A. Request

1. By letter dated 12 December 2022, received electronically by the Registry of the Tribunal on the same day, the Co-Chairs of the Commission of Small Island States on Climate Change and International Law (hereinafter “the Commission”) transmitted to the Tribunal a request for an advisory opinion (hereinafter “the Request”), pursuant to a decision of the third meeting of the Commission held on 26 August 2022. The originals of that letter and of the decision of the Commission were filed with the Registry on 20 December 2022.

2. The Commission was created pursuant to the Agreement for the establishment of the Commission of Small Island States on Climate Change and International Law (hereinafter the “COSIS Agreement”), which was concluded on 31 October 2021 and entered into force on the same date. At the time of the filing of the Request, Antigua and Barbuda, Tuvalu, the Republic of Palau, Niue, the Republic of Vanuatu and Saint Lucia were parties to the COSIS Agreement. Subsequently, Saint Vincent and the Grenadines, Saint Christopher (Saint Kitts) and Nevis, and the Commonwealth of the Bahamas also acceded to it. All parties to the COSIS Agreement are also States Parties to the United Nations Convention on the Law of the Sea (hereinafter “the Convention”).

3. At its third meeting, the Commission adopted the following decisions:

The Commission of Small Island States, pursuant to Article 3(5) of the Agreement of 31 October 2021, has decided as follows:

1. (1) Further to the Co-Chairs' 24 November 2022 request for a recommendation regarding an Advisory Opinion from the International Tribunal for the Law of the Sea (ITLOS), the Commission notes with appreciation the work of the Sub- Committee on Protection and Preservation of the Marine Environment and approves the 18 June 2022 Recommendation CLE. 1/2022/Rec of the Committee of Legal Experts to request the following Advisory Opinion from ITLOS consistent with Article 2(2) of the Agreement:

   “What are the specific obligations of State Parties to the United Nations Convention on the Law of the Sea (‘UNCLOS’), including under Part XII:

   1. (a) to prevent, reduce and control pollution of the marine environment in relation to the deleterious effects that result or are likely to result from climate change, including through ocean warming and sea level rise, and ocean acidification, which are caused by anthropogenic greenhouse gas emissions into the atmosphere?

   2. (b) to protect and preserve the marine environment in relation to climate change impacts, including ocean warming and sea level rise, and ocean acidification?”

2. (2) The Commission expresses it support for the initiative of Vanuatu to request an Advisory Opinion on climate change from the International Court of Justice (“ICJ”) and decides that the Committee of Legal Experts should assist members of the Commission in making submissions to the ICJ as appropriate.

3. (3) The Commission requests the Sub-Committees on Sea-Level Rise, Human Rights, and Loss and Damages respectively, to propose further activities that the Commission may undertake to contribute to the definition, implementation, and progressive development of rules and principles of international law concerning climate change, consistent with its mandate under Article 1(3) of the Agreement.

(*) Adopted unanimously by COSIS Members meeting virtually: (1) Hon. Gaston Browne, Prime Minister of Antigua and Barbuda; (2) Hon. Kausea Natano, Prime Minister of Tuvalu; and (3) Hon. Surangel Whipps Jr., President of the Republic of Palau.

Vote recorded by Meeting Chair, Eselealofa Apinelu, High Commissioner of Tuvalu to Fiji

4. In their letter dated 12 December 2022, the Co-Chairs of the Commission stated that they were “representing the Commission pursuant to Article 3(3) of the Agreement for the Establishment of the Commission” and were “hereby submit[ting] a request for an advisory opinion”. The Co-Chairs of the Commission also referred to article 21 of the Statute of the Tribunal (hereinafter “the Statute”) and article 138 of the Rules of the Tribunal (hereinafter “the Rules”) and noted that,

5. In the same letter, the Co-Chairs informed the Tribunal of the appointment of Mr Payam Akhavan and Ms Catherine Amirfar as the Representative and Co- representative, respectively, of the Commission for the proceedings.

6. Together with the said letter, the Co-Chairs of the Commission transmitted to the Tribunal documents likely to throw light upon the questions contained in the request for an advisory opinion, pursuant to article 131 of the Rules. All these documents were posted on the website of the Tribunal.

7. On 12 December 2022, the Request was entered into the List of cases as Case No. 31, which was named “Request for an advisory opinion submitted by the Commission of Small Island States on Climate Change and International Law”. By letter of the same date, the Registrar of the Tribunal informed the Co-Chairs that the Request had been filed with the Registry on 12 December 2022 and entered into the List of cases as Case No. 31.

8. By a communication dated 19 December 2022, the Representative of the Commission corrected the date in paragraph 1, first line, of the decisions of 26 August 2022 adopted by the Commission to read 24 November 2021 instead of 24 November 2022.

B. Chronology of the procedure

9. By notes verbales dated 13 December 2022, in accordance with article 133, paragraph 1, of the Rules, the Registrar notified all States Parties to the United Nations Convention on the Law of the Sea (hereinafter “States Parties”) of the Request.

10. By letter of the same date, pursuant to the Agreement on Cooperation and Relationship between the United Nations and the International Tribunal for the Law of the Sea of 18 December 1997, the Registrar notified the Secretary-General of the United Nations of the Request.

11. By Order dated 16 December 2022, pursuant to article 133, paragraph 2, of the Rules, the President of the Tribunal decided “that the intergovernmental organizations listed in the annex to the … order are considered likely to be able to furnish information on the questions submitted to the Tribunal for an advisory opinion”. By the same Order, pursuant to article 133, paragraph 3, of the Rules, the President invited the States Parties, the Commission and the aforementioned intergovernmental organizations to present written statements on those questions and fixed 16 May 2023 as the time limit within which written statements could be presented to the Tribunal. By the same Order, the President decided that, in accordance with article 133, paragraph 4, of the Rules, oral proceedings would be held. The Order was notified to the States Parties, the Commission and the intergovernmental organizations listed in its annex.

12. By letter dated 31 January 2023, the African Union requested that it be identified, pursuant to article 133, paragraph 2, of the Rules, “as an intergovernmental organization able to furnish information on the questions submitted to the Tribunal for an advisory opinion, thereby permitting [the African Union] to participate in the proceedings”. By letter dated 2 February 2023, the Registrar informed the African Union of the decision of the President to consider the African Union as such an intergovernmental organization and invited the African Union to furnish information within the time limit fixed by the Order of 16 December 2022.

13. By letter dated 3 February 2023, the European Commission requested the President “to extend the deadline to present written statements pursuant to Order 2022/4 by one month, until 16 June 2023.” By Order dated 15 February 2023, the President extended, pursuant to article 133, paragraph 3, of the Rules, to 16 June 2023 the time limit within which written statements could be presented to the Tribunal. The same Order recorded the President's decision to consider the African Union as an intergovernmental organization likely to be able to furnish information on the questions submitted to the Tribunal for an advisory opinion. The Order was notified to the States Parties, the Commission, the intergovernmental organizations listed in the annex to the Order of 16 December 2022, and the African Union.

14. By letter dated 20 February 2023, the International Seabed Authority (hereinafter “the Authority”) requested the President “to consider the Authority as one of the intergovernmental organizations … likely to be able to furnish information on the questions submitted to the Tribunal and therefore to invite the Authority to present its written statement within the time limit as extended by the President of the Tribunal.” By letter dated 24 February 2023, the Registrar informed the Authority of the decision of the President to consider it as an intergovernmental organization likely to be able to furnish such information and invited the Authority to do so within the extended time limit fixed by the Order of 15 February 2023.

15. By letter dated 31 May 2023, received by the Registry on 8 June 2023, the Pacific Community requested, in accordance with article 133, paragraph 2, of the Rules, “the Tribunal's authorisation to present observations on the questions submitted by the Commission … for an advisory opinion” and that the Tribunal include the Pacific Community “among those intergovernmental organisations invited to present observations in Case No. 31”. By letter dated 8 June 2023, the Registrar informed the Pacific Community of the decision of the President to consider the Pacific Community as an intergovernmental organization likely to be able to furnish information on the questions submitted to the Tribunal for an advisory opinion and invited it to do so within the extended time limit fixed by the Order of 15 February 2023.

16. By note verbale dated 5 June 2023, the Permanent Mission of India to the United Nations requested that “the deadline to submit written statement[s] to the Tribunal … further be extended for at least two months or as appropriate to enable member states to furnish written statements to the Tribunal.” By letter dated 6 June 2023, the Registrar informed the Permanent Mission of India, at the request of the President, that “at this stage of the written proceedings it is not contemplated to grant a further extension of the time limit prescribed” and invited India “to submit a written statement as soon as possible.”

17. Within the time limit fixed by the President in his Order dated 15 February 2023, written statements were submitted by the following 31 States Parties, which are listed in the order in which their statements were received: the Democratic Republic of the Congo, Poland, New Zealand, Japan, Norway, Germany, Italy, China, the European Union, Mozambique, Australia, Mauritius, Indonesia, Latvia, Singapore, the Republic of Korea, Egypt, Brazil, France, Chile, Bangladesh, Nauru, Belize, Portugal, Canada, Guatemala, the United Kingdom, the Netherlands, Sierra Leone, Micronesia (Federated States of) and Djibouti. Within the same time limit, written statements were also submitted by the Commission and the following seven intergovernmental organizations, which are listed in the order in which their statements were received: the United Nations; the International Union for Conservation of Nature (hereinafter “the IUCN”); the International Maritime Organization (hereinafter “the IMO”); the Pacific Community; the United Nations Environment Programme; the African Union and the Authority.

18. By letter dated 20 June 2023, in accordance with article 133, paragraph 3, of the Rules, the Registrar notified the States Parties, the Commission and the intergovernmental organizations that had submitted written statements of the list of those participants. By the same letter, the Registrar also informed them that these statements were accessible in a dedicated section of the Tribunal's website.

19. In addition, statements were submitted by the following entities: the United Nations Special Rapporteurs on Human Rights and Climate Change, Toxics and Human Rights and Human Rights and the Environment (on 31 May 2023); the High Seas Alliance (on 15 June 2023); ClientEarth (on 15 June 2023); Opportunity Green (on 15 June 2023); the Center for International Environmental Law and Greenpeace International (on 15 June 2023); the Advisory Committee on Protection of the Sea (on 16 June 2023); the World Wide Fund for Nature (on 16 June 2023); Our Children's Trust and Oxfam International (on 16 June 2023); the Observatory for Marine and Coastal Governance (on 16 June 2023); and One Ocean Hub (on 17 June 2023).

20. The statements from the High Seas Alliance, Opportunity Green, the Center for International Environmental Law and Greenpeace International, and Our Children's Trust and Oxfam International were accompanied by a petition to be granted permission to act as amici curiae in the proceedings. Furthermore, in a communication transmitting its statement, ClientEarth sought permission to “[i]ntervene in the Advisory Proceedings of Case No. 31”.

21. At the request of the President, the Registrar, by separate letters dated 5, 15, 16 and 19 June 2023, respectively, informed the entities mentioned in paragraph 20 above that their statements would not be included in the case file since they had not been transmitted under article 133 of the Rules; the statements would, however, be transmitted to the States Parties, the Commission and the intergovernmental organizations that had presented written statements, and also posted on the website of the Tribunal in a separate section of documents relating to the case. By letter dated 20 June 2023, the aforementioned States Parties, the Commission and the intergovernmental organizations were informed thereof.

22. By note verbale dated 19 June 2023, after the expiry of the time limit for the submission of written statements, Rwanda submitted a written statement. By the said note verbale, Rwanda also transmitted a letter dated 17 June 2023 from the Minister of Justice/Attorney-General of Rwanda. Therein, the Minister of Justice/Attorney- General stated that “Rwanda recognises the slight delay in this submission, owing to the fact that the Convention did not enter into force for Rwanda until today.” By note verbale of the Tribunal dated 20 June 2023, Rwanda was informed that, in light of the reasons provided in the letter dated 17 June 2023, the President had decided that the written statement of Rwanda should be admitted and included in the case file.

