Spotlight on the Ocean-Climate Nexus in the ITLOS Climate Change Advisory Opinion

Abstract The International Tribunal for the Law of the Sea ( ITLOS ) addresses procedural and substantive matters expansively in its advisory opinion of 21 May 2024. It recognises the advisory jurisdiction of the full Tribunal, supported by a majority of participants, although criticism of its reasoning remains. Most significantly, the Tribunal clarifies the ocean-climate nexus from an international law perspective. To begin with, it reads climate change into ‘pollution of the marine environment’ but fails to expound the threshold requirement for constituting marine pollution. Then, it examines the international environmental obligations of states relating to climate change pursuant to the United Nations Convention on the Law of the Sea ( UNCLOS ) and by frequent reference to external rules, primarily those of international climate law. The Tribunal holds that international climate law is not lex specialis to UNCLOS ; rather, they are separate and complementary regimes. This observation represents the most important contribution to the understanding of the ocean-climate nexus.