Public International Law and Climate Change


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    Executive summary

    Climate change is a pressing issue for the international community. The United Nations Intergovernmental Panel on Climate Change (IPCC) has called the climate crisis a ‘code red’ for humanity as current emissions reduction plans are not sufficient to tackle the rise in global temperatures.[1] As a collective action problem, addressing climate change requires international solutions. The international response has focussed on the development of a multilateral climate change regime as the principal means of stabilising atmospheric concentrations of greenhouse gas emissions, with the adoption of the Paris Agreement a key achievement. The international climate regime has worked in conjunction with other regimes of public international law to address the direct and indirect impacts of climate change. Furthermore, the legal and regulatory responses that the international community has adopted in response to climate change have influenced the development of substantive regimes of public international law. Of note is the emerging general principle of ‘mutual supportiveness’, according to which international rules should be applied and more generally understood as supporting each other.

    • The United Nations Framework Convention on Climate Change and subsequent agreements such as the Paris Agreement have created a comprehensive international framework for addressing climate change. Parties to the Paris Agreement must communicate ‘Nationally Determined Contributions’ which explain how they will reduce emissions, though the Agreement’s compliance mechanism takes a facilitative model rather than allowing for hard enforcement.
    • Other important provisions of the Paris Agreement include Article 6, which addresses global carbon markets, and Article 8, which focusses on compensating developing countries for loss and damage suffered because of climate change.
    • Through its impacts on vulnerable people, climate change also implicates international human rights and migration law.
    • International trade and investment law are crucial to the political and economic changes required to reduce emissions and adapt to climate change. They may offer more concrete commitments and remedies than some other areas of international law.
    • Climate change’s impact on natural areas mean that international biodiversity law and the law of the sea are highly relevant. These areas of law are also relevant to the changing demand for resources caused by the net zero transition.

    The international climate change regime 

    The international community’s main response to the threat of climate change is set out in the international climate change regime, which consists primarily of the United Nations Framework Convention on Climate Change (UNFCCC), the Kyoto Protocol, and the Paris Agreement. The UNFCCC is an international environmental treaty, adopted at the Earth Summit in 1992 and has 197 parties. 

     The UNFCCC’s main objective is the ‘stabilisation of greenhouse gas concentrations’ in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. The legal obligations to achieve this objective were first stipulated in terms of internationally binding emissions targets for industrialised Annex-I countries in the Kyoto Protocol covering the period from 2008 to 2012 and subsequently updated in the 2016 Paris Agreement. 

    Signed by 195 out of 197 parties, the Paris Agreement aims to hold the increase in global average temperature to well below 2°C and pursue efforts to limit it to 1.5°C above pre-industrial levels through a system of bottom-up style nationally determined contributions (NDCs) set out in Article 4. Unlike the Kyoto Protocol, the Paris Agreement leaves it to state parties to determine their mitigation commitment, provided it reflects their ‘highest possible ambition’ in light of different national circumstances, reflecting the notion of ‘common but differentiated responsibilities’. States must submit their NDC and update it every five years. Setting the regime’s direction of travel, each update must represent a progression on a state’s current NDC. While contributions are not legally binding, states must take domestic action to achieve the objectives of their NDC.  

    To encourage states to adopt ambitious mitigation commitments, the Agreement contains a range of binding procedural and transparency obligations. For instance, states must provide information regarding their NDC and progress as part of an enhanced transparency framework which feeds into a five-yearly global stocktake to assess the collective progress towards achieving the long-term temperature goal, which in turn informs parties’ efforts in updating and enhancing their NDCs. These provisions together form what is referred to as the ‘ratchet’ or ‘ambition’ mechanism in the Paris Agreement. Given that states’ current national climate commitments are inadequate to achieve the climate goals of the Paris Agreement, NDCs must be updated and enhanced if the Agreement’s goals are to be met. 

