Sea-level rise scenarios and information to support effective risk assessment and adaptation planning

Sea-level rise (SLR) information and scenarios have improved greatly over the last few decades. This includes spatially explicit online tools which facilitate access for coastal risk and adaptation users. There is also a greater need to provide guidance on the use of this information including the median and extreme projections. In addition to SLR science aspects this also requires consideration of the user perspective and the diverse decisions that are using SLR information. Some would argue that the user perspective and needs are the starting point for such analysis. Key user issues include risk tolerance and timescale of the decision. Co-production of appropriate SLR information among practitioners, policymakers and SLR scientists will support well-informed choices concerning the appropriate SLR information and its application in coastal adaptation and practise. This is a key step in mainstreaming SLR adaptation to a routine, operational activity which is a priority as SLR accelerates. SLR projections around the median are increasingly well understood and consistent across sources, with growing confidence in the methods used to develop them. However, less likely high-end SLR responses remain uncertain, mainly reflecting knowledge gaps and quantitative uncertainties in the Greenland/Antarctic ice sheet components of SLR. Consideration of this information, where appropriate, is important to understand the range of risks and avoid maladaptation. Despite this uncertainty, many decisions on maintenance, upgrade and new adaptation actions need to be made today or in the near future before we expect this uncertainty to be significantly addressed. There is a danger of both under- and over-preparing for these tail risks. Different approaches to tackling decisions under uncertainty will be considered. Taking an adaptive (or multi-step)  approach has many benefits implying a learning approach to adaptation and the need to assess the evolution of SLR over time in addition to projections. The implications for sea-level and associated ice sheet science will be considered.