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Collective Obligation and Individual Ambition in the Paris Agreement

Published online by Cambridge University Press:  12 November 2019

Alexander Zahar*
Research Institute of Environmental Law, Wuhan University (China). Email:


Several scholars have claimed or implied that the Paris Agreement imposes a collective obligation on states to keep global warming below 2°C, but what is a collective obligation from a legal point of view? The literature that asserts the existence of a collective obligation fails to address this question. In this article I argue two points. Firstly, while a legally binding collective obligation for states is not a theoretical impossibility, the Paris Agreement has not demonstrably created such an obligation; therefore, the collective obligation that appears in the treaty constitutes at most an objective of the Agreement, albeit a crucial one. Secondly, while state observance of the Agreement's apparent collective obligation (but, in fact, paramount objective) is necessary for the success of the treaty, the Agreement does not provide for a process to resolve the global mitigation burden into state-level ambition commitments to ensure that the paramount objective is met. While this is a significant failing of the Agreement, the provisions in the 2018 Paris Rulebook on the global stocktake are sufficiently loose to allow for this mechanism to play a role in the ‘individuation’ of the mitigation burden.

Copyright © Cambridge University Press 2019

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I am grateful to Benoit Mayer for his comments on an earlier version of this article. No agreement with the views I express here is implied. I am also grateful to the journal's two referees for their constructive criticism in the course of two rounds of comments.


1 New York, NY (US), 9 May 1992, in force 21 Mar. 1994, available at:

2 European Commission, Directorate General for Climate Action (DG CLIMA), ‘Seventh National Communication and Third Biennial Report from the European Union under the UN Framework Convention on Climate Change’, Dec. 2017, pp. ix–x (emphasis added). Earlier occurrences use the same wording: see, e.g., European Commission, ‘Sixth National Communication and First Biennial Report from the European Union under the UN Framework Convention on Climate Change’, 2014 (European Commission, NC6-BR1), p. vii.

3 A ‘conditional offer’ implies an active monitoring of the conditions that would trigger the making of the offer. No such monitoring was taking place.

4 Paris (France), 12 Dec. 2015, in force 4 Nov. 2016, available at:

5 China, ‘Second National Communication on Climate Change of the People's Republic of China’, 2012 (China, NC2), p. 14.

6 This has been noted by some scholars (n. 11 below). Others, however, have claimed that all obligations under the Paris Agreement are procedural, which is not my position, as I will explain below.

7 Kyoto Protocol to the United Nations Framework Convention on Climate Change (Kyoto Protocol), Kyoto (Japan), 11 Dec. 1997, in force 16 Feb. 2005, available at:

8 Art. 13(3)–(4), Paris Agreement.

9 Consider, by way of contrast, the statement that biodiversity loss is a common concern of humankind. This is a different kind of statement than the one about climate change. Biodiversity loss is divisible into the sum of local losses. Climate change is not divisible into local changes; rather, it is the consequence of the changing composition of the Earth's atmosphere. The changed atmosphere is a single and indivisible object. The preambular statement's affirmation in the Paris Agreement of a ‘common concern’ thus concerns an unprecedented kind of anthropogenic environmental interference.

10 This link is repeated in Decision 1/CP.21, ‘Adoption of the Paris Agreement’ (13 Dec. 2015), UN Doc. FCCC/CP/2015/10/Add.1, para. 13 (‘[A]ll Parties [are] to communicate to the secretariat their intended nationally determined contributions towards achieving the objective of the Convention as set out in its Article 2’).

