Enhanced atmospheric oxidation toward carbon neutrality reduces methane’s climate forcing

Abstract

The hydroxyl radical (OH), as the central atmospheric oxidant, controls the removal rates of methane, a powerful greenhouse gas. It is being suggested that OH levels would decrease with reductions of nitrogen oxides and ozone levels by climate polices, but this remains unsettled. Here, we show that driven by the carbon neutrality pledge, the global-mean OH concentration, derived from multiple chemistry-climate model simulations, is projected to be significantly increasing with a trend of 0.071‒0.16% per year during 2015-2100. The leading cause of this OH enhancement is dramatic decreases in carbon monoxide and methane concentrations, which together reduce OH sinks. The OH increase shortens methane's lifetime by 0.19‒1.1 years across models and subsequently diminishes methane's radiative forcing. If following a largely unmitigated scenario, the global OH exhibits a significant decrease that would exacerbate methane's radiative forcing. Thus, we highlight that targeted emission abatement strategies for sustained oxidation capacity can benefit climate change mitigation in the Anthropocene.