23. By communication dated 21 June 2023, after the expiry of the time limit for the submission of written statements, the Food and Agriculture Organization of the United Nations (hereinafter “the FAO”) submitted a written statement. By letter of the same date, the Registrar informed the FAO that, although the statement had reached the Registry after the expiry of the time limit for the submission of statements, the President had decided that the statement should be admitted and included in the case file.

24. By communication dated 23 June 2023, the Registrar informed the States Parties, the Commission and the intergovernmental organizations that had presented written statements of the submission of the statements of Rwanda and of the FAO. These statements were posted on the Tribunal's website in a section entitled “Statements received after the expiry of the time limit fixed by Order 2023/1 of 15 February 2023”.

25. On 26 June 2023, pursuant to article 134 of the Rules, all written statements submitted to the Tribunal were made accessible to the public on the Tribunal's website.

26. By Order dated 30 June 2023, in accordance with article 133, paragraph 4, of the Rules, the President fixed 11 September 2023 as the date for the opening of the hearing at which oral statements could be made by the States Parties, the Commission and the intergovernmental organizations listed in the annex to the Order of the President of 16 December 2022, as well as the African Union, the Authority and the Pacific Community. The same Order recorded the President's decisions to consider the Authority and the Pacific Community as intergovernmental organizations likely to be able to furnish information on the questions submitted to the Tribunal for an advisory opinion (see paras. 14 and 15 above). By the same Order, the States Parties, the Commission and the above-mentioned intergovernmental organizations were invited to indicate to the Registrar, no later than 4 August 2023, their intention to make oral statements at the hearing. The Order was notified to the States Parties, the Commission and the above-mentioned intergovernmental organizations.

27. By note verbale dated 30 June 2023, after the expiry of the time limit for the submission of written statements, Viet Nam submitted a written statement. By note verbale of the Tribunal dated 13 July 2023, Viet Nam was informed that, although the statement had reached the Registry after the expiry of the time limit for the submission of statements, the President had decided that the statement should be admitted and included in the case file. By communication dated 14 July 2023, the Registrar informed the States Parties, the Commission and the intergovernmental organizations that had presented written statements of the submission of the statement of Viet Nam. The statement was posted on the Tribunal's website in a section entitled “Statements received after the expiry of the time limit fixed by Order 2023/1 of 15 February 2023”.

28. Within the time limit prescribed by the Order of the President of 30 June 2023, 34 States Parties, listed as follows in alphabetical order, expressed their intention to participate in the oral proceedings: Argentina, Australia, Bangladesh, Bolivia, Chile, China, Comoros, the Democratic Republic of Congo, Djibouti, the European Union, France, Germany, Guatemala, India, Indonesia, Italy, Latvia, Mauritius, Mexico, Micronesia (Federated States of), Mozambique, Nauru, the Netherlands, New Zealand, Norway, the Philippines, Portugal, the Republic of Korea, Saudi Arabia, Sierra Leone, Singapore, Timor-Leste, the United Kingdom and Viet Nam. Within the same time limit, the Commission, the African Union, the IUCN and the Pacific Community also expressed their intention to participate in the oral proceedings.

29. By separate notes verbales dated 18 July 2023, the United Kingdom and the Netherlands, respectively, requested the Tribunal “to order a second round of written statements and to revise the date for the oral hearings accordingly”. Both States Parties stated that “introducing a second round of written statements is necessary and appropriate in a case of this significance and complexity”, that “[t]his would allow participating States and intergovernmental organizations to respond in writing to statements” already made, and that it would facilitate “narrowing of the issues before the Tribunal”, leading to “a more efficient oral phase of the proceedings”. In their respective notes verbales, the United Kingdom and the Netherlands further stated that, should the Tribunal decline to accede to that request, they invited it “to bear firmly in mind the lack of opportunity afforded to States Parties and participating intergovernmental organizations to respond in writing to the written statements when the Tribunal comes to consider the appropriate procedure for the hearing, including in particular a fair allocation of time”, and that “all participants should be accorded an equal allocation of time at the hearing”, which “includes the Commission of Small Island States on Climate Change and International Law (COSIS)”. They added that “the status of COSIS as the international organization requesting the advisory opinion should give it no greater procedural rights, including in particular time allocation for oral submissions, than any of the participating States Parties to UNCLOS.”

30. By letter dated 20 July 2023, France requested a postponement of the hearing by a few weeks to allow States more time to prepare the oral statements, taking account of the number of written statements made and the importance and complexity of the legal issues raised in the Request. By letter dated 21 July 2023, Italy suggested a postponement of the hearing “by a few weeks, in consideration of the significant number of statements filed and of the complexity of the issues raised by the Request of Advisory Opinion.”

31. By separate notes verbales of the Tribunal dated 7 August 2023, the United Kingdom and the Netherlands were informed that the matter raised in their respective notes verbales had been brought to the attention of the Tribunal, that the Tribunal had concluded that a second round of written statements was not required, and that no further time limit would be fixed pursuant to article 133, paragraph 3, of the Rules within which States Parties and the intergovernmental organizations which had made written statements could present written statements on the statements made. The United Kingdom and the Netherlands were further informed that the Tribunal would allow delegations sufficient time at the hearing to make their oral submissions and also to respond to the written statements made by other participants.

32. By letters dated 7 and 8 August 2023 addressed to Italy and France, respectively, the Registrar, at the request of the President, informed the two States that the matter raised in their respective letters had been brought to the attention of the Tribunal and that, in the view of the Tribunal, a postponement of the date for the opening of the hearing was not required. The Registrar further indicated that the Tribunal however considered that the schedule of the hearing should be organized in such a manner so as to grant delegations sufficient time to make their oral statements and also to respond to the written statements made by other participants.

33. By letter dated 28 July 2023, the Commission “provide[d] notice of its intention to examine two expert witnesses, Dr. Sarah Cooley and Dr. Shobha Maharaj, each of whom ha[d] submitted a report annexed to the Commission's written statement, and request[ed] permission to proceed as such at the hearing under Articles 73(2), 77(2), and 78(1) of the Rules of the Tribunal.” By letter dated 8 August 2023, the Registrar, at the request of the President, invited the Commission to include Dr Cooley and Dr Maharaj as members of its delegation in order to allow them to address the Tribunal.

34. By letter dated 21 August 2023, the Sub-Regional Fisheries Commission (hereinafter “the SRFC”) requested permission to make oral statements at the hearing. By letter dated 28 August 2023, the Registrar informed the SRFC, at the request of the President, that since the SRFC was not included in the Order of 30 June 2023, its request to participate in the oral proceedings was not granted.

35. By note verbale dated 28 August 2023, after the expiry of the time limit for the submission of written statements, India submitted a written statement. By note verbale of the Tribunal dated 8 September 2023, India was informed that although the statement had reached the Registry after the expiry of the time limit for the submission of statements, the Tribunal had decided that the statement should be admitted and included in the case file. By communication of the same date, the States Parties, the Commission and the intergovernmental organizations that had presented written statements were informed of the submission of the statement of India. The statement was posted on the Tribunal's website in a section entitled “Statements received after the expiry of the time limit fixed by Order 2023/1 of 15 February 2023”.

36. By note verbale dated 5 September 2023, Belize informed the Tribunal of its intention to participate in the hearing. By note verbale of the Tribunal dated 8 September 2023, Belize was informed that, “[w]hile noting that the note verbale dated 5 September 2023 was received after the date fixed in the Order of the President of 30 June 2023 for a State Party to indicate its intention to make an oral statement at the hearing, the Tribunal nevertheless decided to allow Belize to make an oral statement at the hearing.”

37. Prior to the opening of the oral proceedings, the Tribunal held initial deliberations on 7 and 8 September 2023.

38. The Tribunal held 18 public sittings on 11, 12, 13, 14, 15, 18, 19, 20, 21 and 25 September 2023, at which it heard oral statements, in the following order, from:

39. The hearing was broadcast on the Internet as a webcast.

40. On 11 September 2023, the Registrar communicated questions posed by Judge Kittichaisaree pursuant to article 76 of the Rules to the Commission and to the IUCN. The question posed to the Commission was as follows:

The question posed to the IUCN was as follows:

The Commission and the IUCN were requested to respond to the respective questions orally during the oral arguments and/or in writing by the end of the hearing.

41. By letter dated 24 September 2023, the Commission transmitted a written response to the question put to it. During the sitting held on 21 September 2023, the IUCN provided a response to the question put to it. The written response of the Commission and a transcript of the oral response of the IUCN were posted on the Tribunal's website.

42. By communication dated 25 September 2023, the Registrar invited the States Parties, the Commission and the intergovernmental organizations that had participated in the oral proceedings to submit comments on the responses of the Commission and the IUCN by 2 October 2023. Comments were received from Australia, France, Latvia, the Netherlands and the United Kingdom by separate communications dated 2 October 2023 and from Timor-Leste by letter dated 4 October 2023. By communication dated 16 October 2023, the Registrar informed the States Parties, the Commission and the intergovernmental organizations that had participated in the hearing of the comments received. These comments were posted on the Tribunal's website.

43. By communications dated 18 and 20 September 2023, the IMO transmitted two documents to the Tribunal and requested that those documents be considered documents in support of the written statement submitted by the IMO on 16 June 2023. By letter dated 13 October 2023, the Registrar informed the IMO that the Tribunal had decided, on 12 October 2023, to admit the two documents in support of the IMO's written statement and therefore considered them as part of the case file.

44. In accordance with article 17 of the Rules, President Hoffmann and Judges Pawlak, Yanai, Kateka, Paik and Gómez-Robledo, whose term of office expired on 30 September 2023, having participated in the meeting mentioned in article 68 of the Rules, continued to sit in the case until its completion. President Hoffmann continued to preside over the Tribunal in the present case until completion, pursuant to article 16, paragraph 2, of the Rules.

A. Scientific aspects

46. The phenomenon of climate change is central to the Request and the questions contained therein necessarily have scientific aspects. In their written and oral submissions, the participants in the present proceedings addressed at length scientific aspects related to climate change and the ocean, and submitted or referred to abundant materials on scientific issues.

47. In relation to the phenomenon of climate change, the Tribunal notes that, in its resolution 43/53 of 6 December 1988, the United Nations General Assembly (hereinafter “the General Assembly”) recognized, for the first time, that “climate change is a common concern of mankind”. In the same resolution, the General Assembly stated that “the emerging evidence indicates that continued growth in atmospheric concentrations of ‘greenhouse’ gases could produce global warming with an eventual rise in sea levels, the effects of which could be disastrous for mankind if timely steps are not taken at all levels”. In this resolution, the General Assembly also endorsed the action of the World Meteorological Organization and the United Nations Environment Programme in jointly establishing an Intergovernmental Panel on Climate Change (hereinafter “the IPCC”) to provide “internationally coordinated scientific assessments of the magnitude, timing and potential environmental and socio-economic impact of climate change and realistic response strategies”. At present, there are 195 member countries of the IPCC. In its resolution 67/210 of 21 December 2012, the General Assembly declared that “climate change is one of the greatest challenges of our time”. This statement has been subsequently reaffirmed by the General Assembly in several resolutions. The Tribunal further notes that, in its resolution 76/296 of 25 July 2022, the General Assembly endorsed the declaration adopted by the 2022 United Nations Ocean Conference that it was “deeply alarmed by the adverse effects of climate change on the ocean and marine life”.

