Ice sheet contributions to future sea-level rise from structured expert judgment

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Bamber, Jonathan L., Oppenheimer, Michael, Kopp, Robert E., Aspinall, Willy P., Cooke, Roger M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: /dk/atira/pure/core/keywords/globalmass; name=GlobalMass; Antarctica; Climate predictions; Greenland; Ice sheets; Sea-level rise; East Antarctica; Antarc*; glacier; Ice Sheet
• Online Access: https://hdl.handle.net/1983/61ce7e1a-e48e-4e66-a612-33c9995d8b46; https://research-information.bris.ac.uk/en/publications/61ce7e1a-e48e-4e66-a612-33c9995d8b46; https://doi.org/10.1073/pnas.1817205116; https://research-information.bris.ac.uk/ws/files/197623989/Full_text_PDF_final_published_version_.pdf; http://www.scopus.com/inward/record.url?scp=85066795412&partnerID=8YFLogxK

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 °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 °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 °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%.