Policy learning and diffusion of Tokyo's metropolitan cap-and-trade: making a mandatory reduction of total CO2 emissions work at local scales

The process of adopting policy ideas is extremely complex and requires a close examination of the political context in which the idea is learned, articulated, contested, adapted, and accepted by agents, both individual and collective. Why and how was the world's first urban scheme of mandatory reduction of total emissions adopted in Tokyo and not elsewhere? What might cause diffusion of this idea in other urban areas? One key explanation behind the idea adoption is a policy evolution of trial-and-error lessons about effective policy design, desirable policy goals, and politically feasible judgments. This study finds that both agency effects and structural opportunities of policy adoption in the case of Tokyo's cap-and-trade are too specific to result in a more coherent diffusion of ideas, policies, and practices in other urban areas. Although there is a sign of diffusion of Tokyo's cap-and-trade throughout Japan, it is more likely to derive from mimicking behaviors than from learning. The policy transfer of Tokyo's cap-and-trade requires the continuous learning of adaptive capacity to make it better fit to locally specific conditions.