Conceptualizing uncertainty: the IPCC, model robustness and the weight of evidence

Harris, Margherita (2021) Conceptualizing uncertainty: the IPCC, model robustness and the weight of evidence. PhD thesis, London School of Economics and Political Science.

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Abstract

The aim of this thesis is to improve our understanding of how to assess and communicate uncertainty in areas of research deeply afflicted by it, the assessment and communication of which are made more fraught still by the studies’ immediate policy implications. The IPCC is my case study throughout the thesis, which consists of three parts. In Part 1, I offer a thorough diagnosis of conceptual problems faced by the IPCC uncertainty framework. The main problem I discuss is the persistent ambiguity surrounding the concepts of ‘confidence’ and ‘likelihood’; I argue that the lack of a conceptually valid interpretation of these concepts compatible with the IPCC uncertainty guide’s recommendations has worrying implications for both the IPCC authors’ treatment of uncertainties and the interpretability of the information provided in the AR5. Finally, I show that an understanding of the reasons behind the IPCC’s decision to include two uncertainty scales can offer insights into the nature of this problem. In Part 2, I review what philosophers have said about model-based robustness analysis. I assess several arguments that have been offered for its epistemic import and relate this discussion to the context of climate model ensembles. I also discuss various measures of independence in the climate literature, and assess the extent to which these measures can help evaluate the epistemic import of model robustness. In Part 3, I explore the notion of the ‘weight of evidence’ typically associated with Keynes. I argue that the Bayesian (or anyone who believes the role of probability in inductive inference is to quantify the degree of belief to assign to a hypothesis given the evidence) is bound to struggle with this notion, and draw some lessons from this fact. Finally, I critically assess some recent proposals for a new IPCC uncertainty framework that significantly depart from the current one.

Item Type:	Thesis (PhD)
Additional Information:	© 2021 Margherita Harris
Library of Congress subject classification:	B Philosophy. Psychology. Religion > B Philosophy (General) B Philosophy. Psychology. Religion > BC Logic
Sets:	Departments > Philosophy, Logic and Scientific Method
Supervisor:	Frigg, Roman and Bright, Liam Kofi
URI:	http://etheses.lse.ac.uk/id/eprint/4355

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