Following some pushback, the European Commission postponed the release of the EU’s 2040 emission reduction target and appears to consider weakening the proposed 90% emission reduction as compared to 1990. However, weakening the EU’s ambition is not compatible with the European Convention on Human Rights (ECHR).
This blogpost explains why the European Court of Human Rights (ECtHR)’s ruling in KlimaSeniorinnenread in light of the report of the European Scientific Advisory Board for Climate Change (ESABCC) requires the EU to reduce emissions domestically, i.e. on its territory, as quickly as possible but at least by 90% in 2040. In addition, the Bosphorus presumption that would shield the EU and its Member States from strict review in Strasbourg is not applicable to climate litigation challenging emission reduction targets of the Member States. As a consequence, weakening the EU 2040 target would expose the EU Member States to human rights challenges before the ECtHR and national courts.
Climate Obligations post KlimaSeniorinnen
KlimaSeniorinnen requires Contracting Parties to quantify a fair share domestic carbon budget (KS, para 550(a)). This means that they have to explicate what part of the remaining global carbon budget associated with the long-term temperature limit (LTTL) of 1.5°C they appropriate themselves. The LTTL was legally agreed under the Paris Agreement and narrowed down to 1.5°C by the Glasgow Climate Pact. Numerous courts in Europe, including in Klimaatzaak, KlimaSeniorinnen, or Milieudefensie v Royal Dutch Shell, confirmed 1.5°C to be the LTTL.
Importantly, the ECtHR held that states have only “a reduced margin of appreciation” (KS, para 543) in relation to the objective of keeping global warming below the LTTL. This is hence an obligation that is subject to restrained political appraisal and more stringent judicial review than other obligations under the Convention (see, e.g., Eckes, 2025b; Savaresi, 2025; ECHR mechanism supervising the execution of judgements).
The Court further laid out that, in order to be Paris-aligned, the national carbon budget has to comply with fairness and equity principles, such as the ‘Common But Differentiated Responsibilities and Respective Capabilities’ (CBDR-RC) principle (KS, paras 455-6). This is also supported by numerous other considerations, such as that each state has an obligation “to do its part” (para 545) and that “even an ‘equal per capita’ quantification” would be insufficient (para 569). The ECtHR refers to the German Federal Constitutional Court’s ruling in Neubauer when acknowledging the lack of agreement on the precise quantification methods and concluding that this lack does not stand in the way of demanding “states to act on the basis of equity and in accordance with their own respective capabilities” (KS, para 571). In addition to the fair share carbon budget quantification, a binding regulatory framework has to be adopted and adequately implemented in order to stay within this budget (para 549).
In relation to Switzerland, the Court makes clear that quantifying a fair share domestic carbon budget cannot be compensated by reference to nationally determined contributions (NDCs) submitted under the Paris Agreement or reliance on an implicit budget that is derived from its targets (KS, para 570). Targets need to be set based on a fair share budget, not the other way around. This makes sense scientifically. Cumulative emissions determine the contribution to warming, not the level of emissions at some point in time. So, it is only when targets are based on a share of the remaining carbon budget that collective actions by all states can suffice to remain under the overall limit of 1.5C.
In line with KlimaSeniorinnen, it is thus not sufficient to have – as Switzerland had and as the EU has – a net zero target for 2050 and a pathway towards that target. Nor is it sufficient to rely on an implicit domestic carbon budget flowing from NDCs. In short, what is required is an explicit quantification of a domestic fair share carbon budget and the adoption and implementation of a binding regulatory framework for emission reduction.
Application to the European Union
Based on the above, the central question addressed in this blog post is: What does this obligation mean for the European Union and its debate about the 2040 emission reduction target?
The ESABCC is the EU’s scientific advisory body established by law (Art 10a Regulation on the European Environment Agency and the European Environment Information and Observation Network) and charged with the task of providing the EU with up-to-date scientific knowledge, expertise and advice relating to climate change (Art 3(2) ECL). In June 2023, the ESABCC published a report on the EU’s 2040 target and its carbon budget for 2030-2050. As a first step, the ESABCC determined fair share carbon budgets based on a variety of fairness interpretations that are in line with legal principles enshrined in both international law and the EU Treaties (p. 28). It subsequently determined feasible emission reduction pathways towards the 2050 net zero target codified in law (pp. 43-45). By comparing the fair share budgets with the cumulative emissions that would result from the feasible reduction pathways the ESABCC concluded that even under the most ambitious pathway, cumulative emissions will be higher than the most lenient interpretation of a fair share budgets (pp. 47-48).
Based on this analysis the ESABSS concluded that in order for the EU’s contribution to achieving the objectives of the Paris Agreement, namely to reduce emissions in a way that is both fair and consistent with climate science, the EU should aim for the highest level of ambition in domestic emission reductions and compensate for the shortfall between feasible domestic emission reductions and its fair share through contributions to emission reductions outside of the EU (p. 15). Consequently, the ESABCC recommended keeping the EU’s greenhouse gas emissions budget within a limit of 11 to 14 Gt CO2e between 2030 and 2050, which requires emission reductions of 90–95% by 2040 (p. 10). In addition, the ESABCC pointed out in this context that increasing the 2030 target from the current 55% towards the feasible level of 70% would considerably decrease the EU’s cumulative emissions until 2050, thus increasing the fairness of the EU’s contribution to global mitigation.
