ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-8-3973-2008 The role of climate and emission changes in future air quality over southern Canada and northern Mexico Tagaris E. 1 Liao K.-J. 1 Manomaiphiboon K. 1 3 He S. 2 Woo J.-H. 2 4 Amar P. 2 Russell A. G. 1 School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332, USA Northeast States for Coordinated Air Use Management (NESCAUM), 101 Merrimac Street, 10th Floor Boston, MA 02114, USA current address: Joint Graduate School of Energy and Environment, King Mongkut's University of Technology Thonburi, Bangkok, Thailand current address: Department of Advanced Technology Fusion, Konkuk University, Seoul, Korea 24 07 2008 8 14 3973 3983 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/8/3973/2008/acp-8-3973-2008.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/8/3973/2008/acp-8-3973-2008.pdf

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 O<sub>3</sub> and PM<sub>2.5</sub> 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 PM<sub>2.5</sub> concentrations more than O<sub>3</sub> for the projections used in this study: average daily maximum eight (8) hour O<sub>3</sub> (M8hO<sub>3</sub>) concentrations are estimated to be slightly different in all examined sub-regions while average PM<sub>2.5</sub> 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 M8hO<sub>3</sub> concentrations are over 75 ppb in all examined sub-regions but the number of days where PM<sub>2.5</sub> concentration will be over 15 μg/m<sup>3</sup> is projected higher only over western Canada. Climate change combined with the projected emissions lead to greater change in pollutant concentrations: average M8hO<sub>3</sub> concentrations are simulated to be 6% lower over western Canada and 8% lower over eastern Canada while average PM<sub>2.5</sub> 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 M8hO<sub>3</sub> 4% and PM<sub>2.5</sub> 17% over northern Mexico. Significant reductions in the number of days where M8hO<sub>3</sub> concentrations are over 75 ppb and PM<sub>2.5</sub> concentration over 15 μg/m<sup>3</sup> are also projected with a significant reduction in peak values.

 References Binkowski, F. S. and Roselle, S. J.: Models-3 Community Multiscale Air Quality (CMAQ) model aerosol component 1. Model description, J. Geophys. Res., 108(D6), 4183, doi:10.1029/2001JD001409, 2003. Dawson J. P, Adams, P. J., and Pandis, S. N.: Sensitivity of PM$_2.5 $ to climate in the Eastern US: a modeling case study, Atmos. Chem. Phys., 7, 4295–4309, 2007. Dentener, F., Stevenson, D., Ellingsen, K., Van Noije, T., Scultze, M. et al.: The global atmospheric environment for the next generation, Environ. Sci. Technol.,40, 3586–3594, 2006. Giorgi F. and Bates, G. T. : The climatological skill of a regional model over complex terrain, Month. Weather Rev., 117(11), 2325–2347, 1989. Grell, G., Dudhia, J., and Stauffer, D. R.: A description of the fifth generation Penn State/NCAR mesoscale model (MM5), NCAR Tech. Note, NCAR/TN-398+STR, Natl. Center for Atmos. Res., Boulder, Colorado, 1994. Gustafson Jr., W. I. and Leung, L. R.: Regional downscaling for air quality assessment. A reasonable proposition?, B. Am. Meteorol. Soc., 2007, 1215–1227, 2007. Hogrefe, C., Lynn, B., Civerolo, K., Ku, J-Y., Rosenthal, J., Rosenzweig, C., Goldberg, R., Gaffin, S., Knowlton, K., and Kinney, P. L.: Simulating changes in regional air pollution over the eastern United States due to changes in global and regional climate and emissions, J. Geophy. Res., 109, D22301, doi:10.1029/2004JD004690, 2004. IPCC (Intergovernmental Panel on Climate Change): Emissions Scenarios, Cambridge University Press, Cambridge, UK, 2000. Knowlton, K., Rosenthal, J. E., Hogrefe, C., Lynn, B., Gaffin, S., Goldberg, R., Rosenzweig, C., Civerolo, K., Ku, J. Y., and Kinney, P. L.: Assessing ozone related health impacts under a changing climate, Environ. Health Perspect., 112(115), p. 1557, 2004. Langner, J., Bergstrom, R., and Foltescu, V.: Impact of climate change on surface ozone and deposition of sulphur and nitrogen in Europe, Atmos. Environ., 39, 1129–1141, 2005. Leung, L. R. and Gustafson Jr., W. I.: Potential regional climate and implications to US air quality, Geophys. Res. Lett., 32, L16711, doi:10.1029/2005GL022911, 2005. Mickley, L. J., Jacobs, D. J., Field, B. D., and Rind, D.: Effects of future climate change on regional air pollution episodes in the United States, Geophys. Res. Lett.,31, L24103, doi:10.1029/2004GL021216, 2004. Murazaki, K. and Hess, P.: How does climate change contribute to surface ozone change over the United States, J. Geophys. Res., 111, D05301, doi:10.1029/2005JD005873, 2006. Rind, D., Lerner, J., Shah, K., and Suozzo, R.: Use of on line tracers as a diagnostic tool in general circulation model development: 2. Transport between the troposphere and the stratosphere, J. Geophys. Res., 104, 9123–9139, 1999. Tagaris, E., Manomaiphiboon, K., Liao, K. J., Leung, L. R., Woo, J. H., He, S., Amar, P., and Russell, A. G.: Impacts of global climate change and emissions on regional ozone and fine particulate matter concentrations over the United States, J. Geophys. Res., 112, D14312, doi:10.1029/2006JD008262, 2007. Woo, J. H., He, S., Amar, P., Tagaris, E., Manomaiphiboon, K., Liao, K. J., and Russell, A. G.: Development of Mid-Century Anthropogenic Emissions Inventory in Support of Regional Air Quality Modeling under Influence of Climate Change, 15th Annual Emission Inventory Conference Reinventing Inventories New Ideas in New Orleans 16–18 May, New Orleans, Louisiana, available at: http://www.epa.gov/ttn/chief/conference/ei15/ session4/woo2.pdf, 2006. Woo, J.H., He, S., Tagaris, E., Liao, K.J., Manomaiphiboon, K., Amar, P., and Russell, A.G.: Development of North American Emission Inventories for Air Quality Modeling under Climate Change, J. Air Waste Manage. Assoc., J. Air Waste Manage. Assoc., in press, 2008. Wu, S., Mickley, L. J., Jacob, D. J., Logan, J. A., Yantosca, R. M., and Rind D.: Why are there large differences between models in global budgets of tropospheric ozone?, J. Geophys. Res., 112, D05302, doi:10.1029/2006JD007801, 2007. Zeng, C., Pyle, J. A., and Young P. J.: Impact of climate change on tropospheric ozone and its global budget, Atmos. Chem. Phys., 8, 369–387, 2008. % %Woo, J. H., He, S., Amar, P., Tagaris, E., Manomaiphiboon, K., Liao, K. J., and %Russell, A. G.: Development of a Future Emissions Inventory for %Assessing Global Climate Change Impacts on Regional Air Quality over North %America, J. Air Waste Manage. Assoc., under review, 2007.