February 2008: Effects of global change on U.S. ozone air quality
We investigate the effects on U.S. ozone air quality from 2000-2050 global changes in climate and anthropogenic emissions of ozone precursors by using GEOS-Chem driven by meteorological fields from NASA/GISS GCM. We follow the IPCC A1B scenario and separate the effects from changes in climate and anthropogenic emissions through sensitivity simulations.
The above plot shows the simulated mean daily maximum 8h-average surface ozone (ppb) in summer (June-August) for (a) 2000 conditions, and perturbations from 2050 changes in (b) climate, (c) anthropogenic emissions of ozone precursors, and (d) both climate and anthropogenic emissions. The 2000-2050 changes in anthropogenic emissions reduce the U.S. summer daily maximum 8-hour ozone by 2-15 ppb, but climate change causes a 2-5 ppb positive offset over the Midwest and Northeast, partly driven by decreased ventilation from convection and frontal passages. We find that a 50% reduction in U.S. NOx emissions is needed in the 2050 climate to reach the same target in the Midwest as a 40% reduction in the 2000 climate. Emission controls reduce the magnitude of the climate change penalty and can even turn it into a climate benefit in some regions. For more details see Wu et al. [2008]