Archived Global and European sea level

Global mean sea level in 2016 was the highest yearly average since measurements started in the late 19 th century; it was about 20 cm higher than at the beginning of the 20 th century. Estimates for the average rate of global sea level rise over the 20 th century range from 1.2 to 1.7 mm/year, with significant decadal variation. The rate of sea level rise since 1993, when satellite measurements became available, has been significantly higher, at around 3 mm/year. Evidence showing the predominant role of anthropogenic climate change in observed global mean sea level rise and the acceleration of sea level rise during recent decades has strengthened since the publication of the IPCC Fifth Assessment Report (AR5). All coastal regions in Europe have experienced an increase in absolute sea level, but with significant regional variation. Most coastal regions have also experienced an increase in sea level relative to land, with the exception of the northern Baltic Sea and the northern Atlantic coast, which are experiencing considerable land rise as a consequence of post-glacial rebound. Extreme high coastal water levels have increased at most locations along the European coastline. This increase appears to be predominantly due to increases in mean local sea level rather than to changes in storm activity. Global mean sea level rise during the 21st century will very likely occur at a higher rate than during the period 1971–2010. Process-based models considered in the IPCC AR5 project a rise in sea level over the 21st century (2100 vs. 1986–2005 baseline) that is likely (i.e. 66 % probability) in the range of 0.28–0.61 m for a low emissions scenario (RCP2.6) and 0.52–0.98 m for a high emissions scenario (RCP8.5). However, substantially higher values of sea level rise cannot be ruled out. Several recent model-based studies, expert assessments and national assessments have suggested an upper bound for 21st century global mean sea level rise in the range of 1.5–2.5 m. A recent study extending the IPCC AR5 projections estimates global sea level rise by 2300 to be in the range of 0.8–1.4 m for a low emissions scenario (RCP2.6) and 3.4–6.8 m for a high emissions scenario (RCP8.5). These values would rise substantially if the largest estimates of sea level contributions from Antarctica over the coming centuries were included. The rise in sea level relative to land along most European coasts is projected to be similar to the global average, with the exception of the northern Baltic Sea and the northern Atlantic coast, which are experiencing considerable land rise as a consequence of post-glacial rebound. Projected increases in extreme high coastal water levels are likely to mostly be the result of increases in local relative mean sea level in most locations. However, several recent studies suggest that increases in the meteorologically driven surge component could also play a substantial role, in particular along the northern European coastline. All available studies project that the damages from coastal floods in Europe would increase many-fold in the absence of adaptation, whereby the specific projections depend on the assumptions of the particular study.