1. . s Yuqiang Zhang 1, J. Jason West 1, Meridith M. Fry 1, Raquel A. Silva 1, Steven J. Smith 2, Vaishali Naik 4, Zachariah Adelman 1, Susan C. Anenberg 3, Larry W. Horowitz 4, Jean-Francois Lamarque 5, Louisa Emmons 5 1 Environmental Sciences and Engineering, Univ. of North Carolina, Chapel Hill. 2 Joint Global Change Research Institute. 3 US Environmental Protection Agency. 4 NOAA Geophysical Fluid Dynamics Laboratory. 5 National Center for Atmospheric Research. Acknowledgements: This work was funded by an EPA STAR grant #834285, an EPA STAR Graduate Fellowship (MMF), the EPA Office of Air Quality Planning and Standards, and the Department of Energy Office of Science. Contact: jasonwest@unc.edu, www.unc.edu/~jjwest Effect of changes in emissions and climate change on global air quality: A study of the air quality co-benefits of GHGs mitigation 834285 1.Introduction Sources & Policies Air pollutants GHGs EmissionsProblems Air pollution Climate Change 2 1 Connections between air quality and climate change, showing two mechanisms of co-benefits of GHG mitigation on air quality: #1 is immediate and local, #2 is long-term and global. YearsEmissionsMeteorologyName 2000Historical 2000 2030, 2050, 2100 GCAM Reference RCP8.5erefm85 RCP4.5 rcp45 GCAM Reference RCP4.5erefm45 Simulations Modeled in the study 3. Preliminary Results The air quality co-benefits of global GHG mitigation are substantial. The direct co-benefits via changes in co-emitted air pollutants (mechanism #1) appear much more important than the long- term influence via climate change (#2), even in 2100. Co-benefits would likely be larger if the Reference Case scenario had not assumed decreased air pollution in the future. Methane changes in these emissions scenarios are likely important in contributing to the tropospheric O 3 burden change. Future work will include assessing the global health impacts of these air quality changes, and meteorological and chemical downscaling of these results to the US using the WRF and CMAQ models. PM 2.5 and O 3 concentration changes in 2100 Total Co-benefit #2 Meteorology Co-benefit #1 Emissions Co-benefit 5.Conclusions Actions to reduce emissions of greenhouse gases (GHGs) will benefit global and regional air quality through two mechanisms in the future: 1) directly through reductions in emissions of co-emitted air pollutants (short-term and local), and 2) indirectly by slowing the influence of climate change on air pollution (long-term and global). While a large literature discusses the impacts of climate change on air quality, through meteorological changes, biogenic emissions, and other factors, we focus on the co-benefits of GHG mitigation on air quality. Here we aim to quantify the global air quality benefits of GHG mitigation through these two mechanisms, in realistic future scenarios to 2100. We use the global chemical transport model MOZART-4 to simulate changes in ozone and fine particular matter (PM 2.5 ) due to changes in co-emitted air pollutants and climate due to the GHG mitigation. We present results for the changes in global air quality due to GHG mitigation in 2030, 2050, and 2100. We use scenarios from the GCAM global energy economics model, developed as Representative Concentration Pathway Scenarios (RCPs) for the IPCC 5 th Assessment report– a Reference Case and RCP4.5. In GCAM, RCP4.5 differs from the Reference Case only in the application of a climate policy. Therefore, we simulate directly the effects of global GHG mitigation on co-emitted air pollutants. Global meteorology for these future scenarios is from the GFDL general circulation model (AM3) simulations of RCP8.5 (with similar forcing as the Reference Case) and RCP4.5. 2. Methodology Global and regional Air Quality Global and regional anthropogenic emissions OC (Tg C/yr) SO 2 (Tg SO 2 /yr)  The emission reductions due to the GHG mitigation have a large positive effect on both PM 2.5 and O 3, while the changing meteorology has less influence.  Slowing future climate change increases O 3 in remote areas, as increasing water vapor decreases the ozone lifetime. In polluted regions, slowing climate change causes O 3 to decrease due to decreasing temperature and biogenic emissions, and other meteorological factors. PM 2.5 concentration ( population-weighted annual average ) O 3 concentration (population-weighted 6-month of average of 1-hr daily maximum) PM 2.5 O3O3 4. Analysis a b c a: Total co-benefit; b: Emission co-benefit; c: Meteorology co-benefit Methane and isoprene emission change on Tropospheric O 3 burden  Over the long term, the global PM 2.5 and O 3 both decrease for all scenarios, reflecting the assumptions in the RCPs of a cleaner world as economic well-being increases.  The air quality co-benefits of GHG mitigation are large—2.37 ug/m 3 for PM 2.5 and 8.11 ppb for O 3, for the global population-weighted concentrations in 2100.  Anthropogenic changes of organic carbon and sulfur dioxide, due to GHGs mitigation, among different scenarios contribute to the global and regional PM 2.5 benefit.  Organic carbon and sulfur dioxide play different roles in different regions. Global North AmericaIndiaEast Asia NO (Tg NO/yr) Methane concentration (ppb) ISOP emission (Tg C/a -1 ) ∆O 3 burden (Tg /a -1 )  Methane emissions changes likely contribute substantially effect the tropospheric ozone burden  Changes in isoprene emissions, due to meteorological changes, have a smaller influence on tropospheric ozone burden We will present the total co-benefits and those resulting from the two mechanisms as: Total co-benefit: rcp45−erefm85 Emission co-benefit: rcp45−erefm45 Meteorology co-benefit: erefm45−erefm85 Global North America East Asia India Global North America East Asia India Global North AmericaIndiaEast Asia Global North AmericaIndiaEast Asia