    In regard to other aspects of the Paris Agreement, Article 8, which recognizes the importance to address loss and damage associated with the adverse effects of climate change, does not involve or provide a basis for any liability or compensation.[2]  The decision on Torres Strait Islanders,[3] where the UN Human Rights Committee found that Australia breached human rights for climate inaction, sets a precedent in international law as it is the first time a government has been told to pay for climate damages and shows a willingness to move towards the recognition of compensation for loss and damage at the international level.[4]  

    The Commission of Small Island States on Climate Change and International Law (COSIS) is currently awaiting an advisory opinion from the International Court of Justice on countries’ obligations to address climate change. Having originally lodged this legal request to the International Tribunal for the Law of the Sea (ITLOS) in December 2022, leaders from a number of vulnerable island nations look to gain legal clarity on countries’ responsibilities to protect the marine environment under the UN Convention on the Law of the Sea, chiefly through reducing greenhouse gas emissions.[5] 

    Importantly, the Paris Agreement itself does not contain a hard legal enforcement mechanism. Instead, Article 15 created a “facilitative, non-adversarial, and expert-based implementation and compliance mechanism.”[5] 

    Outside of the climate change regime, the amended Gothenburg Protocol to the Convention on Long Range Transboundary Air Pollution addresses the reduction of emissions of black carbon, a powerful greenhouse gas whose reduction would contribute to limiting global warming in the short term, through quantified obligations with separate ceilings for each state. Similarly, the Kigali Amendment to the Montreal Protocol regulates the emissions of HFCs, another powerful greenhouse gas, through a list of implementation measures and schedule for its phase-down and remains a key instrument in terms of effectiveness in the fight against climate change. 

    2030 Agenda for Sustainable Development 

    In the 2030 Agenda for Sustainable Development, Member States express their commitment to protect the planet from degradation and take urgent action on climate change. The Agenda identifies, in paragraph 14, climate change as one of the greatest challenges of our time and worries about its adverse impacts undermining the ability of all countries to achieve sustainable development. To respond to this challenge, Sustainable Development Goal 13 aims to “take urgent action to combat climate change and its impact”, while acknowledging that the UNFCCC is the primary international forum for negotiating the global response to climate change. To respond to the challenges to sustainable development posed by climate change, the Paris Agreement articulates in different ways the ILA New Delhi Declaration on Principles of International Law Relating to Sustainable Development, including inter alia the sustainable use of natural resources, considerations of equity and eradication of poverty, public participation and good governance, and provides a commitment to sustainable development in the international response to combat climate change.[6] 

    The wide-ranging environmental, economic, and social impacts of climate change have implications for all international law regimes, including international human rights law, international refugee law, the law of international trade and investment, international biodiversity law, the law of the sea, international humanitarian law and the law of the use of force, and international dispute settlement. While there are other areas of intersections, the areas mentioned here illustrate the crosscutting nature of climate change as a global issue. 

    Climate change and international human rights law 

    International human rights law addresses the impacts of climate change through the ‘greening’ of existing rights, including the rights to life, food, water, shelter, health and self-determination, the recognition of a specific right to an environment of a certain quality, and the expansion of procedural rights to ensure public participation, access to information, and access to justice on environmental matters. In July 2022, the UNGA adopted its resolution recognising for the first time the right to a clean, healthy, and sustainable environment as a human right at the international level.[7] It affirmed that the promotion of the human right to a clean, healthy, and sustainable environment requires the full implementation of the MEAs under the principles of international environmental law. This recognises environmental protection as an essential component of the enjoyment of human rights. In parallel, the explicit reference to human rights in the preamble of the Paris Agreement signals an enhanced receptivity to rights concerns and discourses in the international climate regime.[8] See the section on human rights law for more information. 

