Scientists and governments are exploring the oceans as a potential solution to slow climate change. Since the sea naturally absorbs large amounts of carbon dioxide, some researchers believe that new technologies could accelerate this process and help remove more CO2 from the atmosphere.

However, a new report commissioned by the European Union cautions that it is too early to rely on these methods. According to the experts, there is currently insufficient evidence that these technologies are safe or effective. They argue that expanding these methods before this evidence is available would be risky.

These methods, referred to as marine carbon dioxide removal techniques, use either biological processes, such as increasing plankton or seaweed growth, or chemical and physical systems that directly remove CO2 from seawater. The goal is to extract carbon from the upper ocean and store it in deep waters, bury it in seabed sediments, lock it away in rock formations, or even incorporate it into long-lasting products.

Exploring New Climate Solutions

Helene Muri, a senior researcher at the Norwegian Institute for Air Research and the Norwegian University of Science and Technology, led the expert group formed by the European Marine Board to evaluate the current state of marine carbon removal. Their findings are detailed in a new report titled Monitoring, Reporting and Verification for Marine Carbon Dioxide Removal, released during the COP30 climate summit in Brazil.

A World Warming Faster Than Expected

Global temperatures are rising more rapidly than countries had anticipated when they signed the Paris Agreement, which aims to limit warming to 1.5°C above pre-industrial levels. Speaking at COP30, UN Secretary-General António Guterres warned that exceeding this 1.5°C limit is now very likely within the next decade.

Despite this, scientists say it is still possible to stay within this limit if the world takes rapid action. The European Marine Board report emphasizes that the most urgent and effective action remains the simplest: reducing emissions.

Why Carbon Removal Is Important

Some aspects of modern life are extremely difficult to make carbon-free. Air travel is a clear example: despite significant research efforts, achieving truly zero-carbon flying remains out of reach.

Countries aiming for net zero emissions by 2050 must balance any emissions they cannot eliminate by removing an equal amount of CO2 from the air. To stay within the 1.5°C warming limit, the world will eventually need to go further and achieve net negative emissions, removing more carbon than we emit.

According to scenarios from the Intergovernmental Panel on Climate Change (IPCC), this could require removing 5-10 gigatonnes of CO2 per year by the end of the century. For context, global CO2 emissions in 2024 exceeded four times that amount. Some land-based methods already exist, such as planting forests or using machines that extract CO2 directly from the air, like the Climeworks facility in Iceland. However, ocean-based options are far less developed.

Marine Carbon Removal

While some trials have tested different ocean-based approaches, many techniques remain in early stages. Others are advancing more quickly, which is why the report calls for strict standards for monitoring, reporting, and verifying their impact.

For instance, some methods aim to restore mangrove swamps or other coastal habitats that naturally store carbon. Others involve adding nutrients to seawater to encourage large plankton blooms, which absorb CO2 as they grow. When they die, some of this carbon sinks into the deep ocean. However, scientists still struggle to measure how much carbon these methods actually remove and for how long.

Looking Ahead

Some companies are already considering offering marine carbon removal as a paid service. However, without solid proof of how much CO2 is removed and where it ends up, Muri argues these methods are not yet ready for use. If carbon credits are to play a role, systems must be completely reliable, transparent, and scientifically sound.

Despite the uncertainties, Muri points out that most future climate scenarios indicate a clear need for carbon removal in some form. However, she warns that ocean-based methods are not a“miracle fix.”

Whether these techniques can be scaled up safely remains an open question. But if society wants to explore them, she argues, we must establish strong standards, proper oversight, and strict environmental protections. Only then can we determine whether the oceans can genuinely help in the fight against climate change.

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