Co-benefits of Global Greenhouse Gas Mitigation for US Air Quality and Health through Dynamical Downscaling, and its Application to China

Speaker: Zhang YuqiangZHANG Yuqiang, postdoctoral researcher, Department of Environmental Science and Engineering, University of North Carolina at Chapel Hill

Sponsored by the China Project, Harvard Paulson School of Engineering and Applied Science

Abstract:

Climate change and air quality are interrelated issues. Policies to mitigate greenhouse gas (GHG) emissions will not only slow climate change, but can also bring co-benefits of improved air quality and avoided mortality. Here I examine the co-benefits of global and regional GHG mitigation on US air quality and human health in 2050 at fine resolution by dynamically downscaling a previous global study on the co-benefits of global GHG mitigation. The US average total co-benefits of global GHG mitigation in RCP4.5 are 0.47 µg m^-3 for annual average PM_2.5 and 3.55 ppb for ozone-season maximum daily 8-hour average O₃, avoiding 24,500 (90% confidence interval, 17,800-31,100) all-cause deaths related to PM_2.5, and 12,200 (5,400-18,900) respiratory deaths for O₃. Reductions in co-emitted air pollutants dominate the total co-benefits, much higher than those via slowing climate change. GHG mitigation from foreign countries avoids 3,700 (2,700-4,700) PM_2.5-related deaths (15% of the total), and contributes more to the US O₃ reduction than domestic GHG mitigation, avoiding 7,600 O₃-related deaths (3,400-11,900, 62%), highlighting the importance of global methane reductions and intercontinental air pollutant transport. The US gains significantly greater co-benefits by coordinating GHG reductions with foreign countries. This also applies to other nations, such as China, which can be expected to gain ancillary air quality benefits from collaborating in international GHG mitigation compared to only reducing domestic GHGs.