11 Voigt, C., ‘The Compliance and Implementation Mechanism of the Paris Agreement’ (2016) 25(2) Review of European, Comparative, and International Environmental Law, pp. 161–73CrossRefGoogle Scholar, at 161 (‘[the Paris Agreement] establish[ed] mainly administrative, procedural obligations of a legally binding nature, leaving the substantive content to a large extent to the discretion of parties’); and 166 (‘[the] legally binding obligations for all parties … are of a procedural nature only, while the substance of mitigation, adaptation and finance obligations is not legally binding and left to the sovereign discretion of parties’); S. Oberthür & R. Bodle, ‘Legal Form and Nature of the Paris Outcome’ (2016) 6(1–2) Climate Law, pp. 40–57, at 40, 56 (‘The Paris Agreement is an international treaty focused on establishing procedural obligations’); Rajamani, L., ‘Ambition and Differentiation in the 2015 Paris Agreement: Interpretative Possibilities and Underlying Politics’ (2016) 65(2) International and Comparative Law Quarterly, pp. 493514, at 493CrossRefGoogle Scholar (‘The Paris Agreement contains aspirational goals, binding obligations of conduct in relation to mitigation’); Rajamani, L. & Brunnée, J., ‘The Legality of Downgrading Nationally Determined Contributions under the Paris Agreement: Lessons from the US Disengagement’ (2017) 29(3) Journal of Environmental Law, pp. 537–51, at 542CrossRefGoogle Scholar (‘Parties do not have binding obligations of result in relation to their NDCs’, and ‘The Paris Agreement deferred to [those states who did not wish to subject themselves to legally binding obligations of result], but enshrined binding obligations of conduct for Parties, coupled with a good faith expectation of results’); Huggins, A., ‘The Evolution of Differential Treatment in International Climate Law: Innovation, Experimentation, and “Hot’ Law”’ (2018) 8(3–4) Climate Law, pp. 195206, at 196CrossRefGoogle Scholar (‘[the regime's] legal frameworks have evolved from relatively vague provisions in the UNFCCC, to binding targets for industrialized countries under the Kyoto Protocol, to obligations of conduct (but not result) under the Paris Agreement’); and Mayer, B., ‘Obligations of Conduct in the International Law on Climate Change: A Defence’ (2018) 27(2) Review of European, Comparative, and International Environmental Law, pp. 130–40, at 132CrossRefGoogle Scholar (‘[while] the UNFCCC established an open-ended obligation of conduct, the Kyoto Protocol, by contrast, created an obligation of result. In turn, the Paris Agreement reverted to an obligation of conduct’).

12 The Paris Agreement's collective obligation is not the same as that of the objective of Art. 3(1) of the Kyoto Protocol of ‘reducing [Annex I party] overall emissions of such gases [listed in Annex A] by at least 5% below 1990 levels in the commitment period 2008 to 2012’. The figure of 5% was to be an aggregate of the mitigation actions of Annex I parties and had no other significance beyond that. Compared with the Paris Agreement's below 2°C requirement, which adds specificity to Art. 2 of the UNFCCC, the Kyoto Protocol's 5% reduction target is an entirely different legal construct. It is a means to an end – the means being the actions of a minority of parties over a period of 5 years – in contrast with the Paris Agreement's 2°C containment outcome, which is an end in itself for all parties. As for the UNFCCC, its wholly vague objective in Art. 2 is not a substantive legal obligation, whether collective or otherwise.

13 See, e.g., Raupach, M.R. et al. , ‘Sharing a Quota on Cumulative Carbon Emissions’ (2014) 4(10) Nature Climate Change, pp. 873–9CrossRefGoogle Scholar; Anderson, K. & Peters, G., ‘The Trouble with Negative Emissions’ (2016) 354(6309) Science, pp. 182–3CrossRefGoogle ScholarPubMed; Rogelj, J. et al. , ‘Differences between Carbon Budget Estimates Unravelled’ (2016) 6(3) Nature Climate Change, pp. 245–52CrossRefGoogle Scholar; Schleussner, C.-F. et al. , ‘Science and Policy Characteristics of the Paris Agreement Temperature Goal’ (2016) 6(9) Nature Climate Change, pp. 827–35CrossRefGoogle Scholar; Peters, G.P. et al. , ‘Key Indicators to Track Current Progress and Future Ambition of the Paris Agreement’ (2017) 7(2) Nature Climate Change, pp. 118–22, at 121CrossRefGoogle Scholar; and Carbon Pricing Leadership Coalition and World Bank Group, ‘Report of the High-Level Commission on Carbon Prices’, 29 May 2017, p. 6, available at:

