Climate and health impacts of US emissions reductions consistent with 2 ◦C

An emissions trajectory for the US consistent with 2 ◦ C warming would require marked societal changes, making it crucial to understand the associated benefits. Previous studies have examined technological potentials and implementation costs1,2 and public health benefits have been quantified for less-aggressive potential emissions-reduction policies (for example, refs 3,4), but researchers have not yet fully explored the multiple benefits of reductions consistent with 2 ◦ C. We examine the impacts of such highly ambitious scenarios for clean energy and vehicles. US transportation emissions reductions avoid ∼0.03 ◦ C global warming in 2030 (0.15 ◦ C in 2100), whereas energy emissions reductions avoid ∼0.05–0.07 ◦ C 2030 warming (∼0.25 ◦ C in 2100). Nationally, however, clean energy policies produce climate disbenefits including warmer summers (although these would be eliminated by the remote effects of similar policies if they were undertaken elsewhere). The policies also greatly reduce damaging ambient particulate matter and ozone. By 2030, clean energy policies could prevent ∼175,000 premature deaths, with ∼22,000 (11,000–96,000; 95% confidence) fewer annually thereafter, whereas clean transportation could prevent ∼120,000 premature deaths and ∼14,000 (9,000–52,000) annually thereafter. Near-term national benefits are valued at ∼US$250 billion (140 billion to 1,050 billion) per year, which is likely to exceed implementation costs. Including longer-term, worldwide climate impacts, benefits roughly quintuple, becoming ∼5–10 times larger than estimated implementation costs. Achieving the benefits, however, would require both larger and broader emissions reductions than those in current legislation or regulations.