Global Climate and Human Health Effects of the Gasoline and Diesel Vehicle Fleets

The global gasoline and diesel fuel vehicle fleets impose substantial impacts on air quality, human health, and climate change. Here we quantify the global radiative forcing and human health impacts of the global gasoline and diesel sectors using the NCAR CESM global chemistry-climate model for year 2015 emissions from the IIASA GAINS inventory. Net global radiative effects of short-lived climate forcers (including aerosols, ozone, and methane) from the gasoline and diesel sectors are +13.6 and +9.4 mW m(-2), respectively. The annual mean net aerosol contributions to the net radiative effects of gasoline and diesel are -9.6 +/- 2.0 and +8.8 +/- 5.8 mW m(-2). Aerosol indirect effects for the gasoline and diesel road vehicle sectors are -16.6 +/- 2.1 and -40.6 +/- 4.0 mW m(-2). The fractional contributions of short-lived climate forcers to the total global climate impact including carbon dioxide on the 20-year time scale are similar, 14.9% and 14.4% for gasoline and diesel, respectively. Global annual total PM2.5- and ozone-induced premature deaths for gasoline and diesel sectors approach 115,000 (95% CI: 69,000-153,600) and 122,100 (95% CI: 78,500-157,500), with corresponding years of life lost of 2.10 (95% CI: 1.23-2.66) and 2.21 (95% CI: 1.47-2.85) million years. Substantial regional variability of premature death rates is found for the diesel sector when the regional health effects are normalized by the annual total regional vehicle distance traveled. Regional premature death rates for the gasoline and diesel sectors, respectively, vary by a factor of eight and two orders of magnitude, with India showing the highest for both gasoline and diesel sectors. Plain Language Summary Emissions from the global transportation system play an important role in affecting our air quality, climate change, and public health. We use an advanced chemistry-climate model to estimate the effects of tailpipe emissions from the gasoline and diesel vehicle fuel types on changes in Earth's energy budget, and premature deaths associated with respiratory and cardiovascular diseases. Our results show that the climatic effects of both gasoline and diesel vehicle fleets, including carbon dioxide, are warming. The fractional contributions from short-lived climate forcers (including aerosols, ozone, and methane) relative to the total radiative effects including carbon dioxide for the gasoline and diesel sectors on a 20-year time scale are 14.9% and 14.4%, respectively. Global annual total premature deaths of 115,000 and 122,100 are attributable to the gasoline and diesel sectors. We also analyze the regional premature death rates, which are calculated as ratios of annual total regional premature deaths to annual total regional vehicle distance traveled for each vehicle fuel type. Our study finds that there exists substantial regional variability of premature death rates for the diesel sector, with India showing the highest compared with other regions.