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Published online by Cambridge University Press:  19 September 2019

Lavanya Rajamani
Professor of International Environmental Law, Faculty of Law, University of Oxford and Yamani Fellow in Public International Law, St Peter's College, Oxford,
Daniel Bodansky
Regents’ Professor of Law, Sandra Day O'Connor College of Law, Arizona State University,


This article discusses the importance of the recently concluded Paris Rulebook, the extent to which it limits national discretion, instils discipline and generates ambition and accountability, and the challenges that lie ahead in implementing the 2015 Paris Agreement. It discusses, in particular, the rules on mitigation, transparency, the global stocktake and the implementation and compliance mechanism, in order to highlight the choices Parties made on three overarching issues that have long bedevilled the climate change regime—prescriptiveness (the level of detail of the rules), legal bindingness (the extent to which particular rules are legally binding) and differentiation (the extent to which particular rules accommodate differences between Parties or apply uniformly to all Parties).

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Copyright © The Authors (2019). Published by Cambridge University Press for the British Institute of International and Comparative Law 

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We are grateful to Susan Biniaz, Harald Winkler and the anonymous ICLQ reviewers for comments on an earlier version of this article.


1 The full set of decisions agreed to in Katowice is available at ‘Katowice Climate Package’ (UNFCCC) <>.

2 UNFCCC, ‘Decision 1/CP.21: Adoption of the Paris Agreement’ (29 January 2016) FCCC/CP/2015/10/Add.1, 21, Annex (hereinafter ‘Paris Agreement’). Notably, Parties were unable to agree on rules for the market mechanisms under Article 6 of the Paris Agreement. Negotiations continue on these, with the goal of adopting a decision at the next Conference of Parties in December 2019.

3 Office of the Spokesperson, U.S. Department of State, ‘Communication Regarding Intent to Withdraw from Paris Agreement’ (4 August 2017) <>.

4 F Maisonnave, ‘Brazil to review Paris Agreement status, says Bolsonaro environment minister’ (Climate Home News, 9 December 2018) <>.

5 IPCC, Global Warming of 1.50C (2018) Summary for Policymakers.

6 UNEP, Emissions Gap Report 2018, Executive Summary.

7 ‘Global Warming Report, an “Ear-Splitting Wake-up Call” Warns UN Chief’ (UN News, 8 October 2018) <>.

8 Illustrating the difficulties of the road ahead, the Katowice conference was unable to agree on language endorsing the IPCC Special Report. Instead it merely expressed its ‘appreciation and gratitude’ to the IPCC and ‘welcomed the completion’ of the Report. UNFCCC, ‘Report of the Conference of the Parties on its twenty-fourth session, held in Katowice from 2 to 15 December 2018’ (19 March 2019) FCCC/CP/2018/10/Add.1, paras 25–26.

9 UNEP Emissions Gap Report 2018 (n 6).

10 Notable elements of the Paris Rulebook not discussed in this article include the decisions on adaptation, finance and other means of support.

11 For a detailed discussion of differentiation in the Paris Agreement see Voigt, C and Ferreira, F, ‘Differentiation in the Paris AgreementClimate Law Special Issue (2016) 6, 58CrossRefGoogle Scholar; and Rajamani, L, ‘Ambition and Differentiation in the 2015 Paris Agreement: Interpretative Possibilities and Underlying Politics’ (2016) 65(2) ICLQ 493Google Scholar.

12 Paris Agreement, art 2.1(a).

13 See UNFCCC, ‘Aggregate Effect of the Intended Nationally Determined Contributions: An Update, Synthesis Report by the Secretariat’ (2 May 2016) FCCC/CP/2016/2.

14 Paris Agreement, art 4.1. The Agreement recognises, however, that peaking will take longer for developing countries, and that efforts to reach zero net emissions will take place on the basis of equity and in the context of sustainable development and efforts to eradicate poverty.

15 On ‘deep-then-broad’ vs ‘broad-then-deep’ approaches, see Bodansky, D, Brunnée, J and Rajamani, L, International Climate Change Law (Oxford University Press 2017) 26Google Scholar.

16 Paris Agreement, art 4.2 read with art 4.9.

17 ibid, art 4.3. Art 4.3 also places expectations in relation to NDCs reflecting Parties' ‘common but differentiated responsibilities and respective capabilities, in the light of different national circumstances’.

18 ibid, art 14.

19 ibid, art 4.8.

20 ibid, art. 13.7.

21 ibid, art 13.11.

