Quantified, localized health benefits of accelerated carbon dioxide emissions reductions

Societal risks increase as Earth warms, and increase further for emissions trajectories accepting relatively high levels of near-term emissions while assuming future negative emissions will compensate, even if they lead to identical warming as trajectories with reduced near-term emissions(1). Accelerating carbon dioxide (CO2) emissions reductions, including as a substitute for negative emissions, hence reduces long-term risks but requires dramatic near-term societal transformations(2). A major barrier to emissions reductions is the difficulty of reconciling immediate, localized costs with global, long-term benefits(3,4). However, 2 degrees C trajectories not relying on negative emissions or 1.5 degrees C trajectories require elimination of most fossil-fuel-related emissions. This generally reduces co-emissions that cause ambient air pollution, resulting in near-term, localized health benefits. We therefore examine the human health benefits of increasing 21st-century CO2 reductions by 180 GtC, an amount that would shift a 'standard' 2 degrees C scenario to 1.5 degrees C or could achieve 2 degrees C without negative emissions. The decreased air pollution leads to 153 +/- 43 million fewer premature deaths worldwide, with -40% occurring during the next 40 years, and minimal climate disbenefits. More than a million premature deaths would be prevented in many metropolitan areas in Asia and Africa, and > 200,000 in individual urban areas on every inhabited continent except Australia.