HAMBURG — In its unanimous Advisory Opinion delivered on May 21, 2024, the International Tribunal for the Law of the Sea (ITLOS) addressed the intersection of climate change and ocean governance.
Following a request by the Commission of Small Island States on Climate Change and International Law (COSIS), the Tribunal ruled that anthropogenic greenhouse gas emissions into the atmosphere constitute pollution of the marine environment under the UN Convention on the Law of the Sea (UNCLOS).
1. Statutory Interpretation: Article 1(1)(4) UNCLOS
UNCLOS Article 1(1)(4) defines marine pollution as:
“The introduction by man, directly or indirectly, of substances or energy into the marine environment… which results or is likely to result in such deleterious effects as harm to living resources and marine life…”
The Tribunal applied a textual interpretation to atmospheric emissions:
- Substances and Energy: Carbon dioxide constitutes a substance, while excess ocean thermal absorption constitutes the introduction of energy.
- Deleterious Effects: Both are introduced indirectly via atmospheric absorption, driving ocean acidification, coral bleaching, and marine deoxygenation.
Through this classification, the substantive environmental duties under UNCLOS Part XII apply directly to anthropogenic greenhouse gas emissions.
2. Article 192 and the Due Diligence Standard
Article 192 requires states to protect and preserve the marine environment, while Article 194(1) mandates all measures necessary to prevent, reduce, and control marine pollution.
The Tribunal clarified that this duty creates an obligation of conduct governed by due diligence:
- Relationship with the Paris Agreement: Compliance with nationally determined contributions (NDCs) under the Paris Agreement does not automatically satisfy a state’s independent obligations under UNCLOS Part XII.
- Objective Standard: Due diligence is evaluated objectively against best available scientific assessments, particularly findings of the Intergovernmental Panel on Climate Change (IPCC) and the 1.5°C threshold.
While acknowledging differing national capacities, the Tribunal confirmed that industrialized states must apply their economic and technological capabilities to mitigate atmospheric pollution affecting the marine environment.