FIGURE 3. Simulated ozone air pollution over the eastern United States by using a downscaled climate model linked to a regional air pollution model.

a, Baseline summertime average daily maximum 8-hour O₃ concentrations for the 1990s. b–d, The following panels show changes in summertime-average daily maximum 8-hour O₃ concentrations for the 2020s (b), the 2050s (c), and the 2080s (d) over the region based on IPCC A2 scenario simulations relative to the 1990s, in parts per billion. Five consecutive summer seasons were simulated in each decade starting with the NASA Goddard Institute for Space Studies (GISS) Atmosphere-Ocean Global Climate Model, with results subsequently downscaled using the mesoscale regional climate model (MM5), and finally coupled to the Community Multiscale Air Quality (CMAQ) model. Simulation results for the 2020s, 2050s and 2080s indicate that summertime average daily maximum 8-hour O₃ concentrations increase by 2.7, 4.2 and 5.0 p.p.b., respectively, as a result of regional climate change. The data were taken from ref. 66.