The ICJ’s Advisory Opinion on Climate Change: What Happens Now?


Photo by Mathias Reding on Unsplash

Climate change litigation has finally reached the world’s highest court. On March 29, 2023, the United Nations General Assembly (UNGA) adopted a resolution requesting an advisory opinion from the International Court of Justice (ICJ) on the obligations of States with respect to climate change. The UNGA adopted resolution (A/77/L.58) by consensus.

The Republic of Vanuatu spearheaded this initiative in a 2021 announcement supported by grassroots youth groups. Vanuatu published the first draft of the resolution in late 2022. The draft was then altered through a series of consultations with UN delegates in the following months. The initiative gained traction. On March 1, 2023, Vanuatu announced overwhelming support for the draft resolution with 105 co-sponsor states.

The ICJ request adds to two requests for advisory opinions on climate change. The requests are pending at the International Tribunal for the Law of the Sea (ITLOS) and the Inter-American Court of Human Rights (IACtHR, see here for an initial analysis of the advisory opinion request).

The questions

The General Assembly requested the ICJ render an opinion on the following questions:

(a) What are the obligations of States under international law to ensure the protection of the climate system and other parts of the environment from anthropogenic emissions of greenhouse gasses (GHG) for States and for present and future generations?

(b) What are the legal consequences under these obligations for States where they, by their acts and omissions, have caused significant harm to the climate system and other parts of the environment, with respect to:

(i) States, including, in particular, small island developing States, which due to their geographical circumstances and level of development, are injured or specially affected by or are particularly vulnerable to the adverse effects of climate change?

(ii) Peoples and individuals of the present and future generations affected by the adverse effects of climate change?

The advisory opinion represents an opportunity to clarify the legal obligations of States with respect to climate change. For Vanuatu and supporters of the resolution, this is also a chance to spur transformative climate action, advance climate justice, and protect the environment for present and future generations.

Part of the discussion on the need for an advisory opinion on climate change focuses on the possibility to interpret the obligations in the Paris Agreement and the United Nations Framework Convention on Climate Change (UNFCCC). However, the request also references international human rights instruments, including the Universal Declaration of Human Rights, the International Covenant on Civil and Political Rights, and the International Covenant on Economic, Social and Cultural Rights.

The human rights implications of climate change were central to Vanuatu’s campaign, particularly because Vanuatu – similarly to other small island developing states – is one of the most climate vulnerable countries in the world. Several courts, especially in Europe, have recently considered the human rights implications of climate change in cases such as Urgenda Foundation v. State of the Netherlands, Neubauer, et al. v Germany, and Future Generations v. Ministry of the Environment and Others. Each of these cases sought to enhance accountability and climate ambition through recognition of the human rights dimensions of climate change. The rich jurisprudence developed worldwide and the links between human rights and climate change identified by domestic courts will likely be leveraged in the ICJ’s analysis of the legal questions posed.

Procedural Developments and Next steps

The process of requesting an advisory opinion from the ICJ is quite unique. Rather than a straightforward request to the Court (similar to how the IACtHR and ITLOS advisory opinion processes began), Vanuatu engaged in a year-long campaign to build strong support within the UNGA. The UNGA adopted the resolution after more than 12 months of worldwide consultations. This participatory process included informal consultations with a wide range of UN member States, as well as the active engagement of more than 1,500 civil society and youth groups across 130 countries. On March 29, 2023, Vanuatu and supporting states put the resolution to a vote. The resolution was adopted by consensus, meaning that the UNGA will now formally adopt the resolution.

Formal requirements

Upon formal adoption, the UNGA will communicate the request for an advisory opinion to the ICJ in written form, specifying the questions the court is being asked to decide. This step should take about a month. The ICJ has discretionary power to decline to give an advisory opinion even if the conditions of jurisdiction are met. However, considering its role as the principal judicial organ of the UN, the ICJ must give careful consideration as to whether there are compelling reasons to decline to respond to a UNGA request. It is worth noting that the ICJ has never, in the exercise of this power, declined to respond to a request for an advisory opinion from the UNGA.

The question put to the ICJ must be a legal question within the meaning of the Statute of the Court and the UN Charter as opposed to a political question. The question must, therefore, be framed in terms of law and raise problems of international law susceptible of a reply based on legal considerations. The ICJ has the authority to interpret and even reformulate the question presented to it. The Court has exercised this authority in cases where the question was unclear or vague, not adequately formulated or did not reflect the “legal questions really in issue”.