14 Decision 1/CP.21, n. 10 above, para. 52 (emphasis added).

15 Rajamani, L., ‘The 2015 Paris Agreement: Interplay between Hard, Soft and Non-Obligations’ (2016) 28(2) Journal of Environmental Law, pp. 337–58, at 343CrossRefGoogle Scholar (‘It matters to whom the provision is addressed or who it identifies as actors. If the provision is addressed to “each Party”, it denotes an individual obligation. If it is addressed to “all Parties”, it could denote a collective obligation. If it refers to “Parties”, in some cases, depending on the context, it could be a cooperative or collective obligation; in others, it could be a blanket or universal reference to “Parties”, not necessarily signalling a collective or cooperative obligation’); and at 352 (where Rajamani recognizes a category of individual ‘hard’ obligations, which ‘lend themselves to assessments of compliance/non-compliance’, and appears to imply that collective ‘hard’ obligations also exist); Rajamani, n. 11 above, pp. 497, 501, 503 (where she distinguishes between collective and individual obligations; contrasts collective and individual ‘requirements’ and collective and individual ‘expectations’); C. Voigt, ‘The Paris Agreement: What Is the Standard of Conduct for Parties?’, Questions of International Law online articles, 24 Mar. 2016, pp. 17–28, at 17, available at: (‘Some [treaty provisions] contain legally binding obligations, either of [a] substantive or of [a] procedural nature. Such obligations can be collective or individual’); Bodansky, D., ‘The Legal Character of the Paris Agreement’ (2016) 25(2) Review of European, Comparative, and International Environmental Law, pp. 142–50, at 145–7CrossRefGoogle Scholar (where he categorizes obligations as collective or individual: e.g. ‘provisions … intended to create collective rather than individual obligations’, and uses ‘collective aim’ differently from ‘collective obligation’); Bodansky, D., Brunnée, J. & Rajamani, L., International Climate Change Law (Oxford University Press, 2017), pp. 18, 218–9, 225, 231, 234–5, 243Google Scholar (where they categorize obligations as collective or individual, and distinguish between collective and individual ‘expectations’ and between collective obligations and ‘goals’); Peel, J., ‘Climate Change’, in Nollkaemper, A. & Plakokefalos, I. (eds), The Practice of Shared Responsibility in International Law (Cambridge University Press, 2017), pp. 1009–50, at 1024CrossRefGoogle Scholar (where reference is made to the UNFCCC, not the Paris Agreement: ‘At their highest, these provisions [in Art. 3 UNFCCC] might give rise to a collective obligation on the part of Convention parties to stabilise emissions at a level adequate to protect the climate system now and in the future, and to avoid dangerous anthropogenic warming’); Rajamani & Brunnée, n. 11 above, pp. 541, 543 (where the authors identify ‘individual obligations’ as well as ‘collective responsibility language’, thus implying that collective obligations also exist); Huggins, n. 11 above, p. 204 (‘the Paris Agreement imposes a collective obligation on all parties to hold the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels’); Voigt, C. & Ferreira, F., ‘Differentiation in the Paris Agreement’ (2016) 6(1–2) Climate Law, pp. 5874, at 69–70CrossRefGoogle Scholar (referring to ‘collective legally binding commitments’ in relation to climate finance and implying the existence of collective obligations by qualifying some obligations as ‘individual’). Note also Peel's claim that the Kyoto Protocol's 5% reduction target for Annex I Parties for the first commitment period was a ‘soft collective obligation’: Peel, ibid., p. 1026.

16 Works that neither mention a collective obligation nor imply its existence through a contrast with ‘individual’ obligations include Bodansky, D., ‘The Paris Climate Change Agreement: A New Hope?’ (2016) 110(2) American Journal of International Law, pp. 288319CrossRefGoogle Scholar; Doelle, M., ‘The Paris Agreement: Historic Breakthrough or High Stakes Experiment?’ (2016) 6(1–2) Climate Law, pp. 120, at 4, 8–9CrossRefGoogle Scholar (referring only to collective ‘goal’ and collective ‘mitigation effort’); Lawrence, P. & Wong, D., ‘Soft Law in the Paris Climate Agreement: Strength or Weakness?’ (2017) 26(3) Review of European, Comparative, and International Environmental Law, pp. 276–86, at 279, 281CrossRefGoogle Scholar (collective ‘goal’ and collective ‘non-binding objective’ only); Oberthür & Bodle, n. 11 above; H. van Asselt, ‘International Climate Change Law in a Bottom-up World’, Questions of International Law online articles, 24 Mar. 2016, pp. 5–15, available at:; Voigt, n. 11 above; Mayer, n. 11 above; Mayer, B., The International Law on Climate Change (Cambridge University Press, 2018), pp. 17, 72, 87, 111, 201, 214, 218Google Scholar (where he mentions collective ‘attempt’, ‘determination’, ‘ambition’, ‘objectives’, ‘commitment’, ‘mobilization goals’, and ‘target’, but not collective obligation).

