J.Jason West, Linking air pollution, climate change, and human health: management of ozone air pollution by reducing methane emissions
Changes in emissions of any ozone precursor - nitrogen oxides (NO/_x /), non-methane volatile organic compounds, carbon monoxide, or methane - affect both ozone air quality and the radiative forcing of climate. Methane is the dominant anthropogenic organic precursor of ozone in the troposphere, yet mitigation of methane is not generally considered for ozone air quality management. Using the MOZART-2 global model, a 20% decrease in anthropogenic methane emissions is shown to decrease ozone globally by ~1 ppbv. This ozone reduction in turn will reduce ~30,000 premature mortalities globally in 2030 and ~370,000 between 2010 and 2030. The monetized benefits to human health can exceed the costs of this 20% decrease. Among all precursors, mitigation of methane emissions is shown to cause the greatest decrease in net radiative forcing per unit improvement in surface ozone air quality. Methane mitigation can therefore be a cost-effective means of international and long-term ozone air quality management, with concurrent benefits for climate. Finally, I analyze the intercontinental transport of ozone by modeling 10% reductions in NO/_x / emissions in each of nine world regions. By comparing the changes in ozone within the source region and in each region globally, the most important inter-continental linkages are identified, for both the change in surface ozone concentrations and ozone-related mortalities.