A number of climate change cases against States have meanwhile been decided by constitutional or supreme courts, the most recent one being the German Federal Constitutional Court (FCC) order of 29/4/2021. Traditionally, in environmental protection cases, constitutional courts tend to afford parliaments and governments a wide margin of discretion in how to fulfil protection duties arsing from environmental clauses or human rights such as life and health or property, only ruling out manifestly unsuitable protection strategies in rare cases. However, in recent climate cases, this relation is being readjusted. Based upon authority of scientific insights, courts increasingly declare legislative acts or government plans unconstitutional due to their insufficient climate efforts. The paper will compare and analyse the doctrinal impact of scientific insights on regulatory discretion in recent climate change case law such as by the FCC.