In December 2024, the International Court of Justice held its hearings on the advisory opinion on climate change. Many states, international organizations and NGOs submitted written statements and provided oral pleadings explaining their views about international climate change law. Probably never before, the ICJ could draw from as much legal expertise as basis for its decision. Thus, it may seem that all the issues have been raised, all arguments have been exchanged. It’s time to wait for the ICJ to render its opinion.
We suggest, however, that the proceedings brought some clarity into a key aspect of the obligation of progression under the Paris Agreement: State parties are under a legal obligation to enhance their national determined contributions at least every five years. They are legally obliged to become more ambitious with their mitigation efforts when communicating their successive NDCs. While this view has been advanced in the literature, it has not been uncontroversial. The proceedings now show that states accept this reading of the Paris Agreement.
a) Beyond Due Diligence
This issue has not received any attention in the many recent posts on the proceedings. The scholarly debate on the interpretation of Article 4 of the Paris Agreement often focuses on the duty of due diligence in international climate change law. Because the scope of this concept is not entirely clear, the General Assembly explicitly asked the International Court of Justice to address due diligence in its advisory opinion.
The focus on the duty of due diligence, however, has put a relevant issue to the side. Are states allowed to downgrade emissions goals when they communicate new national determined contributions? In the past, some observers suggested that the Paris Agreement provides space for such an understanding. States would be incentivized to withdraw from the agreement if they do not have the opportunity to lower their climate protection goals.
However, as this blogpost argues this view is not tenable. First, already the language and context of Article 4 (3) of the Paris Agreement speak against such an understanding (b.). Second, as the position of States presented at the December proceedings demonstrate, the Paris Agreement contains the obligation to progressively enhance the climate change commitments at least every five years (c). The proceedings made the consensus against downgrading manifest (d.).
b) The ‘will’ and legal bindingness
The obligation of progression finds its normative basis in several paragraphs of Article 4 of the Paris Agreement. Article 4 (2) obliges each Party to prepare, communicate and maintain successive nationally determined contributions which must be done every five years (Article 4 (9)). Article 4 (3) then adds a qualitative obligation of progression by providing that: ‘Each Party’s successive nationally determined contribution will represent a progression [emphasis added by the authors] beyond the Party’s then current nationally determined contribution and reflect its highest possible ambition, reflecting its common but differentiated responsibilities and respective capabilities, in the light of different national circumstances.’ Art. 4 (11) stipulates that each state party ‘may at any time adjust its existing nationally determined contribution with a view to enhancing its level of ambition…’. Taken together these paragraphs imply that states are under a legal obligation to enhance their temperature goals.
Some sceptics, however, treat the ‘will’ in Article 4 (3) as an indicator for a mere ‘soft law’ character of the provision. Because the term ‘shall’ was negotiated out of Article 4 (3) at the Paris conference, there would exist no legal obligation of progression.
This argument is based on a mistaken understanding of the term ‘will’. While the term does not necessarily imply legal bindingness, it is also no general indicator for non-bindingness. In fact, provisions in other treaties create legal obligations even though they use ‘will’. See for instance, the 1949 North Atlantic Treaty. Article 5 stipulates:
‘The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that,… if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognised by Article 51 of the Charter of the United Nations, will assist [emphasis added by the authors] the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.’
Although the provision employs the terms ‘will assist’, Article 5 is commonly understood as stipulating a legal duty of mutual assistance for each member of the North Atlantic Treaty Organization. To treat Art. 5 as ‘soft law’ seems absurd. In this light, pointing to the ‘will’ as the key counterargument against a legal obligation of progression is not convincing.
c) The December Proceedings
The December proceedings provide ample evidence that states assume that the ‘will’ has normative character. During the proceedings, the ICJ offered state parties the opportunity to respond to written questions from ICJ judges. The question by Judge Dire Tladi (p. 40) concerned the normative content of Article 4 of the Paris Agreement: ‘… I would like to know from the participants whether, according to them, “the object and purpose” of the Paris Agreement, and the object and purpose of the climate change treaty framework in general, has any effect on th[e] interpretation [of Article 4 as a procedural obligation] and if so, what effect does it have?’