22 We posed and discussed the issues of legal bindingness, prescription and differentiation in the lead up to the Katowice conference in Bodansky, D and Rajamani, L, ‘The Issues That Never Die’ (2018) 12(3) CCLR 184Google Scholar. For a general discussion of these three issues, see Bodansky, Brunnée and Rajamani (n 15) Ch 1.

23 This tension was reflected in the UN press release about the Katowice outcome, which referred to ‘the adopted guidelines package, called the “rulebook” by some’. UN News, ‘At COP24, Countries Agree Concrete Way Forward to Bring the Paris Climate Deal to Life’ (15 December 2018) <>.

24 Paris Agreement, art 4.3.

25 ibid, art 4.4.

26 UNFCCC Synthesis Report (n 13). As of 10 August 2019, 184 NDCs have been submitted but the UNFCCC has not yet updated its analysis of the aggregate effect of NDCs in the light of these additional NDCs.

27 ‘Submission by Latvia and the European Commission on behalf of the European Union and Its Member States; Intended Nationally Determined Contribution of the EU and Its Member States’ (Latvian Presidency of the Council of the European Union, 6 March 2015) <>.

29 UNFCCC Synthesis Report (n 13).

30 ‘Submission to the ADP: New Zealand's Intended Nationally Determined Contribution’ (7 July 2015) <>.

31 ‘India's Intended Nationally Determined Contribution: Working Towards Climate Justice’ (1 October 2015) <>.

32 Decision 1/CP.21 (n 2) paras 26, 28 and 31.

33 ‘Submission on APA Agenda item 3, Further guidance in relation to mitigation section of decision by the Republic of the Maldives on behalf of the Alliance of Small Island States’ (12 April 2017) <>.

34 See UNFCCC, ‘APA agenda item 3–Further guidance in relation to the mitigation section of decision 1/CP.21’ (13 November 2017) <> 4.

35 See eg UNFCCC, ‘Item 3: Further guidance in relation to the mitigation section of decision 1/CP.21’, Turkey (28 April 2017) <> 116.

36 UNFCCC, ‘Decision 4/CMA.1: Further guidance in relation to the mitigation section of decision 1/CP.21’ (19 March 2019) FCCC/PA/CMA/2018/3/Add.1, 6, para 19.

37 ibid, para 20.

38 Paris Agreement, art 4.8.

40 Decision 1/CP.21 (n 2) para 27.

41 Decision 4/CMA.1 (n 36) para 7.

42 ibid, Annex I.

43 UNFCCC, ‘Decision 1/CP.20: Lima Call for Climate Action’ (2 February 2015) FCCC/CP/2014/10/Add.1, para 14; Decision 1/CP.21 (n 2) para 27.

44 ibid, para 7.

45 ibid, para 7.

46 UNFCCC, ‘LMDC Submission on Further Guidance for the Nationally Determined Contributions under the Paris Agreement’ <>.

47 Decision 4/CMA.1 (n 36) preambular recitals 3–4 and paras 1–4.

48 ibid, preambular recital 4.

49 ibid, para 5.

50 ibid, Annex I, Section 6.

51 For example, a study of Parties’ first round of NDCs found that most Parties’ claims regarding equity were either unsubstantiated or drawn from analysis by in-country experts. Few of the NDCs submitted referred to independent evidence in relation to equity claims, and none of these considered the consequences of their approach if extended to all countries. For instance, while many countries chose to justify the fairness of their NDCs by reference to their ‘small share’ of global GHG emissions, none of the countries extended this analysis to other countries. If they had, they would have realised that the emissions of individual ‘small share’ NDCs add up to 24 per cent of annual global emissions, which negates the argument that merely because a country has a ‘small share’ of global emissions, it should not be expected to take ambitious action. Winkler, H et al. , ‘Countries Start to Explain How Their Climate Contributions Are Fair: More Rigour Needed’ (2018) 18(1) International Environmental Agreements: Politics, Law and Economics 99Google Scholar.

52 In this respect, the requirement that each Party say why its NDC is fair and ambitious in light of its national circumstances serves the same function as the requirement that judges give reasons for their decisions, which allows others to argue that a judge's reasoning is faulty.

53 Paris Agreement, art 4.13.

55 Decision 1/CP.21 (n 2) para 31.

56 See Section V.A. below.

57 Decision 4/CMA.1 (n 36) para 13.

58 ibid, para 14.

59 ibid, Annex II, para 1(a) read with UNFCCC, ‘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’ (19 March 2019) FCCC/PA/CMA/2018/3/Add.2, Annex, para 20.

