Jennifer A. Logan
Senior Research Fellow
School of Engineering and Applied Sciences
Harvard University

EFFECTS OF CHANGING CLIMATE ON FIRES IN NORTH AMERICA, AND CONSEQUENCES FOR AIR QUALITY

BACKGROUND:

The occurrence and intensity of wildfires is strongly related to climate. Fires may be more common in a future warmer climate as rainfall patterns change. We are investigating the consequences of climate change on wildfires, and the impact on U.S. air quality.

OBJECTIVES:

  • To quantify the effect of present day fires on air quality in the United States;
  • To explore the relationship between climate and the frequency and magnitude of wildfires in North America, and develop scenarios for future fires;
  • To examine how different scenarios for future fires will affect air quality in a future climate
  • To examine how the use of different GCMs for future climate affects the predictions of future fires

APPROACH:

  • Determine the best predictors for area burned for different ecosystems, using the Canadian Fire Weather Index system
  • Conduct NASA/GISS general circulation model simulations of future climate change including tracers of wildfire pollution;
  • Perform global coupled ozone-aerosol simulations for the present day and future climates using the GEOS-Chem model driven by meteorological and area burned statistics from the GCM;
  • Use the archived output from 15 CMIP3 GCMs to predict future area burned.

FINDINGS:

  • Wildfires drive the interannual variability of organic carbon aerosol in the western U.S.  The observed increase in wildfire activity after the mid-1980s has caused mean OC in summer in the western U.S. to increase by 30% relative to 1970-1984.  (Spracklen et al., 2007)
  • Biomass burning sources of carbonaceous aerosol account for about 30% of total fine aerosol in the western U.S., and 20% in the east. Fires account for 80% of the biomass burning source in the west (20% is from biofuel), and 50% in the east (mainly from prescribed fires in the SE, and fire plumes from Canada). Residential and industrial biofuel are important in the east. (Park et al., 2007).
  • Increases in temperature casue area burned in the western U.S. to increase by ~50% by the 2050s relative to present day, with changes in area ecosystem dependent (Spracklen et al., 2009)
  • Climate change will increase summertime organic carbon aerosol over the western U.S. by 40%, and elemental carbon by 20% (Spracklen et al., 2009)
  • Most of this increase is caused by larger wildfire emissions with the rest by changes in meteorology
  • The use of 15 GCMs confirms that area burned will increase significantly in the western U.S. by the 2050s
  • The length of the fire season wil increse by about three weeks

PEOPLE: Jennifer Logan, Xu Yue (now at Yale Univ.), Rynda Hudman (now at EPA,San Francisco), Dominick Spracklen (now at Leeds Univ.), Loretta Mickley, Rokjin Park (now at Seoul Natl. Univ.).

COLLABORATORS:  Daewon Byun (deceased), David Diner, Davis Nelson (JPL), Ralph Kahn (NASA/Goddard)

REFERENCES:

  • Yue, X., L. J. Mickley, and J. A. Logan, Projection of wildfire activity in southern California in the mid-21st century, Clim. Dyn., in press, 2014. [PDF]
  • Yue, X., L. J. Mickley, J. A. Logan, and J. O. Kaplan, Ensemble projections of wildfire activity and carbonaceous aerosol concentrations over the western United States in the mid-21st century, Atmos. Environ., 77, 767-780, 2013. [PDF, Supplement]
  • Spracklen, D. V., 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., 114, D20301, doi:10.1029/2008JD010966, 2009. [PDF]
  • Spracklen, D. V., J. A. Logan, L. J. Mickley, R. J. Park, R. Yevich, A. L. Westerling, and D. Jaffe (2007), Wildfires drive interannual variability of organic carbon aerosol in the western U.S. in summer, Geophys. Res. Lett., 34, L16816, doi:10.0129/GL030037. [PDF]
  • Park, R. J., D. J. Jacob, and J. A. Logan (2007), Fire and biofuel contributions to annual mean aerosol mass concentrations in the United States, Atmos. Environ., 41 7389-7400. [PDF]

SUPPORT: EPA