In their replies, many states highlight that each state party is legally obliged to raise the level of ambition. The African Union emphasizes that Article 4 ‘is far more than a procedural mechanism’ but ‘imposes binding obligations of conduct that require states to undertake substantive efforts toward mitigation’ (para. 37). Against this background, the AU holds that ‘Article 4(3) […] reinforces the principle of progression, mandating that NDCs reflect each state’s “highest possible ambition” and represent a clear advancement beyond previous contributions […]’ (para. 40). Chile underscores that the NDCs ‘need to represent a progression between one and the next’ (para. 11), while the European Union emphasizes that under Article 4 (3) ‘the successive NDCs must [emphasis added] represent a “progression beyond the Party’s then current nationally determined contribution’’ (p. 7). Similar statements were made by the United Kingdom (para. 6), Germany (p. 2), the Philippines (p. 13, para. 10), Colombia (pp. 6-7, para. 3), the Democratic Republic of Congo (para. 19) and Kenya (paras. 41-42).
While some states take the view that Article 4 contains primarily procedural obligations, they, nonetheless, use language insinuating an obligation of progression. According to Mexico ‘Article 4, paragraphs 2 and 3 of the Paris Agreement outlines procedural obligations’ (para. 9). But these obligations ‘must be interpreted as aiming to promote substantive outcomes’ and ‘are designed to ensure progress toward the Agreement‘s goals’ (para. 10) (see similar statements by Vanuatu (p. 21, para. 8), Switzerland (para. 8) and the Organisation of African, Caribbean and Pacific States (p. 6, para. 5)).
In any case, the obligation of progression was not put into question. Saudi-Arabia (para. 2.5) and China (paras. 11, 13), for example, quote Article 4 (3) without criticizing the above-mentioned understanding by the majority (see also India during the written phase of the proceedings). While Canada (p. 3) and the US (p. 5) suggest that Art. 4 (3) of the Paris Agreement would have no legal character, this is meant to underscore the discretion to determine national contributions in the first place. Neither Canada and the US claim that states are under no legal obligation to enhance their successive NDCs. Instead Canada highlights the ‘the importance, in Article 4, paragraph 3, of ratcheting up ambition for climate action’ (p. 3).
d) Consensus Against Downgrading
The statements made during the proceedings reflect a consensus against downgrading. But how should these statements be treated from the perspective of the sources doctrine under Article 38 of the ICJ Statute?
At least when it comes to disputes between two states, the ICJ should be wary to give too much weight to statements in a proceeding. Written and oral pleadings are designed to win the case at hand. They may not even represent the position taken by the states prior to the proceedings. It is, therefore, questionable whether such statements can be understood to reflect ‘conduct in the application of a treaty’ (Conclusion 4, International Law Commission) and thus ‘subsequent practice’ under article 31, paragraph 3 (b) Vienna Convention on the Law of Treaties.
Nevertheless, in an advisory proceeding, responses to the more abstract legal questions can be seen as serious attempts to find the ‘proper’ interpretation of the obligations. States make general statements about their understanding of the legal obligations. Of course, they will align their statements with their respective political and economic interests, also in an advisory proceeding. But if a consistent interpretation of a particular norm comes to the fore, it tells us something. States agree that emissions targets under the Paris Agreement are to be progressively developed. States take the ‘object and purpose’ of the Paris Agreement seriously.
The proceedings thus show: current NDCs present the floor for future NDCs. States are under a legal obligation to become more ambitious. With a new round of NDCs due this year and calls from the UN Climate Change Secretariat for more ambitious goals, state parties to the Paris Agreement must enhance their mitigation commitments.
