Exploring the Ocean's Carbon Removal Potential

To meet the Paris Agreement’s goal of limiting temperature rise to 1.5 degrees C (2.7 degrees F), greenhouse gas emissions must reach net-zero by mid-century. Achieving this will not only require reducing existing emissions, but also removing carbon dioxide already in the air.

How much carbon to remove from the atmosphere will depend on emissions in the coming years, but estimates point to around 10-20 billion tons of CO2 per year through 2100, globally. This is a tremendous amount, considering that the United States emitted 5.4 billion tons of CO2 in 2018.

As the need for climate action becomes more urgent, the ocean is gaining attention as a potential part of the solution. Approaches like investing in offshore energy production, conserving coastal ecosystems and increasing consumption of sustainable ocean-based protein offer opportunities to reduce emissions. In addition to these opportunities, a range of ocean-based carbon removal approaches could help capture and store billion of tons of carbon.

A few options for increasing the ocean’s capacity to store carbon may also provide co-benefits, such as increasing biodiversity and reducing acidification. However, many approaches remain contentious due to uncertainties around potential ecological impacts, governance and other risks.

If research efforts increase to improve understanding in these areas, a combination of approaches could help address the global climate crisis.

Ocean-based Ways to Remove CO2 from the Atmosphere

Proposed methods for increasing the ocean’s ability to remove and store carbon dioxide — including biological, chemical and electrochemical concepts — vary in technical maturity, permanence, public acceptance and risk.

Governance and Social Considerations of Ocean-based Carbon Removal

Ensuring appropriate governance frameworks — both national and international — for ocean-based carbon removal approaches will be a critical pre-condition before many are ready to scale. International legal frameworks for the ocean, such as the U.N. Convention on the Law of the Sea and the London Convention and Protocol, predate the concept of ocean carbon dioxide removal. As a result, these frameworks are retroactively applied to these approaches, leading to differing interpretations and a lack of clarity in some cases.

Some legal scholars suggest amending existing legal instruments to more directly govern ocean carbon removal, including carbon removal in ongoing negotiations for new international agreements or shifting governance to another international body entirely. Robust environmental safeguards, including transparent monitoring and reporting, must also be in place.

Lastly, ocean carbon removal approaches should not move forward without first considering the impacts on local communities and indigenous populations. Community acceptance of potential pilot testing and impacts on coastal communities must also be a pre-condition to moving forward at scale.

Climate Action Must Include the Ocean

As the world seeks effective tools for the climate action toolbox, employing approaches on land and at sea would prevent over-reliance on any one approach and spread the carbon removal burden over larger systems.

However, before any large-scale application, ocean-based carbon removal approaches require continued research to better understand their effectiveness, cost, capacity and ancillary impacts. Such research will ensure a strong scientific foundation from which to pursue these concepts, while minimizing unintended impacts on ocean ecosystems.

If understood and effectively developed and implemented, ocean-based carbon removal approaches could prove valuable to reaching net-zero and avoiding the worst effects of climate change.