Diversity in global environmental scenario sets

Scenario development and analysis is an important methodological approach in the assessment of global environmental change. Scenarios are used to assess climate change and its impacts on societies, economies, and ecosystems, and identify, test, and improve policy responses to manage the negative consequences of a changing environment. Evaluation of scenarios, especially global scenarios widely used in the climate research and policy community, is therefore urgently needed. While the quality and usefulness of individual scenarios have been extensively examined through a wide array of criteria, standards for systematic evaluation of scenario sets are only emerging. Scenario diversity (i.e., diversity between individual scenarios in a set) has been advanced as a measure to assess the quality of global scenario sets. In this paper, the authors use scenario diversity analysis, a systematic and transparent quantitative method, to examine six major global scenario sets with regards to scenario set diversity. Results show that the assessed scenario sets show relatively good performance with regards to scenario set diversity. However, the use of classic methods for building scenario architectures and the number of scenarios included in a set raise important questions about the potential trade-offs between covering a bigger space of futures possibilities and adding redundancy to the scenario set.