48. Since its establishment in 1988, the IPCC has produced several assessment reports on climate change, the latest within the sixth assessment cycle concluded in 2023. This cycle produced several special reports, such as the 2018 Special Report on Global Warming of 1.5°C (hereinafter “the 2018 Report”) and the 2019 Special Report on the Ocean and Cryosphere in a Changing Climate (hereinafter “the 2019 Report”). The sixth assessment cycle also produced three separate working group reports – the Working Group I report entitled “Climate Change 2021: The Physical Science Basis” finalized on 6 August 2021 (hereinafter “the WGI 2021 Report”), the Working Group II report entitled “Climate Change 2022: Impacts, Adaptation and Vulnerability” finalized on 27 February 2022 (hereinafter “the WGII 2022 Report”), and the Working Group III report entitled “Climate Change 2022: Mitigation of Climate Change” finalized on 4 April 2022 – and a Synthesis Report published in March 2023 (hereinafter “the 2023 Synthesis Report”).

49. The Tribunal notes that the IPCC reports are subject to review and endorsement by the IPCC member countries. According to the IPCC, such endorsement “acknowledges that the report is a definitive assessment that has been developed following the IPCC's defined procedures, underpinning the report's authority” (IPCC Factsheet, “How does the IPCC approve reports?”, first paragraph). Different levels of formal endorsement apply to the different types of materials prepared by the IPCC. The summary for policymakers, which is prepared for each IPCC report, including for synthesis reports, is submitted for “approval”, where approval means that the summary has been subject to detailed, line-by-line discussion and agreement during an IPCC plenary session. The body of the underlying reports is subject to “acceptance” by the plenary. “Acceptance” means that, while “the material has not been subject to line by line discussion and agreement, it nevertheless presents a comprehensive, objective and balanced view of the subject matter” (Principles Governing IPCC Work, Appendix A, p. 2). The synthesis report of an IPCC cycle summarizes the key findings of the working group reports and any special reports of that cycle. While its summary for policymakers is again approved line by line, the body of the synthesis report is subject to “adoption”, section by section and not line by line.

50. With regard to the confidence levels used in IPCC reports, the IPCC explains the following:

51. The Tribunal observes that most of the participants in the proceedings referred to reports of the IPCC, recognizing them as authoritative assessments of the scientific knowledge on climate change, and that none of the participants challenged the authoritative value of these reports.

52. The Tribunal notes that the IPCC defines climate change as:

53. Successive IPCC reports provide important findings in relation to the changes of the Earth's climate that have occurred over time and their causes. The 2023 Synthesis Report states that “[w]idespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred”, and that “[h]uman-caused climate change is already affecting many weather and climate extremes in every region across the globe” (2023 Synthesis Report, p. 46). The same report further states that “[i]t is unequivocal that human influence has warmed the atmosphere, ocean and land” and that “[t]he scale of recent changes across the climate system as a whole and the present state of many aspects of the climate system are unprecedented over many centuries to many thousands of years” (2023 Synthesis Report, p. 46).

54. The IPCC affirms in its 2023 Synthesis Report that human activities, principally through greenhouse gases (hereinafter “GHGs”), “have unequivocally caused global warming” (2023 Synthesis Report, p. 42). Greenhouse gases are “[g]aseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of radiation emitted by the Earth's ocean and land surface, by the atmosphere itself and by clouds” (WGII 2022 Report, p. 2911). The most common GHGs in the Earth's atmosphere include carbon dioxide, methane and nitrous oxide. The IPCC explains that GHGs “absorb infrared radiation, emitted by the Earth's surface, the atmosphere and clouds”, and “[t]hey emit in turn infrared radiation in all directions including downward to the Earth's surface” (Climate Change 2001, The Scientific Basis, pp. 89-90). According to the IPCC, GHGs thus “trap heat within the atmosphere” (Climate Change 2001, The Scientific Basis, p. 90). Anthropogenic GHG emissions, according to the Climate Change 2014 Synthesis Report of the IPCC (hereinafter “the 2014 Synthesis Report”), “have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever”, and this “has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years” (2014 Synthesis Report, p. 4). In this regard, the Tribunal notes that the IPCC defines the term “anthropogenic” as “[r]esulting from or produced by human activities” which “include the burning of fossil fuels, deforestation, land use and land use changes …, livestock production, fertilisation, waste management, and industrial processes,” and the term “anthropogenic emissions” as “[e]missions of greenhouse gases (GHGs), precursors of GHGs, and aerosols, caused by human activities” (2019 Report, p. 679).

55. The IPCC has also assessed the role of the ocean in the climate system. The 2019 Report observes that the ocean is “a fundamental climate regulator on seasonal to millennial time scales” (2019 Report, p. 78). This role is twofold: the ocean “stores heat trapped in the atmosphere caused by increasing concentrations of greenhouse gases” and thus “masks and slows surface warming”; at the same time, it also stores excess carbon dioxide (ibid., p. 456), and such carbon storage represents a major control on atmospheric carbon dioxide. According to the IPCC, “[a]bout a quarter of carbon dioxide (CO2) released by human activities is taken up by the ocean” (ibid., p. 218) and “[a]bsorption by the ocean and uptake by plants and soils are the primary natural CO2 sinks on decadal to centennial time scales” (WGI 2021 Report, p. 179).

56. The IPCC observes that “[c]oastal blue carbon ecosystems, such as mangroves, salt marshes and seagrasses, can help reduce the risks and impacts of climate change, with multiple co-benefits” (WGII 2022 Report, p. 2692). These coastal habitats “are characterised by high, yet variable, organic carbon storage in their soils and sediments” (2019 Report, p. 522) and “have sequestered carbon dioxide from the atmosphere continuously over thousands of years, building stocks of carbon in biomass and organic rich soils” (WGII 2022 Report, p. 1480). The IPCC further observes that “the protection and enhancement of coastal blue carbon can be an important contribution to both mitigation and adaptation at the national scale” (2019 Report, p. 454), while noting that “[t]he potential climatic benefits of blue carbon ecosystems can only be a very modest addition to, and not a replacement for, the very rapid reduction of greenhouse gas emissions” (ibid., p. 454).

57. The reports of the IPCC indicate that the accumulation of anthropogenic GHGs in the atmosphere has had numerous effects on the ocean. The 2023 Synthesis Report states that climate change has caused “substantial damages and increasingly irreversible losses”, including in “cryospheric and coastal and open ocean ecosystems (high confidence)” (2023 Synthesis Report, p. 46). According to the 2019 Report, “[c]limate change-related effects in the ocean include sea level rise, increasing ocean heat content and marine heat waves, ocean deoxygenation, and ocean acidification” (2019 Report, p. 79).

58. With respect to ocean warming, the WGI 2021 Report observes that “the dominant effect of human activities is apparent not only in the warming of global surface temperature, but also in … the warming of the ocean” (WGI 2021 Report, p. 515). The 2019 Report states that “[i]t is virtually certain that the global ocean has warmed unabated since 1970 and has taken up more than 90% of the excess heat in the climate system (high confidence)” (2019 Report, p. 9). The report further states that “[s]ince 1993, the rate of ocean warming has more than doubled (likely). Marine heatwaves have very likely doubled in frequency since 1982 and are increasing in intensity (very high confidence)” (ibid., p. 9). The report states that “[w]arming of the ocean reduces not only the amount of oxygen it can hold, but also tend[s] to stratify it” and that, “[a]s a result, less oxygen is transported to depth, where it is needed to support ocean life” (2019 Report, p. 113). It further states that “[i]n response to ocean warming and increased stratification, open ocean nutrient cycles are being perturbed” (ibid., p. 450) and that “[w]arming-induced changes in spatial distribution and abundance of fish stocks have already challenged the management of some important fisheries and their economic benefits (high confidence)” (ibid., p. 451).

59. Regarding sea level rise, the WGI 2021 Report indicates that “[h]eating of the climate system has caused global mean sea level rise through ice loss on land and thermal expansion from ocean warming” (WGI 2021 Report, p. 11). According to the 2023 Synthesis Report, “[g]lobal mean sea level increased by 0.20 [0.15 to 0.25] m between 1901 and 2018” and “[h]uman influence was very likely the main driver of these increases since at least 1971” (2023 Synthesis Report, p. 46). Among other effects, the 2019 Report indicates that “[g]lobal mean sea level rise will cause the frequency of extreme sea level events at most locations to increase”, that “[c]oastal tidal amplitudes and patterns are projected to change”, that “[r]ising mean sea levels will contribute to higher extreme sea levels associated with tropical cyclones”, and that “[c]oastal hazards will be exacerbated by an increase in the average intensity, magnitude of storm surge and precipitation rates of tropical cyclones” (2019 Report, pp. 20-21). The 2019 Report also states that “[c]oastal ecosystems are observed to be under stress from ocean warming and SLR [sea level rise] that are exacerbated by non-climatic pressures from human activities on ocean and land (high confidence)” (ibid., p. 451). The WGII 2022 Report notes that “[s]ea level rise poses an existential threat for some Small Islands and some low-lying coasts (medium confidence)” (WGII 2022 Report, p. 15).

60. The IPCC defines ocean acidification as follows:

A 2001 IPCC report notes that, “[b]ecause of its solubility and chemical reactivity, CO2 is taken up by the ocean much more effectively than other anthropogenic gases” (Climate Change 2001, The Scientific Basis, p. 197). The IPCC, in its WGI 2021 Report, explains that, “[o]nce dissolved in seawater, CO2 reacts with water and forms carbonic acid” (WGI 2021 Report, p. 714) and that, as it explains in a 2007 report, as carbon dioxide increases, the pH decreases and therefore the ocean becomes more acidic. According to the 2014 Synthesis Report, “[s]ince the beginning of the industrial era, oceanic uptake of CO2 has resulted in acidification of the ocean; the pH of ocean surface water has decreased by 0.1 (high confidence), corresponding to a 26% increase in acidity” (2014 Synthesis Report, p. 41).

61. Regarding the effects of ocean acidification, the same report indicates that “[m]arine ecosystems, especially coral reefs and polar ecosystems, are at risk” from this process, which “has impacts on the physiology, behaviour and population dynamics of organisms” and “acts together with other global changes (e.g., warming, progressively lower oxygen levels) and with local changes (e.g., pollution, eutrophication) (high confidence), leading to interactive, complex and amplified impacts for species and ecosystems” (ibid., p. 67). With regard to the effects on species, a 2014 IPCC report states that “the absorption of rising atmospheric CO₂ by … organisms changes carbonate system variables … in organism internal fluids” and that “[a]ccumulation of CO2 and the resulting acidification can also affect a wide range of organismal functions” (Climate Change 2014, Impacts, Adaptation, and Vulnerability, p. 436). As to species producing calcified exoskeletons, the 2019 Report states that dissolved carbon dioxide taken up by the ocean “makes the water more corrosive for marine organisms that build their shells and structures out of mineral carbonates, such as corals, shellfish and plankton” (2019 Report, p. 113). According to the same report, “[b]iogenic shallow reefs with calcified organisms (e.g., corals, mussels, calcified algae) are particularly sensitive to ocean acidification” (ibid., p. 502). The 2019 Report further states that “[p]rojected ocean acidification and oxygen loss will also affect deep ocean biodiversity and habitats that are linked to provisioning services in the deep ocean” (ibid., p. 509). Furthermore, as stated in the 2018 Report, “[l]arge-scale changes to foodweb structure are occurring in all oceans” (2018 Report, p. 227).

