Chapter 6.1 Examining the impact of changing climate on regional air quality over the U.S.

Abstract

Abstract The Climate Impact on Regional Air Quality (CIRAQ) project is a collaborative research effort involving multiple federal agencies and academic institutions to assess the impact of present and future climate on regional air quality across the United States. Preliminary results are presented which highlight model biases, variability and change of present (∼2000) and future (∼2050) regional climate, emissions and air quality model results for the summer season (June–August). The regional climate scenario derived for CIRAQ appears to reasonably represent large-scale summer-season climate means and variability in the western United States, but it fails to replicate some key summertime features in the eastern United States. A comparison of future and current climate simulation reveals that even though the general weather patterns change little in the future, the summer temperatures are on average 2–3 K warmer over the southwest quadrant of the United States. Other regions of United States are also warmer, but generally by less than 1 K. Preliminary analyses of the interannual and seasonal variability of biogenic and mobile emissions driven by current climate scenarios indicate isoprene and biogenic NO emissions are more temporally and spatially variable than are model generated on-road mobile source emissions. Comparison of these results with modeled emissions under future climate reveals similar spatial and temporal patterns, but elevated levels of biogenic emissions are present in the future simulation due to the warmer future summer temperatures throughout the study domain. Preliminary air quality modeling results identify regional differences in the response of current simulated 8-h maximum ozone concentrations and interannual variability to future climate change. Annual average fine particulate matter (PM 2.5 ) concentrations and the frequency and duration of elevated particulate matter episodes decrease in the future period relative to current period simulations.