Top oceans court delivers advisory opinion on climate change

The International Tribunal for the Law of the Sea (ITLOS) delivered a “historic” pronouncement on climate change last week. In its advisory opinion, ITLOS — the dispute resolution mechanism for ocean space, its uses and resources — outlined the obligations of countries in light of climate change. 

ITLOS is an independent judicial body established by the United Nations Convention on the Law of the Sea (UNCLOS) to adjudicate disputes arising from the Convention’s interpretation and application. The seat of the Tribunal is in Hamburg, Germany.

The advisory opinion was issued on the request submitted by the Commission of Small Island States on Climate Change and International Law (COSIS) in December 2022. COSIS is a group of Small Island Developing States (SIDS) that are low-emitting but highly vulnerable to climate change. 

These low-lying island nations are on the frontlines of climate change despite contributing less than 1 per cent of the global greenhouse gas (GHG) emissions. SIDS are disproportionately impacted by climate change due to frequent extreme weather events, sea level rise and ocean warming and acidification. 

The Commission had requested the tribunal to give an advisory opinion on what the specific obligations of State parties to the UNCLOS are:

• to prevent, reduce and control pollution of the marine environment in relation to the deleterious effects that result or are likely to result from climate change, including through ocean warming and sea-level rise, and ocean acidification, which are caused by anthropogenic GHG emissions into the atmosphere.
• to protect and preserve the marine environment in relation to climate change impacts, including ocean warming and sea level rise, and ocean acidification. 

The UNCLOS, however, does not explicitly mention the words “climate change”. This advisory opinion is particularly significant because ITLOS has now interpreted the UNCLOS provisions as being influenced by climate change. Given the ocean-climate nexus, climate change has been incorporated into the current UNCLOS regime. 

The ocean-climate nexus refers to the negative impacts of climate change on the ocean’s health, and the role that the ocean plays in global climate regulation. According to the World Meteorological Organization’s State of Global Climate Report 2023, towards the end of 2023, over 90 per cent of the ocean had experienced heatwave conditions at some point during the year.

The tribunal has expanded the definition of marine pollution under the UNCLOS to include GHGs. Under the UNCLOS, there is a three-pronged test as to what constitutes “marine pollution”: 

• There must be a substance or energy; 
• This substance or energy must be introduced by humans, directly or indirectly, into the marine environment; and 
• Such introduction must result or be likely to result in deleterious effects. 

The tribunal concluded that anthropogenic GHG emissions met all three criteria, therefore constituting pollution of the marine environment under the UNCLOS.

ITLOS affirmed that states are required to take “all necessary measures” to prevent, reduce and control marine pollution from anthropogenic GHG emissions in the atmosphere. The measures by state parties must be guided by the “best available science”. Parties to the proceedings agreed unanimously in their submissions that the Intergovernmental Panel on Climate Change reports are authoritative assessments of scientific knowledge on climate change. 

In the absence of scientific certainty, states must adopt a precautionary approach. Further, the Tribunal held that the measures must take into account climate change treaties such as the United Nations Framework Convention on Climate Change and the Paris Agreement, especially the 1.5 degrees Celsius pathway. There are also other international instruments adopted within the framework of the International Maritime Organisation that address climate change. 

Regarding the relationship between the obligations under the UNCLOS and the Paris Agreement, the Tribunal was of the view that the Paris Agreement is not lex specialis to the UNCLOS. Lex specialis is a principle of international law that means that a specific law will take precedence over a general one when conflicts arise between them. 

The Paris Agreement addresses climate change, while UNCLOS governs oceans and seas. However, the Paris Agreement does not supersede the obligations under Article 194 of the UNCLOS to prevent, reduce, and control marine pollution from anthropogenic GHG emissions. Instead, it works in tandem with the UNCLOS, complementing these obligations. 

States that are better positioned have an obligation to assist states with fewer capabilities. This particularly refers to developing and least developed countries that are most directly and severely affected by the effects of GHG emissions on the marine environment. The assistance should be directed towards addressing marine pollution from GHG emissions through capacity building, scientific expertise, and technology transfer. 

This recognises the principle of common but differentiated responsibilities and respective capabilities. There are 169 parties to the UNCLOS, including major economic players such as the European Union, China, Russia and India. The United States has yet to ratify the Convention.

The Tribunal stated that “what is required of the states is not to guarantee the prevention, reduction, and control of marine pollution at all times but to make their best efforts to achieve such result”. It was held earlier by the Seabed Disputes Chamber in the Area Advisory Opinion that this is an “obligation of conduct” and not an “obligation of result”. 

To that end, the States are required to act with “due diligence” by putting in place a national system, including legislation, administrative procedures, and an enforcement mechanism. 

In response to COSIS’s second question regarding the obligations to protect and preserve the marine environment in relation to climate change impacts, the tribunal noted that state parties must protect and preserve “rare or fragile ecosystems” and the habitats of marine species.

They must also, among other things, make efforts towards conservation of living resources and highly migratory species in the exclusive economic zone and the high seas. The Convention sets forth duties to conserve living marine resources threatened by climate change impacts and ocean acidification. 

The tribunal stated that Part XII of the Convention, which addresses obligations for the protection and preservation of the marine environment, does not preclude states from implementing more stringent measures to protect and preserve the marine environment than those outlined. However, such measures must be consistent with the Convention and other rules of international law. 

The recently adopted United Nations Agreement on Biodiversity Beyond National Jurisdiction expresses the need for a global framework “to better address the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction and provides for the use of area-based management tools including [marine protected areas] MPAs”.