Summary
On May 21, the International Tribunal for the Law of the Sea (ITLOS) issued a unanimous and historic Advisory Opinion on climate change, in response to a request from the Small Island States Commission on Climate Change and International Law (COSIS).
This decision marks the first time that an international tribunal has explicitly ruled on the international legal obligations of states to mitigate climate change under the 1982 United Nations Convention on the Law of the Sea (UNCLOS).
The Tribunal concluded that the United Nations Convention on the Law of the Sea (UNCLOS) obliges its 169 States Parties to implement specific and concrete measures to prevent, reduce and control marine pollution caused by greenhouse gas emissions.
To read the full case note in English, click here.
Case Context: The Impact of Climate Change on Small Island States
Small island states face an existential threat from climate change, experiencing its effects more intensely and urgently than many other regions. The absorption of 90% of excess heat trapped by greenhouse gases by the ocean leads to acidification and gradual warming of the oceans, resulting in sea level rise that threatens these nations by potentially submerging low-lying areas, intensifying coastal erosion, and causing land loss.
Without adequate adaptation measures, projections suggest that certain small island states could be completely submerged by the end of the century due to current warming trends. In addition, sea level rise could contaminate freshwater aquifers with saltwater, compromising access to drinking water and irrigation for islanders, jeopardizing food security and public health, and potentially rendering these states uninhabitable.
Ocean warming and acidification are having a profound impact on marine life, which is critical to biodiversity and the economy of these states, with coral reefs becoming vulnerable. The loss of coral reefs weakens the protective barrier against waves and puts tourism and fishing industries at risk. In addition, climate change leads to extreme weather events, such as tropical cyclones, causing damage to infrastructure and displacing populations.¹ Small island states are therefore on the frontlines of climate change and urgently seek redress and protection under international law.
The COSIS Request
The Commission on Small Island States on Climate Change and International Law (COSIS) is an intergovernmental organization comprising small island states in the Caribbean and Pacific. It was formed in October 2021 by Antigua and Barbuda and Tuvalu as original signatories, coinciding with the United Nations COP26 climate negotiations in Glasgow.
COSIS aims to promote and contribute to the definition, implementation and progressive development of rules and principles of international law relating to climate change. This includes the obligations of States relating to the protection and preservation of the marine environment and their liability for damage arising from internationally wrongful acts in relation to such obligations².
On 12 December 2022, COSIS requested an advisory opinion from the International Tribunal for the Law of the Sea (ITLOS) on the obligations of States Parties under the 1982 United Nations Convention on the Law of the Sea (UNCLOS), which provides the legal framework governing ocean space and maritime activities.
In its request, COSIS sought clarification on the obligations of States Parties to prevent, reduce and control marine pollution due to the effects of climate change, such as ocean warming, sea level rise and ocean acidification caused by man-made greenhouse gas (GHG) emissions.
In addition, they sought clarification on the obligations of States Parties to protect and preserve the marine environment in response to the impacts of climate change, including ocean warming, sea level rise and ocean acidification.
Throughout the proceedings, 32 States, the European Union and nine intergovernmental organisations, including COSIS, the African Union and the International Union for Conservation of Nature, submitted arguments on States’ obligations under UNCLOS in light of the climate crisis.
ITLOS Advisory Opinion
On 21 May 2024, the Tribunal issued a landmark Advisory Opinion, ruling that GHG emissions constitute marine pollution under UNCLOS, and consequently, states are obliged to take all necessary measures to reduce their GHG emissions to the maximum extent possible, in line with UNCLOS and other relevant international legal obligations.
This Case Note aims to highlight three key findings of the Advisory Opinion on the meaning of pollution of the marine environment, the obligation to implement all necessary measures and the duty to exercise due diligence.
The meaning of marine pollution
Since UNCLOS does not explicitly designate GHG emissions as a distinct pollutant, nor does it make explicit reference to climate change and ocean acidification, the Tribunal faced the preliminary task of determining whether GHG emissions fall within the UNCLOS definition under Article 1(1)(4) of “pollution of the marine environment”.
To this end, the Tribunal had to assess whether the three cumulative criteria determining such pollution are met; namely (1) there must be a substance or energy; (2) this substance or energy must be introduced by man, directly or indirectly, into the marine environment; and (3) such introduction must result or be likely to result in harmful effects.
Following its analysis, the Tribunal concluded that man-made GHG emissions released into the atmosphere – whether from vessels or aircraft, land-based sources or ocean-going activities – constitute pollution of the marine environment under the provisions of the Convention [159-179].
