Climatic Change

, Volume 124, Issue 1–2, pp 21–37 | Cite as

Scientific uncertainty and climate change: Part I. Uncertainty and unabated emissions

  • Stephan Lewandowsky
  • James S. Risbey
  • Michael Smithson
  • Ben R. Newell
  • John Hunter


Uncertainty forms an integral part of climate science, and it is often used to argue against mitigative action. This article presents an analysis of uncertainty in climate sensitivity that is robust to a range of assumptions. We show that increasing uncertainty is necessarily associated with greater expected damages from warming, provided the function relating warming to damages is convex. This constraint is unaffected by subjective or cultural risk-perception factors, it is unlikely to be overcome by the discount rate, and it is independent of the presumed magnitude of climate sensitivity. The analysis also extends to “second-order” uncertainty; that is, situations in which experts disagree. Greater disagreement among experts increases the likelihood that the risk of exceeding a global temperature threshold is greater. Likewise, increasing uncertainty requires increasingly greater protective measures against sea level rise. This constraint derives directly from the statistical properties of extreme values. We conclude that any appeal to uncertainty compels a stronger, rather than weaker, concern about unabated warming than in the absence of uncertainty.


Uncertainty unabated emissions decision making 



Preparation of this paper was facilitated by a Discovery Grant and a Discovery Outstanding Researcher Award from the Australian Research Council, and a Wolfson Research Merit Award from the Royal Society, to the first author, by a Future Fellowship from the Australian Research Council to Ben Newell, and funding from the Australian Research Council Centre of Excellence in Climate Systems Science. The work was also supported by a Linkage Grant from the Australian Research Council, by the National Climate Change Adaptation Research Facility, and the CSIRO Climate Adaptation Flagship. We thank four reviewers for their incisive critique and helpful comments. Correspondence to the first author at the School of Experimental Psychology, University of Bristol, 12A Priory Road, Bristol BS8 1TU, United Kingdom ( Personal web page:

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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • Stephan Lewandowsky
    • 1
    • 2
  • James S. Risbey
    • 3
  • Michael Smithson
    • 4
  • Ben R. Newell
    • 5
  • John Hunter
    • 6
  1. 1.University of Western AustraliaPerthAustralia
  2. 2.University of BristolBristolUK
  3. 3.CSIRO Marine and Atmospheric ResearchHobartAustralia
  4. 4.Australian National UniversityCanberraAustralia
  5. 5.University of New South WalesSydneyAustralia
  6. 6.Antarctic Climate & Ecosystems Cooperative Research CentreHobartAustralia

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