ALBERT

Description: Currently, the ocean carbon sink annually removes about a third of anthropogenic fossil fuel and industrial CO2 emissions, reducing therefore climate change damages and CO2 abatement costs. While the land sinks have entered climate policies, the ocean sink has not—for good reasons since the former stores carbon within the boundaries of a state while the ocean removes carbon from the atmosphere rather in its property as a global common. However, the question remains what is the value of the ocean carbon sink and should it be differently attributed when comparing a coastal state with a large exclusive economic zone (EEZ) compared to landlocked state. Here, we demonstrate different approaches to value the ocean sink, comparing a climate-change damage-based approach with an abatement, market-based approach. We use a high-resolution carbon flux dataset (0.25x0.25 degree) to estimate the ocean carbon sink and source in coastal areas. We assign a net sink of 1.72 GtC proportional to countries with negative carbon fluxes in their EEZ. In our calculation the annual value of the global ocean sink ranges from 61.19 B USD (Std 31.80), equivalent to the 2021 GDP of Slovenia, to 1433 B USD (Std 94.30), equivalent to the 2021 GDP of Spain (World Bank data) for the abatement cost-based assessment approach (assuming full emission trading and low ambition levels in the national determined contribution) and for the climate-change damage-based assessment approach relying on an upper value of the social cost of carbon in our investigation. By breaking down the carbon sink by nations EEZ we estimate which countries are the largest donors of ocean carbon wealth and which countries would be affected the most if a weakening of the ocean sink would need to be compensated by higher emission reduction levels.