This determination was crucial in establishing the obligations imposed on States in relation to marine pollution, as will be discussed below.
The obligation to take all necessary measures
Article 194(1) of UNCLOS imposes on States the obligation to implement, individually or jointly, as appropriate, all necessary measures to prevent, reduce and control pollution of the marine environment from whatever source, using for this purpose the most feasible means available to them and in accordance with their capabilities. The Court emphasised that necessary measures encompass not only actions essential for the prevention, reduction and control of marine pollution, but also other interventions that facilitate the achievement of this objective [203].
In the context of addressing the impacts of climate change, these interventions are commonly referred to as “mitigation measures”, and at their core is the reduction of anthropogenic GHG emissions into the atmosphere [205]. The Court emphasised that defining such measures does not mean accepting any measures that States consider necessary for this purpose. Rather, necessary measures must be based on an objective assessment, taking into account relevant factors [206-207], including:
The best available scientific evidence, in particular the publications of the Intergovernmental Panel on Climate Change (IPCC), which the Court recognised as reflecting “scientific consensus” [208]. When scientific certainty is lacking, ITLOS has emphasized the importance of applying the precautionary and ecosystem-based approach, highlighting the acute need for such an approach for marine pollution resulting from anthropogenic GHG emissions, given the severe and irreversible damage that can be caused to the marine environment by such pollution [213].
International rules and standards, such as those outlined in the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement, serve as crucial references to guide such measures. Of particular significance is the global temperature objective of limiting the temperature increase to 1.5°C above pre-industrial levels, as set out in the Paris Agreement, together with the emission trajectories required to achieve this objective. However, the Tribunal emphasized that simply adhering to the obligations and commitments outlined in the Paris Agreement would not be adequate to meet the obligations under UNCLOS. Although both agreements aim to address environmental issues, they are distinct treaties with different sets of obligations. Therefore, ITLOS emphasized that the protection of the marine environment, a core objective of UNCLOS, requires compliance with its obligations, regardless of those outlined in the Paris Agreement [222-223].
The best available means and capabilities, when exercising their obligation under Article 194 of UNCLOS to take all necessary measures to address marine pollution resulting from anthropogenic GHG emissions. Such flexibility recognizes the varying resources and capabilities among States and aims to alleviate the burden on those with limited resources. However, the Court emphasized that such flexibility should not be used as an excuse to delay or exempt themselves from taking the necessary measures [225-226]. The Court clarified that States with greater resources and capabilities are expected to “take the lead” and undertake more substantial efforts compared to those with fewer resources, recognizing the principle of common but differentiated responsibilities and respective capabilities, in line with the UNFCCC and the Paris Agreement. However, the Court emphasized that although measures to reduce anthropogenic GHG emissions that cause marine pollution may vary between developed and developing States, all States are obliged to undertake mitigation efforts, regardless of their state of development [227-229] [338-339].
The best available means and capabilities, when exercising their obligation under Article 194 of UNCLOS to take all necessary measures to address marine pollution resulting from anthropogenic GHG emissions. Such flexibility recognizes the varying resources and capabilities among States and aims to alleviate the burden on those with limited resources. However, the Court emphasized that such flexibility should not be used as an excuse to delay or exempt themselves from taking the necessary measures [225-226]. The Court clarified that States with greater resources and capabilities are expected to “take the lead” and undertake more substantial efforts compared to those with fewer resources, recognizing the principle of common but differentiated responsibilities and respective capabilities, in line with the UNFCCC and the Paris Agreement. However, the Court emphasized that although measures to reduce anthropogenic GHG emissions that cause marine pollution may vary between developed and developing States, all States are obliged to undertake mitigation efforts, regardless of their state of development [227-229] [338-339].
Notes:
- IPCC, 2023: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland, 184 pp., doi: 10.59327/IPCC/AR6-9789291691647. OHCHR Press Release, Small Island Developing States summit: UN experts urge States and development banks to support endangered islands, 23 de maio de 2024.
- Agreement for the establishment of the Commission of Small Island States on Climate Change and International Law. Edinburgh, 31 de outubro de 2021, Artigo 1 (3).
Notes:
IPCC, 2023: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland, 184 pp., doi: 10.59327/IPCC/AR6-9789291691647. OHCHR Press Release, Small Island Developing States summit: UN experts urge States and development banks to support endangered islands, May 23, 2024.
Agreement for the establishment of the Commission of Small Island States on Climate Change and International Law. Edinburgh, 31 October 2021, Article 1 (3).
Author: Natalie Rosen
