Climate change and marine pollution: twin challenges for international law

Given the ocean’s crucial role for a safe and healthy climate system, it is perhaps surprising that, historically, the international climate change regime has paid little attention to the ocean. However, the first-ever advisory opinion on climate change and the marine environment issued by the International Tribunal for the Law of the Sea (ITLOS) may just be a game changer. This advisory opinion shows that States already have far-reaching obligations with respect to climate change and the ocean under a different regime – namely, the law of the sea.

The ocean in crisis

“Oceans face ‘triple threat’ of extreme heat, oxygen loss and acidification”, “Oceans set heat records for more than 365 days in a row”, and “Scientists identify new Antarctic ice sheet ‘tipping point,’ warning future sea level rise may be underestimated” are just some of the daunting headlines we have read in the news this year.

Climate action and ocean protection go hand in hand, given that the ocean absorbs excess carbon dioxide emissions and heat (and is in fact the world’s largest carbon sink). However, the climate crisis is now causing ocean acidification, deoxygenation, warming and rising sea-levels. These impacts in turn pose an existential threat to vulnerable coastal communities, such as Small Island Developing States (SIDS).

A group of SIDS have come together to rise to this challenge by forming the Commission of Small Island States on Climate Change and International Law (COSIS) and issuing a request for an advisory opinion with ITLOS in December 2022.

COSIS asked ITLOS two questions with a view to clarifying States’ specific obligations under the United Nations Convention on the Law of the Sea (UNCLOS) with respect to climate change and the marine environment. The first one concerns States’ obligations to prevent, reduce and control marine pollution caused by greenhouse gas (GHG) emissions. The second one concerns States’ obligations to protect and preserve the marine environment with respect to climate change impacts.

World’s ocean court responds

Before offering an overview of some (but not all) of the advisory opinion’s key findings, it is worth noting the strong emphasis ITLOS placed on the best available science which it found to be the works of the International Panel on Climate Change (IPCC). Not only did ITLOS offer a detailed overview of the scientific aspects related to climate change and the ocean, but it interweaved these authoritative scientific assessments with States’ obligations under UNCLOS.

In a ground-breaking first, ITLOS found that anthropogenic GHG emissions fulfil the legal definition of “pollution of the marine environment” under UNCLOS, triggering the application of UNCLOS in respect of climate change and the ocean. While most States agreed with this in their submissions, it is vitally important to remove any doubt because the UNCLOS text makes no explicit reference to climate change.

With respect to the first question, which broadly concerns States’ mitigation obligations under UNCLOS, ITLOS issued several strong legal findings:

• States have a general obligation to take “all necessary measures” to prevent, reduce and control marine pollution from “any source” under UNCLOS. While global efforts are important, States must also take individual action as appropriate.

• “All necessary measures” must be determined objectively and guided by the best available science and the 1.5°C temperature goal and timeline for emission pathways. Other objective factors are also relevant, such as international rules and standards (primarily those found in climate change treaties) and the available means and capabilities of States.

• In the context of transboundary pollution, a separate obligation arises with an even more stringent standard of conduct, given that this type of pollution affects the environment of other States.

• Obligations under UNCLOS are not met simply by complying with requirements under the Paris Agreement. UNCLOS contains a separate set of obligations and may require States do to more.

• This general obligation to take “all necessary measures” is complemented and elaborated upon by specific obligations that apply to particular sources of pollution – including global shipping and aviation. These specific obligations include, on the one hand, adoption of domestic legislation and establishment of international rules and standards, and on the other hand, enforcement obligations.

• States also have a range of other specific obligations such as the obligation to provide assistance to (in particular, climate vulnerable) developing States in their mitigation efforts. Such assistance also includes financial assistance.

• Failure of a State to comply with the obligation to take “all necessary measures” to prevent, reduce and control marine pollution from GHG emissions would engage state responsibility.

In response to the second question, which broadly concerns States’ obligations with respect to adaptation and resilience building, in a nutshell, ITLOS found that the obligation to protect and preserve the marine environment from climate change impacts is a broad one and may also encompass adaptation and restoration. It also found States to have a specific obligation to protect and preserve rare or fragile ecosystems as wells threatened species and other forms of marine life from climate change impacts.

Global ripple effects

Often, central governments set baseline standards for energy efficiency. However, whilst an advisory opinion is itself non-binding it carries “great legal weight and moral authority” as the explanation of binding law by an international court, and is expected lead to a number of benefits and opportunities, such as for domestic and international policymaking. Of particular interest in this contribution are the advisory opinion’s possible ripple effects for other climate change litigation.

The role of the ocean has already been highlighted in domestic climate change litigation and explored elsewhere. For example, the Swedish “Aurora Case” highlights the importance of preserving marine carbon sinks. Nevertheless, the main focus of litigation seeking to protect carbon sinks to date lies in the land use, land use changes and the forestry sector.

While the ITLOS advisory opinion pays tribute to the ocean’s function as a carbon sink, it goes beyond that, highlighting severe biodiversity threats that the ocean faces due to climate change impacts as well as outlining States’ specific obligations in this regard. Given that there already exists a number of legal challenges focusing on marine biodiversity threats and that biodiversity litigation is expected to grow in the future, we may expect the ITLOS advisory opinion to give a boost to such cases.

Another strand of climate change litigation with ocean aspects seeks to protect the livelihoods of vulnerable communities dependent on the ocean, an example of which is the “Torres Strait Islanders case. The ITLOS made it clear in its advisory opinion that UNCLOS obligations are a “means” of addressing an “inequitable situation” faced by climate vulnerable States such as SIDS.

Lastly, the ITLOS advisory opinion is also expected to influence climate change litigation in the international arena. Most immediately, ITLOS’ findings are expected to inform other advisory proceedings on States’ obligations with respect to climate change which are currently before the International Court of Justice (ICJ). Crucially, an issue which ITLOS only indirectly addressed (given the questions asked) and the ICJ now has the power to clarify is that of state responsibility and liability. 

Isabela Keuschnigg

Legal Officer, Opportunity Green