Lessons learned from the ITLOS advisory opinion on climate change

On May 21, 2024, the International Tribunal for the Law of the Sea (ITLOS) made history by clarifying states’ legal obligations to protect the marine environment from climate change-related impacts. Here we highlight key points from the landmark advisory opinion that is expected to raise the bar on climate action and its far-reaching implications.

—

We have known for some time that the Earth faces a triple global crisis of climate change, biodiversity loss and pollution. Nevertheless, and I would call my views progressive, I believe that a stronger international system needs to be developed and implemented. Laws to address the multifaceted global crisis are at a persuasive and climactic (pun unintended) stage. Advisory opinions by international courts or tribunals contribute to the exposition of such laws and, although not legally binding, carry both legal weight and moral authority. Such advisory opinions are recognized by legal experts as a new mechanism for the growing number of climate change litigation cases.

Building stronger science-policy partnerships

Translating science into policy action requires a step-by-step interpretation of existing law and recognition of the latest scientific evidence. The International Tribunal for the Law of the Sea (ITLOS) did just that in its landmark Advisory Opinion on Climate Change and the Law of the Sea (hereinafter the “Opinion”) issued on May 21, 2024. The Opinion, which was unanimous, gave legal force to the inextricable scientific link between climate change and ocean health. The Opinion gives legal recognition to the latest and most reliable science from the Intergovernmental Panel on Climate Change (IPCC) on the causal relationship between the accumulation of anthropogenic greenhouse gases (GHGs) in the atmosphere, on the one hand, and its diverse harmful effects on the oceans, on the other. This includes the harmful effects of “sea level rise, increased ocean heat content and marine heatwaves, ocean deoxygenation, and ocean acidification.”

More on this topic: Small island nations threatened by climate change hail ‘historic’ maritime tribunal victory

The International Tribunal is to be commended for its broad and bold examination of the latest authoritative science. ITLOS (the “Tribunal”) explicitly acknowledges and bases its opinion directly on the robust evidence and high level of scientific consensus emerging from the IPCC’s 2023 Synthesis Report that climate change will cause “enormous damage and increasingly irreversible losses”. in Coastal and open ocean ecosystems.

This opinion gives due weight to some of the IPCC’s key findings that deserve widespread attention and emulation. For example:

1. Human influences are very likely the main driver of the 0.20 metre rise in global mean sea level between 1901 and 2018, with the latter likely causing “an increase in the frequency of extreme sea-level events in most locations”.
2. It is “virtually certain” (IPCC scientific terminology that describes an assessment of the likelihood of an outcome) that sustained warming of the Earth’s oceans has occurred since 1970, and we can say with “high confidence” (IPCC scientific terminology that describes the degree of scientific agreement) that the oceans absorb more than 90% of the excess heat in the climate system.
3. “Ocean surface water pH decreased by 0.1 (high confidence), representing a 26% increase in acidity.” Furthermore, marine ecosystems, particularly coral reefs, are at risk from ocean acidification, which “affects organism physiology, behavior and population dynamics” and acts synergistically with global and regional changes (e.g. eutrophication) to produce “complex and amplified impacts on… species and ecosystems.”
4. Risks, projected adverse impacts, and associated loss and damage from climate change “will increase as global warming progresses” (very high confidence).

Small Island States Request to the Arbitral Tribunal

We thank the Commission on Small Island States (COSIS) for requesting an advisory opinion from the Arbitral Tribunal. Very specific Legal Question. COSIS asked the Court to clarify that States Parties to the United Nations Convention on the Law of the Sea (“UNCLOS”) have the following obligations, including under Part 12:

(a) Prevent, reduce and control pollution of the marine environment in relation to the harmful effects resulting or likely to result from climate change, such as ocean warming, sea-level rise and ocean acidification caused by anthropogenic emissions of greenhouse gases into the atmosphere;

(b) To protect and preserve the marine environment in relation to the impacts of climate change, such as ocean warming, sea-level rise, and ocean acidification?

Below are some of the Court’s key decisions that will have far-reaching and significant impact.

• Definition of “Pollution of the Marine Environment”

The Court’s main finding was that the harmful effects of anthropogenic greenhouse gas emissions fall within the scope of “pollution of the marine environment” as defined in UNCLOS. The Court assessed that anthropogenic greenhouse gas emissions meet the three cumulative criteria used to define “pollution of the marine environment” in UNCLOS. In this context, the Court interpreted:

(1) Greenhouse gases are “substances” and the term “energy” includes “thermal energy or heat” within the meaning of Article 1, paragraph 1 (4) of the United Nations Convention on the Law of the Sea.

