The evaluation of climate future scenarios and the assessment of their plausibility is of utmost importance for climate discourse, climate action, and decision-making processes at large. Possible climate future scenarios are often considered side by side on an equal footing. Some existing reports explore feasible climate future scenarios, where feasibility is defined as “the potential for a mitigation or adaptation option to be implemented” (AR6 SPM WGIII). What is not assessed is whether it is plausible that certain mitigation or adaptation options are going to be implemented. Indeed, a feasible pathway may not necessarily be plausible; we interpret plausibility loosely in the sense that implementation can realistically be expected. In the Hamburg Climate Futures Outlook, we show that assessing the plausibility of climate futures involves analyzing the social and physical dynamics that influence the pathways toward or away from a specific climate future scenario. This approach to climate futures research is unique in its combined focus on social and physical dynamics.
In this Townhall Meeting we present the CLICCS Plausibility Assessment Framework, established in the 2023 Outlook edition to assess the plausibility of worldwide deep decarbonization by 2050 and of staying below the 1.5°C limit to global warming. More than 60 social and natural scientists have analyzed the dynamics of the ten dominant social drivers of decarbonization and of six select physical processes of public interest. The physical processes where selected on the basis of one or more of the following criteria: (i) the process is veiled in deep uncertainties, (ii) the process is a potential tipping element, (iii) or the process receives much attention in the public discourse shaping climate risk perception. This Townhall Meeting aims to engage participants in an open discussion on feasibility vs. plausibility in climate futures research and on the implications of our approach and findings.

Reference: Engels, Anita; Jochem Marotzke; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2023. Hamburg Climate Futures Outlook 2023. The plausibility of a 1.5°C limit to global warming—social drivers and physical processes. Cluster of Excellence Climate, Climatic Change, and Society (CLICCS). Hamburg, Germany.