A decision-support framework to construct climate impact storylines using downward counterfactuals

Managing extreme weather events of unprecedented magnitude is one of the main challenges facing climate risk management and climate adaptation. Because of the unprecedented nature of these events, some authors have questioned the use of probabilistic approaches in this context. As an alternative, they introduced the so-called climate storylines approach. Climate storylines do not aim at predicting system states; rather, their focus is on revealing plausible chains of events whose impact might undermine the performance of the system.Conceptually, climate storylines relate to - but are separate from – downward counterfactual histories. Downward counterfactual histories are plausible alternative realizations of historical events that could have turned to the worse. By constructing downward counterfactual histories in a disaster risk reduction context, some authors showed that many disasters that took societies by surprise could have in fact been anticipated.This talk will introduce a decision-support framework to build climate storylines based on downward counterfactual histories. The framework is event-oriented, it focuses on impact and it is designed to be applied in a participatory fashion. By following the framework, the user first constructs climate storylines based on an iterative analysis of what (combinations of) counterfactuals are deemed critical (i.e., downward). Then, the user analyzes the future impact of the constructed storylines under climatic and socio-economic scenarios. Finally, the user explores the effects on the estimated impacts of the value-laden choices involved in the construction of the storylines.The framework is applied to study the impact of tropical cyclones hitting the European Union’s outermost regions on the stability of the European Union Solidarity Fund (EUSF), a public fund that provides financial relief to Member States affected by large disasters. Contrary to what historic evidence would suggest, it is found that extreme - yet plausible - tropical cyclones might deplete the EUSF capital if they happen concurrently with large events in mainland Europe, and that a substantial recapitalization of the fund might be required to cope with future climatic and socio-economic changes.