More rationality and inclusivity are imperative in reference transition scenarios based on IAMs and shared socioeconomic pathways - recommendations for prospective LCA

Prospective life cycle assessment (pLCA) is a key tool for evaluating future environmental impacts and supporting environmental policies. Recent pLCA methods integrate technological projections from transition scenarios modeled with integrated assessment models (IAMs), leveraging the shared socioeconomic pathways (SSPs) and representative concentration pathways developed within the framework of the Intergovernmental Panel for Climate Change (IPCC). However, this computational framework is influenced by subjective modeling choices within IAMs and SSPs, which can affect the robustness and relevance of future technological scenarios thus pLCA results. This article starts by highlighting these subjective choices through the lens of Science and Technology Studies, to then provide recommendations to enhance pLCA practices within this computational framework, especially through the selection of more (a) rational and (b) inclusive technological scenarios. The first step toward better practices is recognizing the inherited choices and limitations of borrowed models. Our recommendations then address the selection of future technological scenarios for pLCA: these scenarios could (a.1) account for the whole variability of mainstream transition scenarios from the latest IPCC report and its effect on pLCA results, (a.2) include only screened IPCC mainstream IAM scenarios based on proposed reality check criteria, (b.1) integrate scenarios rooted in alternative economic schools of thought, such as post-Keynesian economics or ecological macroeconomics, explore scenarios based on alternative (b.2) indicators prioritizing strong sustainability, justice, and well-being, and (b.3) societal narratives such as economic downscaling avenues and degrowth. Finally, we emphasize the need to incorporate ethical considerations into modeling, offering recommendations to (b.4) prioritize more equitable scenarios.