17 See the works by Bodansky and Voigt cited at nn 15 and 16 above.

18 See n. 15 above.

19 Mayer, n. 11 above, p. 135.

20 In fact, the ‘community of states’ does not correspond with the state parties to the Paris Agreement. This is a problem for the Agreement, which will be ineffective if it does not manage to enlist all large emitters, although it is not a problem for the notion of a collective obligation.

21 For a summary of the effect of this law, see UK, Department for Business, Energy and Industrial Strategy, ‘7th National Communication’, Dec. 2017 (UK, NC7), p. 100 (‘The UK passed the Climate Change Act in November 2008, introducing the world's first long-term legally binding framework to reduce GHG emissions. The Act is the central piece of legislation that governs the UK approach to tackling climate change. The Act specifies that the UK must reduce its emissions by at least 80% by 2050 relative to 1990 levels (the international baseline) and by at least 34% by 2020. The Act requires carbon budgets be set providing a framework for meeting our statutory targets by setting a maximum emissions limit over each five-year period. The Act established the Committee on Climate Change – an independent body that advises the government on emissions targets, and reports to Parliament on progress made in reducing GHG emissions, which the Government is required to respond to’).

22 See McHarg, A., ‘Climate Change Constitutionalism? Lessons from the United Kingdom’ (2011) 2(4) Climate Law, pp. 469–84, at 484CrossRefGoogle Scholar.

23 China, NC2, n. 5 above, p. 9 (‘In the 12th Five-Year Plan for National Economic and Social Development … the reduction of CO2 emissions per unit of GDP by 17% is set for the first time as a binding target’).

24 As legal obligations can be ‘owed to the international community as a whole’ (see Art. 48(1)(b) of the International Law Commission (ILC), ‘Draft Articles on Responsibility of States for Internationally Wrongful Acts, with Commentaries’, 2001(II), Part Two, Yearbook of the International Law Commission, p. 31 (ILC Articles on State Responsibility) (emphasis added)), legal obligations can be held by the international community as a whole. The international community as a whole, or the state parties to a given treaty regime, could be deemed a legal person if the circumstances so require. For a quick example, consider that, if ever Mars were settled, Mars and Earth might need to conclude treaties – with the ‘party’ for Earth being the community of states.

25 Reparation for Injuries Suffered in the Service of the United Nations, Advisory Opinion, 11 Apr. 1949, ICJ Reports (1949), p. 174.

26 Sands and Peel recognize the existence of non-actionable obligations: Sands, P. & Peel, J., Principles of International Environmental Law, 4th edn (Cambridge University Press, 2018), p. 198CrossRefGoogle Scholar.

27 In Barcelona Traction, Light and Power Company Ltd (Belgium v. Spain), Judgment, 5 Feb. 1970, ICJ Reports (1970), p. 32, para. 33, the International Court of Justice (ICJ) drew a distinction between obligations owed to particular states and those owed ‘towards the international community as a whole’ (erga omnes) because they are ‘the concern of all States’.

28 ILC Articles on State Responsibility, n. 24 above, p. 118, Commentary on Draft Art. 42(b).

29 Ibid., pp. 118–9.

30 Ibid., p. 126, Commentary on Draft Art. 48.1. Pauwelyn uses the transcendence metaphor to characterize collective obligations: Pauwelyn, J., ‘A Typology of Multilateral Treaty Obligations: Are WTO Obligations Bilateral or Collective in Nature?’ (2003) 14(5) European Journal of International Law, pp. 907–51, at 925CrossRefGoogle Scholar. For the origins of the concept of collective obligation, see ibid., pp. 909–15.

