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‘Dynamic Differentiation’: The Principles of CBDR-RC, Progression and Highest Possible Ambition in the Paris Agreement

Published online by Cambridge University Press:  24 October 2016

Christina Voigt
University of Oslo, Department of Public and International Law, and Center of Excellence ‘PluriCourts’, Oslo (Norway). Email:
Felipe Ferreira
Ministry of Foreign Affairs, Division of Climate and Ozone, Brasilia (Brazil). Email:


The Paris Agreement has struck a careful balance between the need for ambitious and effective climate action and for fair effort sharing among parties based on differentiation. This article provides an overview of the negotiation history of differentiation and analyzes the ‘dynamic differentiation’ as built into the architecture of the Agreement. While being set against the normative background of the United Nations Framework Convention on Climate Change (UNFCCC), the Paris Agreement adopts a more diversified way of differential treatment among parties, approaching it in three complementary ways: firstly, on a principled basis, reflecting common but differentiated responsibilities and respective capabilities (CBDR-RC), in the light of different national circumstances; secondly, in the content of its articles, in particular on mitigation, finance and transparency; and thirdly, on the basis of the principles of progression and highest possible ambition, which represent new and dynamic aspects of differentiation. The authors argue that ‘highest possible ambition’ is reflective of a duty of care that states now need to exercise. It implies a due diligence standard, which requires each government to act in proportion to the risk at stake and to take all appropriate and adequate climate measures according to its responsibility and its best capabilities. By expecting parties to apply this standard at each successive preparation of nationally determined contributions (NDCs), and to progress beyond previous ones, the Paris Agreement has set up reiterative processes, an ‘international normative pull’ and a collective learning environment. This, in turn, creates a reflexive approach to parties’ determination of effort, promoting the evolution of voluntary cooperative behaviour.

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© Cambridge University Press 2016 

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Both authors have been involved in the negotiations under the UNFCCC as part of the Norwegian and Brazilian delegation, respectively. During the negotiations that led to the adoption of the Paris Agreement, Christina Voigt was principal legal adviser to the Norwegian delegation and Felipe Ferreira was mitigation negotiator for the Brazilian delegation. The views expressed in this article are personal and the sole responsibility of the authors. They do not necessarily reflect the views of the Norwegian or the Brazilian government.

This article draws upon and expands on C. Voigt & F. Ferreira, ‘Differentiation in the Paris Agreement’ (2016) 6(1–2) Climate Law, pp. 58–74. Climate Law has kindly agreed to the inclusion of Figure 1 in this article.


1 Koskenniemi, M., The Politics of International Law (Bloomsbury, 2011)Google Scholar; Crawford, J., ‘Sovereignty as a Legal Value’, in J. Crawford & M. Koskenniemi (eds), The Cambridge Companion to International Law (Cambridge University Press, 2012), pp. 117133 CrossRefGoogle Scholar, at 117.

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4 Examples of differentiation in international law abound: it can be reflected as special decision-making rights (e.g., the veto power for permanent members of the United Nations (UN) Security Council; or for the ‘consultative parties’ of the Antarctic Treaty); as specific obligations according to different country categories (e.g., the distinction between ‘nuclear weapon countries’ and ‘non-nuclear weapon countries’ in the Nuclear Non-Proliferation Treaty); or as preferential rights (such as the ‘special and differential treatment’ provisions of the World Trade Organization (WTO) agreements).

5 Voigt, C., ‘Equity in the 2015 Climate Agreement: Lessons from Differential Treatment in Multilateral Environmental Agreements’ (2014) 4(1–2) Climate Law, pp. 5069 CrossRefGoogle Scholar.

6 ‘States shall cooperate in a spirit of global partnership to conserve, protect and restore the health and integrity of the Earth’s ecosystem. In view of the different contributions to global environmental degradation, States have common but differentiated responsibilities. The developed countries acknowledge the responsibility that they bear in the international pursuit of sustainable development in view of the pressures their societies place on the global environment and of the technologies and financial resources they command’: Rio Declaration on Environment and Development, adopted by the UN Conference on Environment and Development, Rio de Janeiro (Brazil), 3–14 June 1992, UN Doc. A/CONF.151/26 (Vol. I), 12 Aug. 1992, Principle 7, available at:

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10 IPCC, ‘Summary for Policymakers’, in Edenhofer, O. et al., Climate Change 2014: Mitigation of Climate Change – Contribution of Working Group III to the Fifth Assessment Report of the IPCC (Cambridge University Press, 2014), pp. 130 Google Scholar, at 5.

11 Ostrøm, E., Governing the Commons: The Evolution of Institutions for Collective Action (Cambridge University Press, 1990)CrossRefGoogle Scholar; see also Ostrøm, E., ‘Polycentric Systems for Coping with Collective Action and Global Environmental Change (2010) 20(4) Global Environmental Change, pp. 550557 CrossRefGoogle Scholar.

