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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 20 | Copyright
Atmos. Chem. Phys., 18, 15471-15489, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 29 Oct 2018

Research article | 29 Oct 2018

The potential effects of climate change on air quality across the conterminous US at 2030 under three Representative Concentration Pathways

Christopher G. Nolte1, Tanya L. Spero1, Jared H. Bowden2, Megan S. Mallard1, and Patrick D. Dolwick3 Christopher G. Nolte et al.
  • 1Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, Triangle Park, North Carolina, USA
  • 2Department of Applied Ecology, North Carolina State University, Raleigh, North Carolina, USA
  • 3Office of Air Quality Planning and Standards, US Environmental Protection Agency, Research Triangle Park, Triangle Park, North Carolina, USA

Abstract. The potential impacts of climate change on regional ozone (O3) and fine particulate (PM2.5) air quality in the United States (US) are investigated by linking global climate simulations with regional-scale meteorological and chemical transport models. Regional climate at 2000 and at 2030 under three Representative Concentration Pathways (RCPs) is simulated by using the Weather Research and Forecasting (WRF) model to downscale 11-year time slices from the Community Earth System Model (CESM). The downscaled meteorology is then used with the Community Multiscale Air Quality (CMAQ) model to simulate air quality during each of these 11-year periods. The analysis isolates the future air quality differences arising from climate-driven changes in meteorological parameters and specific natural emissions sources that are strongly influenced by meteorology. Other factors that will affect future air quality, such as anthropogenic air pollutant emissions and chemical boundary conditions, are unchanged across the simulations. The regional climate fields represent historical daily maximum and daily minimum temperatures well, with mean biases of less than 2K for most regions of the US and most seasons of the year and good representation of variability. Precipitation in the central and eastern US is well simulated for the historical period, with seasonal and annual biases generally less than 25%, with positive biases exceeding 25% in the western US throughout the year and in part of the eastern US during summer. Maximum daily 8h ozone (MDA8 O3) is projected to increase during summer and autumn in the central and eastern US. The increase in summer mean MDA8 O3 is largest under RCP8.5, exceeding 4ppb in some locations, with smaller seasonal mean increases of up to 2ppb simulated during autumn and changes during spring generally less than 1ppb. Increases are magnified at the upper end of the O3 distribution, particularly where projected increases in temperature are greater. Annual average PM2.5 concentration changes range from −1.0 to 1.0µgm−3. Organic PM2.5 concentrations increase during summer and autumn due to increased biogenic emissions. Aerosol nitrate decreases during winter, accompanied by lesser decreases in ammonium and sulfate, due to warmer temperatures causing increased partitioning to the gas phase. Among meteorological factors examined to account for modeled changes in pollution, temperature and isoprene emissions are found to have the largest changes and the greatest impact on O3 concentrations.

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Short summary
Changes in air pollution in the United States are simulated under three near-future climate scenarios. Widespread increases in average ozone levels are projected, with the largest increases during summer under the highest warming scenario. Increases are driven by higher temperatures and emissions from vegetation and are magnified at the upper end of the ozone distribution. The increases in ozone have potentially important implications for efforts to protect human health.
Changes in air pollution in the United States are simulated under three near-future climate...