31 See Section 2.2 above.

32 Nollkaemper, A., ‘Introduction’, in Nollkaemper, A. & Plakokefalos, I. (eds), Principles of Shared Responsibility in International Law: An Appraisal of the State of the Art (Cambridge University Press, 2014), pp. 124, at 6–7CrossRefGoogle Scholar.

33 Ibid., p. 10.

34 Ibid., p. 12.

35 See also Peel, J., ‘New State Responsibility Rules and Compliance with Multilateral Environmental Obligations: Some Case Studies of How the New Rules Might Apply in the International Environmental Context’ (2001) 10(1) Review of European Community and International Environmental Law, pp. 8297, at 85, 89CrossRefGoogle Scholar.

36 N. 10 above.

37 Fitzmaurice, M., ‘International Responsibility and Liability’, in Bodansky, D., Brunnée, J. & Hey, E. (eds), The Oxford Handbook of International Environmental Law (Oxford University Press, 2007), pp. 1011–36, at 1020Google Scholar (‘One of the problems of the law on state responsibility has been how to overcome the classical bilateralism of the duty/right paradigm and how to reflect the features of the many environmental obligations that have as a goal the protection of the common interest’).

38 Decision 1/CP.21, n. 10 above, para. 17.

39 Höhne, N. et al. , ‘Assessing the Ambition of Post-2020 Climate Targets: A Comprehensive Framework’ (2018) 18(4) Climate Policy pp. 425–41, at 425CrossRefGoogle Scholar.

40 Aldy, J.E., Akimoto, W.A. Pizer & K., ‘Comparing Emissions Mitigation Efforts across Countries’ (2017) 17(4) Climate Policy pp. 501–15, at 502CrossRefGoogle Scholar; du Pont, Y. Robiou et al. , ‘Equitable Mitigation to Achieve the Paris Agreement Goals’ (2017) 7(1) Nature Climate Change, pp. 3843, at 38CrossRefGoogle Scholar; Peters et al., n. 13 above, p. 118; Höhne et al., n. 39 above, p. 425.

41 Winkler, H. & Rajamani, L., ‘CBDR&RC in a Regime Applicable to All’ (2014) 14(1) Climate Policy, pp. 102–21, at 111–2CrossRefGoogle Scholar; Robiou du Pont et al., n. 40 above, pp. 38, 40; Peters et al., n. 13 above, p. 118; Van Zyl, H. et al. , ‘The Cost of Achieving South Africa's “Fair Share” of Global Climate Change Mitigation’ (2018) 18(10) Climate Policy, pp. 1327–39, at 1330CrossRefGoogle Scholar.

42 Aldy, Pizer & Akimoto, n. 40 above, p. 506; Höhne et al., n. 39 above, pp. 426, 438.

43 Robiou du Pont et al., n. 40 above, pp. 40, 42–3; Pan, X. et al. , ‘Exploring Fair and Ambitious Mitigation Contributions under the Paris Agreement Goals’ (2017) 74 Environmental Science and Policy, pp. 4956, at 52CrossRefGoogle Scholar; Höhne et al., n. 39 above, pp. 432–3, 436; Van Zyl et al., n. 41 above, p. 1337.

