Climate Change Acts on the move: drivers and limits of horizontal and vertical diffusion in the German federal system

The reduction of greenhouse gas emissions in Germany depends not only on national/ federal climate policy and legislation, but also on the federal states (Länder). Due to the lack of a national/ federal climate change act before 2019, nine out of 16 German states have enacted climate change acts since 2013, and two states have opted for other legal options (ordinances, statutory orders), while in five states the proposed climate change acts were rejected by the state parliaments. Our analysis of these legislative innovations draws, in particular, on the literature on the diffusion of policy innovations. We research the drivers for the horizontal diffusion of state climate change acts in the German multi-level system, the emerging models, and their transformation while traveling between the states. Alongside the sequence of adoptions and the types of legislative innovations, we present case studies on forerunner, follower, and latecomer states. Although the options of states are limited by EU and national/ federal legislation, we find marked differences between them. Traditional coal states, in particular, are reluctant to enact and implement climate change acts. However, political factors seem to be even more important than socio-economic characteristics. The Green Party started legislative initiatives in all 16 states, and these initiatives succeeded in those states where it was in power, and failed where it was in opposition. With the enactment of a national/ federal climate change act in late 2019, the dynamics of the horizontal diffusion between the states changed. No new acts were initiated, but we find a new wave of diffusion of innovative approaches between existing acts (such as the introduction of mandatory heat plans for cities). In addition to the enactment of climate change acts at the subnational level in Germany, we ask whether and how these acts have been implemented and how their implementation has been influenced by the ongoing polycrisis.