National Academies update ocean carbon removal research roadmap as major questions remain

The National Academies of Sciences, Engineering, and Medicine has updated its research strategy for removing carbon dioxide through the ocean, focusing new attention on ocean alkalinity enhancement. The update sets out what researchers need to establish before the technique can be judged an effective and responsible climate tool. Columbia Climate School reported on the installment on September 21, five days after the Academies announced its release.

Ocean alkalinity enhancement involves adding alkaline substances to seawater. The resulting change in ocean chemistry could allow surface water to absorb more carbon dioxide from the atmosphere. Whether a particular intervention removes additional carbon overall depends on more than a measurable change in seawater chemistry: researchers must also account for atmospheric uptake, environmental effects and emissions from the materials and operations involved.

What the update covers

The 2026 installment adds a State of Marine CDR module and updates the introduction, governance and ocean alkalinity enhancement sections of a report first published in 2022. The National Academies says marine carbon removal research and technology have advanced, with greater private-sector involvement and movement toward field testing. It also says the ability to measure and verify removal at meaningful scale, along with potential environmental effects, remains uncertain.

The update is one stage of a continuing report series. Other sections covering marine carbon-removal approaches, as well as the original synthesis and research-strategy chapter, have not yet been updated. According to the Academies, choices about later revisions depend on research priorities, committee capacity, community needs and funding. Readers should therefore treat this installment as an updated assessment of selected topics, rather than a completed reassessment of every method.

The carbon-accounting problem

Galen McKinley, a Columbia researcher who served on the report committee, said the evidence needed to judge the approach at scale is still missing. She also said inconsistent life-cycle accounting makes carbon-removal approaches difficult to compare. That leaves a central distinction for any claimed result: a measured chemical response in seawater is evidence about the intervention, but the climate claim requires an account of additional atmospheric carbon uptake and the emissions caused along the way.

A separate small coastal field trial in Tasmania illustrates the measurement challenge. Researchers adding sodium hydroxide detected local changes in seawater chemistry and observed rapid dilution of the altered water. They said the trial did not detect additional uptake of carbon dioxide from the atmosphere or reduced outgassing. The authors called for larger, longer experiments to establish natural variability, detection limits and monitoring performance.

Ecology and governance remain open

Material choice matters for ecological assessment. In an independently conducted study involving 19 ship-based experiments with Equatorial Pacific seawater, researchers compared sodium hydroxide, olivine and steel slag. Sodium hydroxide had negligible measured effects on phytoplankton in those tests. Olivine disrupted several plankton groups, while steel slag moderately changed communities. Those results concern the tested substances and conditions; they do not establish the effects of deployment across different waters or at much larger scales.

The Academies also identifies long-term and ecosystem-scale effects as unresolved. Technical performance alone will not determine whether marine carbon removal is viable, it says: community concerns, public acceptance and regulatory decisions matter as well. The Tasmania trial’s authors likewise called for ecological monitoring and consultation with local communities in future field work.

Romany Webb, another Columbia member of the committee, said existing legal frameworks were largely developed for other activities and can fit ocean carbon-removal proposals awkwardly. The update calls for clearer governance alongside environmental and social safeguards. That matters because research and any eventual deployment would involve deliberate changes to a shared marine environment, with decisions extending beyond laboratory performance.

What comes next

The National Academies plans periodic updates as research advances, although their timing depends partly on resources and priorities. The immediate research agenda is to test whether additional atmospheric uptake can be verified, assess effects over longer periods and wider ecosystems, and count emissions across the full life cycle. The Academies says marine carbon removal could supplement emissions cuts if it proves feasible and responsible; a meaningful contribution to climate targets would also require substantial scale-up. The current update does not establish that ocean alkalinity enhancement has met those conditions.