(2) Greenhouse gases The emissions in question are anthropogenic, meaning they are produced by humans and released into the marine environment directly (as greenhouse gases) or indirectly (as thermal energy).

(3) The introduction of carbon dioxide (a type of anthropogenic greenhouse gas) and heat (an example of thermal energy) into the marine environment causes climate change and ocean acidification, which, as stipulated in Article 1, paragraph 1 (4) of the United Nations Convention on the Law of the Sea, “may result or be likely to result in harmful effects, including harm to living resources, marine life, etc.”

• Due diligence, high standards and the obligation to adhere to CBDR-RC principles

The nature and openness of the UNCLOS framework was recognised by the Court and several of the countries participating in the hearings. Central to this is Article 194 of UNCLOS, which is broad, comprehensive and positive, requiring all States to “take all necessary measures to prevent, reduce and control pollution of the marine environment from all sources”.

According to the opinion, Article 194 of UNCLOS provides for a duty of due diligence and a duty of action, which explicitly requires all Parties to the Convention to take all necessary measures to prevent, reduce and control marine pollution from anthropogenic greenhouse gas emissions. The opinion also clearly explains that such obligations are closely linked to the precautionary approach, meaning that lack of scientific certainty does not prevent States from taking all necessary measures to control marine pollution from anthropogenic greenhouse gas emissions.

However, according to the opinion, the standard of due diligence will vary depending on the specific circumstances, including scientific and technical information, the existence of relevant international regulations and standards, the risk of harm, and urgency.

Several participants in the hearing expressed the view that the standard of due diligence for marine pollution from anthropogenic greenhouse gas emissions should be set significantly higher than any “best efforts standard.” It is noteworthy that the Court’s final opinion also called for a stricter standard. At the same time, it lends credence to the principle of common but differentiated responsibilities and respective capabilities (CBDR-RC) by acknowledging that the implementation of such due diligence will vary based on each country’s capabilities and available resources. According to the Court, “such implementation requires countries with greater capacities and sufficient resources to be able to do more than less well-off countries.”

However, the principle of CBDR-RC “should not be used as an excuse to avoid the heavy responsibilities that lie on all States, individually and collectively.”

• The Paris Agreement is informative, not preemptive

In a world where international environmental law is fragmented and normative clashes are possible, the opinion’s strong call for coherence and mutual support between UNCLOS and other rules and sources of international law, such as the UNFCCC, the Kyoto Protocol, the Paris Agreement and the Montreal Protocol (including the Kigali Amendment), is commendable.

You might also like: Explained: What is the Paris Agreement?

Even more credibly, the UNFCCC and the Paris Agreement Le specialis’ Regarding the obligations of Parties on climate-related action. Indeed, in the words of ITLOS, States’ broad responsibilities under Article 194 of UNCLOS will not be met solely by complying with their obligations and commitments under the Paris Agreement. In my view, I commend ITLOS for recognizing the uniqueness of each treaty. UNCLOS and the Paris Agreement exist separately from each other and each has its own obligations.

The opinion makes it clear that the UNFCCC and the Paris Agreement do not supersede climate-related actions under UNCLOS, but in fact relate to the interpretation and application of the treaties. Such an interpretation supports the general rule of treaty interpretation under Article 31(c)(3) of the Vienna Convention, which requires taking into account “the relevant rules of international law applicable to the relations between the parties.” For example, ITLOS has commented that the temperature target of 1.5°C above pre-industrial levels and the timeline of the emission pathways set out in the Paris Agreement inform the nature of the measures required under Article 194(1) of the Convention.

Conclusion

This historic opinion has several features with potentially far-reaching implications, not all of which can be covered within the scope of this article. It is notable that the opinion is progressive in its interpretation of the UN Convention on the Law of the Sea regarding states’ obligations regarding climate change, and applies the best available science very frankly. And, as Tara Davenport of the National University of Singapore articulated, the obligation to act (though not to results) is a serious and rigorous standard from which states cannot hide. States can also use this obligation as diplomatic leverage in any forum, or as leverage domestically.

Eran Stoeger, counsel for Timor Leicester in the ITLOS case (as a private citizen), also makes the striking argument that while some countries can carry more political weight and influence than others in international climate change negotiations, advisory litigation offers a unique opportunity for all countries to participate equally and fairly. In his words, “Every country has a similar time frame, a similar voice, and an equal opportunity to influence the court. To some extent, the power dynamics and conversations behind the scenes reflect equality.”

This article is the first of a three-part series looking at groundbreaking climate-related advisory opinions issued by international courts. Stay tuned for parts two and three.