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Environmental Sciences
Seminar Abstract
Background Ozone in Surface Air over the United States:
Variability, Climate Linkages, and Policy Implications
Distinguishing between natural and anthropogenic sources of surface ozone is critical because U.S. air quality standards, set to protect human health, must be attainable via controls on domestic anthropogenic emissions. When setting the ozone air quality standard, the U.S. Environmental Protection Agency (EPA) accounts for a background ozone level above which the risk to human health is assessed. We apply global 3-D chemical transport models to obtain quantitative estimates for background ozone and its variability, and to separate the natural background from the enhancement due to hemispheric pollution. Model results indicate that the traditional approach for estimating background ozone from measurements at remote sites underestimates the contribution from both regional and hemispheric pollution. With an additional suite of sensitivity simulations, we show that controls on methane emissions offer a powerful lever for reducing both air pollution and global warming via decreases in background tropospheric ozone.
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