60 J Penman et al., 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Overview <> 8.

62 Decision 18/CMA.1 (n 59) Annex, para 22; Decision 4/CMA.1 (n 36), Annex II, para 1(b).

63 Decision 1/CP.21 (n 2) para 31. In effect, most of the accounting guidance in the Paris Rulebook is set forth in Part II of the annex to the transparency decision, Decision 18/CMA.1 (n 59) (discussed in Section V.A.1 below), rather than in the mitigation decision.

64 Decision 4/CMA.1 (n 36) Annex II, para 1(c).

65 ibid, Annex II, para 2(e).

66 ibid, Annex II, para 3(b).

67 ibid, Annex II, paras 3–4.

68 Paris Agreement, art 13.13

69 ibid, art 13.7.

70 Decision 18/CMA.1 (n 59) para 77.

71 Decision 1/CP.21 (n 2) para 90.

72 Decision 18/CMA.1 (n 59) Annex.

73 ibid, Annex para 20.

74 ibid, Annex, Part III.B and Part III.D.

75 ibid, Annex, para 64 chapeau.

76 ibid, Annex, para 65.

77 ibid, Annex, para 66.

78 ibid, Annex, paras 65–68.

79 ibid, Annex, para 146.

80 ibid, Annex, para 156 and 158.

82 ibid, Annex, para 149.

84 ibid, Annex, para 158.

85 ibid, Annex, para 153.

86 ibid, Annex, para 159.

87 LMDC Submission (n 46).

88 Decision 18/CMA.1 (n 59), para 3.

89 ibid, Annex, para 5.

90 For an insightful insider's perspective, see S Biniaz, ‘The Who, What and When of “Flexibility” in the Paris Agreement's Transparency Framework’ Climate Law Blog (Sabin Centre for Climate Change Law, 20 December 2018) <>.

91 Paris Agreement, art 13.2 and Decision 18/CMA.1 (n 59) Annex, Section I.B, para 3(c) and Section I. C, para 4.

92 United Nations Framework Convention on Climate Change (adopted 9 May 1992, entered into force 21 March 1994) 1771 UNTS 107, art 12.

93 Decision 18/CMA.1 (n 59) Annex, para 6.

97 ibid, para 6 and para 149(e).

98 ibid. See generally L Rajamani, Innovation and Experimentation in the International Climate Change Regime, Collected Courses of the Hague Academy of International Law/Recueil des Cours (forthcoming 2020).

99 See generally Friedrich, J, ‘Global Stocktake (Article 14)’ in Klein, D et al. (eds), The Paris Agreement on Climate Change (Oxford University Press 2017) 319Google Scholar

100 UNEP Emissions Gap Report 2018 (n 6).

101 UNFCCC, ‘Decision 19/CMA.1: Matters relating to article 14 of the Paris Agreement and paragraphs 99–101 of decision 1/CP.21’ (19 March 2019) FCCC/PA/CMA/2018/3/Add.2, para 3.

102 A joint contact group of the SBI and the SBSTA. ibid, para 4.

103 Decision 19/CMA.1 (n 101) paras 8–10.

104 ‘Submission by the Republic of Mali on behalf of the African Group of Negotiators On Views on issues discussed under agenda item 6’ (2017) <>.

105 Decision 19/CMA.1 (n 101) para 2.

106 ibid, para 36(h).

107 ibid, para. 27.

108 ibid, para 13.

109 ibid, para 35.

110 ibid, para 37.

111 ibid, para 10.

112 ibid, para 14.

113 Paris Agreement, art 15.3.

114 Zihua, G, Voigt, C and Werksman, J, ‘Facilitating Implementation and Promoting Compliance with the Paris Agreement under Article 15 of the Paris Agreement: Conceptual Challenges and Pragmatic Choices’ (2019) 9 Climate Law 65100Google Scholar.

115 Paris Agreement, art 15.2.

116 Decision 19/CMA.1 (n 101), para 22(a).

117 ibid, para 22(b).

118 ibid, paras 32–34.

119 UNFCCC, ‘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’ (19 March 2019) FCCC/PA/CMA/2018/3/Add.2, para 20.

120 ibid, para 22(b).

121 ibid, para 23.

122 ibid, para 28.

123 ibid, para 22(a).

124 Paris Agreement, art 15.2.

125 See ‘LMDC Submission on Modalities and Procedures for the Effective Operation of the Article 15 Committee to Facilitate Implementation and Promote Compliance‘ (14 October 2017) <>.

126 Decision 20/CMA.1 (n 119) para 19(c); see also para 26.

127 Zihua, Voigt and Werksman (n 114).