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The Intergovernmental Panel on Climate Change (IPCC) exists to provide policy-relevant assessments of the science related to climate change. As such, the IPCC has long grappled with characterizing and communicating uncertainty in its assessments. Decision Making under Deep Uncertainty (DMDU) is a set of concepts, methods, and tools to inform decisions when there exist substantial and significant limitations on what is and can be known about policy-relevant questions. Over the last twenty-five years, the IPCC has drawn increasingly on DMDU concepts to more effectively include policy-relevant, but lower-confidence scientific information in its assessments. This paper traces the history of the IPCC’s use of DMDU and explains the intersection with key IPCC concepts such as risk, scenarios, treatment of uncertainty, storylines and high-impact, low-likelihood outcomes, and both adaptation and climate resilient development pathways. The paper suggests how the IPCC might benefit from enhanced use of DMDU in its current (7th) assessment cycle.
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This content will become publicly available on May 14, 2026
Navigating confidence–precision trade-offs in assessment
In this reply, we address a comment on our paper “Combining probability with qualitative degree-of-certainty metrics in assessment” (Helgeson et al. Clim Change 149(3):517–525, 2018). Our original paper proposes an incremental systematization of confidence and likelihood language used by the Intergovernmental Panel on Climate Change (IPCC). Our goals were to improve consistency across findings and support use of confidence judgments in decision making. The comment critiques our proposal and recommends against its adoption. We argue that this recommendation is based on two misunderstandings. The first concerns trading off confidence against the precision of a finding (our proposal endorses and systematizes the practice). We defend this practice and attribute opposition to an overzealous Bayesianism inapt for the IPCC context. The second misunderstanding concerns our purported commitment to a specific procedure for producing confidence judgements. We clarify that our proposal makes no such commitment. We also note, contrary to the comment’s claim, that a version of the procedure in question has been used in the IPCC’s Sixth Assessment Report.
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- Award ID(s):
- 2103754
- PAR ID:
- 10610915
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Climatic Change
- Volume:
- 178
- Issue:
- 5
- ISSN:
- 0165-0009
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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