44 They represent only a sample of works in this category. See, in addition, Ringius, L., Torvanger, A. & Underdal, A., ‘Burden Sharing and Fairness Principles in International Climate Policy’ (2002) 2(1) International Environmental Agreements, pp. 122CrossRefGoogle Scholar; Page, E.A., ‘Distributing the Burdens of Climate Change’ (2008) 17(4) Environmental Politics, pp. 556–75CrossRefGoogle Scholar; Den Elzen, M. & Höhne, N., ‘Sharing the Reduction Effort to Limit Global Warming to 2°C’ (2010) 10(3) Climate Policy, pp. 247–60CrossRefGoogle Scholar; Höhne, N., Den Elzen, M. & Escalante, D., ‘Regional GHG Reduction Targets Based on Effort Sharing: A Comparison of Studies’ (2014) 14(1) Climate Policy, pp. 122–47CrossRefGoogle Scholar; Kallbekken, S., Sælen, H. & Underdal, A., Equity and Spectrum of Mitigation Commitments in the 2015 Agreement (Nordic Council of Ministers, 2014)CrossRefGoogle Scholar; Kuramochi, T. et al. , ‘Comparative Assessment of Japan's Long-Term Carbon Budget under Different Effort-Sharing Principles’ (2015) 16(8) Climate Policy, pp. 1029–47CrossRefGoogle Scholar; Meinshausen, M. et al. , ‘National Post-2020 Greenhouse Gas Targets and Diversity-Aware Leadership’ (2015) 5(12) Nature Climate Change, pp. 1098–107CrossRefGoogle Scholar; Rocha, M. et al. , Analysis of Equitable Mitigation Contribution of Countries (Climate Analytics, 2015)Google Scholar; Hof, A.F., den Elzen, M. & Beltran, A.M., ‘The EU 40% Greenhouse Gas Emission Reduction Target by 2030 in Perspective’ (2016) 16(3) International Environmental Agreements, pp. 375–92CrossRefGoogle Scholar; Rogelj, J. et al. , ‘Paris Agreement Climate Proposals Need a Boost to Keep Warming Well Below 2°C’ (2016) 534(7609) Nature, pp. 631–9CrossRefGoogle Scholar; and Glynn, J. et al. , ‘Zero Carbon Energy System Pathways for Ireland Consistent with the Paris Agreement’ (2019) 19(1) Climate Policy, pp. 3042CrossRefGoogle Scholar.

45 Höhne et al., n. 39 above, p. 437.

46 Tirole proposes a more ‘realistic’ alternative of negotiating ‘rough formulas based on a few country parameters (income, population, present and foreseeable pollution, sensitivity to global warming, for example) rather than trying to determine the contributions country by country’: Tirole, J., Economics for the Common Good, trans. Rendall, S. (Princeton University Press, 2017), p. 226CrossRefGoogle Scholar. For another alternative, based on ‘major-economy-country leadership’, see Meinshausen et al., n. 44 above.

47 Winkler & Rajamani, n. 41 above; Aldy, Pizer & Akimoto n. 40 above, p. 502.

48 Ibid., p. 508.

49 See, e.g., Mayer, n. 16 above, p. 49 (‘The challenge for the implementation of the Paris Agreement will be to initiate a process that is able to spur the willingness of every State to commit to more significant climate action’); Van Asselt, n. 16 above, p. 10 (‘These inputs [to the global stocktake] could allow for an analysis of how the NDCs, in aggregate, fare against the global temperature goals. However, the Paris Agreement does not explicitly call for such an analysis. Moreover, even if such an analysis would be carried out and it would find that the NDCs are out of step with the goals of the agreement, it is unclear whether and how such a finding about collective efforts could influence individual NDCs’). One scholar claimed (as it turns out, incorrectly) that the equity puzzle would need to be solved as a condition of states agreeing on a post-2020 treaty: Voigt, C., ‘Equity in the 2015 Climate Agreement: Lessons from Differential Treatment in Multilateral Environmental Agreements’ (2014) 4(1) Climate Law, pp. 5069, at 51CrossRefGoogle Scholar (‘The success of the negotiations under the ADP will depend, among other things, on a common understanding of equitable sharing of efforts and benefits’). No such common understanding is evident in the 2015 Paris Agreement or 2018 Paris Rulebook.

