Science-based approach and INDCs

Legal assistance paper

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Date produced: 18/11/2014

If and to what extent does the process of submitting Intended Nationally Determined Contributions that reflect states’ voluntary efforts to address climate change conflict with the science-based approach under public international law?


The science-based approach under the UNFCCC does not affect the validity or political relevance of voluntary INDCs submitted by parties. However, it may raise certain concerns as to the credibility and consistency of the negotiation process under their general treaty obligations.


Science based approach

A “science-based approach” can be broadly described as the incorporation of scientific expertise and evaluation into decision-making processes that set goals and priorities, develop strategies, take action and measures etc. Requirements for ‘science-based’ decision-making are found in several international instruments including, for example: the WTO Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement), agreements dealing with regulation of hazardous chemicals, marine resources, ozone and industrial pollution, and threats to biodiversity. These regimes call for different standards of scientific proof to justify environmental inaction.

International trade law has emphasised the need for positive scientific evidence in order to establish risks justifying the introduction of trade measures. The use of expert opinions in the WTO GMO case has been highlighted as an example of science’s centrality in international environmental and health law. (1)

The ultimate objective of the UNFCCC is to stabilise emissions “at a level that would prevent dangerous anthropogenic interference with the climate system”. Access to the best available and timely scientific information is recognised as critical to the UNFCCC regime. The Convention obligates all Parties to “consider the best scientific evidence available” in decision-making. (2)

The main institutional channel for transmitting scientific input is through the SBSTA, whose mandate is to “provide the COP with timely information and advice on scientific and technological matters relating to the Convention”. It serves as a political negotiating forum on scientific and technical issues, serving as the “link between … assessments and … information provided by competent international bodies and the policy-oriented needs of the COP”. (3)

Decisions by the Conference of the Parties to the UNFCCC often refer to science (4) while SBSTA regularly underlines the importance of science in decisions and determining measures to combat climate change – most recently in the chair’s address to the ADP in Bonn in October 2014.

Thus, the most plausible interpretation of the science-based approach to international law as it pertains to the UNFCCC is an approach that obligates Parties to consider the best available scientific evidence in decision making processes. It calls for relevant scientific evidence to be distilled and summarised by the IPCC and fed into the policy process through negotiating bodies such as the SBSTA.

However, the science-based approach does not provide a substantive legal roadblock that could trump collective decisions by the COP/MOP that fail to align with the global 2-degree goal. It does not obligate Parties to preference scientific evidence over social, economic, cultural, or political factors.


In considering the legal framework for the process of submitting INDCs in the context of a ‘science based approach’, two elements are important: first, the extent to which the Convention requires the Parties to adopt such a science based approach in this context and (second) the general duty of good faith in the performance of treaty obligations under public international law.

In relation to the first element the extent to which the Convention requires a science based approach in this context, the starting point is Article 4(2)(d) of the Convention which requires the COP: “…at its first session, [to] review the adequacy of subparagraphs (a) and (b) above [relating to commitments of Annex 1 Parties]. Such review shall be carried out in the light of the best available scientific information and assessment on climate change and its impacts, as well as relevant technical, social and economic information.”

This indicates the importance of reliance on the best available scientific evidence by the Parties collectively in considering the mitigation actions of Annex I Parties, together with other relevant information. In determining the extent to which individual Parties are required to seek and rely on the best available scientific advice in drawing up INDCs it will be important to have regard to the capacity of non-Annex I states in this regard, but also to the extent to which the ability of the Parties collectively to review INDCs (by analogy with Article 4(2)(d) review but taking account of differing views as to the legal status of the contributions) is affected by the integrity of the scientific basis on which the assessment of the impact of national contributions has been conducted at national level.

Good faith

In relation to the second element, there is a general duty to act in good faith in the performance of treaty obligations expressed under Article 26 of the Vienna Convention on the Law of Treaties (VCLT): “Every treaty in force is binding upon the parties to it and must be performed by them in good faith.” Treaties must also be interpreted in good faith in accordance with Article 31(1) VCLT.

In submitting their INDCs, pursuant to COP Decision 1/CP19, the Parties are acting under the auspices of the UNFCCC. In the preamble to Decision 1/CP19, the Parties ‘underline’: “… the significant gap between the aggregate effect of Parties’ mitigation pledges in terms of global annual emissions of greenhouse gases by 2020 and aggregate emission pathways consistent with having a likely chance of holding the increase in global average temperature below 2 °C or 1.5 °C above pre-industrial levels,”

The Parties then affirm: “…that fulfilling the ultimate objective of the Convention will require strengthening the multilateral, rules-based regime and the urgent and sustained implementation of existing commitments under the Convention.”

The International Court of Justice has considered the scope of the duty of good faith in a number of cases. In its 1997 Gabcikovo Nagymaros judgment the Court held that: “Every treaty in force is binding upon the parties to it and must be performed by them in good faith. This latter element, in the Court’s view, implies that, in this case, it is the purpose of the Treaty, and the intentions of the parties in concluding it, which should prevail over its literal application. The principle of good faith obliges the parties to apply it in a reasonable way and in such a manner that its purpose can be realized.”

Thus the duty of good faith should be considered in the context of the overall goal set by Article 2 of the Convention and in the context of subsequent commitments made by the Parties in this regard. The submission of the INDCs including the scientific basis for the contributions made must be considered in the light of the realisation of the purpose of the Convention. Parties must act reasonably in this context in order to realise that purpose.


In relation to the process for submitting INDCs, it is thus arguable in my view that the duty to perform their obligations under the Convention in good faith requires parties to do the following:

  • To make all reasonable efforts to secure the best available scientific advice in setting goals and determining national contributions under the INDC process and in assessing the impact of proposed measures and policies, including by reference to GHG inventories, the understanding of mitigation potential and reference to GHG projections;
  • To have regard to the best available scientific advice in determining the level of ambition required in contributions to be made under the INDC process;
  • To incorporate scientific review as part of the process of drawing up contributions under the INDC process;
  • According to their capabilities, to offer support to other countries with more limited access to scientific expertise in this area and to respond to requests for support in preparing INDCs;
  • To explain the extent to which they have departed from scientific advice in the setting of goals or in assessing the impact of measures put forward as contributions in INDCs.

For example, it could be argued that a Party needs to quantify, on the basis of the best scientific evidence available to it, the GHG impact of its contribution in order to allow for effective assessment of the impact of its contribution on global emissions. Furthermore, for such an assessment to be done in good faith, a Party must be transparent about the scientific basis for the assessment and must explain any departure from scientific advice in this regard.

(1) cf. Jacqueline Peel, Science and Risk Regulation in International Law (Cambridge: Cambridge University Press, 2010), ch. 2.

(2) UNFCCC, Article 4(2)(c). For other formulations of this kind in environmental treaties, see Convention on the Conservation of Migratory Species of Wild Animals, Bonn, 23 June 1979, 1651 UNTS 333, in force 1 November 1983, Article III; Convention on the Conservation of Antarctic Marine Living Resources, Canberra, 5 May 1980, 1329 UNTS 48, in force 7 April 1982, Article IX(1)(f); Protocol on Environmental Protection to the Antarctic Treaty, Madrid, 4 October 1991, 30 ILM 1455 in force 14 January 1998, Article 10(1).

(3) FCCC/SBSTA/1996/6.

(4) For example 2/CP.17 Outcome of the work of the Ad Hoc Working Group on Long-term Cooperative Action under the Convention.