The impact of climate change and emissions control on future ozone levels: Implications for human health

Overwhelming evidence has shown that, from the Industrial Revolution to the present, human activities influence ground-level ozone (O₃) concentrations. Past studies demonstrate links between O₃ exposure and health. However, knowledge gaps remain in our understanding concerning the impacts of climate change mitigation policies on O₃ concentrations and health. Using a hybrid downscaling approach, we evaluated the separate impact of climate change and emission control policies on O₃ levels and associated excess mortality in the US in the 2050s under two Representative Concentration Pathways (RCPs). We show that, by the 2050s, under RCP4.5, increased O₃ levels due to combined climate change and emission control policies, could contribute to an increase of approximately 50 premature deaths annually nationwide in the US. The biggest impact, however, is seen under RCP8.5, where rises in O₃ concentrations are expected to result in over 2,200 additional premature deaths annually. The largest increases in O₃ are seen in RCP8.5 in the Northeast, the Southeast, the Central, and the West regions of the US. Additionally, when O₃ increases are examined by climate change and emissions contributions separately, the benefits of emissions mitigation efforts may significantly outweigh the effects of climate change mitigation policies on O₃-related mortality.