50 Decision 1/CP.20, ‘Lima Call for Climate Action’ (14 Dec. 2014), UN Doc. FCCC/CP/2014/10/Add.1, para. 14.

51 E.g., United States (US), Department of State, ‘Climate Action Report 2014: First Biennial Report and Sixth National Communication under the United Nations Framework Convention on Climate Change’, 2014, p. 6 (‘the U.S. Biennial Report … outlines how U.S. action on climate change puts the United States on a path to reach the ambitious but achievable goal of reducing U.S. GHG emissions in the range of 17 percent below 2005 levels by 2020’); UK, NC7, n. 21 above, p. 104 (‘the Government's ambitious long-term carbon reduction targets’); Indonesia, Directorate General of Climate Change, Ministry of Environment and Forestry, ‘Indonesia: First Biennial Update Report under the United Nations Framework Convention on Climate Change’, 2015, p. i (‘The Government of Indonesia has committed to [an] ambitious emissions reduction target [26% reduction compared to business as usual in 2020] and is implementing a comprehensive nationwide response to climate change’); India, Ministry of Environment, Forest and Climate Change, ‘First Biennial Update Report to the United Nations Framework Convention on Climate Change’, 2015, p. 104 (‘India has been making specific and ambitious budgetary outlays to address the challenges of climate change’); New Zealand, Ministry for the Environment, ‘New Zealand's Seventh National Communication’, 2017 (New Zealand, NC7), p. 72 (‘The New Zealand Government is committed to doing its fair share to reduce global emissions’); Australia, Department of the Environment and Energy, ‘7th National Communication on Climate Change: A Report under the United Nations Framework Convention on Climate Change’, 2017, p. 11 (‘The Australian Government has set an ambitious target to reduce emissions by 26 to 28 per cent on 2005 levels by 2030. This is equivalent to halving per capita emissions or reducing the energy intensity of Australia's economy by two-thirds’). Australia's last sentence may be intended to suggest that the proposed reduction is ambitious by any standard, and the unguarded reader of its National Communication may very well also understand it that way.

52 E.g., Germany, Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety, ‘Third Biennial Report under the United Nations Framework Convention on Climate Change’, 2017 (Germany, BR3), p. 18 (‘Germany is pursuing ambitious climate change mitigation goals. The German government has set itself the target of reducing the country's greenhouse gas emissions by at least 40% by 2020 in relation to 1990. This target goes well beyond Germany's target to cut its emissions by 14% as its contribution to the EU target of a 20% reduction for 2020 under the Effort Sharing Decision’); New Zealand, NC7, n. 51 above, p. 69 (‘Because New Zealand's emissions profile is very different from that of other developed countries … the cost of further mitigation by New Zealand is likely to be higher. All of New Zealand's targets are therefore ambitious’); South Africa, Department of Environmental Affairs, ‘South Africa's 2nd Biennial Update Report’, 2017, p. 130 (‘South Africa's overall approach to mitigation is informed by two contexts: first, its contribution as a responsible global citizen to the international effort to reduce global GHG emissions’); UK, NC7, n. 21 above, p. 11 (‘the UK has outperformed the target emissions reductions of its domestically set first carbon budget (2008 to 2012) by one per cent and projects that it will outperform against our second and third budgets, covering the years 2013 to 2022, by about four per cent and six per cent respectively. In doing so, we also expect to over-achieve our international commitments under the Kyoto Protocol’). While each of these examples contains a gesture of acknowledgement of the mitigation effort of other states, there is no meaningful interstate comparison. Moreover, each state can be seen to be evaluating its ambition only self-referentially.

53 E.g., European Commission, NC6-BR1, n. 2 above, p. vii (‘The EU sets its climate change mitigation objectives within the international commitment to limit the average global temperature increase to less than 2°C compared to pre-industrial levels’); Canada, Environment and Climate Change, ‘Canada's Seventh National Communication on Climate Change and Third Biennial Report’, 2017, p. 53 (‘The Pan-Canadian Framework and Mid-Century Strategy are aligned with the Paris Agreement's goal to limit the increase in global average temperature to well below 2°C, and pursue efforts to limit the increase to 1.5°C’); New Zealand, NC7, n. 51 above, p. 69 (‘This NDC … was set after extensive analysis … The analysis included estimating costs to the economy of reaching the target, and comparison with other developed country proposals to ensure New Zealand proposed at least comparable ambition’). No more relevant information is given by the European Commission, Canada, or New Zealand on these points.

54 Winkler, H. et al. , ‘Countries Start to Explain How Their Climate Contributions Are Fair: More Rigour Needed’ (2018) 18(1) International Environmental Agreements, pp. 99115, at 101CrossRefGoogle Scholar.

55 Ibid., p. 103.

57 Ibid., pp. 104–5 (the 101 ‘small shares’ in fact added up to almost a quarter of global emissions (including emissions from land use, land-use change, and forestry)).