62. With regard to climate-related risks, the IPCC, in its 2023 Synthesis Report, concludes that “[r]isks and projected adverse impacts and related losses and damages from climate change escalate with every increment of global warming (very high confidence)” (2023 Synthesis Report, p. 14), and, in the 2018 Report, states that they “are higher for global warming of 1.5°C than at present, but lower than at 2°C (high confidence)” (2018 Report, p. 5). The WGI 2021 Report also indicates that “[m]any changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level” (WGI 2021 Report, p. 21). In addition, the 2019 Report anticipates that, “[o]ver the 21st century, the ocean is projected to transition to unprecedented conditions with increased temperatures (virtually certain), greater upper ocean stratification (very likely) [and] further acidification (virtually certain)” (2019 Report, p. 18). According to the 2023 Synthesis Report, the “[i]ncreasing frequency of marine heatwaves will increase risks of biodiversity loss in the oceans, including from mass mortality events (high confidence)” (2023 Synthesis Report, p. 98). In particular, “[w]arm-water corals are at high risk already and are projected to transition to very high risk even if global warming is limited to 1.5°C (very high confidence)” (2019 Report, p. 24).

63. In the 2018 Report, the IPCC states that “[l]imiting warming to 1.5°C implies reaching net zero CO2 emissions globally around 2050 and concurrent deep reductions in emissions of non-CO2 forcers, particularly methane (high confidence)” (2018 Report, p. 95). As to what is required to reach this goal, in the same report, the IPCC further states:

64. Furthermore, the 2018 Report observes that “1.5°C implies very ambitious, internationally cooperative policy environments that transform both supply and demand (high confidence)” (2018 Report, p. 95) and that, “[i]n comparison to a 2°C limit, the transformations required to limit warming to 1.5°C are qualitatively similar but more pronounced and rapid over the next decades (high confidence)” (ibid., p. 95).

65. The IPCC concludes, in its 2023 Synthesis Report, that “[g]lobal warming will continue to increase in the near term in nearly all considered scenarios and modelled pathways” (2023 Synthesis Report, p. 68). With regard to climate change mitigation, i.e., “human intervention to reduce emissions or enhance the sinks of greenhouse gases” (2023 Synthesis Report, Annex I, p. 126), the IPCC finds in the same report that “[d]eep, rapid, and sustained GHG emissions reductions, reaching net zero CO2 emissions and including strong emissions reductions of other GHGs, in particular CH4, are necessary to limit warming to 1.5°C … or less than 2°C … by the end of century (high confidence)” (2023 Synthesis Report, p. 68).

66. The Tribunal notes that the IPCC, in its 2023 Synthesis Report, states that “climate change is a threat to human well-being and planetary health” (2023 Synthesis Report, p. 89), and that “[v]ulnerable communities who have historically contributed the least to current climate change are disproportionately affected (high confidence)” (2023 Synthesis Report, p. 5). The 2019 Report observes that “[h]uman communities in close connection with coastal environments … are particularly exposed to ocean and cryosphere change” (2019 Report, p. 5). For instance, the same report identifies future shifts in fish distribution and decreases in fisheries which would affect “income, livelihoods, and food security of marine resource-dependent communities”, as well as impacts on marine ecosystems which would put “key cultural dimensions of lives and livelihoods at risk” (ibid., p. 26). In addition, the WGII 2022 Report indicates that “[c]limate hazards are a growing driver of involuntary migration and displacement” and that “[c]limate-related illnesses … and threats to mental health and well-being are increasing” (WGII 2022 Report, p. 1044). In this respect, the Tribunal notes that climate change represents an existential threat and raises human rights concerns.

B. International instruments on climate change

67. The Tribunal notes that various international agreements and other instruments have been negotiated and adopted to address the issue of climate change. At the core of these agreements is the United Nations Framework Convention on Climate Change (hereinafter “UNFCCC”), which opened for signature in June 1992 at the United Nations Conference on Environment and Development in Rio de Janeiro and entered into force on 21 March 1994. To date, there are 198 Parties to the UNFCCC, including all States Parties to the Convention.

68. The objective of the UNFCCC, as set out in its Article 2, is to achieve “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.” This provision further specifies that such a level should be achieved “within a timeframe sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner.” The UNFCCC defines climate change in Article 1, paragraph 2, as “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.” In Article 1, paragraph 4, the term “[e]missions” is defined as “the release of greenhouse gases and/or their precursors into the atmosphere over a specified area and period of time.” In Article 1, paragraph 5, the term “[g]reenhouse gases” is defined as “those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and re-emit infrared radiation.” The use by the UNFCCC of the plural (“emissions”) and of the qualifier “over a period of time” suggests that these are multiple and, to a certain extent, lasting releases of GHGs, which, inter alia, indicates their eventual accumulation or concentration.

69. With a view to achieving the objective of the UNFCCC and the implementation of its provisions, the Parties to the UNFCCC are guided by the provisions of Article 3.

These provisions refer, inter alia, to common but differentiated responsibilities and respective capabilities, specific needs and special circumstances of developing country Parties, precautionary measures, sustainable development and cooperation. Article 4, paragraph 1, contains general commitments for all Parties to the UNFCCC, while paragraph 2 of the same article formulates specific commitments applicable only to Parties listed in Annex I to the UNFCCC (hereinafter “Annex I Parties”), which includes developed country Parties and country Parties that are undergoing the process of transition to a market economy. These commitments relate to all GHGs not controlled by the Montreal Protocol on Substances that Deplete the Ozone Layer (hereinafter “the Montreal Protocol”). The UNFCCC also establishes the Conference of the Parties (hereinafter “COP”), which, in accordance with Article 7, is entrusted to “keep under regular review the implementation of the [UNFCCC] and any related legal instruments that the [COP] may adopt, and shall make, within its mandate, the decisions necessary to promote the effective implementation of the [UNFCCC].” In the implementation of commitments, “full consideration” is to be given to the specific needs and concerns of developing country Parties arising from the adverse effects of climate change or the impact of the implementation of response measures (see Article 4, para. 8). Low-lying and other small island countries, countries with low-lying coastal, arid and semi-arid areas or areas liable to floods, drought and desertification, and developing countries with fragile mountainous ecosystems are identified as those particularly vulnerable to the adverse effects of climate change (see nineteenth preambular paragraph).

70. On 11 December 1997, the third COP adopted the Kyoto Protocol to the UNFCCC, which entered into force on 16 February 2005. To date, there are 192 Parties to it, including 167 States Parties to the Convention. The Kyoto Protocol operationalizes the UNFCCC by setting quantified emission reduction targets for Annex I Parties. It establishes commitments for these Parties to limit and reduce their GHG emissions in accordance with agreed individual targets over a first commitment period from 2008 to 2012 (see Article 3, para. 1). Moreover, the Kyoto Protocol introduces flexible market-based mechanisms that rely on the trade of emissions permits (see Articles 6, 12 and 17) and establishes an extensive monitoring, review and verification system for ensuring compliance with commitments (see Articles 5, 7, 8 and 18). The Doha Amendment, which was adopted on 8 December 2012, inter alia, established a second commitment period for Annex I Parties from 2013 until 2020.

71. Under the Kyoto Protocol, Annex I Parties are also required to limit or reduce GHG emissions from aviation and marine bunker fuels. This commitment is to be achieved by “working through” the International Civil Aviation Organization (hereinafter “ICAO”) and the IMO, respectively (see Article 2, para. 2, of the Kyoto Protocol).

72. On 12 December 2015, the twenty-first COP adopted the Paris Agreement, which entered into force on 4 November 2016. To date, there are 195 Parties to it, including 168 States Parties to the Convention. The Paris Agreement aims to strengthen the global response to the threat of climate change, including by setting a temperature goal which is defined in Article 2, paragraph 1(a), as follows:

73. In order to achieve the temperature goal set out in Article 2 of the Paris Agreement, Article 4, paragraph 1, thereof provides that

74. In accordance with Article 4, paragraph 2, of the Paris Agreement, the temperature and emissions goals of this treaty are to be attained, inter alia, through the preparation, communication and maintenance of successive nationally determined contributions that each Party intends to achieve and the pursuance of domestic mitigation measures. In accordance with Article 4, paragraph 3,

Article 4, paragraph 6, provides that the least developed countries and Small Island Developing States “may” prepare and communicate strategies, plans and actions for low GHG emissions development reflecting their special circumstances.

75. A further aim of the Paris Agreement is to increase the ability to adapt to the adverse impacts of climate change and foster climate resilience and low GHG emissions development in a manner that does not threaten food production (see Article 2, para. 1(b)). Accordingly, each Party is required, as appropriate, to engage in adaptation planning processes and the implementation of actions, including the development or enhancement of relevant plans, policies and/or contributions (see Article 7, para. 9).

76. Making finance flows consistent with a pathway towards low GHG emissions and climate-resilient development is another aim of the Paris Agreement (see Article 2, para. 1(c)). In this regard, Article 9, paragraph 1, of the Paris Agreement requires developed country Parties to provide financial resources to assist developing country Parties with respect to both mitigation and adaptation in continuation of their existing obligations under the UNFCCC.

77. The Tribunal also notes that the COP has adopted numerous decisions in relation to the UNFCCC, the Kyoto Protocol and the Paris Agreement. Thus, on 20 November 2022, the twenty-seventh COP adopted the Sharm el-Sheikh Implementation Plan, in which it “[r]ecognizes that limiting global warming to 1.5°C requires rapid, deep and sustained reductions in global greenhouse gas emissions of 43 per cent by 2030”, “[a]lso recognizes that this requires accelerated action” and “requests Parties that have not yet done so to revisit and strengthen the 2030 targets in their nationally determined contributions as necessary to align with the Paris Agreement temperature goal by the end of 2023, taking into account different national circumstances” (Decision 1/CMA.4 of 20 November 2022, paras. 15, 16 and 23). In its decision 1/CP.27 of 20 November 2022, the COP “[r]eiterates that the impacts of climate change will be much lower at the temperature increase of 1.5°C compared with 2°C and resolves to pursue further efforts to limit the temperature increase to 1.5°C”. On 13 December 2023, the twenty-eighth COP adopted the First Global Stocktake, where it, inter alia, in paragraph 28, recognized “the need for deep, rapid and sustained reductions in greenhouse gas emissions in line with 1.5°C pathways” and called on Parties to contribute to certain global efforts enumerated therein (Decision FCCC/PA/CMA/2023/L.17 of 13 December 2023). Several COP decisions address matters relating to climate change and the ocean (Decision 1/CP.25 of 15 December 2019, para. 31; Decision 1/CP.26 of 12 November 2021, paras. 60-61; Decision 1/CP.27 of 20 November 2022, paras. 49-50; Decision 1/CMA.4 of 20 November 2022, para. 79).

78. The Tribunal further notes that international instruments adopted within the framework of the IMO, ICAO and the Montreal Protocol also address matters related to climate change.

79. On 15 July 2011, the IMO adopted amendments to Annex VI to the International Convention for the Prevention of Pollution from Ships of 2 November 1973, as modified by the Protocol of 1978 (hereinafter “MARPOL”). Annex VI deals with the prevention of air pollution from ships. The 2011 amendments were made with a view to reducing GHG emissions from ships through the inclusion of regulations concerning energy efficiency (Resolution MEPC.203(62), Annex). Pursuant to the regulations, new ships engaged in international voyages are required to meet gradually increasing levels of energy efficiency. In 2018, the IMO introduced the Initial IMO Strategy on reduction of GHG emissions from ships. In 2021, the IMO adopted amendments to Annex VI (Resolution MEPC.328(76), Annex), which entered into force in November 2022. Regulation 20 of Annex VI, as amended, states that the goal of the relevant regulations “is to reduce the carbon intensity of international shipping, working towards the levels of ambition set out in the Initial IMO Strategy on reduction of GHG emissions from ships [adopted in 2018].”

