Comparative policy analysis revealed the phenomenon that certain national environmental policy initiatives have been adopted by a variety of countries. This empirical finding inspired the research interest: What are the reasons for this observable spreading? Is it coincidence, is it lesson-drawing, competition, emulation or is it the result of decreasing nation state’s discretion due to mandatory compliance requirements of international law? The concept of policy diffusion has been found quite suitable to analyse the spreading of different environmental policy innovations. The analysis of diffusion processes is a challenging endeavour as it has to consider a complex interplay of three factors: International and transnational factors which horizontally and vertically interlink jurisdictions and enable the transfer of policy content; national factors which filter experiences from abroad and determine national responsiveness to external stimuli; and the characteristics of the policy innovation which may indicate its “diffusablity”. This research note is a synthesis of findings of the project on “The Diffusion of Environmental Innovations as an Aspect of Globalisation” financed by the Volkswagen Foundation. It confronts central assumptions of diffusion research with the findings of various project researchers. The empirical core of the project consists of a set of data concerning the adoption of 21 environmental policy innovations in 48 countries over a time period of 50 years. In a first step the paper analyses whether across all of the 21 environmental innovations typical pattern of spread can be identified in order to detect those channels of diffusion which seemingly further diffusion processes. Following up this discussion the paper debates international factors which are assumed to have an crucial impact on the pattern of diffusion. Within this section interrelations with other types of global or regional governance are discussed. This comprises both special features of the EU context as well as the impact of global norms. After giving a short overview concerning the micro-foundations of the diffusion effects of international stimuli the paper proceeds to discuss the restrictions in the diffusion process, which heavily depend on innovation characteristics and national capacities to innovate. The paper concludes with raising new research questions in order to inspire the scientific debate on globalisation and policy convergence.
