The feasibility ladder of energy transitions for climate change: An intellectual history and the road ahead

There is a vibrant debate on the feasibility of different low-carbon energy technologies ranging from concerns about the reliance on negative emission technologies to the implausibility of low energy demand and rapid upscaling of renewables. At the moment, this debate is largely stalled because different scholars use diverse types of evidence for feasibility. However, systematically assessing and comparing the feasibility of different climate solutions requires a rigorous scientific language. Here we propose such a language and develop a framework to assess the theoretical and empirical evidence for the feasibility of climate solutions based on a novel tool called the ‘feasibility ladder’. We use this framework to resolve the current impasse on the feasibility by developing a systematic approach to compare different types of evidence on the feasibility of low-carbon options based on the presence and strength of different causal analogies. We depart from recent attempts to project ladders of evidence from other policy relevant fields such as health care and instead develop the ladder based on the intellectual history of the climate and energy field. At the base of the ladder are visionary climate solutions such as the seminal work from 1985 which argued that a sustainable world was “feasible” if the most efficient energy technologies were deployed universally to achieve Western European lifestyles while keeping energy demand at a low level. At this rung of the ladder, the empirical evidence are best practices in laboratories or demonstrations, and the theoretical evidence are general principles, such as the laws of physics and the belief that there is public and political support for convergence in living standards. At the next rung of the ladder are models used for scenarios for transforming technical and social systems which stay within carbon budgets or meet emission targets while improving living standards. This approach emerged relatively early in the climate debate most notably with the IPCC. Mitigation pathways have since come to dominate discussions around the feasibility of climate mitigation. This rung relies on techno-economic theories and stylized mechanisms but has been criticized for neglecting key theories and mechanisms of social and political feasibility. These gaps have been addressed at the third rung of the ladder where scholars evaluate the feasibility of modeled pathways based on the presence of historical precedents for similar types of changes. Here the rate of technological change and overall decarbonization are used as a historical precedent to assess the feasibility of the change depicted in climate change mitigation pathways. We conclude our contribution with an outlook for how to further develop the feasibility ladder and how to use this tool to structure the current stalemate in the current debate. While most of the work on feasibility has used historical evidence, we point to how current policies and targets can complement these historical analogies. And second we argue for shifting from using the term “feasible” in a binary sense to using it probabilistically and that feasibility spaces a tool is a useful analytical tool to make this shift.