EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Quantifying ambiguity in sea-level projections

Goneri Le Cozannet1, Jeremy Rohmer1, Jean-Charles Manceau1, Gael Durand2, Catherine Ritz2, Angélique Melet3, Benoit Meyssignac4, David Salas y Mélia5, Mark Carson6, Aimée Slangen7, Jochen Hinkel8, Erwin Lambert9, Rémi Thiéblemont1, Dewi Le Bars10, Detlef Stammer6, Roderik Van De Wal9, and Robert Nicholls11
Goneri Le Cozannet et al.
  • 1BRGM, Risks and Prevention, Orleans, France (
  • 2Institut des Géosciences de l’Environnement (IGE)
  • 3Mercator Ocean International
  • 4LEGOS
  • 5CNRM, Université de Toulouse
  • 6CEN, Centrum für Erdsystemforschung und Nachhaltigkeit, Universität Hamburg
  • 7NIOZ, Royal Netherlands Institute for Sea Research
  • 8Global Climate Forum (GCF)
  • 9Institute for Marine and Atmospheric Research Utrecht, Utrecht University
  • 10KNMI
  • 11Engineering and the Environment, University of Southampton

Coastal impacts of climate change and the related mitigation and adaptation needs requires assessments of future sea-level changes. Following a common practice in coastal engineering, probabilistic sea-level projections have been proposed for at least 20 years. This requires a probability model to represent the uncertainties of future sea-level rise, which is not achievable because potential ice sheets mass losses remain poorly understood given the knowledge available today. Here, we apply the principles of extra-probabilistic theories of uncertainties to generate global and regional sea-level projections based on uncertain components. This approach assigns an imprecision to a probabilistic measure, in order to quantify lack of knowledge pertaining to probabilistic projections. This can serve to understand, analyze and communicate uncertainties due to the coexistence of different processes contributing to future sea-level rise, including ice-sheets. We show that the knowledge gained since the 5th Assessment report of the IPCC allows better quantification of how global and regional sea-level rise uncertainties can be reduced with lower greenhouse gas emissions. Furthermore, Europe and Northern America are among those profiting most from a policy limiting climate change to RCP 2.6 versus RCP 4.5 in terms of reducing uncertainties of sea-level rise.

How to cite: Le Cozannet, G., Rohmer, J., Manceau, J.-C., Durand, G., Ritz, C., Melet, A., Meyssignac, B., Salas y Mélia, D., Carson, M., Slangen, A., Hinkel, J., Lambert, E., Thiéblemont, R., Le Bars, D., Stammer, D., Van De Wal, R., and Nicholls, R.: Quantifying ambiguity in sea-level projections, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2779,, 2021.

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