80. On 7 July 2023, the IMO adopted the 2023 IMO Strategy on Reduction of GHG Emissions from Ships (hereinafter “the 2023 IMO GHG Strategy”). It seeks to enhance IMO's contribution to global efforts by addressing GHG emissions from international shipping. The 2023 IMO GHG Strategy identifies a set of levels of ambition for the sector, notably “to peak GHG emissions from international shipping as soon as possible and to reach net-zero GHG emissions by or around, i.e. close to, 2050, taking into account different national circumstances” (see paras. 1.10.1, 3.1 and 3.3.4 of the 2023 IMO GHG Strategy).

81. In 2017 and 2018, the ICAO adopted Volumes III and IV, respectively, of Annex 16 to the Convention on International Civil Aviation (hereinafter “the Chicago Convention”). Annex 16 to the Chicago Convention contains international standards and recommended practices that govern the environmental impacts of international aviation. Volumes III and IV of Annex 16 relate to climate change mitigation. Volume III concerns the certification of aeroplane carbon dioxide emissions, while Volume IV establishes a carbon offsetting and reduction scheme for international aviation.

82. On 16 September 1987, the Montreal Protocol was adopted as a protocol to the Vienna Convention for the Protection of the Ozone Layer and entered into force on 1 January 1989. To date, there are 197 Parties to it, including all States Parties to the Convention. The Montreal Protocol deals with the phase-out of the production and consumption of chemicals that deplete the ozone layer, including chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which are GHGs. An amendment to the Montreal Protocol adopted on 15 October 2016 (hereinafter “the Kigali Amendment”) provides for the phase-down of hydrofluorocarbons (HFCs), used to replace HCFCs, and which are substances that are not ozone depleting but are potent GHGs. The Kigali Amendment entered into force on 1 January 2019 (with the exception of the amendment to article 4 of the Montreal Protocol (control of trade with non-parties) which will enter into force on 1 January 2033). To date, there are 159 Parties to the Kigali Amendment.

A. Jurisdiction

84. The Tribunal's jurisdiction to render an advisory opinion is based on article 21 of its Statute. This provision reads: “The jurisdiction of the Tribunal comprises all disputes and all applications submitted to it in accordance with this Convention and all matters specifically provided for in any other agreement which confers jurisdiction on the Tribunal.”

85. In Request for an Advisory Opinion submitted by the Sub-Regional Fisheries Commission (SRFC) (hereinafter “the SRFC Advisory Opinion”), the Tribunal stated that its jurisdiction comprises three elements:

86. The Tribunal further stated that the term “all matters” (“toutes les fois que cela” in French) includes advisory opinions, if specifically provided for in “any other agreement which confers jurisdiction on the Tribunal” (Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 21, para. 56).

87. The Tribunal also clarified that the expression “all matters specifically provided for in any other agreement which confers jurisdiction on the Tribunal” does not by itself establish the advisory jurisdiction of the Tribunal. In terms of article 21 of the Statute, it is the “other agreement” which confers such jurisdiction on the Tribunal. When the “other agreement” confers advisory jurisdiction on the Tribunal, the Tribunal is then rendered competent to exercise such jurisdiction with regard to “all matters” specifically provided for in the “other agreement”. Article 21 and the “other agreement” conferring jurisdiction on the Tribunal are interconnected and constitute the substantive legal basis of the advisory jurisdiction of the Tribunal (Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 22, para. 58).

88. Article 2, paragraph 2, of the COSIS Agreement states:

The Tribunal considers that by providing for authorization enabling the Commission to request advisory opinions from the Tribunal, the COSIS Agreement “confers jurisdiction on the Tribunal” within the meaning of article 21 of the Statute.

89. Thus, article 21 of the Statute and the COSIS Agreement conferring jurisdiction on the Tribunal constitute the substantive legal basis of the advisory jurisdiction of the Tribunal in this case.

90. The Tribunal notes that its finding in the SRFC Advisory Opinion regarding the legal basis of its advisory jurisdiction has been supported by most States Parties to the Convention.

91. The Tribunal further notes that most participants in the current proceedings expressed the view that the Tribunal has jurisdiction to render the advisory opinion requested by the Commission.

92. The Tribunal also observes that the 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 (hereinafter “the BBNJ Agreement”), the latest agreement adopted to ensure the effective implementation of the Convention, specifically provides that the Conference of the Parties may request the Tribunal to give an advisory opinion. This Agreement was adopted by consensus on 19 June 2023 and has not yet entered into force.

93. The Tribunal now turns to the prerequisites to be satisfied in order for the Tribunal to exercise its jurisdiction. Article 138, paragraphs 1 and 2, of the Rules reads as follows:

1. 1. The Tribunal may give an advisory opinion on a legal question if an international agreement related to the purposes of the Convention specifically provides for the submission to the Tribunal of a request for such an opinion.

2. 2. A request for an advisory opinion shall be transmitted to the Tribunal by whatever body is authorized by or in accordance with the agreement to make the request to the Tribunal.

94. As the Tribunal clarified in the SRFC Advisory Opinion, article 138 of the Rules does not establish the jurisdiction of the Tribunal but only furnishes the prerequisites that must be met before the Tribunal can exercise its advisory jurisdiction (see Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 22, para. 59).

95. These prerequisites are as follows: (a) there is an international agreement related to the purposes of the Convention which specifically provides for the submission to the Tribunal of a request for an advisory opinion; (b) the request has been transmitted to the Tribunal by a body authorized by or in accordance with the agreement; and (c) the request submitted to the Tribunal concerns a legal question.

96. As regards the first prerequisite, the Tribunal notes that the COSIS Agreement is an international agreement which entered into force on 31 October 2021 and to which six States were Parties at the time the Request was filed.

97. As set out in its preamble, the basis for the COSIS Agreement is the need to address the adverse effects that GHG emissions have on the marine environment, including marine living resources, and their devastating impact for small island States. Furthermore, the Commission's mandate, as stated in article 1, paragraph 3, of the COSIS Agreement, is “to promote and contribute to the definition, implementation, and progressive development of rules and principles of international law concerning climate change, including, but not limited to, the obligations of States relating to the protection and preservation of the marine environment and their responsibility for injuries arising from internationally wrongful acts in respect of the breach of such obligations.”

98. Considering that one of the main objectives of the Convention is the protection and preservation of the marine environment, to which Part XII is dedicated, it is clear that the COSIS Agreement is an international agreement related to the purposes of the Convention.

99. In article 1, paragraph 1, the COSIS Agreement establishes the Commission of Small Island States on Climate Change and International Law as an intergovernmental organization with international legal personality. Pursuant to article 3, membership of the Commission is open to all members of the Alliance of Small Island States (AOSIS) that become parties to the COSIS Agreement.

100. The Tribunal further observes that article 2, paragraph 2, of the COSIS Agreement specifically states that “the Commission shall be authorized to request advisory opinions from the International Tribunal for the Law of the Sea (“ITLOS”) on any legal question within the scope of the 1982 United Nations Convention on the Law of the Sea, consistent with Article 21 of the ITLOS Statute and Article 138 of its Rules.”

101. As to the second prerequisite whereby the request must be transmitted to the Tribunal by a body authorized by or in accordance with the COSIS Agreement, the Tribunal notes that the Commission, during its Third Meeting, convened on 26 August 2022, unanimously decided to submit to the Tribunal a request for an advisory opinion pursuant to article 3, paragraph 5, of the Agreement. The Request was subsequently transmitted to the Tribunal by the Co-Chairs of the Commission (see paras. 1 and 3 above).

102. The Tribunal now turns to the third prerequisite whereby the request for an advisory opinion must concern a legal question. The questions read as follows:

103. The Tribunal considers that these questions have been framed in terms of law. To respond to these questions, the Tribunal is called upon to interpret the relevant provisions of the Convention and of the COSIS Agreement and to identify other relevant rules of international law (see Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at pp. 23-24, para. 65).

104. The Tribunal therefore concludes that the questions raised by the Commission are of a legal nature.

105. In addition to the aforementioned prerequisites, article 21 of the Statute lays down that the jurisdiction of the Tribunal extends to “all matters specifically provided for in any other agreement which confers jurisdiction on the Tribunal.” Accordingly, it is necessary for the Tribunal to assess whether the questions posed by the Commission constitute matters which fall within the framework of the COSIS Agreement (see Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 24, para. 67).

106. In this regard, the questions need not necessarily be limited to the interpretation or application of any specific provision of the COSIS Agreement. It is enough if the questions have a “sufficient connection” with the purpose of the COSIS Agreement (see Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 24, para. 68).

107. The Tribunal notes that article 2, paragraph 1, of the COSIS Agreement provides that the purpose of the Commission is to, inter alia, “[assist] Small Island States to promote and contribute to the definition, implementation, and progressive development of rules and principles of international law concerning climate change, in particular the protection and preservation of the marine environment”.

108. The Tribunal is satisfied in the present case that the questions posed by the Commission (see para. 102 above) have a sufficient connection with the purpose of the COSIS Agreement. The questions are directly relevant to matters which fall within the framework of the Agreement.

109. For the aforementioned reasons, the Tribunal finds that it has jurisdiction to give the advisory opinion requested by the Commission.

B. Discretion

110. Having found that it has jurisdiction to entertain the Request, the Tribunal will now turn to the issue of its discretionary power to decline to render an advisory opinion in the present case.

111. The Tribunal stated in the SRFC Advisory Opinion that “[a]rticle 138 of the Rules, which provides that ‘the Tribunal may give an advisory opinion’, should be interpreted to mean that the Tribunal has a discretionary power to refuse to give an advisory opinion even if the conditions of jurisdiction are satisfied” (see Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 25, para. 71). The Tribunal further stated that “[i]t is well settled that a request for an advisory opinion should not in principle be refused except for ‘compelling reasons’” (see ibid.; see also Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, I.C.J. Reports 1996, p. 226, at p. 235, para. 14).

112. Some participants in the present proceedings expressed the view that the lack of consent of States not party to the COSIS Agreement to any aspect of the Request might constitute a ground for the Tribunal to decline to give an advisory opinion.

113. Contrary to this view, it was contended that the fact that the advisory opinion has been requested by some States Parties to the Convention, and not by all, cannot be a reason for the Tribunal to refrain from giving the opinion. The lack of consent, it was stated, has no bearing on the discretionary power of the Tribunal to refuse to give an advisory opinion to an entity entitled to request it.

114. The Tribunal notes that an advisory opinion is given to the requesting entity, which considers it desirable in order to obtain enlightenment as to the course of action it should take. An advisory opinion as such has no binding force and the consent of States not members of the requesting entity is not relevant (see Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 26, para. 76).

115. The Tribunal observes that, in response to its invitation, a large number of participants in the written and oral proceedings furnished the Tribunal with information relevant to the Request. A vast majority of the participating States Parties expressed support for an advisory opinion to be rendered by the Tribunal and were of the view that the present proceedings did not give rise to any compelling reasons for the Tribunal to exercise its discretion to decline to give an advisory opinion. Some participants drew attention to the urgency of the threat of climate change to member States of the Commission and also to the collective interest of States Parties to the Convention in emphasizing that there were compelling reasons for the Tribunal to proceed expeditiously to answer the questions.

116. Another reason the Tribunal might decline to exercise its jurisdiction is the possibility that the questions raised in the Request may be closely related to questions which are the subject of a dispute affecting the rights and obligations of third States that have not consented to the Request (see Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at pp. 25-26, para. 75). The Tribunal is not aware of any legal dispute between the members of the Commission and any other States relating to the subject matter of the advisory opinion which would require the latter's consent.

117. Some participants expressed the view that the Commission, in this case, was not seeking guidance in respect of its own actions but rather clarification in respect of the obligations of States Parties to the Convention regarding the protection and preservation of the marine environment.

