Atmospheric health burden across the century and the accelerating impact of temperature compared to pollution

Anthropogenic emissions alter atmospheric composition and therefore the climate, with implications for air pollution- and climate-related human health. Mortality attributable to air pollution and non-optimal temperature is a major concern, which is subject to change in the future under different climate change and socioeconomic scenarios. We use model outputs from the recent Intergovernmental Panel on Climate Change multi-institution simulations to assess future changes in mortality attributable to long-term exposure to both non-optimal temperature and air pollution. We show that, under a moderate scenario (SSP2-4.5), end-of-century mortality could quadruple from present-day values to around 30 (confidence level 95%:12-53) million/year, potentially reaching 44 million/year in a more pessimistic scenario (SSP5-8.5). While pollution-related mortality is projected to increase five-fold by the end of the century in a moderate scenario, temperature-related mortality will experience a seven-fold rise, making non-optimal temperature exposure more important than air pollution as health risk factor for at least 20% of the world's population. Population aging emerges as the primary driver of increased mortality, countering efforts to improve air quality and mitigate climate change. These findings underscore the urgency not only to improve air quality but, more importantly, to simultaneously implement more effective climate change policies to prevent significant loss of lives in the future.