Advancing the development and use of climate-change scenarios : A multi-scale analysis to explore socio-economic European futures

Abstract

Climate change is one of the greatest challenges of our time and requires unprecedented changes to mitigate greenhouse gas emissions and adapt to climate-change impacts. Different viewpoints and definitions are used by scientists, decision makers and stakeholders to meaning of this challenge. The complexity of this diversity is amplified by the lack of a clear goal and methodology for the exploration of alternative futures in the form of future climate-change scenarios. Such scenarios need, at the same time, to be scientifically credible (credibility) and to reflect different viewpoints (legitimacy) in order to be generalised enough while representing contextual diversity (consistency) to be relevant for decision-making (salience). This thesis develops and analyse European and Central Asian socio-economic scenarios based on the global Shared Socio-economic Pathways (SSPs) to evaluate their credibility, legitimacy, consistency and relevance, with novel analytical methodologies. State-of-the-art scenario methodologies are framed on grounds of the objectives (exploratory and normative) and their links across scales (tight and loose links) and types (qualitative and quantitative). The first methodology is based on a fuzzy-set methodology to link qualitative (narratives) and quantitative (input variables to integrated assessment modelling) scenarios by assessing the different uncertainties resulting from their inherent complexities. In the second and third methodologies, a quantitative pan-European urbanisation model, stakeholder-led narratives and a qualitative concept of archetype are used discuss both the quantitative and qualitative scalability of the scenarios in a multi-scale approach. The fourth methodology combines a capital-capacities framework to link the goal of exploratory scenarios in relation to their relevance to decision-making by assessing their potential to achieve a (normative) desirable future. Overall, results suggest that linking directly the uncertainties contributes to more transparent qualitative and quantitative conversion and therefore yield more credible scenarios. When analysed across scales, global and European scenarios are consistent with both downscaled scenarios and local stakeholder-led narratives contribute to the creation of holistic and more legitimate scenarios. However, important divergences have emerged too. For instance, the scenario with high challenges to mitigation and low challenges to adaptation (SSP5) varies hugely across the European continent. The local versions of SSP5 tend to diverge from the global archetype more than the other SSPs. This divergence reflects different worldviews that challenge state-of-the-art knowledge and can ultimately question the role of global scenarios in guiding local scenario versions with a nested approach. I recommend the role of both narratives and quantifications to be equally important in capturing different uncertainties, stakes and worldviews, as well as a reframing of SSP uncertainty space as one of challenges to societal transformation, rather than one of challenges to mitigation and adaptation.