Abstract

This paper provides a synthesis of results that have emerged from recent modeling studies of the potential impacts of global climate change (c. 2050) on U.S. regional ozone concentrations. This research has been carried out under the auspices of an ongoing U.S. Environmental Protection Agency (EPA) assessment effort to increase scientific understanding of the multiple complex interactions between climate, emissions, atmospheric chemistry, and air quality, the ultimate goal of which is to enhance the ability of air quality managers to consider global change in their decisions through improved characterization of the potential impacts of global change on air quality, including O3, particulate matter (PM), and mercury (Hg).

The results discussed here are interim, representing the first phase of the EPA assessment whose aim was to consider the effects of climate change alone, without accompanying changes in anthropogenic emissions of precursor pollutants. Across all of the modeling experiments carried out by the different groups, simulated global climate change causes increases in summertime O3 concentrations over some substantial regions of the country. These regional patterns of change, however, are not, in general, the same across the different simulations. These differences result from variations in the simulated patterns of mean changes in key meteorological drivers, such as temperature and surface insolation. Some regions, such as the Northeast/Mid-Atlantic and Midwest, show greater agreement across groups, whereas others, such as the West Coast and the Southeast, show wider disagreements. How isoprene nitrate chemistry is represented in the different modeling systems is an additional critical factor in the simulated O3 response to climate change.