Communicating future sea-level rise uncertainty and ambiguity to assessment users

Future sea-level change is characterized by both quantifiable and unquantifiable uncertainties. Effective communication of both types of uncertainty is a key challenge in translating sea-level science to inform long-term coastal planning. Scientific assessments play a key role in the translation process and have taken diverse approaches to communicating sea-level projection uncertainty. Here we review how past IPCC and regional assessments have presented sea-level projection uncertainty, how IPCC presentations have been interpreted by regional assessments and how regional assessments and policy guidance simplify projections for practical use. This information influenced the IPCC Sixth Assessment Report presentation of quantifiable and unquantifiable uncertainty, with the goal of preserving both elements as projections are adapted for regional application.R.E.K. and M.O. were supported by US National Science Foundation award ICER-2103754 as part of the Megalopolitan Coastal Transformation Hub. R.E.K. and G.G.G. were also supported by the US National Aeronautics and Space Administration (award 80NSSC20K1724 and JPL task 105393.509496.02.08.13.31). J.L.O. was supported by US National Science Foundation award 1643524. H.T.H. and M.D.P. were supported by the Met Office Hadley Centre Climate Programme funded by the UK Department for Science, Innovation, and Technology and Department for Environment, Food and Rural Affairs. B.F.-K. was supported by the National Oceanic and Atmospheric Administration (NA19OAR4310366) and Schmidt Futures (Scale-Aware Sea Ice Project). S.N. was supported by the US National Aeronautics and Space Administration (awards 80NSSC21K0915 and 80NSSC21K0322). N.R.G. was supported by the Ministry of Business, Innovation and Employment, New Zealand (grants RTUV1705 and ANTA1801) and Royal Society Te Apārangi (grant VUW-1501). B.P.H. was supported by the Singapore Ministry of Education Academic Research Fund (MOE2019-T3-1-004), National Research Foundation Singapore and Singapore Ministry of Education under the Research Centres of Excellence initiative. A.B.A.S. and T.L.E. were supported by the European Union’s Horizon 2020 research and innovation programme (PROTECT; grant agreement number 869304). T.L.E. was also supported by the UK Natural Environment Research Council (NE/T007443/1)