The ocean’s ability to absorb carbon is weakening as climate change intensifies, the UN warns

The report is the result of collaboration between the UN environmental agency, UNEP, and the UN climate secretariat, UNFCCC, who participated in organizing COP31.

“The ocean has long provided huge benefits to us in the face of climate change, but these benefits are now under increasing pressure,” said Sara Traerup, lead author of the report. UN News.

Rising temperatures and changes in ocean chemistry, circulation and ecosystems are weakening their ability to absorb and store carbon, resulting in more CO₂ in the atmosphere.

And this process “can definitely be accelerated” in the future, Ms. Traerup warned.

Bridging our knowledge gaps

The biggest challenge is the lack of reliable ocean monitoring data, especially in the Southern and Indian Oceans, the Arctic and many coastal areas.

Therefore, this report calls for stronger “ocean carbon intelligence” – using science, technology, data and local knowledge to better understand and manage marine carbon systems.

“Until now, we didn’t have complete information about the oceans, and what we didn’t know, we couldn’t manage and protect,” explained Ms. Traerup.

From sensors to seagrass

UNEP looked at three main types of ocean climate technology, each of which offers different opportunities and risks.

The first is ocean monitoring: observation systems, sensors, data systems and modeling. Mrs. Traerup called this technology the most mature and most needed technology today.

Second, blue carbon ecosystems such as mangrove forests, seagrass and salt marshes. They already absorb about 407 million tons of CO₂ per year, and recovering them could increase the amount of CO₂ significantly. Forests also protect coastlines, support biodiversity and sustain livelihoods.

The third is marine carbon dioxide removal, which aims to extract CO₂ from the atmosphere and store it long-term. Although potentially promising, these approaches remain highly uncertain and require further research, monitoring, and regulation.

“We must not treat ocean-based technology as a shortcut,” Ms. Traerup warns, as such technologies must complement, not replace, emissions reductions and ecosystem protection.

The islands lead the way

Small Island Developing States (SIDS) account for less than 1 percent of global emissions, but they “are at the forefront of addressing ocean and climate impacts,” said Ms. Traerup.

The report calls for greater access to funding, technology transfer and capacity building so that countries can develop marine solutions tailored to their needs. Some islands have shown how this works.

In 2015, Seychelles, for example, benefited from a debt-for-nature swap, which involved restructuring part of its external debt in exchange for marine conservation commitments. This allows states to regulate a trust fund to finance marine conservation, climate resilience and a sustainable blue economy.

In the Pacific, Fiji, Papua New Guinea, Solomon Islands, and Vanuatu accept support to map seagrass beds and mangrove forests, and measure how much carbon is stored in them. As a result, more than 100 people were trained on blue carbon assessments, which provide data to governments to incorporate into their national climate plans.

The report also emphasizes the importance of integrating local knowledge and indigenous communities.

“Society has been dealing with climate change for years,” said Ms. Traerup, referring to their experience in protecting coastlines through natural habitats and in sustainably managing fisheries and coastal resources.