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Tuesday, March 17, 2009

E. Kriegler, J.W. Hall, H. Held, R. Dawson & H.J. Schellnhuber, PNAS Vol 106, Imprecise probability assessment of tipping points in the climate system

Proceedings of the National Academy of Sciences, Vol. 106, No. 11.

Imprecise probability assessment of tipping points in the climate system

  1. Elmar Kriegler*,a,b,
  2. Jim W. Hallc,d,
  3. Hermann Helda,
  4. Richard Dawsonc,d and
  5. Hans Joachim Schellnhubera,e,f
  1. aPotsdam Institute for Climate Impact Research, PO Box 60 12 03, 14412 Potsdam, Germany;
  2. bDepartment of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA 15213-3890;
  3. cSchool of Civil Engineering and Geosciences, Newcastle University, Newcastle-upon-Tyne NE1 7RU, United Kingdom;
  4. dTyndall Centre for Climate Change Research, University of Newcastle-upon-Tyne, Newcastle-upon-Tyne NE1 7RU, United Kingdom;
  5. eEnvironmental Change Institute, Oxford University, Oxford OX1 3QY, United Kingdom; and
  6. fTyndall Centre for Climate Change Research, University of East Anglia, Norwich NR4 7TJ, United Kingdom
  1. Edited by William C. Clark, Harvard University, Cambridge, MA, and approved February 2, 2009 (received for review September 16, 2008)


Major restructuring of the Atlantic meridional overturning circulation, the Greenland and West Antarctic ice sheets, the Amazon rainforest and ENSO are a source of concern for climate policy. We have elicited subjective probability intervals for the occurrence of such major changes under global warming from 43 scientists. Although the expert estimates highlight large uncertainty, they allocate significant probability to some of the events listed above. We deduce conservative lower bounds for the probability of triggering at least one of those events of 0.16 for medium (2–4 °C), and 0.56 for high global mean temperature change (above 4 °C) relative to year 2000 levels.

  • *To whom correspondence should be addressed. e-mail:
  • Author contributions: E.K., J.W.H., and H.-J.S. designed research; E.K., J.W.H., and R.D. performed research; E.K., J.W.H., and H.H. contributed new reagents/analytic tools; E.K., J.W.H., and R.D. analyzed data; and E.K. wrote the paper. The authors declare no conflict of interest.

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