Indicator Assessment

Global and European sea-level rise

Indicator Assessment

Prod-ID: IND-193-en

Also known as: CSI 047 , CLIM 012

Published 28 Jul 2014 Last modified 11 May 2021

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Topics: Climate change adaptation Water and marine environment

This page was archived on 16 Sep 2014 with reason: Other (New version data-and-maps/indicators/sea-level-rise-2/copy_of_assessment was published)

The rate of global mean sea level rise has accelerated during the last two centuries. Tide gauges show that global mean sea level rose at a rate of around 1.7 mm/year over the 20^th century, but there have been significant decadal variations around this value.
Satellite measurements show a rate of global mean sea-level rise of around 3.2 mm/year over the last two decades.
Global mean sea level rise during the 21^st century will likely occur at a higher rate than during 1971–2010. Process-based models project a rise in 2081–2100, compared to 1986–2005, that is likely to be in the range 0.26–0.54 m for a low emissions scenario (RCP2.6) and 0.45–0.81 m for a high emissions scenario (RCP8.5). There is low confidence in the projections of semi-empirical models, which project a rise up to twice as large as the process-based models.
Available process-based models indicate global mean sea level rise by 2300 to be less than 1 m for greenhouse gas concentrations that peak and decline and do not exceed 500 ppm CO₂-equivalent but 1–3 m for concentrations above 700 ppm CO₂-equivalent.
Absolute sea level is not rising uniformly at all locations, with some locations experiencing much greater than average rise. Coastal impacts also depend on the vertical movement of the land, which can either add to or subtract from climate-induced sea-level change, depending on the particular location.

Observed change in global mean sea level

Note: The figure shows the global mean sea level from 1860 to 2009 as estimated from coastal and island sea-level data (1880 – 2009, blue) and from satellite altimeter data (1993 – 2009, grey).

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Contributions to global mean sea level budget

Note: Global mean sea level budget (in mm per year) over different time intervals in the past from observations and from model-based contributions. Uncertainty intervals denote the 5 to 95% range. The modelled thermal expansion and glacier contributions are computed from the CMIP5 results. The land water contribution is due to anthropogenic intervention only, not including climate-related fluctuations. Further information is available in the source document.

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Trend in relative sea level at selected European tide gauge stations

Note: The map shows the trend in relative sea level at selected European tide gauge stations since 1970. These measured trends are not corrected for local land movement. No attempt has been made to assess the validity of any individual fit, so results should not be treated as suitable for use in planning or policymaking. Geographical coverage reflects the reporting of tide gauge measurements to the Permanent Service for Mean Sea Level (PSMSL).

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Trend in absolute sea level in European seas based on satellite measurements (1992–2013)

Note: Trend in absolute sea level in European seas based on satellite measurements (1992–2013)

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Projections for global mean sea level rise and its contributions

Note: Projections for global mean sea level rise and its contributions in 2081–2100 relative to 1986–2005 from process-based models for the four representative concentration pathways (RCPs) and emisions scenario SRES A1B used in the IPCC Fourth Assessment Report. The grey boxes show the median of the model projections (central bar) as well as the likely range, which comprises two thirds of the model projections. The coloured bars and boxes show estimates for the different contributions to global sea-level rise. For further information, see the source document.

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Projected change in relative sea level

Note: The map shows the projected change in relative sea level in 2081-2100 compared to 1986-2005 for the medium-low emission scenario RCP4.5 based on an ensemble of CMIP5 climate models. Projections consider land movement due to glacial isostatic adjustment but not land subsidence due to human activities. No projections are available for the Black Sea.

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Past trends - Global

Sea-level changes can be measured using tide gauges and remotely from space using altimeters. Many tide gauge measurements have long multi-decade time series, with some exceeding more than 100 years. However, the results can be distorted by local effects. Satellite altimeters enable sea level to be measured from space and give much better spatial coverage (except at high latitudes). However, the length of the record is limited.

The rate of global mean sea level (GMSL) rise has accelerated during the last two centuries. The long-term rate of rise between 1901 and 2010 was around 1.7 mm/year (Figure 1). Rates of GMSL rise during the more recent period of 1993 to 2010 are considerably higher at about 3.2 mm/year [i].

