Casey Helgeson

Expert Judgment for Climate Change Adaptation

Climate change adaptation is largely a local matter, and adaptation planning can benefit from local climate change projections. Such projections are typically generated by accepting climate model outputs in a relatively uncritical way. We argue, based on the IPCC’s treatment of model outputs from the CMIP5 ensemble, that this approach is unwarranted and that subjective expert judgment should play a central role in the provision of local climate change projections intended to support decision-making.

What Selection Can and Cannot Explain: A Reply to Nanay’s Critique of Sober

In The Nature of Selection, Elliott Sober argued that natural selection is in principle powerless to explain why any individual organism has the traits it does rather than the very same individual having different traits. In this note, I argue that in a recent and prominent critique of Sober’s position, Bence Nanay talks past that position rather than addressing it.

Climate Change Assessments: Confidence, Probability, and Decision

The Intergovernmental Panel on Climate Change has developed a novel framework for assessing and communicating uncertainty in the findings published in their periodic assessment reports. But how should these uncertainty assessments inform decisions? We take a formal decision-making perspective to investigate how scientific input formulated in the IPCCs novel framework might inform decisions in a principled way through a normative decision model.

Modus Darwin Reconsidered

‘Modus Darwin’ is the name given by Elliott Sober to a form of argument that he attributes to Darwin in the Origin of Species, and to subsequent evolutionary biologists who have reasoned in the same way. In short, the argument form goes: similarity, ergo common ancestry. In this article, I review and critique Sober’s analysis of Darwin’s reasoning. I argue that modus Darwin has serious limitations that make the argument form unsuitable for supporting Darwin’s conclusions, and that Darwin did not reason in this way. 1 Introduction 2 Modus Darwin 3 Limitations of Sober’s Formal Framework 3.1 Anatomical space 3.2 Branch lengths 4 Did Darwin Use Modus Darwin? 4.1 Adaptive characters 4.2 Galapagos 5 Modus Darwin versus Phylogenetic Inference 6 Conclusion 1 Introduction 2 Modus Darwin 3 Limitations of Sober’s Formal Framework 3.1 Anatomical space 3.2 Branch lengths 3.1 Anatomical space 3.2 Branch lengths 4 Did Darwin Use Modus Darwin? 4.1 Adaptive characters 4.2 Galapagos 4.1 Adaptive characters 4.2 Galapagos 5 Modus Darwin versus Phylogenetic Inference 6 Conclusion

Toward best practice framing of uncertainty in scientific publications: A review of Water Resources Research abstracts

Uncertainty is recognized as a key issue in water resources research, amongst other sciences. Discussions of uncertainty typically focus on tools and techniques applied within an analysis, e.g. uncertainty quantification and model validation. But uncertainty is also addressed outside the analysis, in writing scientific publications. The language that authors use conveys their perspective of the role of uncertainty when interpreting a claim —what we call here “framing” the uncertainty. This article promotes awareness of uncertainty framing in four ways. 1) It proposes a typology of eighteen uncertainty frames, addressing five questions about uncertainty. 2) It describes the context in which uncertainty framing occurs. This is an interdisciplinary topic, involving philosophy of science, science studies, linguistics, rhetoric, and argumentation. 3) We analyze the use of uncertainty frames in a sample of 177 abstracts from the Water Resources Research journal in 2015. This helped develop and tentatively verify the typology, and provides a snapshot of current practice. 4) Provocative recommendations promote adjustments for a more influential, dynamic science. Current practice in uncertainty framing might be described as carefully-considered incremental science. In addition to uncertainty quantification and degree of belief (present in ∼5% of abstracts), uncertainty is addressed by a combination of limiting scope, deferring to further work (∼25%) and indicating evidence is sufficient (∼40%) – or uncertainty is completely ignored (∼8%). There is a need for public debate within our discipline to decide in what context different uncertainty frames are appropriate. Uncertainty framing cannot remain a hidden practice evaluated only by lone reviewers.

There Is No Asymmetry of Identity Assumptions in the Debate over Selection and Individuals

A long-running dispute concerns which adaptation-related explananda natural selection can be said to explain. (The issue is conceptual—not empirical—and orthogonal adaptationism.) At issue are explananda of the form: why a given individual organism has a given adaptation rather than that same individual having another trait. It is broadly agreed that one must be ready to back up a “no” answer with an appropriate theory of trans-world identity for individuals. I argue, against the conventional wisdom, that the same is true for a “yes” answer. My conclusion recasts the landscape and opens the door to a potential resolution.

The Confirmational Significance of Agreeing Measurements

Agreement between “independent” measurements of a theoretically posited quantity is intuitively compelling evidence that a theory is, loosely speaking, on the right track. But exactly what conclusion is warranted by such agreement? I propose a new account of the phenomenon’s epistemic significance within the framework of Bayesian epistemology. I contrast my proposal with the standard Bayesian treatment, which lumps the phenomenon under the heading of “evidential diversity.”

Combining probability with qualitative degree-of-certainty metrics in assessment

Reports of the Intergovernmental Panel on Climate Change (IPCC) employ an evolving framework of calibrated language for assessing and communicating degrees of certainty in findings. A persistent challenge for this framework has been ambiguity in the relationship between multiple degree-of-certainty metrics. We aim to clarify the relationship between the likelihood and confidence metrics used in the Fifth Assessment Report (2013), with benefits for mathematical consistency among multiple findings and for usability in downstream modeling and decision analysis. We discuss how our proposal meshes with current and proposed practice in IPCC uncertainty assessment.