Written and Oral Proceedings

Once the ICJ has decided there is a legal question at hand, it may hold written and oral proceedings to gather information on the question. States may submit written statements, comment on statements submitted by other states, and make oral statements during public proceedings. The rules governing written proceedings are quite flexible. The ICJ has usually given states 6 months to submit written comments, although an extension may be requested given the complexity of the issue. Afterwards, the ICJ could take several months to deliberate.

For instance, in the The Legality of the Threat or Use of Nuclear Weapons advisory opinion, the ICJ gave states approximately four months to submit written statements and three months to comment on others’ statements. The Court rendered an opinion almost 19 months after the submission of the request. Following a similar timeline, it is likely that the ICJ will render an opinion in the second half of 2024 or in the first half of 2025.

What can we expect? Building on Recent Legal Developments

This is not the first attempt to request an advisory opinion on climate change from the ICJ. Palau and the Marshall Islands spearheaded a similar effort about a decade ago. That initiative ultimately failed due to strong political opposition. But a lot has changed since then. Both the science and law around climate change have progressed.

In its latest report, the Intergovernmental Panel on Climate Change (IPCC) concluded that anthropogenic emissions of greenhouse gases (GHGs) are unequivocally the dominant cause of global warming. It is also well-documented that climate change has caused “widespread adverse impacts and related losses and damages”, particularly in the most vulnerable countries and communities in the world. Relying on these and other scientific studies, domestic courts around the world have ruled in favor of plaintiffs challenging governments and private actors that contribute to climate change.

Scientific Consensus

Some scholars have suggested that the advisory opinion could build on the scientific consensus around climate change/ The Court could provide an authoritative determination of the validity of the science, confirming the need to reduce GHG emissions to stay below the Paris Agreement temperature threshold. The request for an advisory opinion took note of the scientific consensus expressed in the reports of the IPCC. Whether or not the ICJ considers there is a scientific dispute to settle, the science – and the IPCC reports – could play a relevant role in the Court’s analysis. There may even be an opportunity for scientific experts to testify directly to the Court, as occurred in the Japanese whaling case (2014).

International Climate Change Law and the Right to a Healthy Environment

The ICJ will also need to examine the growing body of international law with respect to climate change. The 2015 Paris Agreement represents one of the most important expressions of the determination of States to address climate change. The treaty will be instrumental in determining the obligations of States. For instance, some of the obligations of conduct in the Paris Agreement may inform the interpretation of legally binding obligations under other sources of international law, such as human rights law treaties and multilateral environmental agreements.

The ICJ might also consider the resolutions on climate change from the UNGA, the resolutions on human rights and climate change from the Human Rights Council, and the work of the Office of the UN High Commissioner of Human Rights and the Special Rapporteurs, including the Special Rapporteur on human rights and the environment and the Special Rapporteur on climate change.

For instance, the ICJ could rely on the unanimous resolution A/76/L.75, in which the UNGA recognized the right to a clean, healthy, and sustainable environment as a human right. In this resolution, the UNGA underscored that the aforementioned right is “related to other rights and existing international law” and that it requires “the full implementation of the multilateral environmental agreements under the principles of international environmental law.” The resolution further recognized climate change as one of the “most pressing and serious threats to the ability of present and future generations to effectively enjoy all human rights.” Unsurprisingly, the request also referenced this resolution.

Human Rights

The work of the Committee on the Rights of the Child (CRC) may also be relevant for the advisory opinion, considering that the questions submitted to the ICJ deal with the obligations of States towards present and future generations. For instance, the ICJ could consider the CRC decision in Sacchi et al. v. Argentina et al (2021), where the CRC analyzed “novel jurisdictional issues of transboundary harm related to climate change,” and the forthcoming general comment No. 26 on children’s rights and the environment with a special focus on climate change, which will likely be published in the second half of 2023.

Domestic litigation, legal scholarship, and several reports or resolutions of the UN human rights treaty bodies have explored the relationship between climate change and human rights. The request for an advisory opinion provides an opportunity to advance a years-long evolution in the recognition of this relationship not only by clarifying the ways in which climate change affects human rights but also by identifying and reaffirming the human rights obligations of States in the context of climate change.