The causes of global sea-level rise over recent decades are now reasonably well understood (Figure 2). Thermal expansion and glaciers account for around 75% of the measured sea-level rise since 1971. During the last decade, most ice was lost from glaciers in Alaska, the Canadian Arctic, the periphery of the Greenland ice sheet, the Southern Andes and the Asian Mountains. Together these regions account for more than 80% of the total ice loss. The contribution from melting of the Greenland and Antarctic ice sheets has increased since the early 1990s. Changes in land water storage have made only a small contribution, but the rate of groundwater depletion has increased recently and now exceeds the rate due to storage in reservoirs [ii].

Past trends - Europe

Sea-level measurements for the European region are available from tide gauges (relative sea-level; sometimes more than 100 years; Figure 3) and from satellite observations (absolute sea level; since 1992; Figure 4). These measurements show significant differences in the rate of both relative and absolute sea-level change across Europe.

Trends in absolute sea-level in the North Sea are typically around 2 mm/year, except for some parts of the southern-most North Sea where they are larger. Parts of the English Channel and the Bay of Biscay show a small decrease in sea level over this period. The Baltic Sea shows an increase of between around 2 mm/year and 5 mm/year. In the Mediterranean Sea there are regions with increases of more than 6 mm/year, and with decreases of more than -4 mm/year. The Black Sea has seen an increase in sea level of between zero and around 5 mm/year.

These big differences, even within a particular sea or basin, are due to different physical processes being the dominant cause of sea-level change at different locations. For instance, the Mediterranean Sea is a semi-closed, very deep basin, exchanging water with the Atlantic Ocean through the narrow Gibraltar Strait only. It is a concentration basin where evaporation greatly exceeds precipitation and river run-off. Therefore, salinity is one of the main physical parameters influencing the thermohaline circulation and sea-level variability in the Mediterranean, which may counteract the thermal expansion due to a rise in temperature. The NAO, interannual wind variability, changes in global ocean circulation patterns, and the location of large scale gyres are further factors that can influence local sea level in the European seas. Trends in sea level from selected tide gauge stations in Europe can differ from those measured by satellites because of the different time periods covered and because tide gauge measurements are influenced by vertical land movement whereas satellite measurements are not. In particular, the lands around the northern Baltic Sea are still rising since the last ice age due to the post-glacial rebound [iii].

Projections - Global

Currently there are two main approaches to projecting future sea level: process-based models that represent the most important known processes, and empirical-statistical models that apply the observed relationship between temperature or radiative forcing on the one hand and sea level on the other hand in the past and extrapolate it to the future. Both approaches produce a spread of results, which results in large uncertainties around future sea-level rise. A significant recent step forward in projecting future sea levels using process-based models is the improved understanding of the contributions to recent sea-level rise, which has increased confidence in the use of process-based models for projecting the future [iv].

The rise in GMSL for the period 2081–2100, compared to 1986–2005, based on process-based models is likely to be in the range 0.26–0.54 m for RCP2.6, 0.32–0.62 m for RCP4.5, 0.33–0.62 m for RCP6.0, and 0.45–0.81 m for RCP8.5. There is currently insufficient evidence to evaluate the probability of specific levels above the likely range. Based on current understanding, only the collapse of marine-based sectors of the Antarctic Ice Sheet, if initiated, could cause global mean sea level to rise substantially above the likely range projected for the 21st century by up to several tenths of a metre.

Projections from empirical-statistical models produce sea-level rise projections that are up to twice as high as those from current process-based models. Whilst these models have been successfully calibrated and evaluated against observed 20^th century sea-level changes, there is no consensus in the scientific community about their reliability and only low confidence in their projections [v].

Global mean sea level rise will continue beyond 2100. The limited number of available simulations with process-based models indicate GMSL rise by 2300 to be less than 1 m for greenhouse gas concentrations that do not exceed 500 ppm CO₂-equivalent but 1–3 m for concentrations above 700 ppm CO₂-equivalent (Figure 5). Projections based on process-based models suggest a quasi-linear sea-level commitment of 2.3 m per °C (uncertainty range: 1–3 m per °C) for a sustained warming over a period of 2000 years [vi].

Projections – Europe

Several factors, such as vertical land movement and projected changes in ocean circulation and storminess, cause local and regional sea level change to differ from the global mean. Projections for regional sea-level rise are available from the CMIP5 experiment with global climate models. Whilst there remains considerable uncertainty in the spatial patterns of future sea-level rise, around 70% of the world’s coastlines are expected to experience a sea level change within ±20% of the projected global mean sea level change.

Relative sea level rise in European seas is projected to be similar to the global average, with the exception of the northern Baltic Sea and the northern Atlantic, which are experiencing considerable land rise as a consequence of post-glacial rebound (Figure 6) [vii].

