Reliable and Valid Identification of a Small Number of Global Emission Scenarios

Numerous scenarios of global greenhouse gas emissions have been created, that aredifficult to communicate to decision makers. To identify few significantly different and consistent scenariosis time consuming, requires deep understanding of the underlying driving forces, and may depend on theindividual perspective of the scenario analyst. Developed from an expert based scenario technique a newmethod was developed, which in step 1 analyzes each given scenario with respect to the relations between itscharacteristics (e.g. parameters, state variables). This analysis may include a very large number of qualitative('nominal'), logical, ordinal and metric characteristics. In step 2, a few consistent and significantly differentscenarios are reliably determined according to modifications of three recently published scenarioidentification methods. The comparison of the different methods for scenario identification shows theconvergent validity of the methodology. The presentation sketches the mathematical background of theanalysis and of the identification and shows results of an application to the IPCC emission scenarios. It isconcluded that the quantitative scenario selection procedure presented is very helpful for the communicationof scenarios to decision makers. Because the mathematical methodology complies with approaches used inqualitative scenario techniques, in which experts estimate scenario consistency, a combination of qualitativeand quantitative knowledge could be possible, but has not yet been investigated.