Article | Published:

An expert judgement assessment of future sea level rise from the ice sheets

Nature Climate Change volume 3, pages 424427 (2013) | Download Citation


A major gap in predictive capability concerning the future evolution of the ice sheets was identified in the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change. As a consequence, it has been suggested that the AR4 estimates of future sea-level rise from this source may have been underestimated. Various approaches for addressing this problem have been tried, including semi-empirical models and conceptual studies. Here, we report a formalized pooling of expert views on uncertainties in future ice-sheet contributions using a structured elicitation approach. We find that the median estimate of such contributions is 29 cm—substantially larger than in the AR4—while the upper 95th percentile value is 84 cm, implying a conceivable risk of a sea-level rise of greater than a metre by 2100. On the critical question of whether recent ice-sheet behaviour is due to variability in the ice sheet–climate system or reflects a long-term trend, expert opinion is shown to be both very uncertain and undecided.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    , , , & Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise. Geophys. Res. Lett. 38, L05503 (2011).

  2. 2.

    , , , & Acceleration of Jakobshavn Isbrae triggered by warm subsurface ocean waters. Nature Geosci. 1, 659–664 (2008).

  3. 3.

    , , , & Recent dramatic thinning of largest West Antarctic ice stream triggered by oceans. Geophys. Res. Lett. 31, L23401 (2004).

  4. 4.

    et al. Antarctic ice-sheet loss driven by basal melting of ice shelves. Nature 484, 502–505 (2012).

  5. 5.

    , , & 21st-century evolution of Greenland outlet glacier velocities. Science 336, 576–578 (2012).

  6. 6.

    et al. Rapid response of Helheim Glacier in Greenland to climate variability over the past century. Nature Geosci. 5, 37–41 (2012).

  7. 7.

    , & Large fluctuations in speed on Greenland’s Jakobshavn Isbrae glacier. Nature 432, 608–610 (2004).

  8. 8.

    & Why is it hard to predict the future of ice sheets? Science 315, 1503–1504 (2007).

  9. 9.

    Experts in Uncertainty-Opinion and Subjective Probability in Science (Oxford Univ. Press, 1991).

  10. 10.

    A route to more tractable expert advice. Nature 463, 294–295 (2010).

  11. 11.

    et al. Assessing dangerous climate change through an update of the Intergovernmental Panel on Climate Change (IPCC) reasons for concern. Proc. Natl Acad. Sci. USA 106, 4133–4137 (2009).

  12. 12.

    et al. Expert judgements on the response of the Atlantic meridional overturning circulation to climate change. Climatic Change 82, 235–265 (2007).

  13. 13.

    & TU Delft expert judgment data base. Reliab. Eng. Syst. Saf. 93, 657–674 (2008).

  14. 14.

    et al. Partitioning recent Greenland mass loss. Science 326, 984–986 (2009).

  15. 15.

    , , , & Twenty-first-century warming of a large Antarctic ice-shelf cavity by a redirected coastal current. Nature 485, 225–228 (2012).

  16. 16.

    & Ice-sheet contributions to future sea-level change. Phil. Trans. R. Soc. A 364, 1709–1731 (2006).

  17. 17.

    , , , & Estimation of the Greenland ice sheet surface mass balance for the 20th and 21st centuries. Cryosphere 2, 117–129 (2008).

  18. 18.

    & Regionally differentiated contribution of mountain glaciers and ice caps to future sea-level rise. Nature Geosci. 4, 91–94 (2011).

  19. 19.

    et al. Relative outcomes of climate change mitigation related to global temperature versus sea-level rise. Nature Clim. Change 2, 576–580 (2012).

  20. 20.

    et al. The next generation of scenarios for climate change research and assessment. Nature 463, 747–756 (2010).

  21. 21.

    , , & Long-term sea-level rise implied by 1.5 °C and 2 °C warming levels. Nature Clim. Change 2, 867–870.

  22. 22.

    et al. in IPCC Climate Change 2007: The Physical Science Basis (ed. Solomon, S.) Ch. 10 (Cambridge Univ. Press, 2007).

  23. 23.

    et al. Sea-level rise and its possible impacts given a ‘beyond 4 degrees C world’ in the twenty-first century. Philos. Trans. R. Soc. A 369, 161–181 (2011).

Download references


We thank the experts who participated in the two surveys. Each is a pre-eminent scientist in the field, with many other demands on their time and expertise; their individual views are authoritative, and collectively invaluable. J.L.B. would like to thank M. New and J. Sky for their assistance with the first questionnaire and D. Vaughan for his comments on a draft of the paper. This work was largely funded by the European Commission’s 7th Framework Programme through grant number 226375 (ice2sea contribution number 129). W.P.A. was supported in part by an Advanced European Research Council grant to Prof RSJ Sparks (VOLDIES Project).

Author information


  1. School of Geographical Sciences, University of Bristol, Bristol BS8 1SS, UK

    • J. L. Bamber
  2. Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK

    • W. P. Aspinall


  1. Search for J. L. Bamber in:

  2. Search for W. P. Aspinall in:


J.L.B. conceived and carried out the study and solicited the expert judgements. W.P.A. analysed the elicitations and carried out the Monte Carlo simulations. Both authors wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to J. L. Bamber.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    Supplementary Information

About this article

Publication history





Further reading