118. In this regard, the Tribunal is aware of the importance of the questions in the Request for the members of the Commission and that by answering the questions, the Tribunal would be assisting the Commission in the performance of its activities and contributing to the fulfilment of its mandate, including the implementation of the Convention.

119. It was further argued by some participants that the Request contains questions that are wide, abstract and of a general nature and that since the Request is framed in broad terms, the Tribunal should have careful regard to the parameters of its judicial function. On the other hand, it was contended that the questions in the Request are clear enough and that there is sufficient information and evidence to enable the Tribunal to give an advisory opinion.

120. The Tribunal is of the view that the questions raised by the Commission are clear and specific enough to enable it to give an advisory opinion. The Tribunal considers that sufficient information and evidence have been made available on which to base its findings. The Tribunal further finds that the Request is compatible with its judicial functions, as it is called upon to clarify and provide guidance concerning the specific obligations of States Parties to the Convention by interpreting and applying the provisions of the Convention, in particular the provisions of Part XII, and other relevant rules of international law. As the Tribunal made clear in the SRFC Advisory Opinion, it “does not take a position on issues beyond the scope of its judicial functions” (see Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 25, para. 74).

121. In light of the foregoing, the Tribunal deems it appropriate to render the advisory opinion requested by the Commission.

122. The Tribunal is mindful of the fact that climate change is recognized internationally as a common concern of humankind. The Tribunal is also conscious of the deleterious effects climate change has on the marine environment and the devastating consequences it has and will continue to have on small island States, considered to be among the most vulnerable to such impacts. Bearing this in mind, the Tribunal will provide clarification on the issues raised by the Commission.

A. Scope of the Request

138. Before responding to the questions submitted to it, the Tribunal wishes to examine the scope of the Request.

139. There are two questions before the Tribunal:

The phrase: “What are the specific obligations of State Parties to the United Nations Convention on the Law of the Sea …, including under Part XII”, applies both to Question (a) and Question (b). As the Tribunal has stated above, the questions raised by the Commission are clear enough to enable it to give an advisory opinion (see para. 120 above). However, certain elements of that phrase have elicited divergent views in the present proceedings. Since the phrase is important to the scope of the Request, the Tribunal will now address these elements.

140. The questions posed to the Tribunal are concerned with the specific obligations “of State Parties to the United Nations Convention on the Law of the Sea”. This wording suggests that the Commission seeks an opinion from the Tribunal on the specific obligations under the Convention. However, in the present proceedings, certain participants invited the Tribunal to provide guidance on States Parties' obligations under international law to curb anthropogenic GHG emissions into the atmosphere and the marine environment. In particular, it was suggested that the Tribunal could determine specific obligations assumed by States under the UNFCCC and the Paris Agreement.

141. Article 2, paragraph 2, of the COSIS Agreement authorizes the Commission to request advisory opinions from the Tribunal “on any legal question within the scope of the 1982 United Nations Convention on the Law of the Sea, consistent with Article 21 of the ITLOS Statute and Article 138 of its Rules” (emphasis added). The Commission itself has suggested that both questions concern States Parties' obligations under the Convention. Specifically, in its final oral statement in the present proceedings, the Commission asked the Tribunal “to state, clearly and objectively what the current legal duties of States Parties are under UNCLOS in relation to the impact of climate change on the marine environment” (emphasis added).

142. The Tribunal concludes that it is requested to render an advisory opinion on the specific obligations of States Parties under the Convention. In order to identify these obligations and clarify their content, the Tribunal will have to interpret the Convention and, in doing so, also take into account external rules, as appropriate.

143. The questions posed to the Tribunal refer to the specific obligations of States Parties to the Convention, “including under Part XII”. Many participants focused their pleadings on the obligations contained in Part XII. However, other participants noted that the questions are not limited to the obligations under Part XII of the Convention and addressed obligations under other parts of the Convention as well.

144. The Tribunal is of the view that, as a matter of ordinary interpretation, the word “including” in the above phrase indicates that the Tribunal is requested to provide guidance as to the specific obligations of the States Parties under Part XII as well as other relevant provisions of the Convention.

145. The Tribunal will now consider whether the issues of responsibility and liability fall within the scope of the Request. Some participants in the present proceedings have stated that issues of responsibility and liability are relevant, in particular because the Request refers to obligations without characterizing them as primary or secondary. In contrast, it has been argued that the Request concerns only primary obligations and does not involve issues of responsibility and liability, nor does it invite the Tribunal to consider legal consequences arising from the breach of obligations. The Commission, for instance, has explained that it is asking the Tribunal to state what the legal duties of States Parties are in relation to the impacts of climate change on the marine environment and not for which acts or omissions injunctive relief or compensation is available.

146. The Commission asks the Tribunal to identify specific “obligations” under the Convention; terms such as “responsibility” and “liability” do not appear in the Request. The Tribunal notes that article 1, paragraph 3, of the COSIS Agreement clearly distinguishes between the obligations, on the one hand, and responsibility for their breaches, on the other (see para. 97 above). Considering the Request against the backdrop of this provision, the Tribunal is of the view that if the Commission had intended for the Tribunal to address issues of responsibility and liability, it would have expressly formulated the Request accordingly.

147. In this regard, the Request is notably different from the requests for advisory opinion previously dealt with by the Seabed Disputes Chamber and the Tribunal. The request submitted to the Seabed Disputes Chamber explicitly asked not only about the responsibilities and obligations of States Parties with respect to the sponsorship of activities in the Area but also, inter alia, about the extent of liability of a State Party for any failure to comply with the provisions of the Convention and the Agreement relating to the Implementation of Part XI of the United Nations Convention on the Law of the Sea of 10 December 1982 by an entity it has sponsored (Responsibilities and obligations of States with respect to activities in the Area, Advisory Opinion, 1 February 2011, ITLOS Reports 2011, p. 10, at p. 15, para. 1). The request to the Tribunal for an advisory opinion submitted by the SRFC expressly asked not only about the obligations of the flag State but also, inter alia, about the extent to which a State should be held liable for illegal, unreported and unregulated fishing activities conducted by vessels under its flag (Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 8, para. 2).

148. In both previous advisory opinions, a distinction has been made between primary and secondary obligations under international law (see Responsibilities and obligations of States with respect to activities in the Area, Advisory Opinion, 1 February 2011, ITLOS Reports 2011, p. 10, at pp. 30-31, paras. 64-71; Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 44, para. 145). In the present case, the Tribunal will confine itself to primary obligations. However, to the extent necessary to clarify the scope and nature of primary obligations, the Tribunal may have to refer to responsibility and liability.

149. The Tribunal wishes to address another issue concerning the Request's scope. Some participants, referring to the mention of sea level rise in the Request, invited the Tribunal to deal with the issue of the relationship between sea level rise and existing maritime claims or entitlements. On the other hand, other participants expressed the view that, while acknowledging the importance of this issue, the present proceedings should focus instead on environmental issues. The Commission, in particular, explained that questions relating to consequences of sea level rise upon maritime zones, entitlements and boundaries are not before the Tribunal in the present case.

150. The Request mentions sea level rise in both questions. The preamble of the COSIS Agreement states, inter alia, that the Parties to the Agreement affirm that maritime zones, as established and notified to the Secretary-General of the United Nations in accordance with the Convention, and the rights and entitlements that flow from them, “shall continue to apply, without reduction, notwithstanding any physical changes connected to climate change-related sea-level rise”. However, neither the Request nor the decision that approved it refers to this provision or otherwise addresses the issue of base points, baselines, claims, rights or entitlements to maritime zones established under the Convention, or maritime boundaries, and the corresponding obligations in the context of “physical changes connected to climate change-related sea-level rise”. Instead, the Request employs sea level rise to form part of the context within which the Tribunal should consider the specific obligations concerning the protection and preservation of the marine environment, a matter on which the Request clearly concentrates. The Tribunal is of the view that if the Commission had intended to solicit an opinion on the consequences of sea level rise for base points, baselines, claims, rights or entitlements to the maritime zones established under the Convention, or maritime boundaries, and the corresponding obligations, it would have expressly formulated the Request accordingly.

B. Relationship between the questions

151. Before examining the two questions in the Request, the Tribunal wishes to address the relationship between them. Several participants in the proceedings expressed the view that the obligation to protect and preserve the marine environment reflected in the second question is more comprehensive than the obligation to prevent, reduce and control pollution of the marine environment reflected in the first question; therefore, the second question is broader than the first question. In this regard, some participants proposed that the Tribunal address Question (b) prior to Question (a).

152. The Tribunal considers that the obligation addressed in the second question is broader in scope than the obligation addressed in the first question. The obligation to protect and preserve the marine environment encompasses the obligation to prevent, reduce and control marine pollution. In addition, it extends to the protection of the marine environment from any negative impacts. As the arbitral tribunal in the Chagos Marine Protected Area case stated, “[w]hile the control of pollution is certainly an important aspect of environmental protection, it is by no means the only one” (Arbitration regarding the Chagos Marine Protected Area between Mauritius and the United Kingdom of Great Britain and Northern Ireland, Award of 18 March 2015, RIAA, Vol. XXXI, p. 359, at pp. 499-500, para. 320; see also Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 37, para. 120; Southern Bluefin Tuna (New Zealand v. Japan; Australia v. Japan), Provisional Measures, Order of 27 August 1999, ITLOS Reports 1999, p. 280, at p. 295, para. 70; The South China Sea Arbitration between the Republic of the Philippines and the People's Republic of China, Award of 12 July 2016, RIAA, Vol. XXXIII, p. 153, at pp. 521-522, para. 945). Thus, implementing the obligation to prevent, reduce and control pollution of the marine environment does not exhaust the implementation of the obligation to protect and preserve it. Given this relationship between the two obligations addressed in the questions before the Tribunal, it is plain that the second question is more comprehensive than the first question. The Tribunal will follow the order of the questions as they were posed in the Request and in its response to the second question will deal with the obligations not addressed in the first question.

A. Clarification of terms and expressions

154. The first question posed to the Tribunal by the Commission concerns the specific obligations of States Parties to the Convention to prevent, reduce and control marine pollution in relation to the deleterious effects that result or are likely to result from climate change and ocean acidification, which are caused by anthropogenic GHG emissions into the atmosphere. Before responding to the question, the Tribunal wishes to clarify certain terms and expressions employed therein to determine the precise meaning of the question.

155. The Tribunal first notes that the question asks the Tribunal to identify specific obligations of “State Parties to UNCLOS”. The term “State Parties” refers to States and international organizations which have become Parties to the Convention in accordance with article 1, paragraph 2, subparagraphs 1 and 2, of the Convention. Currently, 168 States and one international organization are Parties to the Convention.

156. The next point the Tribunal wishes to clarify is the meaning of “specific obligations” to prevent, reduce and control pollution of the marine environment. The term “specific obligations” may denote concrete or particularized obligations, in contrast to general obligations. It may also mean obligations specific to pollution of the marine environment in relation to the deleterious effects arising from climate change and ocean acidification. In responding to the question, the Tribunal will bear in mind both aspects of the term “specific”.

157. The terms “climate change”, “greenhouse gas emissions”, and “ocean acidification” do not appear in the Convention. The Tribunal understands that those terms are used in Question (a) as they are defined in relevant legal instruments relating to climate change or in authoritative scientific works such as in the IPCC reports. For the purpose of responding to Question (a), the Tribunal accepts those definitions and usage, which have already been explained in paragraphs 52, 54, 60 and 68 above.

