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Abstract Beside climate‐change‐induced sea‐level rise (SLR), land subsidence can strongly amplify coastal risk in flood‐prone areas. Mapping and quantifying contemporary vertical land motion (VLM) at continental scales has long been a challenge due to the absence of gridded observational products covering these large domains. Here, we fill this gap by using the new European Ground Motion Service (EGMS) to assess the current state of coastal VLM in Europe. First, we compare the InSAR‐based EGMS Ortho (Level 3) with nearby global navigation satellite systems (GNSS) vertical velocity estimates and show that the geodetic reference frame used to calibrate EGMS strongly influences coastal vertical land velocity estimates at the millimeter per year level and this needs to be considered with caution. After adjusting the EGMS vertical velocity estimates to a more updated and accurate International Terrestrial Reference Frame (ITRF2014), we performed an assessment of VLM in European low elevation coastal flood plains (CFPs). We find that nearly half of the European CFP area is, on average, subsiding at a rate faster than 1 mm/yr. More importantly, we find that urban areas and populations located in the CFP experience a near −1 mm/yr VLM on average (excluding the uplifting Fennoscandia region). For harbors, the average VLM is even larger and increases to −1.5 mm/yr on average. This demonstrates the widespread importance of continental‐scale assessments based on InSAR and GNSS to better identify areas at higher risk from relative SLR due to coastal subsidence.

Abstract We produce projections of global mean sea‐level rise to 2500 for low and medium emissions scenarios (Shared Socioeconomic Pathways SSP1‐2.6 and SSP2‐4.5) relative to 2020, based on extending and combining model ensemble data from current literature. We find that emissions have a large effect on sea‐level rise on these long timescales, with [5, 95]% intervals of [0.3, 4.3]m and [1.0, 7.6]m under SSP1‐2.6 and SSP2‐4.5 respectively, and a difference in the 95% quantile of 1.6 m at 2300 and 3.3 m at 2500 for the two scenarios. The largest and most uncertain component is the Antarctic ice sheet, projected to contribute 5%–95% intervals of [−0.1, 2.3]m by 2500 under SSP1‐2.6 and [0.0, 3.8]m under SSP2‐4.5. We discuss how the simple statistical extensions used here could be replaced with more physically based methods for more robust predictions. We show that, despite their uncertainties, current multi‐centennial projections combined into multi‐study projections as presented here can be used to avoid future “lock‐ins” in terms of risk and adaptation needs to sea‐level rise.

Abstract Global coastal flood exposure (population and assets) has been growing since the beginning of the industrial age and is likely to continue to grow through 21st century. Three main drivers are responsible: (a) climate‐related mean sea‐level change, (b) vertical land movement contributing to relative sea‐level rise, and (c) socio‐economic development. This paper attributes growing coastal exposure and flood risk from 1860 to 2100 to these three drivers. For historic flood exposure (1860–2005) we find that the roughly six‐fold increase in population exposure and 53‐fold increase in asset exposure are almost completely explained by socio‐economic development (>97% for population and >99% for assets). For future exposure (2005–2100), assuming a middle‐of‐the‐road regionalized socio‐economic scenario (SSP2) without coastal migration and sea‐level rise according to RCP2.6 and RCP6.0, climate‐change induced sea‐level rise will become the most important driver for the growth in population exposure, while growth in asset exposure will still be mainly determined by socio‐economic development.

Abstract Port infrastructure is critical to the world's economy and has seen major expansion over the last few decades. In the future there are likely to be further demands for port capacity which will require additional port area while existing ports will need upgrading in response to sea‐level rise to maintain current levels of operability. This analysis considers potential changes to 2050 under four climate‐based scenarios which aim to explore changes in international maritime trade consistent with global temperature increases of 2 °C and 4 °C and the implications of associated sea‐level rise. All scenarios anticipate a significant increase in trade, and a change in distribution across commodities. The demand for port handling areas in 2050 is roughly double to quadruple that of the baseline (2010) across scenarios. The maximum demand occurs under an unmitigated climate and high intensity in commodity movement with a maximum area in 2050 of 5,054km2. The minimum demand (2,510km2) occurs under a scenario of regionalized green energy production and lower material intensity. The total global investment costs for port adaptation to sea‐level rise and provision of new areas are between 223 and 768 billion USD to 2050. These are dominated by the need for new area construction with the adaptation of base year areas to relative sea‐level rise representing a maximum of 6% of total costs globally. Therefore, in addition to adapting existing port areas to sea‐level rise, it is equally or more important to consider provision of new ports.