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Indicator Assessment

Global and European sea level rise

Indicator Assessment
Prod-ID: IND-193-en
  Also known as: CSI 047 , CLIM 012
Published 11 Dec 2020 Last modified 11 May 2021
13 min read

Global mean sea level (GMSL) has risen about 19 cm since 1900, at an accelerating rate. GMSL reached its highest value ever in 2019. Climate models project a GMSL rise during the 21st century that will likely be in the range of 0.29-0.59 m for a low emissions scenario and 0.61-1.10 m for a high one. GMSL projections that include the possibility of faster disintegration of the polar ice sheets predict a rise of up to 2.4 m in 2100 and up to 15 m in 2300. Most coastal regions in Europe have experienced an increase in sea level relative to land, except for the northern Baltic coast.

Observed and projected change in global mean sea level

Note: The left panel depicts the rise in global mean sea level from 1880 to 2019 based on two data sources. The red line (DMW) shows the hybrid sea-level reconstruction of sea level anomalies during 1900–2015 (Dangendorf et al., 2019). The uncertainty interval around is shaded. The dark blue line (CMEMS) shows the filtered sea level anomalies for the time period from 1993 to 2019 based on satellite observations (Ablain et al., 2017; WCRP Sea Level Budget Group, 2018). All values are relative to the average level of the period 1993-2012, during which the two datasets overlap. The right panel shows projections of global mean sea level until 2100 for three emissions scenarios based on the IPCC SROCC (Special Report on the Ocean and Cryosphere in a Changing Climate).

Data source:

The global mean sea level (GMSL) in 2019 was the highest ever measured. GMSL reconstructions based on tide gauge observations show a rise of 19 cm over the period since 1900 (Dangendorf et al., 2019).

GMSL is rising at an accelerating rate. The rate of GMSL rise during the period 1993-2019, for which satellite-based measurements are available, has been around 3.1 mm/year; more than twice as fast as during the period 1900-1992 (Oppenheimer et al., 2019; Dangendorf et al., 2019). Over the period 2010-2019, the rate of GMSL rise has further increased to 4.4 mm/year (Nerem et al., 2018; WMO, 2019).

Since 1970, anthropogenic forcing has been the predominant cause of this accelerating sea level rise both globally and in European regional seas. Thermal expansion of ocean water was initially the main driver, but melting of glaciers and disintegration of the Antarctic and Greenland ice sheets have exceeded the effects of thermal expansion since about 2000 (Dangendorf et al., 2017; WCRP Global Sea Level Budget Group, 2018; Oppenheimer et al., 2019).

Process-based global climate models project that the rise in GMSL during the 21st century (i.e. in 2100, compared with 1986-2005) will likely (66 % confidence) be in the range of 0.29-0.59 m for a low emissions scenario (RCP2.6), 0.39-0.72 m for a medium emissions scenario (RCP4.5) and 0.61-1.10 m for a high emissions scenario (RCP8.5) (Oppenheimer et al., 2019)

The Greenland and Antarctic ice sheets are the largest potential contributors to GMSL rise, but their future behaviour is still rather uncertain, particularly under high emissions scenarios. Studies considering processes that can lead to a faster disintegration of the Antarctic ice sheet, including a potential collapse of marine-based sectors, have estimated a GMSL rise of up to 2.4 m by 2100 and up to 15 m by 2300 (Bakker et al., 2017; Kopp et al., 2017; Bamber et al., 2019; Oppenheimer et al., 2019). The consideration of such high-end scenarios is important for long-term coastal risk management, in particular in densely populated coastal zones. Each 5-year delay in the peaking of global greenhouse gas emissions increases the median sea-level rise projections for 2300 by 0.2 m and extreme sea-level rise projections (95th percentile) by up to 1 m (Mengel et al., 2018).

Past trend and projected change in relative sea level across Europe

Note: The arrows show the trend in relative sea level at selected European tide gauge stations since 1970 (in mm/year) based on data from the Permanent Service for Mean Sea Level (PSMSL). The background colours show projections of European sea level change for 2081–2100 for RCP8.5 (in metres). Results are median values based on the values in the IPCC SROCC Table 4.4.

