Thursday, March 16, 2006
Those of you interested in air quality and climate issues should take a look at this open access article by Unger et al. published last week in the Proceedings of the National Academy of Sciences. Link: Cross influences of ozone and sulfate precursor emissions changes on air quality and climate -- Unger et al., 10.1073/pnas.0508769103 -- Proceedings of the National Academy of Sciences.
Tropospheric O3 and sulfate both contribute to air pollution and climate forcing. There is a growing realization that air quality and climate change issues are strongly connected. To date, the importance of the coupling between O3 and sulfate has not been fully appreciated, and thus regulations treat each pollutant separately. We show that emissions of O3 precursors can dramatically affect regional sulfate air quality and climate forcing. At 2030 in an A1B future, increased O3 precursor emissions enhance surface sulfate over India and China by up to 20% because of increased levels of OH and gas-phase SO2 oxidation rates and add up to 20% to the direct sulfate forcing for that region relative to the present day. Hence, O3 precursors impose an indirect forcing via sulfate, which is more than twice the direct O3 forcing itself (compare -0.61 vs. 0.35 W/m2). Regulatory policy should consider both air quality and climate and should address O3 and sulfate simultaneously because of the strong interaction between these species.