Methane Emissions Offsetting With Temporary Carbon Sinks

Abstract

Methane accounts for more than 20% of current anthropogenic warming. While fossil methane emissions can likely be reduced substantially, biogenic methane from agriculture and waste will remain difficult to fully abate. Achieving climate neutrality therefore requires counterbalancing the warming effect of residual emissions. The rapid atmospheric decay of methane suggests that temporary carbon sinks can serve this purpose, yet current accounting approaches do not consistently quantify their time-dependent cooling effect. Here we develop a time-explicit method that enables offsetting the 100-year warming impact of a methane emission pulse with an equally sized cooling effect delivered by carbon dioxide removal over 20 years. Based on a CO₂ atmospheric impulse–response function (IRF), we define the total climate effect (TCE) as time-integrated warming and cooling of greenhouse gas emissions and dynamic carbon sinks expressed in CO₂-equivalent units. The developed method yields the amount of CO₂ removal and storage duration over a chosen time horizon to counterbalance methane-induced warming. For example, over a 20-year horizon, complete offsetting of 1 t CH₄ of biogenic origin requires 94.6 t CO₂e stored in a constant C-sink. The method allows differentiation between temporary and geologically persistent carbon dioxide removal by explicitly accounting for storage duration and time horizon. By providing a physically grounded basis for valuing temporary carbon storage—a question actively debated in the EU Carbon Removals and Carbon Farming Regulation and Article 6.4 of the Paris Agreement—the approach supports near-term climate mitigation and may bridge the decades required for scaling permanent CDR solutions by creating financial incentives for temporary carbon sink technologies.