ITLOS Advisory Opinion on Climate Change

The ITLOS Advisory Opinion on Climate Change was delivered unanimously on 21 May 2024 by the International Tribunal for the Law of the Sea in Hamburg, in response to a request submitted in December 2022 by the Commission of Small Island States on Climate Change and International Law (COSIS). COSIS, founded in 2021 by Antigua and Barbuda and Tuvalu and later expanded to include states such as Palau, Niue, Vanuatu, Saint Lucia, Saint Vincent and the Grenadines, the Bahamas, and Saint Kitts and Nevis, asked the Tribunal two questions about state obligations under the 1982 UN Convention on the Law of the Sea (UNCLOS) regarding marine pollution and protection of the marine environment in the context of climate change.

The Tribunal held that anthropogenic greenhouse gas emissions constitute "pollution of the marine environment" within the meaning of UNCLOS Article 1(1)(4). Accordingly, states parties have specific obligations under Part XII of UNCLOS, particularly Article 192 (general obligation to protect and preserve the marine environment) and Article 194 (measures to prevent, reduce, and control pollution).

Key findings include:

• States must take all necessary measures to prevent, reduce, and control marine pollution from GHG emissions, applying a standard of due diligence that is stringent given the high risks of climate harm.
• The Paris Agreement's temperature goals and best available science inform but do not exhaust UNCLOS obligations; UNCLOS imposes independent and potentially more demanding duties.
• Obligations include cooperation, monitoring, environmental impact assessment, and assistance to developing states, particularly small island developing states.

The opinion is non-binding but carries significant interpretive weight. It feeds into a wider wave of climate jurisprudence, including the ICJ advisory proceedings on climate obligations and the Inter-American Court of Human Rights advisory opinion requested by Chile and Colombia. Delegates often cite it in debates on loss and damage, climate finance, and small-island state security.