Using inter-glacials to assess future sea-level scenarios (iGlass)

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The vulnerability of extensive near-coastal habitation, infrastructure, and trade makes global sea-level rise a major global concern for society. The UK coastline, for example, has ~£150 billion of assets at risk from coastal flooding, of which with £75 billion in London alone. Consequently, most nations have developed/ implemented protection plans, which commonly use ranges of sea-level rise estimates from global warming scenarios such as those published by IPCC, supplemented by worst-case values from limited geological studies. UKCP09 provides the most up-to-date guidance on UK sea-level rise scenarios and includes a low probability, high impact range for maximum UK sea level rise for use in contingency planning and in considerations regarding the limits to potential adaptation (the H++ scenario). UKCP09 emphasises that the H++ scenario is unlikely for the next century, but it does introduce significant concerns when planning for longer-term future sea-level rise. Currently, the range for H++ is set to 0.9-1.9 m of rise by the end of the 21st century. This range of uncertainty is large (with vast planning and financial implications), and - more critically - it has no robust statistical basis. It is important, therefore, to better understand the processes controlling the maximum sea-level rise estimate for the future on these time-scales. This forms the overarching motivation for the consortium project proposed here. iGlass is a broad-ranging interdisciplinary project that will integrate field data and modelling, in order to study the response of ice volume/sea level to different climate states during the last five interglacials, which include times with significantly higher sea level than the present. This will identify the likelihood of reduced ice cover over Greenland and West Antarctica, an important constraint on future sea-level projections. A key outcome will be to place sound limits on the likely ice-volume contribution to maximum sea-level rise estimates for the future. Our project is guided by three key questions: Q1. What do palaeo-sea level positions reveal about the global ice-volume/sea-level changes during a range of different interglacial climate states? Q2. What were the rates of sea-level rise in past interglacials, and to what extent are these relevant for future change, given the different climate forcing? Q3. Under a range of given (IPCC) climate projection scenarios, what are the projected limits to maximum sea-level rise over the next few centuries when accounting for ice-sheet contributions? The research will directly inform decision-making processes regarding flood risk management in the UK and abroad. In this respect, the project benefits from the close co-operation with scientists and practitioners in the UK Environment Agency, UKCIP, the UK insurance industry, as well as the wider global academic and user communities.