Changing meteorology is anticipated to affect average levels of PM2.5 in the US, according to a modeling analysis by researchers at the Harvard ACE Center. Changes in local and synoptic-scale air circulation between 2000 and 2050, in addition to the resulting changes in natural emissions, are expected to result in annual average PM2.5 decreases of 0.3-1.2 mg/m3 for the Intermountain West, while increases of 0.4 to 1.4 mg/m3 are projected for the Eastern US, making it respectively easier and more difficult to meet air quality standards. Seasonal variability results in increases up to 2-3 mg/m3 in the summer over the NE, while wintertime concentrations could decrease by 0.3-3 mg/m3 over most of the US. This analysis used an ensemble of 19 models under the assumption of constant anthropogenic emissions, and the observed relationships of PM2.5 to meteorology to estimate this climate penalty. While these results provide a useful first approximation of the penalty, further modeling under scenarios that take into consideration changing emissions, as well as economic and policy changes, are needed to estimate the net effect on PM2.5 for air quality management.
