Sensitivity to meteorology of regional contributions to air pollution in Eastern Canada: Part 1: Ozone and NOx

Abstract

Air pollution is well known to have harmful effects on human health. The mechanisms of production, elimination and transport of air pollutants are sensitive to atmospheric conditions. Therefore, future concentrations of air pollutants, and the transboundary transport of these air pollutants, may vary with climate change. Based on GEOS-Chem chemical transport model output, we created emulators to capture the effects of meteorology on the concentrations of O3 and NO in eastern Canada. We then used the emulators with regional climate model output to project how climate change will affect the concentrations of these pollutants. We project that spring O3 concentrations in eastern Canada will increase by ~5 ppb in the RCP8.5 scenario, primarily due to increases in temperature. We project that NOx concentrations will increase by less than 0.5 ppb, except for the Greater Toronto Area where we project increases of more than 1 ppb. We also created emulators based on additional model simulations with anthropogenic emissions zeroed out in one of three regions: the province of Quebec, the rest of Canada, and the US. We used these additional emulators to project how the contributions from each of these three regions to O3 and NOX concentrations may be altered due to climate change. We project that climate change will increase the US contribution to O3 concentrations in eastern Canada more than the Canadian and Quebec contributions. Higher temperatures increase the efficiency of O3 formation from anthropogenic precursors, thus enhancing pre-existing disparities due to the different quantities of O3 precursor emissions from each region. This result suggests that climate change has the potential to exacerbate the export of air pollution across political boundaries.