158. Question (a) points to the specific obligations under the Convention to prevent, reduce and control marine pollution “in relation to” the deleterious effects that result or are likely to result from climate change and ocean acidification, which are caused by anthropogenic GHG emissions. The Tribunal observes that the question is formulated on the premise that these obligations necessarily apply to climate change and ocean acidification. However, in the Tribunal's view, the validity of this premise cannot be presumed and needs to be examined. Therefore, the Tribunal will first address whether the obligations under the Convention apply to climate change and ocean acidification. If they do, the Tribunal will then examine how those obligations should be interpreted and applied in relation to the deleterious effects caused by anthropogenic GHG emissions.

B. Whether anthropogenic GHG emissions fall within the definition of marine pollution under the Convention

159. In responding to Question (a), the first issue that should be addressed is whether anthropogenic GHG emissions into the atmosphere fall under the definition of “pollution of the marine environment” under article 1, paragraph 1, subparagraph 4, of the Convention.

160. A large majority of the participants in the proceedings recognized that anthropogenic GHG emissions meet the definition of “pollution of the marine environment” under article 1, paragraph 1, subparagraph 4, of the Convention. On the other hand, some participants argued that GHG emissions should not be considered “pollution of the marine environment” and that to include them within the ambit of “pollution of the marine environment” would be tantamount to the Tribunal exercising legislative functions.

161. Article 1, paragraph 1, subparagraph 4, of the Convention reads:

This definition does not provide a list of pollutants or forms of pollution of the marine environment. Instead, it sets out three criteria to determine what constitutes such pollution: (1) there must be a substance or energy; (2) this substance or energy must be introduced by humans, directly or indirectly, into the marine environment; and (3) such introduction must result or be likely to result in deleterious effects. These criteria are cumulative; all of them must be satisfied to meet the definition. The definition is general in that it encompasses whatever satisfies these criteria.

162. The Tribunal will now examine whether anthropogenic GHG emissions satisfy the criteria set out above.

163. The terms “substance” and “energy” have a broad meaning. The Tribunal is of the view that, in the context of the present case, the term “substance” refers to any particular kind of matter with uniform properties or a kind of matter of a definite chemical composition. As to the term “energy”, the Tribunal notes that one of the forms of energy is thermal energy or heat. It further notes that the ILC, in its commentary to the definition of “atmospheric pollution” – and specifically to the “introduction of energy” – in the 2021 Draft guidelines on the protection of the atmosphere, explains that this reference to energy is understood to include heat (ILC Draft guidelines on the protection of the atmosphere, Commentary to Guideline 1, subpara. (b)).

164. The term “gas”, in the context of the present case, refers to a substance in a form like air that is neither solid nor liquid. It is clear from the ordinary meaning of the word “gas” and from the UNFCCC and IPCC definitions of the term “greenhouse gases” (see paras. 54 and 68 above) that they are substances. Consequently, the first criterion of the Convention's definition of “pollution of the marine environment” is satisfied.

165. The Tribunal will now address the second criterion. The first question concerns, in the context of pollution of the marine environment, not GHGs as such but “anthropogenic emissions” thereof. In view of the definitions of the term “emissions” in the UNFCCC (see para. 68 above) and of the terms “anthropogenic” and “anthropogenic emissions” by the IPCC (see para. 54 above), it is clear that anthropogenic GHG emissions are produced “by man”, within the meaning of article 1, paragraph 1, subparagraph 4, of the Convention.

166. The term “marine environment” appears in many provisions of the Convention. However, the Convention does not give a definition of it. The term “marine” means belonging to, existing or found in, or produced by, the sea; belonging to, or situated at, the sea-side, bounded by the sea. The term “environment” denotes the area surrounding a place or thing; the surroundings or physical context and conditions in which an organism lives, develops, or a thing exists; the external conditions in general affecting the life, existence, or properties of an organism or object. The ICJ has recognized that the environment “represents the living space, the quality of life and the very health of human beings, including generations unborn” (Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, I.C.J. Reports 1996, p. 226, at p. 241, para. 29). Thus, it may be assumed that the term “marine environment” in article 1, paragraph 1, subparagraph 4, of the Convention combines both spatial and material components. This is supported, in particular, by the context in which the term is used in the Convention, in light of its object and purpose, by the relevant subsequent practice of the States Parties to the Convention regarding its interpretation, and by the corresponding international jurisprudence.

167. According to its fourth preambular paragraph, one of the main goals of the Convention is to establish a legal order for the seas and oceans that will promote the protection and preservation of the marine environment. Here, the marine environment is referred to in a general sense. The Tribunal notes that most of the provisions of Part XII and, in particular, articles 192 and 194, use the term “marine environment” generally, without specifying to which maritime zone it relates.

168. Article 1, paragraph 1, subparagraph 4, of the Convention refers to “the marine environment, including estuaries”. Articles 145, paragraph (a), and 211, paragraph 1, refer to “the marine environment, including the coastline”. This indicates that the marine environment under the Convention encompasses certain spaces beyond maritime zones established thereunder.

169. Under article 194, paragraph 5, of the Convention, the measures taken in accordance with Part XII, i.e., protection and preservation of the marine environment, “shall include those necessary to protect and preserve rare or fragile ecosystems as well as the habitat of depleted, threatened or endangered species and other forms of marine life.” The term “ecosystem” is not defined in the Convention, but article 2 of the Convention on Biological Diversity (hereinafter “the CBD”), which was adopted on 5 June 1992 and entered into force on 29 December 1993, defines ecosystem to mean “a dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit.” The IPCC defines “ecosystem” as a “functional unit consisting of living organisms, their non-living environment and the interactions within and between them” (2019 Report, Annex I, Glossary, p. 684). In this regard, the Tribunal recalls that in the Southern Bluefin Tuna cases and in the SRFC Advisory Opinion, it held that living resources of the sea and marine life are part of the marine environment (Southern Bluefin Tuna (New Zealand v. Japan; Australia v. Japan), Provisional Measures, Order of 27 August 1999, ITLOS Reports 1999, p. 280, at p. 295, para. 70; Request for Advisory Opinion submitted by the Sub-Regional Fisheries Commission, Advisory Opinion, 2 April 2015, ITLOS Reports 2015, p. 4, at p. 61, para. 216; see also Arbitration regarding the Chagos Marine Protected Area between Mauritius and the United Kingdom of Great Britain and Northern Ireland, Award of 18 March 2015, RIAA, Vol. XXXI, p. 359, at p. 580, para. 538).

170. The Tribunal notes that the term “marine environment” is defined in the regulations relating to prospecting and exploration of mineral resources in the Area adopted by the Authority. These regulations all provide the same definition of the term “marine environment”, stating that it

This definition of the marine environment has spatial and material dimensions. In clarifying the term “marine environment”, the Tribunal has taken these regulations into account as representing the practice of the States Parties to the Convention and of the Authority in this respect.

171. The Tribunal also notes that the participants in the present proceedings who addressed the meaning of the term “marine environment” expressed the view that it should be understood broadly.

172. The ordinary meaning of the word “introduction” relevant in the present context is the action of introducing, bringing in or inserting. The ordinary relevant meaning of the word “directly” indicates the absence of an intervening medium or agent; that is to say, through a direct process or mode. The ordinary relevant meaning of the word “indirectly” suggests indirect action or through indirect means, connection, agency or instrumentality, or an intervening person or thing. Given these ordinary meanings of “direct” and “indirect”, the introduction of the anthropogenic GHGs into the marine environment may take place either immediately, through a direct mode or in stages. According to the science (see para. 60 above), because of its solubility and chemical reactivity, carbon dioxide from human activities, which has the largest share and growth in gross GHG emissions (2023 Synthesis Report, p. 4), is taken up by the ocean much more effectively than other emitted gases. Carbon dioxide then dissolves in sea water and mixes into the deep ocean (see, e.g., Climate Change 2001, The Scientific Basis, pp. 187, 197-199). Thus, GHGs, as substances, are directly introduced by humans into the marine environment. Furthermore, according to the science (see para. 54 above), GHGs trap heat within the atmosphere and the ocean then stores this heat. In this way, and considering that heat is a form of energy, humans indirectly introduce energy into the marine environment through anthropogenic GHG emissions.

173. In light of the above, the Tribunal concludes that anthropogenic GHG emissions satisfy the second criterion of the “pollution of the marine environment” definition.

174. To fall within the definition of marine pollution, the introduction of substances or energy must result or be likely to result “in such deleterious effects as harm to living resources and marine life, hazards to human health, hindrance to marine activities, including fishing and other legitimate uses of the sea, impairment of quality for use of sea water and reduction of amenities”. The Tribunal notes that the “deleterious effects” illustrated in article 1, paragraph 1, subparagraph 4, of the Convention are not exhaustive, as implied by the words “such … as” and, in any case, are not limited to the marine environment. This is clear, considering, for instance, that effects on human health, marine activities or amenities are mentioned. The definition also points to actual (“results”) or potential (“likely to result”) deleterious effects. The Tribunal further notes that the definition neither qualifies the “likelihood” of the deleterious effects nor specifies the level of “harm” that can be considered a deleterious effect.

175. The introduction of excess heat (energy) into the marine environment due to the accumulation of GHGs in the atmosphere results in ocean warming. Being itself a component of climate change, ocean warming, according to the IPCC findings made with high confidence, “accounted for 91% of the heating in the climate system” (WGI 2021 Report, p. 11). Anthropogenic GHG emissions thereby cause climate change, which includes ocean warming and sea level rise. The introduction of anthropogenic GHGs into the marine environment also causes ocean acidification (see para. 60 above). In turn, climate change, including ocean warming and sea level rise, and ocean acidification, interacting with other climatic and non-climatic factors, produce multiple deleterious effects on the marine environment and beyond. These effects of climate change and ocean acidification are observed and explained by the science and are widely acknowledged by States (see paras. 51 to 61 above). In particular, adverse effects of climate change are recognized by international climate treaties.

176. The UNFCCC has already acknowledged that human activities have been substantially increasing the atmospheric concentrations of GHGs, that this will result on average in an additional warming of the Earth's surface and atmosphere and may adversely affect natural ecosystems and humankind, and that climate change has adverse effects (UNFCCC, first and second preambular paragraphs). This has been further recognized in the Kyoto Protocol and the Paris Agreement.

177. The UNFCCC defines the adverse effects of climate change as

178. The adverse effects of climate change and ocean acidification satisfy the criterion relating to “deleterious effects” provided in article 1, paragraph 1, subparagraph 4, of the Convention. Thus, through the introduction of carbon dioxide and heat (energy) into the marine environment, anthropogenic GHG emissions cause climate change and ocean acidification, which results in the deleterious effects illustrated in the definition of pollution of the marine environment.

179. In light of the above, the Tribunal concludes that anthropogenic GHG emissions into the atmosphere constitute pollution of the marine environment within the meaning of article 1, paragraph 1, subparagraph 4, of the Convention.

C. Part XII of the Convention and marine pollution

180. Having found that anthropogenic GHG emissions into the atmosphere constitute “pollution of the marine environment” within the meaning of article 1, paragraph 1, subparagraph 4, of the Convention, the Tribunal will now turn to the specific obligations of States Parties to the Convention to prevent, reduce and control such pollution.

181. In this regard, the Tribunal will first identify the provisions of the Convention relevant to its response to Question (a). It will then interpret those provisions to the extent necessary to respond to the question and examine how they should be applied in relation to anthropogenic GHG emissions causing pollution of the marine environment. The Tribunal will conclude by setting out the specific obligations of States Parties to prevent, reduce and control pollution of the marine environment arising from climate change and ocean acidification.

182. The provisions of the Convention which are relevant to answering Question (a) are those dealing with the obligations to prevent, reduce and control pollution of the marine environment. These provisions are mostly found in Part XII of the Convention. Before identifying and analysing them, the Tribunal finds it appropriate to give an overview of the system for the protection and preservation of the marine environment set out in Part XII of the Convention, in particular the marine pollution regime.

