Temporary carbon dioxide removals to offset methane emissions

Methane emissions cause a large but short-lived (30 yr) spike in temperature, whereas CO₂ emissions deliver a small but essentially permanent effect. We show that 87 tonnes of CO₂ removals over 30 years are welfare equivalent to an emission of 1 tonne of methane. Offsetting methane with CO₂ removal contracts of 30 year has several advantages over offsetting with permanent removal contracts.

1. Many nature-based solutions such as forestry projects are cost-effective, but hard to guarantee over long term periods. 30 year-contracts will be easier to monitor and manage than eternal contracts. 
2. After 30 years, the same forest storing 87 tonnes of carbon can deliver a new contract offsetting 1 tonne of methane emissions (provided that it is still additional).  
3. Since both the methane’s warming and the CO₂ projects’ cooling are essentially happening over the same 30 years, there are no long-term intergenerational transfers. 
4. As the cooling of the CO₂ project happens simultaneously, our ratio of 87 tonnes of CO₂ per tonne of methane is insensitive to the discount rate, future warming, the damage function and long term project failure rates. 

Venmans, F., Rickels, W. & Groom, B. Temporary carbon dioxide removals to offset methane emissions. Nat. Clim. Chang. (2025). https://doi.org/10.1038/s41558-025-02487-8