Editorial note: I just learned that additional credits have been issued in the meantime, for the continued CO2 uptake simulated to have occurred after the first crediting period.

Lots of things to be done, and I look forward to tackling some of them by coordinating the upcoming #OAEMIP. Stay tuned.

⏳ The largest cut to the gross CDR estimate (>30%) comes from limiting the crediting period to three months beyond deployment. This is required for ex-post crediting, but I’m wondering how we will handle this in the future — especially for larger-scale interventions.

📉 There is no established routine to propagate the individual uncertainty components in the simulated CO₂ uptake into a transparent uncertainty budget. Developing these routines would strengthen verification and reveal where model improvements are most urgently needed.

⚖️ Model uncertainties are subtracted from the gross CDR estimate to obtain the carbon removal that can be credited. I like this conservative approach, but based on my experience with quantifying the “natural” ocean carbon sink, I’m wondering if the reported ~10% uncertainty is high enough.

If you agree, consider submitting a proposal to our joined learning opportunity accompanying the next major OAE experiment: www.carbontosea.org/2025/11/10/h...

🚢 It is not required to demonstrate through measurements at sea that the added feedstock dissolved and increased alkalinity as expected. Quantifying OAE in the far field is certainly tough — but shouldn’t it be possible in the near field?

🎉 But first of all: huge congratulations to everyone involved! Quantifying the carbon removal required combining four different types of models with measurements from the field and in the lab. It’s a massive effort and truly at the forefront of what science can deliver today.

As a newbie to the field, moving over from fundamental ocean carbon research, there are a couple of aspects that surprised me.

The assessment includes ocean alkalinity enhancement (OAE) as a mCDR approach, but the field trials that are reported involved different chemical compositions of the feedstock to achieve the alkalinity addition.

Yes, to my understanding these numbers represent reported activities with the direct purpose to achieve CDR. But I'll confirm this with the colleagues from the @stateofcdr.bsky.social , and ask how liming / wastewater treatment are considered.

Great progress! Maybe resolve more decimals places to make the orders of magnitude between conventional and novel CDR comparable? Could be done at least in the data file.

Many thanks to @pfriedling.bsky.social for leading the effort, and @jhauck.bsky.social and Peter Landschützer for onboarding my to the GCB ocean team. It was a great experience to be part of this community.

🔬 Strengthening and expanding our global carbon flux observing systems across the ocean, atmosphere, and land seems more important than ever. @wmo-global.bsky.social

⚖️ Despite advances in understanding the global carbon cycle, the 2024 budget imbalance is one of the largest in six decades, due to an overestimate of atm. CO₂ growth or of land and/or ocean sinks.
This underscores major challenges in tracking carbon-cycle changes and detecting emerging shifts.

🔧 We also included ocean-based carbon dioxide removal (CDR) estimates for the first time. These fluxes are still tiny compared to CO₂ emissions, but we wanted to start documenting their growth. Thanks to Kirsty Harrington from the @stateofcdr.bsky.social report for sharing updated 2024 estimates.

🌊 I was in charge of integrating ocean interior carbon sink estimates, established by Lydi Keppler, Tobias Ehmen, Tim DeVries, Niki Gruber, and myself. A newly added composite ocean interior estimate aligns well with the general ocean carbon sink estimate based on fCO₂ products + GOBMs (-> Tab. 6)

Agreed! Note that we have also (for the first time) quantified this "tiny fraction" of #mCDR in this years update of the #GCB, with great help from the @stateofcdr.bsky.social

🙏 I was marginally involved in this effort and am here to take questions 👋😜