Why do we need to measure the progress of the ecological transition? How has the climate and its warming led us to establish a whole new generation of impact metrics and – even more importantly – of accountability metrics in these areas? In what crucial ways does decarbonization differ from resilience when we get to measure them? These questions will be addressed through a brief recourse to history, physics, chemistry, biology, but also to economics, the sociology of actors and, last but not least, design and planning. The objective is to arm participants with cross-knowledge tools, to help them build their own lines of reasoning for their future practice as transition strategists.