183. As stated in the fourth preambular paragraph of the Convention, the protection and preservation of the marine environment is one of the goals to be achieved by the Convention. To that end, the Convention, in particular Part XII, sets out fundamental principles to provide direction and guidance to States in their endeavour to protect and preserve the marine environment, and imposes upon States various obligations in this regard.

184. Article 192 of the Convention, the first article of Part XII, provides that “States have the obligation to protect and preserve the marine environment.” While article 192 imposes upon States a legal obligation, this provision is, at the same time, a statement of principle upon which the legal order for the protection and preservation of the marine environment under the Convention is based.

185. Article 193 of the Convention provides that

186. These two articles together reflect, in the context of the protection and preservation of the marine environment, a principle of international environmental law, which has its origin in the Stockholm Declaration on the Human Environment adopted on 16 June 1972 (hereinafter “the Stockholm Declaration”). Principle 21 of the Stockholm Declaration reads:

This principle was further developed in Principle 2 of the Rio Declaration on Environment and Development adopted on 14 June 1992 (hereinafter “the Rio Declaration”), which refers to the sovereign right of States to exploit their own resources pursuant to their own environmental and “developmental” policies.

187. It should be noted that, while article 193 of the Convention recognizes the sovereign right of States to exploit their natural resources pursuant to their environmental policies, it further provides that States must exercise such right “in accordance with their duty to protect and preserve the marine environment.” This article thus places a constraint upon States' exercise of their sovereign right. This shows the importance the Convention attaches to the protection and preservation of the marine environment.

188. The approach of the Convention to the protection and preservation of the marine environment is manifest in the subsequent provisions of Part XII. Those provisions impose upon States, among other obligations, those to prevent, reduce and control pollution of the marine environment. While the obligation to protect and preserve the marine environment is much broader in scope than the obligation to prevent, reduce and control marine pollution, the latter obligation constitutes the main component of the former obligation under the Convention.

189. Many provisions of Part XII of the Convention are directly or indirectly concerned with the prevention, reduction and control of pollution of the marine environment. They are structured in such a way as to provide for what may be called the regime for regulating marine pollution. The key provision in this regard is article 194 of the Convention, which requires States, inter alia, to take all necessary measures to prevent, reduce and control pollution of the marine environment from “any source”. Thus, this article lays down an obligation common to all sources of pollution with which States must comply.

190. This obligation under article 194 of the Convention is complemented and elaborated upon by provisions in section 5 of Part XII (articles 207 to 212), which address the obligations of States with respect to specific sources of pollution. Those provisions are essentially concerned with the adoption of national legislation and the establishment of international rules and standards to regulate marine pollution. Section 6 of Part XII (articles 213 to 222), which corresponds to source-specific obligations under section 5, addresses the obligations of States to enforce national legislation and to implement international rules and standards.

191. In addition, there are other provisions in Part XII relevant to the prevention, reduction and control of pollution of the marine environment. They include provisions in section 2 on global and regional cooperation, section 3 on technical assistance and section 4 on monitoring and environmental assessment.

192. For the purpose of the present Advisory Opinion, the Tribunal will first consider the obligations of States under article 194 of the Convention and how they should be interpreted and applied in relation to marine pollution arising from anthropogenic GHG emissions. It will then proceed to examine the obligations of States with respect to the specific sources of pollution provided for in sections 5 and 6 of Part XII. The Tribunal will subsequently consider other relevant obligations under sections 2, 3 and 4 of Part XII.

D. Obligations applicable to any source of pollution under article 194 of the Convention

193. Article 194 of the Convention is the primary provision in the marine pollution regime set out in Part XII. This article provides for obligations to prevent, reduce and control marine pollution applicable to any source. Most of the participants in the proceedings took the view that article 194 of the Convention is a key provision in responding to Question (a).

194. Article 194 of the Convention reads:

195. This article provides for three main obligations of States: first, the obligation under paragraph 1 to take necessary measures to prevent, reduce and control marine pollution; second, the obligation under paragraph 2 to take necessary measures to ensure that certain situations relating to pollution do not occur; and third, the obligation under paragraph 5 to take necessary measures to protect and preserve rare or fragile ecosystems as well as the habitat of depleted, threatened or endangered species and other forms of marine life.

196. Although the third obligation is included in article 194 of the Convention addressing measures to prevent, reduce and control marine pollution, it is clear that the measures envisaged under paragraph 5 are not circumscribed to merely those concerning pollution. For that reason, this paragraph refers to the measures taken in accordance with “this Part” rather than “this article”. The Tribunal considers that the third obligation can be more adequately addressed in the context of its reply to Question (b) as to the specific obligations to protect and preserve the marine environment. In its response to Question (a), the Tribunal will accordingly confine itself to the two obligations under paragraphs 1 and 2.

E. Obligations applicable to specific sources of pollution

259. Having addressed the obligations of States common to the prevention, reduction and control of pollution from any source, the Tribunal will now proceed to examining obligations relating to pollution from specific sources. The relevant provisions in this regard are found in sections 5 and 6 of Part XII of the Convention.

260. Section 5 of Part XII of the Convention addresses the obligations to adopt national laws and regulations and establish international rules and standards to prevent, reduce and control marine pollution from six different sources: pollution from land-based sources (article 207), pollution from seabed activities subject to national jurisdiction (article 208), pollution from activities in the Area (article 209), pollution by dumping (article 201), pollution from vessels (article 211), and pollution from or through the atmosphere (article 212). In particular, this section addresses the relationship between national legislation and international rules and standards, and how States should refer to international rules and standards in adopting their national laws and regulations. Depending on the specific sources of pollution, different formulations of reference to international rules and standards are introduced in section 5.

261. Section 6 of Part XII of the Convention addresses the obligation to enforce national laws and regulations and implement international rules and standards. This section follows the source-specific approach of the previous section. The provisions of section 6, as an enforcement sequel to national legislation and international rules and standards adopted in accordance with section 5, need to be read together with the corresponding provisions of that section.

262. The initial issue the Tribunal should consider is how to characterize pollution of the marine environment from anthropogenic GHG emissions in terms of specific sources of pollution. This is necessary because the scope and content of the obligations of States under section 5 of Part XII vary depending on the specific source of pollution. Most participants in the proceedings took the view that marine pollution from anthropogenic GHG emissions can be considered either pollution from land-based sources or pollution from or through the atmosphere. They also expressed the view that marine pollution from such emissions from vessels can be considered either pollution from vessels or pollution from or through the atmosphere. The Tribunal notes in this regard that Question (a) asks it to identify the specific obligations of States Parties to prevent, reduce and control marine pollution in relation to deleterious effects caused by “anthropogenic GHG emissions into the atmosphere”.

263. According to the information submitted to the Tribunal, most anthropogenic GHG emissions into the atmosphere causing marine pollution originate from land- based sources. In addition, such emissions originate from vessels or aircraft. There are also some GHG emissions from other sources, including from certain seabed activities such as venting and flaring.

264. While there are multiple sources of GHG emissions into the atmosphere, the Tribunal considers that the types of pollution most relevant to the present proceedings are confined to marine pollution caused by anthropogenic GHG emissions into the atmosphere from land-based sources, vessels and aircraft. The relevant provisions under the Convention addressing such pollution are found in articles 207 (pollution from land-based sources), 211 (pollution from vessels) and 212 (pollution from or through the atmosphere). The corresponding provisions for enforcement are articles 213 (enforcement with respect to pollution from land-based sources), 217 (enforcement by flag States) and 222 (enforcement with respect to pollution from or through the atmosphere).

F. Other obligations

292. The Tribunal will now proceed to examine other obligations relevant to its response to Question (a). Such obligations may be found in Part XII of the Convention, section 2 on global and regional cooperation, section 3 on technical assistance, and section 4 on monitoring and environmental assessment.

293. At the outset, the Tribunal points out that its findings in this regard apply not only in response to Question (a) but also in response to Question (b).

A. Clarification of terms and expressions

373. Certain terms employed in the Request are common to the first and second questions as formulated by the Commission. The Tribunal has already clarified some terms in determining the precise meaning of Question (a), including the references made to “specific obligations”, “climate change” and “ocean acidification”.

374. As previously explained, the Tribunal accepts the definitions and usage of such terms as “climate change” and “ocean acidification” as they are defined in climate change treaties or widely used in authoritative scientific works such as the IPCC reports, which have already been explained in paragraphs 52, 60 and 68 above.

375. Question (b) concerns “climate change impacts”. The Tribunal observes that the word “impacts” is neutral. However, as formulated in the question submitted to the Tribunal, and in the arguments presented in the proceedings, the word is used in relation to circumstances in which drivers of climate change cause deleterious effects to the marine environment. The Tribunal is of the view that Question (b) concerns the negative impacts of climate change and ocean acidification on the marine environment.

376. As regards the term “specific obligations”, the Tribunal has already drawn attention to the fact that the term may denote concrete or particularized obligations in contrast to general obligations. It may also mean obligations specific to the protection and preservation of the marine environment in relation to climate change impacts and ocean acidification. In responding to Question (b), the Tribunal will bear in mind both aspects of the term “specific”.

B. Relevant provisions of the Convention

377. The Tribunal will now proceed to address the specific obligations of States Parties under the Convention to protect and preserve the marine environment in relation to climate change impacts and ocean acidification that go beyond the prevention, reduction and control of marine pollution as addressed in Question (a).

378. In this regard, the Tribunal will first identify the provisions of the Convention relevant to its response to Question (b). It will then interpret those provisions to the extent necessary to respond to the question, and examine how they should be applied in protecting and preserving the marine environment in relation to climate change impacts and ocean acidification. Subsequently, the Tribunal will set out the specific obligations of States Parties under the Convention to protect and preserve the marine environment against climate change impacts and ocean acidification.

379. The provisions of the Convention which are relevant to answering Question (b) are found in Part XII, as well as other parts of the Convention. The Tribunal has already presented an overview of the system for the protection and preservation of the marine environment set out in Part XII (see paras. 182 to 191 above). The primary provision in this regard is article 192 of the Convention which provides for the general obligation.

380. The relationship between articles 192 and 193 of the Convention is also addressed in the overview of Part XII (see paras. 184 to 187 above). In the overview, it is noted that article 193 places a constraint upon States' exercise of their sovereign right to exploit their natural resources, which has to be exercised in accordance with their duty to protect and preserve the marine environment.

381. In addressing article 194 of the Convention on measures to regulate marine pollution in relation to the first question, the Tribunal observed that measures envisaged under paragraph 5 of that article cover more than those to regulate pollution, and for that reason, this paragraph refers to the measures taken in accordance with “this Part” rather than “this article”. Paragraph 5 of article 194 is particularly relevant to the Tribunal's response to the second question concerning specific obligations to protect and preserve the marine environment.

382. The provisions of Part XII of the Convention that are not aimed exclusively at addressing marine pollution include article 196 on the use of technologies or introduction of alien or new species. Other provisions concerning the protection and preservation of the marine environment are found, in particular, in Part V, including articles 61, 63 and 64, and in Part VII, including articles 117, 118 and 119. These provisions are pertinent in addressing climate change impacts and ocean acidification.

383. The Tribunal's response to the first question addressed the provisions of Part XII of the Convention in section 2 on global and regional cooperation, section 3 on technical assistance, and section 4 on monitoring and environmental assessment. These provisions are also relevant to the Tribunal's consideration of the second question. The Tribunal will elaborate, as necessary, on the significance of these provisions in responding to the second question.

C. Obligations to protect and preserve the marine environment in relation to climate change impacts and ocean acidification