Paris Agreement

For instance, in interpreting the Paris Agreement, the ICJ could consider its Preamble, which calls on States to “respect, promote and consider their respective obligations on human rights” when taking action to address climate change. It is worth noting that the Paris Agreement is the first global environmental agreement that recognizes human rights obligations as an integral element of the regime it establishes. An analysis of the Preamble of the Paris Agreement could advance the understanding of the relationship between the operative part of the treaty and States’ human rights obligations.

The ICJ could also link the goals and obligations set out in the Paris Agreement with the international human rights instruments included in the request for an advisory opinion. For example, the ICJ could analyze how human rights principles such as the principle of progressivity relate to article 4.3 of the Paris Agreement. This article indicates that the efforts of all Parties “will represent a progression over time” and establishes a standard of conduct to attain the “highest possible ambition”, which is reminiscent of a due diligence standard in international law that could constitute a powerful tool to enhance climate action in the Nationally Determined Contributions (NDCs).

ICJ’s Environmental Jurisprudence

The Legality of the Threat or Use of Nuclear Weapons

The advisory opinion will further rely on the ICJ’s jurisprudence on environmental matters. For instance, in its advisory opinion on The Legality of the Threat or Use of Nuclear Weapons (1996), the ICJ recognized that “the environment is not an abstraction but represents the living space, the quality of life and the very health of human beings, including generations unborn.” The ICJ also recognized that “the general obligation of States to ensure that activities within their jurisdiction and control respect the environment of other States or of areas beyond national control is now part of the corpus of international law relating to the environment.”

Gabčíkovo-Nagymaros case

Furthermore, in the Gabčíkovo-Nagymaros case (1997), the ICJ noted that “mankind has, for economic and other reasons, constantly interfered with nature.” According to the Court, this intervention “was often done without consideration of the effects upon the environment.” Nonetheless, “[o]wing to new scientific insights and to a growing awareness of the risks for mankind – for present and future generations – of pursuit of such interventions at an unconsidered and unabated pace, new norms and standards have been developed.” This is certainly the case with climate change.

Pulp Mills case and Costa Rica v Nicaragua/Nicaragua v Costa Rica 

There are additional, well-established principles of international law that substantiate the obligations in need of clarification in the advisory opinion. For instance, in the Pulp Mills case (2010) the ICJ considered the principle of prevention and pointed out that, “as a customary rule, [it] has its origins in the due diligence that is required of a State in its territory.” The ICJ clarified that States must use all the means at their disposal to avoid transboundary harm from activities in their territory or under their jurisdiction.

To exercise due diligence, the State has to “ascertain  whether there is a risk of significant transboundary harm prior to undertaking an activity having the potential adversely to affect the environment of another State. If that is the case, the State concerned must conduct an environmental impact assessment” (EIA). In Costa Rica v Nicaragua/Nicaragua v Costa Rica cases (2015), the ICJ reiterated this interpretation.

The advisory opinion could also rely on these decisions to explore the applicability of the no-harm principle and the related due diligence obligations in the context of climate change. This analysis could lead the ICJ to conclude that States have an obligation to ensure that their GHG emissions do not cause significant harm to other states. The advisory opinion could also elaborate on specific criteria of due diligence and identify benchmarks to assess state action. The Court could also delve into the application of principles and standards relating to climate change in EIAs. This analysis has precedents in domestic climate litigation.

Potential Benefits and Opportunities from an ICJ Advisory Opinion on Climate Change

ICJ advisory opinions have no binding force. However, they carry great “legal weight and moral authority.” The ICJ is the main judicial organ of the UN and has a strong reputation as an expert legal body. Furthermore, the strength of the advisory opinion’s legal arguments, among other factors, carry great weight.

Obligations of states under international law

As Vanuatu noted, the ICJ is the only main UN organ that has not had the chance to clarify the implications of climate change. The advisory opinion can clarify and concretize the legal obligations of states to prevent and redress the adverse effects of climate change. This clarification could provide clear standards and benchmarks for climate action. In this context, the advisory opinion would offer a solid basis for scrutinizing state actions. Furthermore, this basis would assess compliance with the objectives of the climate treaties, for example, through the analysis of states’ NDCs. This is important considering the constructive ambiguity that imbues some of the provisions of these international instruments.

