Projected land ice contributions to twenty-first-century sea level rise
Edwards, T., Nowicki, S., Goelzer, H., Helene Seroussi , Ben Marzeion , Christopher Smith , Nicolas Jourdain , Donald Slater , Christine McKenna , Erika Simon , Ayako Abe-Ouchi , Jonathan Gregory , Regine Hock , Eric Larour , William Lipscomb ,
Antony Payne , Andrew Shepherd , Cecile Agosta , Patrick Alexander , Torsten Albrecht , Brian Anderson , Xylar Asay-Davis , Andy Aschwanden , Alice Barthel , Reinhard Calov , Christopher Chambers , Nicholas Golledge , Ralf Greve ,
ore Hattermann , Matthew Hoffman , Angelika Humbert , Matthias Huss , Philippe Huybrechts , Walter Immerzeel , Thomas Kleiner , Philip Kraaijenbrink , Sébastien Le clec'h , Victoria Lee , Gunter Leguy , Christopher Little , Daniel Lowry ,
Jan-Hendrik Malles , Fabien Maussion , Mathieu Morlighem , Isabel Nias , Frank Pattyn , Tyler Pelle , Stephen Price , Aurelien Quiquet , Valentina Radi? , Ronja Reese , David Rounce , Martin Rückamp , Akiko Sakai , Nicole-Jeanne Schlegel , Sarah Shannon ,
Robin Smith , Fiammetta Straneo , Sainan Sun , Lev Tarasov , Luke Trusel , Jonas Van Breedam , Roderik van de Wal , Michiel van den Broeke , Ricarda Winkelmann , Chen Zhao , Tong Zhang , Harry Zekollari , Thomas Zwinger ,
Nicolas Champollion , Youngmin Choi , Richard Cullather , Joshua Cuzzone , Christophe Dumas , Denis Felikson , Xavier Fettweis , Koji Fujita , Rupert Gladstone , Fiona Turner , Benjamin Galton-Fenzi , Daniel Martin , James O'Neill , Courtney Shafer ,
Andrew Bliss

The land ice contribution to global mean sea level rise has not yet been predicted using ice sheet and glacier models for the latest set of socio-economic scenarios, nor using coordinated exploration of uncertainties arising from the various computer models involved. Two recent international projects generated a large suite of projections using multiple models, but primarily used previous-generation scenarios and climate models, and could not fully explore known uncertainties. Here we estimate probability distributions for these projections under the new scenarios using statistical emulation of the ice sheet and glacier models. We find that limiting global warming to 1.5 degrees Celsius would halve the land ice contribution to twenty-first-century sea level rise, relative to current emissions pledges. The median decreases from 25 to 13 centimetres sea level equivalent (SLE) by 2100, with glaciers responsible for half the sea level contribution. The projected Antarctic contribution does not show a clear response to the emissions scenario, owing to uncertainties in the competing processes of increasing ice loss and snowfall accumulation in a warming climate. However, under risk-averse (pessimistic) assumptions, Antarctic ice loss could be five times higher, increasing the median land ice contribution to 42 centimetres SLE under current policies and pledges, with the 95th percentile projection exceeding half a metre even under 1.5 degrees Celsius warming. This would severely limit the possibility of mitigating future coastal flooding. Given this large range (between 13 centimetres SLE using the main projections under 1.5 degrees Celsius warming and 42 centimetres SLE using risk-averse projections under current pledges), adaptation planning for twenty-first-century sea level rise must account for a factor-of-three uncertainty in the land ice contribution until climate policies and the Antarctic response are further constrained.