TF Colloquium: Enhancing Scenario Assessment Through Discomposition Methods

Speaker: Francesco Nappo (Università Cattolica del Sacro Cuore and Politecnico di Milan)

Exercises of climate policy evaluation in the scientific domain often rely on the assessment of long-term emission scenarios, viz., simulations of future climate based on observed linkages between economic growth, greenhouse gas emissions, and rising global temperatures. Typically, scenarios from many different models are collected and compared to one another to draw lessons about effective mitigation strategies, viz., about the policies that can help us achieve temperature stabilization goals. In the first part of this talk, I will introduce the main modeling frameworks and ensemble methodologies that currently allow for the systematic assessment of emission scenarios. In the second part, I will then provide a critical evaluation of an emerging family of ensemble assessment methods, which adopt statistical decomposition tools for large datasets to provide information about the representation of mitigation strategies across emission scenarios in an ensemble. I argue that the appropriate use for these tools is providing insights into the stability of mitigation strategies under alternative assumptions about the future. Based on this framing, I articulate three requirements on the quality of decomposition analyses in climate policy evaluation, namely model diversity, well-assortedness, and regional integration, and exemplify their stringency through the example of selecting an adequate energy supply mix for achieving ambitious mitigation goals.