European participatory scenario development: strengthening the link between stories and models

Scenario development methods get to grips with taking a long-term view on complex issues such as climate change through involvement of stakeholders. Many of the recent (global) scenario exercises have been structured according to a Story-and-Simulation approach. Although elaborately studied, conceptual and practical issues remain in linking qualitative stories and quantitative models. In this paper, we show how stakeholders can directly estimate model parameter values using a three-step approach called Fuzzy Set Theory. We focus on the effect of multiple iterations between stories and models. Results show that we were successful in quickly delivering stakeholder-based quantification of key model parameters, with full consistency between linguistic terms used in stories and numeric values. Yet, values changed strongly from one iteration to the next. A minimum of two and preferably at least three iterations is needed to harmonise stories and models. We conclude that the application of Fuzzy Set Theory enabled a highly valuable, structured and reproducible process to increase consistency between stories and models, but that future work is needed to show its true potential, particularly related to the effect of iterations. Additionally, the number of tools that need to be applied in a short period of time to execute a Story-And-Simulation approach introduces drawbacks that need to be studied. However, an approach such as Story-And-Simulation is indispensable and effective in marrying the perspectives of scientists and other stakeholders when studying complex systems and complex problems.