Projecting policy-relevant metrics for high summertime ozone pollution events over the eastern United States due to climate and emission changes during the 21st century

Here we analyze the effect of changing emissions and climate, in isolation and combination, on EUS summertime surface ozone (O₃) over the recent past and the 21st century in an ensemble of simulations performed with the Geophysical Fluid Dynamics Laboratory CM3 chemistry-climate model.

The simulated summertime EUS O₃ is biased high but captures the structure of observed changes in regional O₃ distributions following NOx emission reductions. We introduce a statistical bias correction, which allows derivation of policy-relevant statistics by assuming a stationary mean state bias in the model, but accurate simulation of changes at each quantile of the distribution. We contrast two different 21st century scenarios: (i) representative concentration pathway (RCP) 4.5 and (ii) simulations with well-mixed greenhouse gases (WMGG) following RCP4.5 but with emissions of air pollutants and precursors held fixed at 2005 levels (RCP4.5_WMGG).