How oceans can help mitigate climate change

Written by Dr Sian Henley, Reader in Marine Science, School of GeoSciences

The global ocean covers more than 70 per cent of the surface of planet Earth. It plays a critically important role in stabilising global climate, by absorbing 25 to 30 per cent of the carbon dioxide (CO2) emissions and more than 90 per cent of the excess heat caused by human activity.

The polar oceans – in the Arctic and Antarctica – are disproportionately important in these climate-stabilising processes. For example, the Southern Ocean around Antarctica takes up 40 to 50 per cent of total ocean CO2 uptake and around 75 per cent of the total ocean heat uptake. However, the ocean worldwide is in peril because of human-driven climate change, causing ocean warming, acidification and oxygen loss.

Alongside this, pollution and overfishing reduce the resilience of ocean systems and undermine their ability to cope with the impacts of climate change. Once thought pristine, the polar oceans are not immune from these global threats and, in fact, are particularly at risk from the impacts of ocean warming, acidification and rapid declines of sea ice, which has regulated these ocean systems for thousands of years.

Researchers in the School of GeoSciences’ Global Change Research Institute are actively involved in scientific investigations that aim to improve our understanding of the importance of these ocean systems, the threats that they are facing, and the best ways to safeguard them now and in the future. I have led, and am currently involved in, several projects aiming to better understand, and more effectively protect, the Southern Ocean.¹

The rapid changes underway and the severe impacts of change have implications far beyond the Arctic and Antarctic regions, which influence global ocean health and productivity, underpin globally significant fisheries, and regulate climate on regional-to-global scales. This places the Arctic and Southern Oceans and their connectivity with ocean regions around the world as high priorities under COP 30’s Action Agenda Theme 2, Stewarding Forests, Oceans and Biodiversity, and the subsequent focus on Oceans and Seas for COP 31 later this year.

In particular under this theme, efforts to conserve, protect and restore nature and ecosystems with solutions for climate, biodiversity and desertification, and efforts to preserve and restore oceans and coastal ecosystems, must take a comprehensive and interconnected approach, including the polar oceans alongside all other regions of the global ocean.

As part of the Global Mutirão mobilisation that was envisioned at the heart of Brazil’s COP 30 presidency in November 2025, there was strong emphasis on calling on science and ancestral wisdom to prepare now for an unpredictable future.² This combination of science and traditional knowledge will be fundamental in meeting oceans-focused objectives, including centring those most vulnerable to climate-driven ocean change around the world. Special emphasis must be placed on Indigenous and local communities as rights holders of land, coastal and ocean territories, through the United Nations Framework Convention on Climate Change (UNFCCC) Local Communities and Indigenous Peoples Platform and other relevant mechanisms, in line with the UN Declaration on the Rights of Indigenous Peoples (UNDRIP, 2007).

The importance of the ocean in helping humanity to mitigate and adapt to climate change is recognised within the UNFCCC via the Ocean and Climate Change Dialogue, mandated by COP 25 (2019) and conducted in December 2020 and annually since 2022. The need to address the global climate and biodiversity crises together in a coherent and well-connected manner is also increasingly recognised and led to the first joint workshop and report of the Intergovernmental Panel on Climate Change (IPCC) and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) in June 2021. These efforts see active participation from Prof Sandy Tudhope, Dr Meriwether Wilson and several members of their Edinburgh Ocean Leaders programme.

The role of the global ocean, and the polar oceans in particular, in mitigating climate change and supporting globally important biodiversity relies on healthy ecosystems and natural processes being in equilibrium; yet this is threatened by the very climate change it is key to protecting against. Restoring and maintaining this equilibrium and safeguarding these ecosystems requires urgent and deep cuts in greenhouse gas emissions, in line with the Paris Agreement target of limiting warming to 1.5 degrees celsius above preindustrial levels, as well as effective marine environmental protection.

The UNFCCC COP process has the potential to deliver the step change in climate and ocean action that is required, as long as Parties, civil society and other actors operate in good faith to prioritise the long-term sustainability of ocean, coastal and land systems, and the human societies that rely on them, rather than short-term profits and financial gain.

The recent ratification and entry into force of the UN BBNJ Agreement or ‘High Seas Treaty’ – in which Dr Harriet Harden-Davies and several members of her Ocean Voices programme are involved – is proving that multilateralism still works, even in the face of mounting environmental and geopolitical challenges, to safeguard the global ocean beyond national jurisdiction. The UNFCCC, and in particular this year’s COP 31 conference, has a huge opportunity to show that the same can be achieved for addressing climate change. The Paris Agreement targets are still within reach through decisive global action and reaching them is fundamental to protecting the oceans in the polar regions and worldwide, as well as human societies that rely on them directly and indirectly.

^{Photos courtesy of Sian Henley.}

1. The climate case for enhanced marine protection of the Southern Ocean ↩︎
2. The second letter of the COP 30 Brazil President ↩︎