The role of climate and emission changes in future air quality over southern Canada and northern Mexico

E Tagaris,J.-H Woo,K Manomaiphiboon,A G Russell,S He,P Amar,K.-J Liao

doi:10.5194/acp-8-3973-2008

Abstract

Abstract. Potential impacts of global climate and emissions changes on regional air quality over southern (western and eastern) Canada and northern Mexico are examined by comparing future summers' (i.e., 2049–2051) average regional O3 and PM2.5 concentrations with historic concentrations (i.e., 2000–2002 summers). Air quality modeling was conducted using CMAQ and meteorology downscaled from the GISS-GCM using MM5. Emissions for North America are found using US EPA, Mexican and Canadian inventories and projected emissions following CAIR and IPCC A1B emissions scenario. Higher temperatures for all sub-regions and regional changes in mixing height, insolation and precipitation are forecast in the 2049-2051 period. Future emissions are calculated to be lower over both Canadian sub-regions, but higher over northern Mexico. Global climate change, alone, is predicted to affect PM2.5 concentrations more than O3 for the projections used in this study: average daily maximum eight (8) hour O3 (M8hO3) concentrations are estimated to be slightly different in all examined sub-regions while average PM2.5 concentrations are estimated to be higher over both Canadian sub-regions (8% over western and 3% over eastern) but 11% lower over northern Mexico. More days are forecast where M8hO3 concentrations are over 75 ppb in all examined sub-regions but the number of days where PM2.5 concentration will be over 15 μg/m3 is projected higher only over western Canada. Climate change combined with the projected emissions lead to greater change in pollutant concentrations: average M8hO3 concentrations are simulated to be 6% lower over western Canada and 8% lower over eastern Canada while average PM2.5 concentrations are simulated to be 5% lower over western Canada and 11% lower over eastern Canada. Although future emissions over northern Mexico are projected higher, pollutant concentrations are simulated to be lower due to US emissions reductions. Global climate change combined with the projected emissions will decrease average M8hO3 4% and PM2.5 17% over northern Mexico. Significant reductions in the number of days where M8hO3 concentrations are over 75 ppb and PM2.5 concentration over 15 μg/m3 are also projected with a significant reduction in peak values.

Highlights

Global climate and emissions changes are critical factors for future air quality
Climate change impacts on regional air quality have been examined to some degree (e.g. Mickley et al, 2004; Hogrefe et al, 2004; Knowlton et al, 2004; Murazaki and Hess, 2006; Langner et al, 2005) and have been summarized by Tagaris et al (2007) there are limited studies examining the effect of long term emission changes on air quality
For Mexico, the US EPA’s 1999 Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study Emissions Inventory was updated with the Mexico National Emissions Inventory (NEI)

Summary

Introduction

Global climate and emissions changes are critical factors for future air quality. Climate change impacts on regional air quality have been examined to some degree Mickley et al, 2004; Hogrefe et al, 2004; Knowlton et al, 2004; Murazaki and Hess, 2006; Langner et al, 2005) and have been summarized by Tagaris et al (2007) there are limited studies examining the effect of long term emission changes on air quality. The different emissions scenarios result in different global and regional ozone levels. Dentener et al (2006) found that climate change alone seems to play a minor role other studies (e.g., Hogrefe et al, 2004) estimate a significant change in ozone level due to climate change. The different emissions scenarios result in different global and regional ozone levels. Dentener et al (2006) found that climate change alone seems to play a minor role other studies (e.g., Hogrefe et al, 2004) estimate a significant change in ozone level due to climate change. Tagaris et al (2007) examined the impacts

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