12 Fleurbaey, M. & Kartha, S., ‘Sustainable Development and Equity’, in Edenhofer et al., n. 10 above, Ch. 4, pp. 283350 Google Scholar, at 295.

13 With regard to effective climate mitigation action, Young has identified three general conditions for equitable burden sharing under which the successful formation and eventual effectiveness of a collective action regime may hinge: (i) the absence of actors who are powerful enough to coercively impose their preferred burden-sharing arrangements; (ii) the inapplicability of standard utilitarian methods of calculating costs and benefits; and (iii) the fact that regime effectiveness depends on a long-term commitment of members to implement its terms: O. Young, ‘Does Fairness Matter in International Environmental Governance? Creating an Effective and Equitable Climate Regime’, in Todd, Hovi & McEvoy, n. 8 above, pp. 16–28.

14 Fleurbaey & Kartha, n. 12 above, p. 295.

15 For an overview see C. Kolstad & K. Urama, ‘Social, Economic, and Ethical Concepts and Methods’, in Edenhofer et al., n. 10 above, pp. 207–82, at 215–9.

16 Fleurbaey & Kartha, n. 12 above, pp. 318–9.

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

18 Art. 3.1 UNFCCC, ibid.: ‘The Parties should protect the climate system for the benefit of present and future generations of humankind, on the basis of equity and in accordance with their common but differentiated responsibilities and respective capabilities. Accordingly, the developed country Parties should take the lead in combating climate change and the adverse effects thereof’.

19 Rajamani, L., ‘The Doctrinal Basis for and Boundaries of Differential Treatment in International Environmental Law’, in Rajamani, n. 2 above, pp. 129175 CrossRefGoogle Scholar.

20 There are other forms of category-based differentiation under the UNFCCC, such as the flexibility given to ‘economies in transition’ under Art. 4.2, and the 9 types of developing country that have specific needs listed in Art. 4.8.

21 Kyoto (Japan), 11 Dec. 1997, in force 16 Feb. 2005, available at:

22 Pauw, P. et al., ‘Different Perspectives on Differentiated Responsibilities’, Deutsches Institut für Entwicklungspolitik, Discussion Paper 6/2014, available at: Google Scholar.

23 Decision 1/CP.1, ‘The Berlin Mandate: Review of the Adequacy of Art. 4, paras 2(a) and (b), including Proposals related to a Protocol and Decisions on Follow-up’, UN Doc. FCCC/CP/1995/7/Add.1, 6 June 1995, paras 2(a) and (b). The Berlin Mandate was the outcome of the review referred to in Art. 4.2(d) UNFCCC.

24 Kyoto Protocol, n. 21 above, Art. 3 in conjunction with Annex B.

25 The authors note that ‘bifurcated’ and ‘binary’ have been widely used as synonyms in the negotiations for the Paris Agreement (n. 27 below). For the sake of precision and recognizing that developing countries also have obligations under the UNFCCC, it is useful to distinguish these terms. This article refers to ‘binary’ as a differentiation approach that sets an obligation or process for a category of countries and exempts the other category (like ‘1’ and ‘0’ in a binary system); while ‘bifurcated’ refers to differentiation that sets different obligations or processes for each category.

26 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’, UN Doc. FCCC/CP/2010/7/Add.1, 15 Mar. 2011, para. 102.

27 Paris Agreement, Paris (France), 13 Dec. 2015, not yet in force (in UNFCCC Secretariat, Report of the Conference of the Parties on its Twenty-First Session, Addendum, UN Doc. FCCC/CP/2015/10/Add.1, 29 Jan. 2016).

28 Decision 1/CP.17, ‘Establishment of an Ad Hoc Working Group on the Durban Platform for Enhanced Action’, UN Doc. FCCC/CP/2011/9/Add.1, 15 Mar. 2012, para 2.

29 Ibid., paras 6 and 7.

30 The negotiations during the second commitment period of the Kyoto Protocol, the Bali Action Plan (Decision 1/CP.13, UN Doc. FCCC/CP/2007/6/Add.1, 14 Mar. 2008) and the conditionalities expressed in the Copenhagen pledges clearly illustrate this point.

31 Voigt, n. 5 above, p. 50; and Ulfstein & Voigt, n. 8 above, p. 191.

32 Winkler, H. & Rajamani, L., ‘CBDR&RC in a Regime Applicable to All’ (2013) 14(1) Climate Policy, pp. 102121 CrossRefGoogle Scholar, at 103.

33 Bodansky, D., ‘Reflections on the Paris Conference’, Opinio Juris, 15 Dec. 2015, available at: Google Scholar.

34 Brazil was not the only country to propose specific concepts to address differentiation. Other proposals included New Zealand’s ‘bounded flexibility’ and Switzerland’s ‘circumstance-based’ proposal: see the submissions available at: http://

35 The Copenhagen Accord established ‘targets’ for Annex I Parties and ‘actions’ for developing countries, while the Cancun Agreements further elaborated this by requesting developed countries to raise the ambition of their ‘quantified economy-wide emission reduction targets’, and developing countries to put forward their ‘nationally appropriate mitigation actions’ (NAMAs).