    Climate change, migration and displacement 

    Climate change impacts are anticipated to lead to human mobility and is therefore relevant to migration and displacement rules. Such climate-induced movements could be internal or cross-border. The legal framework for the protection of internally displaced persons is contained in the 1998 Guiding Principles on Internal Displacement (GPID) that, although not binding, are widely applied. Its description of internally displaced persons could encompass those displaced due to climate impacts. In relation to cross-border displacement, there is no single international legal framework for the protection of those displaced across national borders for climate-related reasons. Climate-induced displacement is not covered by the definition of a ‘refugee’ under the 1951 Refugee Convention, nor contemplated by the drafters. The string of (thus far) unsuccessful claims by Pacific Islanders for asylum in Australia and New Zealand based on climate impacts illustrate the hurdles of using the Refugee Convention to address climate-induced displacement. [9] However, the New Zealand courts have not ruled out the application of the Refugee Convention, advocating instead a case-by-case approach.[10]  Some initiatives at the international level, such as the 2016 New York Declaration and the COP decision accompanying the Paris Agreement, include commitments from governments to address the drivers of large-scale movements and developed recommendations for integrated approaches to address the displacement related to the adverse impacts of climate change. 

    Linked to climate-induced displacement, the situation of ‘sinking islands’ due to climate change raises complex legal and technical questions and strains against the traditional boundaries of international law. The very notion of statehood under general international law in the Montevideo Convention on the Rights and Duties of States may be challenged by territorial alterations caused by sea level rise. While rules exist relating to the creation of states, there are no rules relating to their termination in cases of physical disappearance, despite the prospect of entire populations of low-lying island states being forced to move to other states. The treaties relating to statelessness – the 1954 Convention Relating to the Status of Stateless Persons and the 1961 Convention on the Reduction of Statelessness — however, are unlikely to be of use to the inhabitants of sinking islands as they are to address the situation of territories that have disappeared or been rendered uninhabitable and are not universally ratified. See the section on immigration law for more information. 

    Climate change and international trade and investment law 

    International trade and investment law are critically implicated in the climate change arena. Global economic activity, encouraged and facilitated by international trade and investment regimes, is the major source of greenhouse gas emissions. Responding to climate change requires new trade measures. Many environmental measures to address climate change affect international trade and therefore present issues under international trade law. These include not only direct trade measures, such as carbon border measures that states take to ease potential competitive disadvantages for domestic industries subject to costly climate policy requirements, but also general environmental policies such as carbon taxes, emissions trading schemes, energy efficiency standards, and subsidies for renewable energy such as feed-in tariffs. 

    To promote states’ shared interest in free trade, the World Trade Organisation regime imposes a range of limitations on states’ freedom to devise national policy measures, including climate-related measures. WTO provisions include clauses regarding the protection of the environment, most notably in the GATT. A state may be able to justify a climate-related measure that restricts trade under one of the exceptions that WTO law recognises in Article XX GATT. This entails a two-step analysis: determining, first, whether the measure falls under one of the exceptions, and second, whether it is applied consistently with the Article XX ‘chapeau’ requirements. According to these articles, measures violating GATT rules may still be valid on the grounds of protecting human, animal or plant life or health (Article XX(b)), or if the measure relates to the conservation of exhaustible natural resources if such measures are made effective in conjunction with restrictions on domestic production or consumption (Article XX(g)). In the Shrimp/Turtle Case, the WTO Appellate Body observed that the words of Article XX(g) “exhaustible natural resources” must be read by a treaty interpreter in the light of contemporary concerns about environmental protection. It seems plausible to argue that the global climate itself is an ‘exhaustible natural resource’ which would bring mitigation policies within the ambit of Article XX(g) since they relate to the conservation of that exhaustible natural resource. 

    In addition to the WTO exemptions, of note are also the ongoing efforts to negotiate an Environmental Goods Agreement that would eliminate tariffs on a broad range of goods with a positive climate impact, in an attempt to reconcile climate protection measures with trade rules. In any event, since the climate regime has left the resolution of the tensions between trade and climate policy considerations to trade law, considering that the Paris Agreement does not include provisions regarding a binding dispute settlement system, standard setting and dispute settlement in trade law will play significant roles in shaping bottom-up climate action. See the section on trade law  for more information. 

