Climate change is a global-scale structural change, affecting economies across the world, alongside global fragmentation, digitalisation and demographics. This paper analyses the diffusion of climate policies and technologies and the role of institutions and governance in that process. It discusses theory, models and data available to date, and the empirical evidence for the 20 European Union and all 40 countries covered by the OECD’s Environmental Policy Stringency index. The results indicate that institutions and governance have significant effects towards a greater speed and spread of diffusion of climate policies and technologies, and that separating the speed and spread effects is essential for assessing the green transition.