Temporary carbon dioxide removals to offset methane emissions.

Unlike CO2, methane emissions have a particularly large short-term effect on temperature. We argue that these largely temporary temperature effects of methane emissions are apt to be offset by temporary CO2 removal. Temporally matching offsetting temperature reductions to the temperature impulse of methane eliminates the sizable intertemporal welfare transfers that occur when methane is offset by equivalent permanent CO2 removals. Assessing equivalence based on avoided economic damages suggests that about 87 temporary CO2 removals over a period of 30 years are needed to offset 1 t of methane. Agreement on the appropriate quantity of temporary CO2 offsets is insensitive to controversial parameters such as the social discount rate, climate damages and future emission scenarios. Short-term monitoring periods of 20-30 years are likely to be more credibly enforceable for various nature-based CO2 removal projects than long-term monitoring requirements.