AbstractThe 2015 Paris Agreement is falling short of its aspirations, as signatory countries are struggling to implement the policies required to meet the targets. The global scenario framework formed by the Shared Socioeconomic Pathways (SSPs) and the Representative Concentration Pathways (RCPs) places little emphasis on the dynamics of climate policy implementation. Social science approaches to understanding these dynamics are not well-integrated into climate scenario research. We apply an implementation research approach to analyse the transition to clean energy in the US and China, as well as two examples from Europe – Germany and Spain – which have shown markedly diverging implementation trajectories. We propose four implementation scenarios (ISs) for clean energy worldwide which relate to different configurations of actors in the policy system. These are: (1) Civil Society Takes Control (IS1) – where ideologically opposed governments are marginalised by citizens and forward-thinking investors; (2) Strong-arm Transition (IS2) – where a single party state drives the transition without the involvement of civil society; (3) Systemic Limits (IS3) – which highlights the need to focus on the whole energy system, not just renewables; and (4) Renewable Austerity (IS4) – where an economic downturn offers powerful anti-transition actors the opportunity to advocate removal of support for climate mitigation, as they did after the 2007–2008 financial crisis. This scenario could be repeated as countries seek to recover from the Covid-19 pandemic. Our study offers a framework for structured analysis of real-world constraints faced by implementing actors, which we argue is urgently needed to help national and international policy makers achieve climate goals.