The Potential for Ocean-Based Climate Action: Negative Emissions Technologies and Beyond

The effectiveness, feasibility, duration of effects, co-benefits, disbenefits, cost effectiveness and governability of four ocean-based negative emissions technologies (NETs) are assessed in comparison to eight other ocean-based measures. Their role in revising UNFCCC Parties' future Nationally Determined Contributions is discussed in the broad context of ocean-based actions for both mitigation and ecological adaptation. All measures are clustered in three policy-relevant categories (Decisive, Low Regret, Concept Stage). None of the ocean-based NETs assessed are identified as Decisive at this stage. One is Low Regret ( Restoring and increasing coastal vegetation ), and three are at Concept Stage, one with low to moderate potential disbenefits ( Marine bioenergy with carbon capture and storage ) and two with potentially high disbenefits ( Enhancing open-ocean productivity and Enhancing weathering and alkalinization ). Ocean-based NETs are uncertain but potentially highly effective. They have high priority for research and development.