Temporary carbon dioxide removals to offset methane emissions

nature climate change Article https://doi.org/10.1038/s41558-025-02487-8 Temporary carbon dioxide removals to offset methane emissions Received: 20 February 2025 Frank Venmans , Wilfried Rickels 1 2 & Ben Groom 1,3 Accepted: 15 October 2025 Published online: xx xx xxxx Check for updates 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. Anthropogenic methane (CH4) emissions are the second largest cause of climate change after carbon dioxide (CO2) emissions, contributing 0.5 °C (estimated range, 0.3–0.8 °C) to global warming between the preindustrial era and 2010–20191. Unlike CO2, CH4 emissions have a particularly large short-term effect on temperature2. Various initiatives have been taken to reduce CH4 emissions, most notably the global methane pledge which aims to reduce CH4 emissions by at least 30% below 2020 levels by 2030, in particular targeting low abatement cost options in the energy sector3,4. However, about 40% of global CH4 emissions come from the agriculture, forestry and other land uses (AFOLU) sector5. Even in the most ambitious scenarios of the Sixth Assessment Report of the IPCC6, the minimum annual amount of CH4 emissions in the AFOLU sector is still about 33 MtCH4 by 20507. At the same time, the AFOLU sector plays a crucial role in mitigating climate change by removing atmospheric CO2 to offset residual CO2 and other greenhouse gas (GHG) emissions. The AFOLU sector achieves this primarily through nature-based solutions (NBS), such as afforestation. These solutions often provide only temporary carbon storage, unlike permanent CO2 removals achieved by methods involving geological carbon storage such as direct air carbon capture and storage. While offsetting can result in net-zero GHG emissions in simulated emission scenarios based on a 100-year global warming potential (GWP), it fails on two fronts: near-term climate benefits of CH4 emission reductions are not achieved8–15; and the integration of offsetting with temporary CO2 removal (for example, afforestation) into emissions trading systems is not addressed. Various advances have been proposed to improve the representation of short-lived climate forces, and of CH4 emissions in particular, in climate policies and carbon budget calculations12–14. In this study, we focus on offsetting residual CH4 emissions. We argue that offsetting the short-term warming effect of CH4 emissions with equivalent temporary CO2 removals has several practical advantages. First, temporary and temporally coincident CO2 removals better mitigate the large short-run temperature effect of CH4 emissions and smooth out the damages of climate change across generations. Second, short-term monitoring periods for CO2 removal are more credibly enforced (as part of the crediting process and the contractual documentation) compared with long-term monitoring periods, and more easily renegotiated in the event of under- or overperformance16,17. Third, even if NBS have a long-term effect, they can still be administered by short-term monitoring periods. If the project has still removed carbon compared with a well-defined counterfactual at the end of the initial monitoring period (that is, it is still additional), the same project can compensate other CH4 emissions. Indeed, 20- to 30-year contractually agreed monitoring periods are used in the economy at large (for example, mortgages), are seen in policy (for example, biodiversity offsets in the United Kingdom18), Grantham Research Institute on Climate Change and the Environment, London School of Economics and Political Science, London, UK. 2Kiel Institute for the World Economy, Kiel, Germany. 3LEEP Institute, Department of Economics, University of Exeter Business School, Exeter, UK. e-mail: 1 Nature Climate Change Article and have the same duration as the main temperature effect of CH4 emissions. Finally, because both warming by CH4 emissions and cooling by temporary CO2 removal take place in the short run, the calculation of how much CO2 removal is equivalent to 1 t of CH4 emissions is insensitive to key determinants of intertemporal trade-offs of welfare: the social discount rate, economic damage parameters and the expected representative concentration pathway (RCP) scenario. In terms of the value of damages avoided in the long run, we show that 1 t of CH4 emitted can be offset by between 78 and 117 temporary CO2 removals with a duration of 30 years across all scenarios presented, with 87 t CO2 in our central RCP 2.6 case. This narrow range illustrates the modest effect of assumptions about the discount rate, future warming and the failure risk within the 30 storage years. Matching schedules of CH4 emissions to temporary CO2 removals Despite recent advances in comparing the climate change impact of CH4 emission rate changes to CO2 emissions pulses12–14,19, the most commonly applied metric to measure the impact of a GHG is still the global warming potential (GWPX), defined as the extra energy that is absorbed by the Earth as a consequence of 1 t of emission over a given number of years (X). Over 20 (100) years, the GWP of 1 t of CH4 is approximately 82.5 (29.8) times larger than 1 t of CO2. Values for non-fossil CH4 emissions are slightly lower (79.7 and 27.0 respectively) because the carbon atom of CH4 originates from atmospheric CO2 (IPCC WGI Table 7.15)20. The difference in GWPX between CH4 and CO2 reflects their different energy forcing and how this forcing gradually dissipates over time. CH4 oxidizes to CO2 within decades, while CO2 is absorbed by oceans over centuries. As a result, when establishing GWPX equivalence of CH4 and CO2 over X years (usually 100), the effect of CO2 beyond 100 years is ignored, making it hard to assess the dynamic trade-offs between both gases8–13,15. The permanent removal of 1 t of CO2 has the same GWP as the emission of 1 t of CO2, but of opposite sign. A temporary removal will have a more modest GWP. Table 1 (last row) reports the number of temporary CO2 removals (each removing 1 t) with an equivalent GWP of 1 t of CH4 emitted. For example, 80 ( (...truncated)