Climate politics in liberal democracies has hit an invisible but solid ‘glass ceiling’: the inability of industrialised countries (democratic or not) to radically decarbonise stands out against a ubiquitous political consensus about the urgent need to do so in most democratic countries. In this paper, I first explore the nature of that structural barrier from the perspective of institutional lock-in. This relates, as I argue, to mechanisms of democratic legitimation that tie the liberal democratic order to a productivist, growth-based political economy, which is structurally unable to terminate its own dependence on massive (fossil) energy input. The modern democratic state has co-evolved with the fossil energy system to an extent that renders modern democracy ‘fossil democracy’ in a more than literal sense.