Taking into account the current draft version of the EU Climate Framework Regulation of 5 November 2025
1. Introduction
The report by the German Advisory Council on the Environment (SRU) dated 15 October 2025 bases far-reaching constitutional demands on the adoption of a binding German CO₂ residual budget. It refers to the climate ruling of the Federal Constitutional Court (BVerfG) of 24 March 2021 (1 BvR 2656/18 et al.) and places the concept of a national residual budget at the centre of climate policy legislation. This statement shows that the approach advocated by the SRU of a binding national CO₂ residual budget is not legally or climatically viable. It highlights the methodological and normative weaknesses of a one-sided focus on national CO₂ budgets.
2. Misinterpretation of the constitutional requirements for CO₂ budgets
The Federal Constitutional Court’s climate ruling expressly did not establish the concept of a national CO₂ residual budget as a legally binding quantity. The budget values used serve merely as guidelines for ensuring intertemporal freedom – expressly subject to scientific uncertainties and EU legal, political and technological contextual factors (BVerfG Rn. 210, 213). The SRU’s attempt to derive a binding national quantitative commitment from this ignores the uncertainties highlighted in the decision and therefore does not require an independent national budget to be set, but rather clearly links German climate policy to the EU’s regulatory architecture.
3. Priority of the EU climate framework architecture
Under the current and future EU climate framework, German climate policy must be governed within an overall European architecture that can be regarded as a regulated greenhouse gas or CO₂ budget. The EU Climate Law and the revised target mechanisms in the Council’s “General Approach” of 5 November 2025 define binding, quantity-based emission limits at EU level.
The EU has set itself the legally binding target of becoming climate neutral by 2050. This target implies that only a limited volume of greenhouse gases, in particular CO₂, can be emitted. The specific figures are set out in the legislative package implementing the European Green Deal:
- The EU ETS 1 for industry, energy and now maritime transport, which has been in place since 2005, covers around 40% of European CO₂ emissions.
- The EU ETS 2 for transport and buildings, which will apply from 2028, will cover a further 40% or so, meaning that by the end of the decade, a good 80% of European CO₂ emissions are expected to be subject to a quantity-regulated emissions trading system.
- The remaining greenhouse gas and CO₂ emissions fall under the Effort Sharing Regulation (ESR), which obliges Member States to reduce emissions in sectors not covered by the ETS and opens up cross-sectoral flexibility with the new General Approach.
The ESR currently only applies until 2030, but following the adoption of the new EU climate target for 2040 in November 2025 by the Council and the European Parliament, it can be assumed that the ESR will be extended accordingly until 2040 and that its validity will likely be considered until 2050, the target year for European climate neutrality.
The result is a comprehensive European greenhouse gas or CO₂ budget until climate neutrality is achieved in 2050, the scope of which can be derived from the aforementioned EU regulations. Against this backdrop, the question arises as to what independent added value an additional rigid national budget could still offer.
4. Methodological and scientific uncertainty of CO₂ budgets
Model-based calculations of CO₂ residual budgets are very sensitive to assumptions about climate sensitivity, aerosols, future sink capacities and feedback effects, for example. The IPCC and the Federal Environment Agency expressly warn against the apparent accuracy of such calculations and emphasise that residual budgets are inevitably rough estimates that can change substantially as scientific knowledge progresses.
The Expert Council for Climate Issues also sees considerable risks of missing targets for the period after 2030. A rigid national budget model does not do justice to this systemic uncertainty; politically and legally, therefore, an adaptive, revisable mechanism is preferable, as the EU is already striving for in its institutional structures.
5. Germany’s low global emissions impact and the importance of international cooperation
The immediate climate impact of isolated German emission reductions is marginal on a global scale. Analyses by Ockenfels and Rostalski (2024) and the IPCC show that large emitters such as China and the USA dominate global emission dynamics. For climate policy to be truly effective, it is therefore crucial that it be embedded in international mechanisms – in particular the NDC (Nationally Determined Contribution) system and the cooperation mechanisms under Article 6 of the Paris Agreement.
National solo efforts primarily have a symbolic effect, but do not make a substantial contribution to global temperature limitation. From a constitutional perspective, it is more important that Germany contributes to the fulfilment of international objectives through ambitious contributions in the form of technology transfer and cooperation architecture.
6. Criticism of the SRU’s per capita approach
The per capita approach proposed by the SRU for determining national residual budgets is based on specific assumptions of equality and is not supported by international law. In UNFCCC practice and EU law, differentiated mixed models are used instead, which take into account common but differentiated responsibilities, economic capacity and technological maturity. The SRU largely ignores this differentiated view.
In its climate legislation, the EU places particular emphasis on economic efficiency, technological openness and sectoral compensation mechanisms rather than flat-rate per capita allocations; in both the international and EU legal contexts, the SRU approach is thus confirmed as alien to the system.
7. Assessment of the amendments to the Climate Protection Act (KSG) and integration into the EU framework
The 2021 and 2024 amendments to the KSG significantly raise Germany’s level of ambition and effectively adapt the regulatory framework. The targets of climate neutrality by 2045 and a reduction in emissions of at least 65% by 2030 not only comply with EU law requirements, but exceed them and thus go beyond the requirements of the Federal Constitutional Court’s climate ruling of 2021. The increased level of protection created by the KSG 2021 – which is not required by constitutional law – remains unaffected by the KSG amendment of 2024. The 2024 amendment optimises the control mechanism, removes rigid sectoral requirements and focuses more on technology-neutral, economically efficient emission reductions in line with the EU architecture.
The new system also corresponds to the architecture of flexibility, cross-sectoral target optimisation and industrial policy integration laid out in the EU’s General Approach.
The criticism levelled by the SRU therefore fails to recognise the actual compatibility with European control mechanisms.
8. The new EU approach strengthens revisable law
Climate models are probabilistic tools and involve considerable uncertainty in terms of temperature projections and budget calculations. In its Sixth Assessment Report (AR6), the IPCC emphasises the need for emission budgets to be subject to revision.
The EU is translating this scientific uncertainty, which is also recognised by the IPCC, into political law by institutionalising regular reassessments by the Commission, flexible cross-sectoral mechanisms and adjustment procedures. This enables a dynamic and resilient climate architecture that overcomes rigid national quantity restrictions in favour of adaptive control.
9. Special international responsibility
According to analyses by the UNFCCC and leading climate research institutes, the NDCs agreed to date are not sufficient to stay within the 1.5-degree pathway or even the 2-degree limit. International coordination and the use of Article 6 and now also EU cooperation mechanisms are therefore of central importance under constitutional law.
Germany’s responsibility must be understood as part of a cooperative, global climate strategy, not as an isolated national mission. The BVerfG’s ruling follows this logic and emphasises systemic, international and European legal obligations.
10. Conclusion: The unsustainability of national CO₂ budget concepts and impetus for dynamic climate policy
The SRU report is based on a conceptually and empirically outdated idea of climate control. In view of advancing scientific knowledge, European legal requirements and constitutional requirements, rigid national budget models are neither practicable nor resilient and do not provide a sufficient legal basis.
Developments in the EU and the amendments to the KSG reinforce the criticism of a fixed residual budget orientation and instead strengthen a flexible, revisable and internationally cooperative control architecture. This is the only way to achieve effective and legally viable climate protection.
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Grafik 1(siehe PDF-Dokument)
Sources
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