Benjamin P. Bryant, Projected Effects of Climate and Development on California Wildfire Emissions through 2100, Environmental Science & Technology 2014, 48, 2298−2304 DOI: dx.doi.org/10.1021/es4050133

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