    Climate change and biodiversity 

    Climate change and biodiversity are increasingly recognised as intertwined planetary crises. The UN Decade on Ecosystem Restoration 2021–2030 declared by the UN General Assembly aims to massively scale up the restoration of degraded and destroyed ecosystems as a proven measure to fight the climate crisis and enhance food security, water supply, and biodiversity. Both UNFCCC and CBD parties have indicated a willingness to link biodiversity and climate change-related issues but coordinated policy responses to ensure synergies between related policies at the international level have been limited. 

     The CBD COP has been quite active in integrating climate change-related considerations in the CBD work, advancing technical work to enhance understanding of the linkages, and promoting coordination between secretariats. These include the establishment of two Ad Hoc Technical Expert Groups on Biodiversity and Climate Change in 2001 and 2008, several decisions on biodiversity and climate change, and the adoption of Voluntary Guidelines for the design and effective implementation of ecosystem-based approaches to climate change adaptation and disaster risk reduction (DRR) in 2018. Several of the Aichi Biodiversity Targets are explicitly or implicitly linked to climate change, in particular Target 5 on halving habitat loss, Target 7 on sustainable agriculture, aquaculture and forestry, Target 11 on protected areas, and Target 15 on ecosystem restoration. In parallel, at the UNFCCC COP26, the role of nature within the climate regime was recognised through a series of pledges and commitments with a focus on nature. These included the Glasgow Declaration on Forests and Land Use, signed by 141 countries, and the United Kingdom’s contribution of up to GBP 40 million in international climate finance to establish the Global Centre on Biodiversity for Climate to address critical research gaps.[11] In addition, following the impetus to integrate policy solutions offered by initiatives launched at the UNFCCC COP 26, the ongoing GBF negotiations under the CBD provide the legal and policy space to advance such synergies in the overall context of the 2030 Agenda for Sustainable Development. 

    Climate change and the law of the sea 

    Climate change reinforces the need for the protection of the marine environment under the law of the sea. Part XII of the UNCLOS provides the framework for the protection of the marine environment and international negotiations have begun on enhanced conservation measures for the protection of marine genetic resources in the areas beyond national jurisdiction.[12] The International Maritime Organisation has begun to develop technical and operational measures to enable the shipping industry to reduce its emissions. Regional fisheries management organisations have started factoring the effects of climate change on fish stocks into management measures. Furthermore, the law of the sea has been particularly implicated in the discussions surrounding geoengineering. The London Dumping Convention and its London Protocol have been amended to permit previously prohibited mitigation activities such as sub-seabed carbon sequestration while other proposed marine geo-engineering ‘solutions’ such as ocean fertilization have been regulated for the first time. Legal developments, including the development of the International Court of Justice’s advisory opinion on the COSIS case mentioned earlier, will provide needed insight into the future of maritime climate jurisdiction.  

    International humanitarian law and the law on the use of force 

    Climate change and its detrimental environmental effects such as extreme weather events and droughts will further increase the vulnerability of populations caught up in armed conflict and the problem of unpredictability for military planning and operations. Rules governing civilian protection and humanitarian assistance, as well as targeting rules are likely to be called into question. Some changes to the law will be needed to ensure the adequate protection of civilians caught up in conflicts. In relation to the law on the use of force, the existing powers of the Security Council to deal with threats to international peace and security are sufficient to enable it to deal with future climate-related conflicts. 

    Climate change and international criminal law 

    International criminal justice has been discussed as a piece of global governance that might assist with efforts to address climate change. Currently, there is no substantive framework for the criminalisation of environmental crimes as international crimes and the necessary enforcement jurisdiction at international and national levels.[13] Calls for the potential recognition of the international criminal crime of ‘ecocide’ are being considered. However, the question remains whether an international criminal justice response or responses would be meaningful, appropriate, and effective to address climate change. See the section on criminal law for more information. 

