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Background: Future climate change may cause air quality degradation via climate-induced changes in meteorology, atmospheric chemistry, and emissions into the air. Few studies have explicitly modeled the potential relationships between climate change, air quality, and human health, and fewer still have investigated the sensitivity of estimates to the underlying modeling choices., Objectives: Our goal was to assess the sensitivity of estimated ozone-related human health impacts of climate change to key modeling choices., Methods: Our analysis included seven modeling systems in which a climate change model is linked to an air quality model, five population projections, and multiple concentration-response functions. Using the U.S. Environmental Protection Agency's (EPA's) Environmental Benefits Mapping and Analysis Program (BenMAP), we estimated future ozone (O(3))-related health effects in the United States attributable to simulated climate change between the years 2000 and approximately 2050, given each combination of modeling choices. Health effects and concentration-response functions were chosen to match those used in the U.S. EPA's 2008 Regulatory Impact Analysis of the National Ambient Air Quality Standards for O(3)., Results: Different combinations of methodological choices produced a range of estimates of national O(3)-related mortality from roughly 600 deaths avoided as a result of climate change to 2,500 deaths attributable to climate change (although the large majority produced increases in mortality). The choice of the climate change and the air quality model reflected the greatest source of uncertainty, with the other modeling choices having lesser but still substantial effects., Conclusions: Our results highlight the need to use an ensemble approach, instead of relying on any one set of modeling choices, to assess the potential risks associated with O(3)-related human health effects resulting from climate change.

Future changes in climate and precursor emissions will likely have important consequences on ground-level ozone concentrations for the City of Chicago and its surrounding suburban/rural areas. Here we use a regional climate–air quality modeling system to evaluate the combined and individual effects of climate warming (and resulting biogenic emissions increases) and anthropogenic emissions perturbations from 1996–2000 to 2048–2052 and 2095–2099 in this region. Two scenarios are considered, including A1FI (higher warming with increasing anthropogenic emissions) and B1 (less warming with reduced anthropogenic emissions). Relative to 1996–2000, projected changes in climate and anthropogenic emissions together lead to little ozone change for the City of Chicago under A1FI but 5.0–7.8 ppb increases under B1 by 2048–2052 and 2095–2099. For A1FI, the decreasing ratio of volatile organic compounds (VOCs) to nitrogen oxides (NOx) reduces ozone concentrations over Chicago, despite the increasing emissions for both NOx and VOCs. Averaged over the Chicago urban and surrounding suburban area, however, surface ozone increase 2.3–7.1 ppb under A1FI by 2095–2099. Additionally, the seasonal ozone variation is projected to increase 84–127% under A1FI but decrease 23–30% under B1 over the Chicago area. By comparison, projected climate warming alone increases the surface ozone by 2.1–8.7 ppb and its seasonal variation by 22–89% over the Chicago area from 1996–2000 to 2095–2099 under both scenarios. Therefore, effective emission regulation and climate considerations are both important to pollution mitigation in the Chicago area. [Copyright &y& Elsevier]