When (non-majoritarian) expert bodies like the ESABCC give policy recommendations that are based on fairness considerations, the question arises whether they act within the legal boundaries of their competences. The ESABCC’s legal tasks are: “providing scientific advice and issuing reports on existing and proposed Union measures, climate targets and indicative greenhouse gas budgets, and their coherence with the objectives of this Regulation and the Union’s international commitments under the Paris Agreement” (Art 3(2)(b) ECL, emphasis added). In other words, the ESABCC does not only have the mandate to give scientific advice on targets, i.e., how to reach net zero in 2050, but also on budgets and assess them in light of the objectives of the European Climate Law and the Paris Agreement. First, the ESABCC could not speak to an “EU budget” without considering what the EU’s fair share is of the global carbon budget associated with the 1.5°C LTTL. Second, the reference to the Paris Agreement requires the ESABCC to consider the equity principles in that agreement, including CBDR-RC in its advice. Fairness considerations are hence explicitly required by law and necessarily entail distributive consequences.
KlimaSeniorinnen, as outlined above, demands from the ECHR’s Contracting Parties that they do precisely what the ESABCC does in its report on the 2040 target – to quantify a fair share carbon budget that is in line with the LTTL of 1.5°C and to explicate the fairness considerations on which the quantification is based. These considerations must allow a reasonable claim of alignment with the fairness principles under the UNFCCC and the Paris Agreement.
An EU-wide 2040 Target below 90% is not Compliant with Human Rights
The ECHR, as interpreted in KlimaSeniorinnen, requires the quantification of a fair share carbon budget and the regulatory and implementation measures to stay within this budget. The EU has set up the ESABCC to advise on climate matters. Within its legal mandate and based on an assessment of more than 1,000 scenarios, the ESABCC has explicated that a 90% emission reduction by 2040 is not only feasible but also the bare minimum for domestic emission reductions. A minimum that, however, in and of itself does not meet the yardstick of fairness, rather, it would have to be supplemented with contributions to emission reductions outside the EU to remain even within its most lenient fair share budget. In other words, without such contributions – which are even still insufficient at this moment – the EU’s climate policies are incompatible with the ECHR in light of KlimaSeniorinnen and the advice of the ESABCC.
No Deference as Bosporus does not apply
The EU should not just want to comply with the ECHR for political reasons, but also because of the potential legal consequences. If the EU ignored KlimaSeniorinnen, national courts and the ECtHR, if prompted by litigants, would likely be obliged to review the Convention compliance of national climate policies giving effect to EU law.
As is well-known, the EU is not (yet) a Contracting Party to the ECHR; yet, it is bound by the ECHR by virtue of Article 6(3) TEU, which declares the ECHR to form part of the EU’s general principles. The core difference between being directly bound by the ECHR as a Contracting Party and being bound by the ECHR as general principles of EU law is that the European Court of Justice (ECJ) is the interpretative authority what these general principles mean. The EU is hence only bound to the ECHR as part of a legal obligation that is interpreted by the ECJ and not directly by the case law of the ECtHR (Eckes, 2013). In addition, the European Charter of Fundamental Rights (CFR) requires the ECJ to interpret CFR rights that correspond to the ECHR “the same as those” in the Convention (Art 52(3) CFR – no mention of the (case law of the) ECtHR). The ECJ hence establishes what these norms require from the EU institutions and the Member States in terms of human rights protection, and it usually does so in line with the ECtHR’s case law (Tinière, 2023; Krommendijk, 2015). However, the argument of this post does not focus on the direct or indirect bindingness of the ECHR on the EU, but rather considers the legal consequences for the EU, if the ECtHR and national courts are asked to review national climate policies giving effect to EU climate policies that do not meet the requirements of the ECHR.
So far, the ECtHR and the ECJ have demonstrated considerable deference towards each other. However, in the present context of climate mitigation obligations, the EU and the Member States may not be able to count on the ECtHR’s deference as developed in its settled case law starting with Bosphorus (see also: Michaud and case law below). This creates a compelling legal reason for the EU’s political institutions and the ECJ to avoid any such potential conflicts.
The Bosphorus doctrine protects international cooperation by presuming compliance with the Convention when states give effect to their obligations via an international organisation “as long as the relevant organisation is considered to protect fundamental rights, as regards both the substantive guarantees offered and the mechanisms controlling their observance, in a manner which can be considered at least equivalent to that for which the Convention provides” (Bosphorus, para 155, emphasis added; see also Rizcallah, 2023). The ECtHR generally confirms such equivalence for the EU and refrains from reviewing Member States’ actions when implementing EU law. However, as the below arguments show, this doctrine does not apply in general emission reduction cases.
