Cooperative Institute for Climate Science

Writing in the March 14, 2006 issue of the Proceedings of the National Academy of Sciences,
researchers at the Cooperative Institute for Climate Science (CICS) at Princeton University and the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) report that reductions in methane emissions would decrease ground-level ozone pollution globally, and yield substantial benefits for human health. Authors Jason West (CICS), Arlene Fiore (GFDL), Larry Horowitz (GFDL), and Denise Mauzerall (Princeton University, Woodrow Wilson School) conclude that a 20% reduction of the total methane emissions from human activities would reduce ozone pollution globally by about 1 part per billion by volume. This ozone reduction is estimated to prevent about 30,000 premature human mortalities globally in the year 2030, and about 370,000 mortalities between 2010 and 2030. When these health benefits are monetized, they can exceed the costs of this 20% methane reduction, suggesting that methane emission controls can be justified for ozone air quality purposes.

Background: Methane is an important greenhouse gas that also contributes to ground-level ozone pollution. Methane affects the global ozone background, and observed increases in background ozone concentrations have been attributed in part to increases in methane. Mitigating methane emissions therefore decreases ozone globally, improving air quality everywhere by lowering the background upon which pollution episodes build.

Significance: While ozone air quality management has not traditionally considered methane, this study shows that the benefits of methane mitigation for human health can exceed the costs. Methane is also the main component of natural gas, and some emission controls (such as capturing methane from landfills) can come at a cost-savings due to the value of the energy recovered. Because reducing methane emissions improves ozone air quality globally, methane mitigation can be best considered as a means of international long-term ozone management. Methane mitigation therefore brings multiple benefits for air quality, public health, energy, and climate. This research supports the NOAA Mission Goal 2 (Understand Climate Variability and Change to Enhance Society's Ability to Plan and Respond).