Abstract:

Methane is the second-most important greenhouse gas after carbon dioxide, accounting for about 25% of the anthropogenic warming since pre-industrial. Methane concentration has increased from the preindustrial level of ~720 ppb to the current level of ~1920 ppb. Large variations in the growth of atmospheric methane are driven by a diverse range of anthropogenic and natural emissions and by atmospheric loss primarily from oxidation by the hydroxyl radical. Atmospheric methane observations have exhibited periods of increasing concentrations (from 1982 to 2000), stabilization (from 2000 to 2007), and renewed growth (from 2007 onward), with an accelerating rate. Record-high increases in atmospheric methane concentration have been observed since 2020, and the causes remain debated. In this talk, I will discuss results from top-down atmospheric inversions, bottom-up wetland model simulations, and information from other trace gases to discuss possible mechanisms for the recent surge in methane growth rates.