First, Bosporus does not apply to cases where Member States exercise discretion under EU law (M.S.S., para 338). They remain fully responsible for discretionary acts under the Convention and the ECtHR carries out an in-depth review (Moslims van België and Others; M.B.; Satakunnan Markkinapörssi Oy and Satamedia Oy). All relevant emission reduction measures (European Climate Law (ECL); Emission Trading System Directive; Effort Sharing Regulation) are adopted on the basis of Article 192 TFEU (or its predecessor Article 175 EC), which, according to Article 193 TFEU and the relevant secondary law instruments, expressly allows Member States to adopt and implement more ambitious targets and policies than those required under EU law (Eckes, 2025a; see also: Dutch Supreme Ct, Urgenda, para 54). As all EU emission reduction measures require only minimum harmonisation, this constrains Member States even less than provisions of secondary EU law that grant firmly circumscribed discretion (as in M.S.S.). Hence, logically, applying the Bosphorus doctrine to EU emission reduction measures should be excluded on even stronger grounds. Also from a human rights perspective, this seems to be the only defendable conclusion, since, by contrast with situations where Member States implement EU law with discretion, the CFR is not directly applicable to Member State action under minimum harmonisation (Terveys; Eckes, 2025a; see also: Král and Mádr, 2021).Thus, if Bosphorus were applied, those whose fundamental rights are infringed by an act of a Member State giving effect to an EU instrument of minimum harmonisation would be left without human rights protection as neither the CFR nor the ECHR would be (fully) applicable.
Second, in mitigation cases the excluding condition of “manifestly insufficient human rights protection” is met, both in terms of (1) “substantive guarantees” and (2) the “mechanism controlling the observance” (Bosphorus, para 155). This leads also in and of itself to a rebuttal of the Bosphorus presumption. (1) As demonstrated above, the EU’s current climate targets and policies (without additional funding of emission reductions abroad) do not meet the fairness standard developed in KlimaSeniorinnen and concretised by the ESABCC. (2) Accessible domestic remedies to challenge inadequate EU emission reduction policies in Luxembourg are structurally missing because of the restrictive interpretation of the standing requirements for individual applicants (Carvalho; Winter, 2023; Eckes, 2025a). Thus, in certain contexts, this lack of remedies in Luxemburg combined with a lack of effective judicial remedies for challenging climate (in)action in some Member States (such as in Austria (see Prantl, 2024), Spain, Czech Republic and Italy, where national courts disallowed challenges because of EU law (Eckes, 2025a)) would in the worst case result in a denial of justice, especially if the ECtHR applied the Bosphorus presumption and also denied (full) review.
Third, prior case law of the ECtHR establishes that, even without discretion of the defendant EU Member State, the Bosphorus presumption only applies if the “the full potential of the supervisory mechanism provided for by [EU] law” has been deployed (Bivolaru and Moldovan, paras 98 et seq; see also: Ronkes Angerbeek, 2024). Hence, the Bosphorus presumption is also excluded where the EU Courts have not been given the opportunity to review climate (in)action – because no reference was made or even possible (e.g., because the national legal system did not offer an adequate procedure (as e.g., in Austria, see Prantl, 2024)).
States thus likely cannot hide behind Bosphorus in Strasbourg when mitigation targets and policies are challenged and the potential review by the ECtHR puts pressure on the ECJ and national courts to ensure ECHR compliance in their respective legal layers. The ECJ should therefore “wish to ensure that the EU offers at least as much protection as the Convention” (Ronkes Angerbeek, 2024). Moreover, national courts cannot refrain from examining a well-founded complaint on the sole ground that the state in question is applying EU law, they will have to review Convention compliance (Michaud, para 116). Pending cases before the ECtHR, such as Max Müllner, where the climate policy of an EU Member State is challenged, may soon bring the relationship between the ECHR, national, and EU law to the test.
It is the Primary Duty of Politics to Take Account of Human Rights!
Pressure from a potential review by the Strasbourg Court should influence the positions of the ECJ and national courts, but more importantly also the efforts of EU political institutions to ensure Convention compliance when adopting climate targets and policies. Ensuring such compliance from the outset, rather than waiting for courts to step in would be a real contribution to avoid the fault lines that are emerging between the political (majoritarian) institutions of the EU and the Member States, on the one hand, and the respective judiciaries, on the other.
The EU’s political institutions are in the process of setting the 2040 emission reduction target. For the reasons set out in this blogpost, they should keep the requirements of KlimaSeniorinnen in mind. If they don’t, they should not be surprised if courts again draw boundaries of lawful climate action – as they did earlier in Urgenda, Neubauer, L’ Affaire du Siècle; Grand Synthe, Klimaatzaak, KlimaSeniorinnen.
Christina Eckes is Professor of European Law at the University of Amsterdam and Principal Investigator of the ERC research project ‘Strategic Climate Litigation’s Direct and Indirect Consequences for Democracies’ (https://climatelitigation.uva.nl/).