    Climate change and international dispute settlement 

    While there is no ongoing attempt for the law of state responsibility to be transformed by climate change, it could potentially serve to impact the international law of climate change. A state could attempt to sue other states for the injurious consequences of their contributions to climate change. In addition, while climate change has not yet figured prominently in inter-state dispute resolution processes and the adoption of the rules of procedure of the Paris Agreement Implementation and Compliance Committee in November 2022, it has begun to feature in other international fora where it has been the subject of petitions such as to the Inter-American Commission on Human Rights,[14] and the UN Committee on the Rights of the Child.[15] 

    [1] IPCC Working Group I, Sixth Assessment Report: The Physical Science Basis, 2021. 

    [2] The Third Pillar of International Climate Change Law: Explaining ‘Loss and Damage’ after the Paris Agreement. 

    [3] Human Rights Committee, Views adopted by the Committee under article 5 (4) of the Optional Protocol, concerning communication No. 3624/2019, 22 September 2022, CCPR/C/135/D/3624/2019. 

    [4] Maria Antonia Tigre, ‘U.N. Human Rights Committee finds that Australia is violating human rights obligations towards Torres Strait Islanders for Climate Inaction’ (Climate Law Blog, Sabin Center for Climate Change Law, 27 September 2022) <>. 

    [5] See Request for an Advisory Opinion submitted by the Commission of Small Island States on Climate Change and International Law (Request for Advisory Opinion submitted to the Tribunal). International Tribunal for the Law of the Sea. <Request for an Advisory Opinion submitted by the Commission of Small Island States on Climate Change and International Law (Request for Advisory Opinion submitted to the Tribunal)>.  

    [6] Daniel Bodansky, ‘Paris Agreement Introductory Note’ (UN Audiovisual Library of International Law, 2021). <>. 

    [7] Cordonier Segger, M.C. “Advancing the Paris Agreement on Climate Change for Sustainable Development” (2016) 5(2) Cambridge Journal of International & Comparative Law 202. 

    [8] UNGA – the human right to a clean, healthy and sustainable environment of 26 July 2022. 

    [9] Lavanya Rajamani, ‘Human Rights in the Climate Change Regime: From Rio to Paris and Beyond’ in J. Knox & R. Pejan (Eds.), The Human Right to a Healthy Environment (Cambridge University Press 2018). 

    [10] See e.g. Teititota v The Chief Executive of the Ministry of Business, Innovation and Employment [2015] NZSC 107; AF (Kiribati) [2013] NZIPT 800413; 1004726 [2010] RRTA 845 (Sept 2010) (Tonga). 

    [11]AF Kiribati, ibid, para 64. 

    [12] Department for Environment, Food & Rural Affairs, Department for Business, Energy & Industrial Strategy, The Rt Hon George Eustice MP, and The Rt Hon Greg Hands MP, 2021. 

    [13] BBNJ Draft: United Nations General Assembly, Revised draft text of an agreement under the United Nations Convention on the Law of the Sea on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction, A/CONF.232/2020/3 (18 November 2019). 

    [14] Gerhard Kemp, ‘Climate Change, Global Governance and International Criminal Justice’ in Oliver C. Ruppel, Christian Roschmann and Katharina Ruppel-Schlichting (Eds.), Climate Change: International Law and Global Governance (Nomos 2013).

    [15] Petition To The Inter-American Commission on Human Rights Seeking Relief From Violations Resulting from Global Warming Caused By Acts and Omissions of the United States (2005). 

    [16] CRC, Communication No. 104/2019 (Argentina), Communication No. 105/2019 (Brazil), Communication No. 106/2019 (France), Communication No. 107/2019 (Germany), Communication No. 108/2019 (Turkey).