Beyond CO2 equivalence: The impacts of methane on climate, ecosystems, and health.

In this article we review the physical and chemical properties of methane (CH 4) relevant to impacts on climate, ecosystems, and air pollution, and examine the extent to which this is reflected in climate and air pollution governance. Although CH 4 is governed under the UNFCCC climate regime, its treatment there is limited to the ways in which it acts as a "CO 2 equivalent" climate forcer on a 100-year time frame. The UNFCCC framework neglects the impacts that CH 4 has on near-term climate, as well its impacts on human health and ecosystems, which are primarily mediated by methane's role as a precursor to tropospheric ozone. Frameworks for air quality governance generally address tropospheric ozone as a pollutant, but do not regulate CH 4 itself. Methane's climate and air quality impacts, together with its alarming rise in atmospheric concentrations in recent years, make it clear that mitigation of CH 4 emissions needs to be accelerated globally. We examine challenges and opportunities for further progress on CH 4 mitigation within the international governance landscapes for climate change and air pollution. [Display omitted] • CH 4 's impacts on climate, ecosystems, and air quality are significant. • The concept of "CO 2 equivalence" does not adequately capture these impacts. • These impacts are not adequately treated under international climate or air policy. • Opportunities for improving methane governance are discussed. [ABSTRACT FROM AUTHOR]