36 The image of the concentric circles may also have originated through some subconscious process – the COP-20 logo consisted of several concentric circles, the seats at the main plenary in Bonn (the former German Parliament) are also roughly arranged in circles, causing ADP co-chair Kishan Kumarsingh to joke that ‘we are now seeing circles everywhere!’.

37 Decision 1/CP.20, ‘Lima Call for Climate Action’, UN Doc. FCCC/CP/2014/10/Add.1, 2 Feb. 2015.

38 White House, Office of the Press Secretary, ‘U.S.-China Joint Announcement on Climate Change’, Beijing (China), 12 Nov. 2014, available at:

39 ‘Practical application of differentiation will vary depending on the element of the agreement (mitigation, adaptation, support, transparency)’: First Informal Ministerial Consultations to Prepare COP21, Paris (France), 20–21 July 2015: Aide-Mémoire Produced by France and Peru, Paris (France), 31 July 2015, available at:

40 See the handout by the facilitator of the informal meeting on ‘differentiation’ for the facilitated group on mitigation: Annex I of ADP 2.10 Working Document (version of 8 Sept. 2015 at 18:00h), available at:

41 Paris Agreement, n. 27 above, Annex, Preamble, para. 3.

42 Ibid., Annex, Art. 2.2.

43 It is worth noting that the category ‘economies in transition’ is not referred to in any provision of the Agreement or the accompanying decision. This is clearly an example of how differentiation can evolve in response to changing circumstances – countries that formerly belonged to the Soviet Republic are now either part of the European Union or identify themselves as developing countries, with the exception of the Russian Federation, of course, which stands in a category of its own.

44 Paris Agreement, n. 27 above, Annex, Art. 2.2.

45 Rajamani, L., ‘Differentiation in a 2015 Climate Agreement’, Center for Climate and Energy Solutions (C2ES) Papers, June 2015, p. 2 Google Scholar, available at:

46 Winkler, H. et al., ‘What Factors Influence Mitigation Capacity’ (2007) 35(1) Energy Policy, pp. 692703 CrossRefGoogle Scholar.

47 The Agreement serves to ‘enhance the implementation of the Convention’ (Art. 2.1), which allows for the interpretation that the terms of the UNFCCC are not ‘set in stone’, but that the UNFCCC is a living document; it is not ‘static’ in its content but is rather, by further implementation of the Paris Agreement, evolutionary.

48 See also Deleuil, T., ‘The Common but Differentiated Responsibilities Principles: Changes in Continuity after the Durban Conference of the Parties’ (2012) 3(21) Review of European Community and International Environmental Law, pp. 271281 CrossRefGoogle Scholar.

49 Legally binding obligations for all parties are contained in Paris Agreement, n. 27 above, Arts 4.2, 4.3, 4.8, 4.9, 4.13, 7.1, 13.7.

50 See, e.g., Voigt, C., ‘The Paris Agreement: What is the Standard of Conduct for Parties?’, Questions of International Law, 24 Mar. 2016 Google Scholar, available at:; and Voigt, C., ‘The Potential Roles of the ICJ in Climate Change-related Claims’, in D. Farber & M. Peeters (eds), Climate Change Law (Edward Elgar, 2016), pp. 152166 Google Scholar, at 159–61.

51 See, e.g., the first report of the International Law Association (ILA) Study Group on Due Diligence: D. French (Chair) & T. Stephens (Rapporteur), ‘Due Diligence in International Law’, 7 Mar. 2014; available at:

52 See, e.g., the CAIT Equity Explorer, by the World Resources Institute (WRI), available at:; and the methodology of the Climate Action Tracker, by Ecofys and Climate Analytics, available at:

53 Cf. the language in Art. 4.3 and 4.4 with para. 20 of the ‘Geneva Negotiating Text’ (UN Doc. FCCC/ADP/2015/1, 25 Feb. 2015), proposed by Norway in ADP 2.8, Geneva (Switzerland), 8–13 Feb. 2015; paras 8 and 11 of the 20th BASIC Ministerial Meeting on Climate Change Joint Statement (New York, NY (US), 27–28 June 2015, available at:; as well as para. 5 of the China–France Joint Presidential Statement on Climate Change (Beijing (China), 2 Nov. 2015, available at:

54 Art. 7.13, nevertheless, contains an indirect reference to developed countries, in the context of support.

55 To this end, Decision 1/CP.21 establishes a ‘capacity-building initiative for transparency’ to support developing countries in meeting enhanced transparency requirements: Decision 1/CP.21, ‘Adoption of the Paris Agreement’, UN Doc. FCCC/CP/2015/10/Add.1, 29 Jan. 2016, paras 85–89.

56 Decision 1/CP.21, ibid., para. 90.

57 Axelrod, R., The Evolution of Cooperation (Basic Books, 1984), pp. 135147 Google Scholar, and Ch. 9, pp. 169–91, at 177.

58 Ibid.