Climate Ambition in Cross-National Comparison: A Policy Output Perspective

Climate policy ambition varies 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. The index descriptively finds a significant rise in global climate ambition following the enforcement of the Paris Agreement, higher levels of ambition exhibited by European countries on average, and the divergence of intensity levels across policy fields. To assess its validity, I use a multi-method analysis to explore the determinants of cross-national variations in climate policy ambition. The empirical results illustrate that ambition is embedded in broader policy concerns, whereas the linkages between green ideology and trade integration highlight the importance of global engagement in strengthening the climate ambition of countries (especially climate laggards).