Methane radiative forcing controls the allowable CO2 emissions for climate stabilization

A number of recent studies have highlighted the potential for economically efficient climate change mitigation through the abatement of anthropogenic emissions of methane and nitrous oxide. In the case of methane there are likely to be considerable co-benefits in terms of reduced ground-level ozone and therefore avoided damages to human health and crop yields. Climate mitigation policy has tended to focus most strongly on carbon dioxide because it has produced three times as much radiative forcing as methane since the pre-industrial era, and because it has a longer lifetime in the atmosphere. However, here we argue that changes in methane radiative forcing also provide a sensitive control on the allowable integrated CO2 emissions for climate stabilization. A feasible 40% sustained abatement of CH4 emissions could increase the allowable CO2 emissions for stabilization at an additional global radiative forcing of +1 W m(-2), by about a third. As such, reductions in anthropogenic methane emissions have the potential to make climate stabilization at less than 2 degrees C of global warming far more achievable.