“Ambition” and its variants “progression” and “highest possible ambition” are cornerstones of the Paris Agreement and its 2/1.5 degrees C global warming goals, while ambition is at best implicit in the Framework Convention on Climate Change. Even though only a normative expectation in a system of self-assessment, under the Paris Agreement ambition serves as a yardstick for judging and discussing the adequacy of the NDCs. However, the content and meaning of “ambition” are far from being agreed upon and the applicability of the reformulated principle of common but differentiated responsibilities and respective capabilities does not provide clear answers. In these circumstances, the article looks for guidance from national court decisions that interpret, apply or consider the notion of ambition “on the ground”. These decisions address a number of elements of ambition. They may encourage more ambitious national action. However, they are mostly not specific enough to draw robust conclusions from them regarding concrete questions of application.