Eri Saikawa, Ph.D. Candidate/ Consultant, Princeton University
BAQ 2008, 12-14 November 2008 (Bangkok, Thailand)
Aerosols are harmful to human health and have both direct and indirect effects on climate. China is a major contributor to global emissions of sulfur dioxide (SO2), a sulfate (SO42-) precursor, organic carbon (OC), and black carbon (BC) aerosols. Although increasingly examined, the effect of present and potential future levels of these emissions on global premature mortality and climate change has not been well quantified. Through both direct and indirect effects, SO42- and OC exert negative radiative forcing (cooling) while BC exerts positive forcing (warming). We analyze the effect of China’s emissions of SO2, SO42-, OC and BC in 2000 and for three emission scenarios in 2030 on global surface aerosol concentrations, premature mortality, and radiative forcing. Using global models of chemical transport (MOZART-2) and radiative transfer (GFDL RTM), and combining simulation results with gridded population data, mortality rates, and concentration-response relationships from the epidemiological literature, we estimate the contribution of Chinese aerosols to global annual premature mortality and to radiative forcing in 2000 and 2030. In 2000, we estimate these aerosols cause 385,300 premature deaths in China and an additional 18,200 globally. In 2030, depending on the emission scenario, 198,300 to 595,700 premature deaths occur in China, and an additional 7,800 to 29,900 occur globally. Because the negative radiative forcing from SO42- and OC is larger than the positive forcing from BC, these Chinese aerosols lead to global net direct radiative forcing of -74 mWm-2 in 2000 and between -15 and -97 mWm-2 in 2030. Environmental policies that focus on reducing BC emissions would simultaneously both improve public health and mitigate climate change.