Despite considerable advances in process understanding, numerical modeling, and the observational record of ice sheet contributions to global mean sea-level rise (SLR) since the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change, severe limitations remain in the predictive capability of ice sheet models. As a consequence, the potential contributions of ice sheets remain the largest source of uncertainty in projecting future SLR. Here, we report the findings of a structured expert judgement study, using unique techniques for modeling correlations between inter-and intra-ice sheet processes and their tail dependences. We find that since the AR5, expert uncertainty has grown, in particular because of uncertain ice dynamic effects. For a +2 degrees C temperature scenario consistent with the Paris Agreement, we obtain a median estimate of a 26 cm SLR contribution by 2100, with a 95th percentile value of 81 cm. For a +5 degrees C temperature scenario more consistent with unchecked emissions growth, the corresponding values are 51 and 178 cm, respectively. Inclusion of thermal expansion and glacier contributions results in a global total SLR estimate that exceeds 2 m at the 95th percentile. Our findings support the use of scenarios of 21st century global total SLR exceeding 2 m for planning purposes. Beyond 2100, uncertainty and projected SLR increase rapidly. The 95th percentile ice sheet contribution by 2200, for the +5 degrees C scenario, is 7.5 m as a result of instabilities coming into play in both West and East Antarctica. Introducing process correlations and tail dependences increases estimates by roughly 15%.
1.Univ Bristol, Sch Geog Sci, Bristol BS8 1SS, Avon, England 2.Princeton Univ, Dept Geosci, Princeton, NJ 08544 USA 3.Princeton Univ, Woodrow Wilson Sch Publ & Int Affairs, Princeton, NJ 08544 USA 4.Rutgers State Univ, Dept Earth & Planetary Sci, New Brunswick, NJ 08854 USA 5.Rutgers State Univ, Inst Earth Ocean & Atmospher Sci, New Brunswick, NJ 08901 USA 6.Univ Bristol, Sch Earth Sci, Bristol BS8 1RJ, Avon, England 7.Aspinall & Associates, Tisbury SP3 6HF, England 8.Land Water & Nat Resources Future, Washington, DC 20036 USA 9.Delft Univ Technol, Dept Math, NL-2600 GA Delft, Netherlands
Recommended Citation:
Bamber, Jonathan L.,Oppenheimer, Michael,Kopp, Robert E.,et al. Ice sheet contributions to future sea-level rise from structured expert judgment[J]. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA,2019-01-01,116(23):11195-11200