Effects of a changing climate on summertime fine particulate matter levels in the eastern US

The chemical transport model PMCAMx is used to examine the effect of climate change on fine (under 2.5 mu ms) particulate matter (PM2.5) during the summer in the eastern United States. Meteorology from 10years in the 1990s (present) and 10years in the 2050s (future) based on the Intergovernmental Panel on Climate Change A2 scenario is used. Anthropogenic pollutant emissions are assumed to remain constant, while biogenic emissions are climate sensitive and, depending on species, increase between 15 and 27% on average. The predicted changes of PM2.5 are modest (increases of less than 10% on average across the domain) and quite variable in space, ranging from +13% in the Plains to -7% in the Northeast. Variability is driven concurrently by changes in temperature, wind speed, rainfall, and relative humidity, with no single dominant meteorological factor. Sulfate and organic aerosol are responsible for most of the PM2.5 change. The improved treatment of organic aerosol using the volatility basis set does not increase significantly its sensitivity to climate change compared to traditional treatments that neglect the volatility of primary particles and do not simulate the chemical aging processes. Future organic aerosol is predicted to be more oxidized due to increases of its secondary biogenic and anthropogenic components. These results suggest that the effects of planned and expected emission anthropogenic emission controls will be more important than those of climate change for PM2.5 concentrations in 2050. Maximum daily 8h average ozone increases by 5% on average are predicted, with a marked increase in the Northeast, Southeast, and Midwest.