Modeling the contribution of wildfire to atmospheric composition and air quality
Speaker
Larry Horowitz
Princeton University
Abstract
Modeling the contribution of wildfire to atmospheric composition and air quality
Wildfire activity has been observed to increase globally over the past decades. Using observations and several versions of the GFDL chemistry-climate model, I examine historical trends of wildfire, its drivers, and the contribution to air quality. Wildfires are shown tocontribute significantly to historical interannual variations of fine particulate (PM2.5) and ozone pollution in regions downwind from fires, as the emissions interact with anthropogenic
emissions. Wildfires in western Canada contribute to air quality exceedances over western U.S. cities. Models project that the observed trend towards increased fires will likely continue over the current century. Idealized model simulations suggest that biogeochemical feedbacks, rather than climate warming and drying, are responsible for much of the projected increase in fire with increasing CO 2 . However, most global chemistry-climate models have not typically included interactive emissions of aerosols and reactive gases from fires, and so likely underestimate these future emissions and the resulting air quality impacts. Projections of wildfire from three CMIP6 Earth system models, combined with an empirical statistical model, indicate that
enhanced wildfire activity over western North America will likely result in a doubling to tripling of PM2.5 pollution within the current century. In order to better capture anticipated future trends in fire activity, a new version of the GFDL chemistry-climate model (ESM4.5) incorporates interactive emission of gas-phase and aerosol pollutants from wildfire, as well as dynamic injection height based on fire radiative power and atmospheric stability. Results from ESM4.5 will be included in GFDL’s submission to CMIP7 and will help to address couplings between fires and atmospheric composition.
Bio
Dr. Larry Horowitz is an atmospheric chemist at the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory (NOAA/GFDL) in Princeton, where he serves as the deputy leader of the Earth System Processes and Interactions division. He is also a Lecturer in the Department of Geosciences at Princeton University. Larry received his Ph.D. in Applied Mathematics from Harvard University in 1997, followed by a postdoctoral fellowship in the Advanced Study Program at the National Center for Atmospheric Research. He then joined GFDL in 1999. His research focuses on tropospheric and stratospheric chemistry and aerosols, including long-range transport, air quality, and chemistry-climate-biosphere interactions. He has played a leading role in the development of global chemical transport models, chemistry-climate models, and Earth system models. His recent studies focus on the radiative forcing and climate impacts of short-lived gases and aerosols, the drivers of variability in atmospheric composition and air quality on timescales from years to centuries, and couplings of atmospheric composition with the terrestrial biosphere. Larry’s work has been recognized with the Atmospheric Sciences Ascent Award from the American Geophysical Union (2017), a Gold Medal (2012) and two Silver Medals (2005, 2009) from the Department of Commerce, the Administrator’s award from NOAA (2008), and a Highly Cited Researcher award from Clarivate Analytics (2014-2022).