Ambition to mitigate GHG emissions

An ICJ advisory opinion could also foster ambition in the pledges made by States under the Paris Agreement. Vanuatu has argued that the resolution sends “a clear signal to present and future generations that no stone is being left unturned in this critical decade to address the climate impacts on human rights, justice and inter-generational equity.” This would be particularly significant considering that the campaign for an advisory opinion was led by youth, small island developing states, and some of the most vulnerable countries in the world.

Effects on domestic litigation

More broadly, one of the clear benefits of the ICJ advisory opinion would be the possibility of influencing other courts and domestic litigation. The Sabin Center’s global climate change litigation database shows that domestic courts are increasingly comfortable with relying on international climate change law obligations. The ICJ advisory opinion could provide these courts with greater clarity on the obligations of States under international law.

This was the case with the advisory opinion on human rights and the environment issued by the Inter-American Court of Human Rights (IACtHR) (OC-23/17). The IACtHR advisory opinion opened the door for rights-based climate litigation, recognized States’ responsibilities for transboundary harm, and broadened the interpretation of extraterritorial jurisdiction. The opinion has been invoked by several domestic courts in the region and even by the CRC in its decision in Sacchi et al. v. Argentina et al.

The ICJ advisory opinion could have a similar (or potentially greater) reach. This is not only because the ICJ is the principal judicial organ of the UN but also because, unlike specialist international tribunals such as the International Tribunal on the Law of the Sea and the IACtHR, its jurisdiction is general and it may entertain “any question of international law.”

Loss and damage

Furthermore, the ICJ advisory opinion presents an opportunity to obtain an authoritative statement on “the long-neglected matter of loss and damage.” International climate negotiations have seen a decades-long conversation on funding for loss and damage. However, progress has been slow. It was not until COP27 that countries decided to establish and operationalize a loss and damage fund, particularly for the most vulnerable nations. The success of the fund and its capacity to reach its objectives will depend, to a large extent, on the existence of clear rules of operation and accountability mechanisms that consider the needs of developing countries.

In this context, the ICJ could provide insights into the substantive content of obligations that are particularly relevant in the context of loss and damage. Nonetheless, the issue of loss and damage remained a point of contention even in some states’ support of the advisory opinion request. For instance, the Transitional Committee established in Sharm el-Sheikh will begin to operate in early 2023, making recommendations to operationalize new funding arrangements for loss and damage. With the upcoming work of the committee and its recommendations, the ICJ could have a more limited capacity to “fill the gaps” in this field.

International climate negotiations

Lastly, the ICJ advisory opinion could influence the ongoing international climate negotiations. There has been a sense of frustration with the slow pace of these negotiations and the difficulty in reaching a consensus on certain issues. This is especially true for loss and damage. The opinion could help break this gridlock. The opinion could help “shape and stabilize normative expectations among the wider set of public and private actors engaged in climate-related work.”

Potential risks and pitfalls of the advisory opinion

According to Dr. Margaretha Wewerinke-Singh, “there is always a risk that the ICJ may deliver an underwhelming or an unhelpful opinion.” For instance, the ICJ may issue an advisory opinion solely focused on States’ obligation to cooperate under the Paris Agreement and the UNFCCC. Similarly, an advisory opinion reiterating the content of climate treaties would not be particularly useful for clarifying the States’ obligations. Regardless, these are not worst-case scenarios. The ICJ would still be providing an authoritative statement on the importance of addressing climate change. In light of the arguments in this post, there are reasons to believe that the ICJ may do much more.


The ICJ could play an important role in developing the law and clarifying the climate obligations of States. Philippe Sands argued that international courts occupy a “space in which global public consciousness is formed.” With this request, the ICJ can uniquely contribute to a more climate-sensitive global consciousness, essential to catalyze crucial and much needed action. The ICJ could also take a step forward in protecting the rights of future generations. As Judge Weeramantry asserted 26 years ago, if there is any tribunal that can recognize and protect the rights of future generations, “it is this Court”.

Global Climate Litigation Fellow at Sabin Center for Climate Change Law at Columbia Law School | Website | + posts

Dr. Maria Antonia Tigre is the Global Climate Litigation Fellow at the Sabin Center for Climate Change Law at Columbia Law School.

Jorge Alejandro Carrillo Bañuelos
National Rapporteur for the International Court of Justice at Sabin Center for Climate Change Law | + posts

Jorge Alejandro Carrillo Bañuelos is the Sabin Center's rapporteur for the International Court of Justice.