One study estimates absolute sea-level rise (which exclude changes in land level) around the UK for the 21^st century in the range of 12 cm (the lower bound of the low emission scenario) to about 76 cm (the upper bound of the high emission scenario). Larger rises could result from an additional ice sheet term, but this is more uncertain [viii]. Another study estimated the plausible high-end scenario for 21^st century sea-level rise on the North Sea coast of the Netherlands in the range 40 to 105 cm [ix]. Making multi-decadal regional projections for relatively small isolated and semi-isolated basins, such as the Mediterranean, is even more difficult than for the global ocean. One study made projections for the Mediterranean Sea based on the output of 12 global climate models for 3 emission scenarios [x]. The results project an ocean temperature-driven sea-level rise during the 21st century between 3 and 61 cm over the basin, which needs to be combined with a salinity-driven sea-level change between -22 and 31 cm.

[i] J. A. Church et al., ‘Sea-Level Change’, inClimate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, ed. T. F. Stocker et al. (Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press, 2013), Chapter 13, http://www.climatechange2013.org/images/report/WG1AR5_Chapter13_FINAL.pdf.

[ii] I. Velicogna, ‘Increasing Rates of Ice Mass Loss from the Greenland and Antarctic Ice Sheets Revealed by GRACE’,Geophysical Research Letters 36, no. 19 (13 October 2009), doi:10.1029/2009GL040222; Church et al., ‘Sea-Level Change’.

[iii] J. M. Johansson et al., ‘Continuous GPS Measurements of Postglacial Adjustment in Fennoscandia 1. Geodetic Results’,Journal of Geophysical Research 107, no. B8 (10 August 2002): 2157, doi:10.1029/2001JB000400.

[iv] Church et al., ‘Sea-Level Change’.

[v] Jason A. Lowe and Jonathan M. Gregory, ‘A Sea of Uncertainty’,Nature Reports Climate Change, 4 January 2010, 42–43, doi:10.1038/climate.2010.30; Church et al., ‘Sea-Level Change’.

[vi] Anders Levermann et al., ‘The Multimillennial Sea-Level Commitment of Global Warming’,Proceedings of the National Academy of Sciences 110, no. 34 (20 August 2013): 13745–50, doi:10.1073/pnas.1219414110; Church et al., ‘Sea-Level Change’.

[vii] Church et al., ‘Sea-Level Change’; A. B. A. Slangen et al., ‘Projecting Twenty-First Century Regional Sea-Level Changes’,Climatic Change 124, no. 1–2 (2014): 317–32, doi:10.1007/s10584-014-1080-9; HELCOM,Climate Change in the Baltic Sea Area - HELCOM Thematic Assessment in 2013, Baltic Sea Environment Proceedings (Helsinki: HELCOM, 2013), http://helcom.fi/Lists/Publications/BSEP137.pdf.

[viii] J. A. Lowe et al.,UK Climate Projections Science Report: Marine and Coastal Projections (Exeter, UK: Met Office Hadley Centre, 2009), http://ukclimateprojections.defra.gov.uk/media.jsp?mediaid=87905&filetype=pdf.

[ix] Caroline A. Katsman et al., ‘Exploring High-End Scenarios for Local Sea Level Rise to Develop Flood Protection Strategies for a Low-Lying Delta—the Netherlands as an Example’,Climatic Change 109, no. 3–4 (24 February 2011): 617–45, doi:10.1007/s10584-011-0037-5.

[x] Marta Marcos and Michael N. Tsimplis, ‘Comparison of Results of AOGCMs in the Mediterranean Sea during the 21st Century’,Journal of Geophysical Research 113, no. C12 (31 December 2008), doi:10.1029/2008JC004820.

Supporting information

Indicator definition

This indicator comprises several metrics to describe past and future sea-level rise globally and in European seas. Global sea-level rise is reported because it is the second-most important metric of global climate change (after global mean surface temperature), and because it is a proxy of sea-level rise in Europe. Past sea-level trends across Europe are reported in two different ways: first, absolute sea level change based on satellite altimeter measurements that reflect primarily the contribution of global climate change to sea-level rise in Europe; second, relative sea-level change based on tide gauges that also include local land movement, which is more relevant for the development of regional adaptation strategies.

