There is a decision by the German constitutional court dated 24. March 2021 (1 BvR 2656/18 - https://www.bundesverfassungsgericht.de/SharedDocs/Downloads/DE/2021/03/rs20210324_1bvr265618.pdf).

It states that the German constitution obliges the government to "to protect the climate. This also aims at achieving climate neutrality. [...] b) If there is scientific uncertainty about environmentally relevant causal relationships, the special duty of care imposed on the legislature by Article 20a of the Constitution, also for the benefit of future generations, includes taking into account already reliable indications of the possibility of serious or irreversible damage.

c) As a climate protection requirement, Article 20a of the Constitution has an international dimension. The national obligation to protect the climate is not contradicted by the fact that the global nature of the climate and global warming precludes any one state from solving the problems of climate change on its own. The climate protection requirement demands that the state take internationally oriented action to protect the global climate and obliges it to work towards climate protection within the framework of international coordination. The state cannot shirk its responsibility by pointing to greenhouse gas emissions in other countries.

d) In fulfilling its mandate and prerogative to specify, the legislature has currently defined the climate protection goal of Article 20a of the Basic Law in a manner that is constitutionally permissible, namely that the rise in global average temperature must be limited to well below 2 °C and, if possible, to 1.5 °C above pre-industrial levels."

Further, there is the decision of the European court of Human Right dated 9 April 2024 in the CASE OF VEREIN KLIMASENIORINNEN SCHWEIZ AND OTHERS v. SWITZERLAND (https://hudoc.echr.coe.int/eng?i=001-233206). It (inter alia) states:

450. However, this does not exclude the possibility that where complaints raised before the Court relate to State policy with respect to an issue affecting the Convention rights of an individual or group of individuals, this subject matter is no longer merely an issue of politics or policy but also a matter of law having a bearing on the interpretation and application of the Convention. In such instances, the Court retains competence, albeit with substantial deference to the domestic policy-maker and the measures resulting from the democratic process concerned and/or the judicial review by the domestic courts. Accordingly, the margin of appreciation for the domestic authorities is not unlimited and goes hand in hand with a European supervision by the Court, which must be satisfied that the effects produced by the impugned national measures were compatible with the Convention.

451. It follows from the above considerations that the Court’s competence in the context of climate-change litigation cannot, as a matter of principle, be excluded. Indeed, given the necessity of addressing the urgent threat posed by climate change, and bearing in mind the general acceptance that climate change is a common concern of humankind (see paragraphs 420 and 436 above), there is force in the argument put forward by the UN Special Rapporteurs that the question is no longer whether, but how, human rights courts should address the impacts of environmental harms on the enjoyment of human rights (see paragraph 379 above).

Cf also: https://en.wikipedia.org/wiki/Urgenda_Foundation_v_State_of_the_Netherlands

ECHR: Verein KlimaSeniorinnen Schweiz v. Switzerland