Reflecting regional variation in the U.S. public health burden of air pollution under climate change

Here, we assess regional variation in the U.S. public health burden of air pollution due to climate change in 2050 and 2100. Climate change can affect concentrations of ozone and fine particulate matter through, for example, temperature-dependent reactions, resulting in a so-called "climate penalty" on air quality. Projecting the public health implications of the climate penalty is critical for informing climate change adaptation and assessing the benefits of mitigation. However, developing sufficiently robust estimates is made challenging by uncertainty related to projecting climate and health systems. Here, we seek to examine the regional variation of climate-related uncertainty in the public health burden due to the climate penalty. Specifically, we use a large ensemble of simulations of the future economy, climate, air quality, and human health impacts to project mortality and morbidity associated with the climate penalty on ozone and fine particulate matter. Since there is significant variation within the U.S. with respect to natural variability in the climate, demographics, and health characteristics, we evaluate regional variation of impacts under different simulations of the future climate. This multi-decadal, multiple initial condition ensemble reflects variation due to natural variability and different levels of climate policy ambition. We present health incidence rates and associated economic damages. We assess regional variation in the uncertainty in these projected impacts due to natural climate variability compared with health-related uncertainty sources. We provide metrics including the number of simulation years needed to reduce noise due to natural variability to sufficiently distinguish public health burdens under different climate mitigation scenarios. These results can provide guidance for assessing and reducing uncertainty in projections of the health impacts of air pollution under a changing climate.