A global goal to limit dangerous climate change has been agreed through the 2015 Paris Accords. The scientific case for action has been accepted by nearly all governments, at national and local or state level. Yet in all legislatures, there is a gap between the stated climate ambitions and the implementation of the measures necessary to achieve them. This paper examines this gap by analysing the experience of the following three UK cities: Belfast, Edinburgh, and Leeds. Researchers worked with city officials and elected representatives, using interviews and deliberative workshops to develop their shared understandings. The study finds that local actors employ different strategies to respond to the stated climate emergency, based on their innate understanding, or ‘phronetic knowledge’, of what works. It concludes that rapid climate action depends not just on the structures and mechanisms of governance, but at a deeper level, the assumptions, motivations and applied knowledge of decision-makers.