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

An emissions trajectory for the US consistent with 2 degrees C warming would require marked societal changes, making it crucial to understand the associated benefits. Previous studies have examined technological potentials and implementation costs(1,2) 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 degrees C. We examine the impacts of such highly ambitious scenarios for clean energy and vehicles. US transportation emissions reductions avoid similar to 0.03 degrees C global warming in 2030 (0.15 degrees C in 2100), whereas energy emissions reductions avoid similar to 0.05-0.07 degrees C 2030 warming (similar to 0.25 degrees 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 similar to 175,000 premature deaths, with similar to 22,000 (11,000-96,000; 95% confidence) fewer annually thereafter, whereas clean transportation could prevent similar to 120,000 premature deaths and similar to 144,000 (9,000-52,000) annually thereafter. Near-term national benefits are valued at similar to 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 similar to 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.