The GlobalMass team has a new paper published this week in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).
Using a technique called structured expert judgement (SEJ), an international team of scientists lead by GlobalMass PI Jonathan Bamber, asked 22 ice sheet experts to estimate plausible ranges for future sea level rise due to the projected melting of each of the Greenland, West Antarctic and East Antarctic ice sheets under low and high future global temperature rise scenarios.
Melting ice sheets in Greenland and the Antarctic, and subsequent sea level rise (SLR) this will cause, are widely recognised as posing a significant threat to coastal communities and ecosystems. Strategies and measures to mitigate and plan for the potential impacts are reliant on scientific projections of future SLR, conventionally provided using numerical modelling.
Yet such projections remain challenging due to ongoing uncertainty regarding the evolution of the Greenland and Antarctic ice sheets, and particular their response to climate change. The SEJ process provided an opportunity for experts to discuss their scientific rationales for the quantitative judgments they make on uncertainties relating to future ice sheet contributions to sea level.
Projections of total global SLR using this method suggest a small but meaningful probability of SLR exceeding two metres by the year 2100 under the high temperature scenario (roughly equivalent to “business as usual”), well above the ‘likely’ upper limit presented in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC).
The findings suggest that coastal communities should therefore not rule out the possibility of 21st-century SLR in excess of two metres when developing adaptation strategies.
Jonathan Bamber said of the work: “SEJ provides a formal approach for estimating uncertain quantities based on current scientific understanding, and can be useful for estimating quantities that are difficult to model”.
The research has already been picked up by several media outlets:
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BBC – Rise in global sea levels could have ‘profound consequences’
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New Scientist – Sea level rise could hit 2 metres by 2100 – much worse than feared
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The Independent – Global sea levels may rise more than two metres by 2100
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USA Today – Earth’s oceans could rise over 6 feet by 2100 as polar ice melts, swamping coastal cities such as NYC
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Stuff.co.nz – Increased sea level predictions could result in displacement of 187m people, study finds
Full paper: ‘Ice sheet contributions to future sea-level rise from structured expert judgement’ by Jonathan L Bamber, Michael Oppenheimer, Robert E. Kopp, Willy P. Aspinall, Roger M. Cooke (2019) in Proceedings of the National Academy of Sciences of the United States of America (PNAS) (doi: 10.1073/pnas.1817205116 
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We have also produced a plain language summary.