Dear fellow UPTAKErs,
After some discussions we had about what CO2/C storage duration as part of CDR would be sufficient and the lack of a paper that shows the climate outcome of CDR with different CO2 storage durations, we wrote a research article that come out yesterday:
https://www.nature.com/articles/s43247-024-01808-7
Firstly, the climate outcome all depends on how we assume the re-release of CO₂ to happen: All at once after x years, continuously over x years, or as a result of a leak or a chemical decomposition, with an average re-release time of x years. We focus on the latter but show the other cases in the supplementary materials.
Fundamentally, CDR induces a cooling that–in a net zero framework–aims to neutralize the induced warming of a CO₂ (or greenhouse gas) emission. Because most of the warming of emitted CO₂ remains for thousands of years, the induced cooling of CDR must be maintained for as long.
If the CO₂ after its removal is stored only temporarily, the induced cooling of CDR will get lost, too. If done so as part of a net zero CO₂ emissions claim, over time, a net warming sets in similar to if there hadn’t been any CDR in the first place.
Thus, if we along with strong reductions in other GHG emissions claim that global CO₂ emissions have been reduced to “net zero” because a CDR activity only needs to store the removed CO₂ for 1000 years or less, we miss the targeted climate-neutral case and continue to warm.
These results reinforce the “like-for-like” principle: credible neutralization claims using CDR in a net zero framework require balancing emissions with removals of similar atmospheric residence time and storage reservoir, e.g., geological or biogenic. https://doi.org/10.1146/annurev-environ-112320-105050
However, lower-durability removals have value, too:
- In the absence of specific net zero or neutralization claims Temporary nature-based carbon removal can lower peak warming in a well-below 2 °C scenario | Communications Earth & Environment
or: - If the re-release of CO₂ is treated the same as an emission of CO₂, so it must be neutralized with new CDR.