Climate ambition flexibly engages with broad policy frameworks of countries, typically referring to the holistic policy efforts in the climate field. However, levels of ambition vary greatly across countries. Understanding of these cross-national variations is limited, owing to conceptual complexity, limited data, and methodological challenges. I propose a comparative measure of ‘climate policy ambition’ based on the combination of depth and breadth of policy outputs. Drawing on this comparative framework, I introduce a new dataset to explore the climate policy ambitions of 35 major emitters (each contributing at least 0.5% of global emissions) from 1990 to 2020. The added value of this measurement model lies in its ease of construction, data transparency, and adaptability for extension across various timeframes and localities.