Data source:

Most European coastal regions experience increases in both absolute sea level (as measured by satellites) and relative sea level (as measured by tide gauges), the latter being more relevant for coastal protection. There are sizeable differences in the rates of sea level change across Europe. Notably, sea levels relative to land along the northern Baltic Sea coast and -to a lesser degree- the northern Atlantic coast are sinking because land levels are still rising, because of post-glacial rebound since the last ice age.

In future, relative sea level change along most of the European coastline is projected to be reasonably similar to the global average. The main exceptions are the northern Baltic Sea and the northern Atlantic coasts, which are experiencing considerable land rise as a consequence of post-glacial rebound and changes in the gravity field of the Greenland ice sheet. As a result, sea level relative to land in these regions will continue to rise more slowly than elsewhere or may even decrease (Slangen et al., 2014; Oppenheimer et al., 2019).

Supporting information

Indicator definition

This indicator comprises several metrics to describe past and future sea level rise globally and along European coastlines:

  • observed change in global mean sea level, based on reconstructions from tide gauge measurements (since 1900) and on satellite altimeter data (since 1993);
  • projected change in global sea level for three different forcing scenarios;
  • spatial trends in relative sea level along the European coastline, based on tide gauge stations with long time series (since 1970); and
  • projected change in relative sea level across European seas

Units

  • Change in sea level (mm).
  • Rate of sea level change (mm/year).

 

Policy context and targets

Context description

Sea level is an important indicator of climate change because it can have significant impacts on settlements, infrastructure, people and natural systems. The potential impacts include flooding, coastal erosion and the submergence of flat regions along continental coastlines and on islands. Rising sea levels can also cause saltwater intrusion into low-lying aquifers, thus threatening water supplies and endangering coastal ecosystems and wetlands.

Changes in global mean sea level result from a combination of several physical processes. Thermal expansion of the oceans occurs as a result of warming ocean water. Additional water is added to the ocean from a net melting of glaciers and small ice caps, and from the disintegration of the large Greenland and Antarctic ice sheets.

The locally experienced changes in sea level differ from global average changes for various reasons, including changes in large-scale ocean circulation, changes in the gravity field, and vertical land movement due to the ongoing effects of post-glacial rebound, local groundwater extraction or other processes.

Targets

No targets have been specified.

Related policy documents

No related policy documents have been specified

 

Methodology

Methodology for indicator calculation

Sea level changes can be measured using tide gauges and remotely from space using satellite altimeters. Many tide gauge measurements have long multi-decadal time series, with some exceeding 100 years. However, the data can be distorted by various regional and local effects, such as vertical land motion processes. Furthermore, there are significant gaps in the spatial coverage of tide gauges with long time series, including in Europe.

Satellite altimeters enable absolute sea level to be measured from space and provide much better spatial coverage (except at high latitudes); however, their record is limited to about 25 years. The global and European sea level trends are calculated from a combination of nine partly overlapping satellite missions. The data are corrected for seasonal variations, the inverse barometer effects and post-glacial rebound.

Sea level projections are based on process-based models, which are rooted in state-of-the-art climate model simulations. Projections for relative mean sea level in Europe consider the gravitational and solid Earth response and land movement due to glacial isostatic adjustment, but not land subsidence as a result of human activities.

Model-based projections for changes in regional sea level rise included only grid cells that are covered at least half by sea. Data for other grid cells partly covered by land and by sea were extrapolated using the nearest-neighbour method.

Methodology for gap filling

No methodology for gap fillings have been specified.

Methodology references

No methodology references available.

 

Uncertainties

Methodology uncertainty

No uncertainty has been specified

Data sets uncertainty

No uncertainty has been specified

Rationale uncertainty

No uncertainty has been specified

Data sources

Other info

DPSIR: Impact
Typology: Efficiency indicator (Type C - Are we improving?)
Indicator codes
  • CSI 047
  • CLIM 012
Frequency of updates
Updates are scheduled once per year
EEA Contact Info info@eea.europa.eu

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