58 Ibid., p. 111.

59 Decision 1/CP.21, n. 10 above, para. 27.1 (emphasis added).

60 Art. 13(3)–(4) Paris Agreement.

61 See Decision 4/CP.5, ‘Guidelines for the Preparation of National Communications by Parties Included in Annex I to the Convention, Part II: UNFCCC Reporting Guidelines on National Communications’ (4 Nov. 1999), UN Doc. FCCC/CP/1999/6/Add.1; Decision 22/CMP.1, ‘Guidelines for Review under Article 8 of the Kyoto Protocol’ (30 Nov. 2005), UN Doc. FCCC/KP/CMP/2005/8/Add.3; Decision 1/CP.16, ‘The Cancun Agreements: Outcome of the Work of the Ad Hoc Working Group on Long-Term Cooperative Action under the Convention’ (10–11 Dec. 2010), UN Doc. FCCC/CP/2010/7/Add.1; UNFCCC Guidelines on Reporting and Review (2000), paras 40–7 and 60–4; Decision 2/CP.17, ‘Outcome of the Work of the Ad Hoc Working Group on Long-Term Cooperative Action under the Convention’ (11 Dec. 2011), UN Doc. FCCC/CP/2011/9/Add.1, paras 12–62, and Annex I; Decision 19/CP.18, ‘Common Tabular Format for “UNFCCC Biennial Reporting Guidelines for Developed Country Parties”’ (8 Dec. 2012), UN Doc. FCCC/CP/2012/8/Add.3; Decision 13/CP.20, ‘Guidelines for the Technical Review of Information Reported under the Convention Related to Greenhouse Gas Inventories, Biennial Reports and National Communications by Parties Included in Annex I to the Convention’ (12 Dec. 2014), UN Doc. FCCC/CP/2014/10/Add.3.

62 Decision 18/CMA.1, ‘Modalities, Procedures and Guidelines for the Transparency Framework for Action and Support Referred to in Article 13 of the Paris Agreement’ (2–14 Dec. 2018), UN Doc. FCCC/PA/CMA/2018/3/Add.2 (Transparency Framework Decision), Annex, para. 7.

63 Art. 13.5 Paris Agreement.

64 Transparency Framework Decision, n. 62 above, Annex, para. 149; see also Mayer, B., ‘Transparency under the Paris Rulebook: Is the Transparency Framework Truly Enhanced?’ (2019) 9(1–2) Climate Law, pp. 4064CrossRefGoogle Scholar.

65 Art. 15.1 Paris Agreement.

66 Ibid., Art. 15.2.

67 See Decision 20/CMA.1, ‘Modalities and Procedures for the Effective Operation of the Committee to Facilitate Implementation and Promote Compliance referred to in Article 15, Paragraph 2, of the Paris Agreement’ (15 Dec. 2018), UN Doc. FCCC/PA/CMA/2018/3/Add.2, Annex, para. 22. See also Gu, Z., Werksman, C. Voigt & J., ‘Facilitating Implementation and Promoting Compliance with the Paris Agreement under Article 15: Conceptual Challenges and Pragmatic Choices’ (2019) 9(1–2) Climate Law, pp. 65100Google Scholar.

68 Art. 14.2 Paris Agreement.

69 Decision 19/CMA.1, ‘Matters relating to Article 14 of the Paris Agreement and Paragraphs 99–101 of Decision 1/CP.21 (15 Dec. 2018), UN Doc. FCCC/PA/CMA/2018/3/Add.2 (Global Stocktake Decision), para. 14.

70 See Zahar, A., ‘Collective Progress in the Light of Equity under the Global Stocktake’ (2019) 9(1–2) Climate Law, pp. 101–21CrossRefGoogle Scholar.

71 See Global Stocktake Decision, n. 69 above, para. 3(c).

72 Ibid., paras 6, 30.

73 Ibid., para. 10.

74 Decision 4/CMA.1, ‘Further Guidance in relation to the Mitigation Section of Decision 1/CP.21’ (15 Dec. 2018), UN Doc. FCCC/PA/CMA/2018/3/Add.2, Annex I.

75 Ibid., para. 6.

76 Global Stocktake Decision, n. 69 above, para. 36(h), albeit at the ‘collective level’ (chapeau of para. 36). Just how ambition (and fairness) information at the state level will be aggregated into collective ambition when ambition has been left undefined and unquantified is not clear from the Rules.

77 Global Stocktake Decision, n. 69 above, para. 13.

78 Ibid., para. 33.