The following components on observed sea-level rise are included:

Change in global mean sea level (time series starting in 1880, in mm), based on a reconstruction from various data sources (since 1880) and on satellite altimeter data (since 1993)
Trend in relative sea level across Europe (map, in mm/year), based on selected European tide gauge stations (since 1970)
Trend in absolute sea level across Europe (map, in mm/year), based on satellite measurements (since 1992)

In addition, this indicator informs about the contributions from various sources to the observed global sea level rise (since 1901).

Finally, this indicator presents projections for sea level rise in the 21st century, both globally and for the European seas.

Units

Sea level rise (mm)
Rate of sea level rise (mm/yr)

Rationale

Justification for indicator selection

Sea level is an important indicator of climate change because it is associated with significant potential impacts on settlements, infrastructure, people and natural systems. It acts on time scales much longer than those of indicators that are closely related to near-surface temperature change. Even if GHG concentrations were stabilised immediately, sea level would continue to rise for centuries.

Low-lying coastlines with high population densities and small tidal ranges are most vulnerable to sea-level rise, in particular where adaptation is hindered by a lack of economic resources or by other constraints. In Europe, the potential impacts of sea-level rise include flooding, coastal erosion, and the loss of flat coastal regions. Rising sea levels can also cause salt-water intrusion into low-lying aquifers and endanger coastal ecosystems and wetlands. Higher flood levels increase the risks to life and property, including sea dikes and other infrastructure, with possible follow-up effects on tourism, recreation and transportation functions. Damage associated with sea-level rise would frequently result from extreme events, such as storm surges, the frequency of which would increase as the mean sea level rises.

Scientific references

IPCC, 2013. Climate Change: The Physical Science Basis Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P. M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.
IPCC, 2014: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C.B. and V.R. Barros (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, in press.

Policy context and targets

Context description

In April 2013 the European Commission presented the EU Adaptation Strategy Package (http://ec.europa.eu/clima/policies/adaptation/what/documentation_en.htm). This package consists of the EU Strategy on adaptation to climate change /* COM/2013/0216 final */ and a number of supporting documents. One of the objectives of the EU Adaptation Strategy is Better informed decision-making, which should occur through Bridging the knowledge gap and Further developing Climate-ADAPT as the ‘one-stop shop’ for adaptation information in Europe. Further objectives include Promoting action by Member States and Climate-proofing EU action: promoting adaptation in key vulnerable sectors. Many EU Member States have already taken action, such as by adopting national adaptation strategies, and several have also prepared action plans on climate change adaptation.

The European Commission and the European Environment Agency have developed the European Climate Adaptation Platform (Climate-ADAPT, http://climate-adapt.eea.europa.eu/) to share knowledge on observed and projected climate change and its impacts on environmental and social systems and on human health; on relevant research; on EU, national and subnational adaptation strategies and plans; and on adaptation case studies.

Targets

No targets have been specified.

Methodology

Methodology for indicator calculation

Sea-level changes are measured using tide gauges and remotely from space using altimeters.

Currently there are two main approaches to projecting future sea level: physically-based models that represent the most important known processes, and statistical models that apply the observed relationship between temperature or radiative forcing on the one hand and sea level on the other hand in the past and extrapolate it to the future. Both approaches produce a spread of results, which results in large uncertainties around future sea-level rise.

As far as the satellite altimetry derived indicator is concerned, the global sea level trends are calculated from the along-track T/P Jason-1&2 series of sea level anomalies obtained. For the regional mean sea level, other altimetry missions (Envisat, ERS-1, ERS-2, Geosat-FollowOn) are also used after being adjusted on these reference missions in order to compute mean sea level at high latitudes (higher than 66°N and S), and also to improve spatial resolution by combining all these missions together. The data are corrected for seasonal variations and the inverse barometer effects. There is a correction for post-glacial rebound. For the global trend maps defined on a 1/3° Mercator-grid the maps combining all available altimeter data are used. For the Mediterranean and Black Seas, regional products defined on a 1/8° grid are used. Data are provided by the MyOcean project.

Methodology for gap filling

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 references

Church et al. (2013): Evaluating the ability of process based models to project sea-level change John A Church, Didier Monselesan, Jonathan M Gregory and Ben Marzeion: Evaluating the ability of process based models to project sea-level change. Environ. Res. Lett. 8 (2013) 014051 (8pp). doi:10.1088/1748-9326/8/1/014051
Woodworth and Player (2003): The Permanent Service for Mean Sea Level: An Update to the 21stCentury Journal of Coastal Research , Vol. 19, No. 2, Spring, 2003
Church and Clark (2013): Sea Level Change J. A. Church and P. U. Clark, “Sea-Level Change (Final Draft Underlying Scientific-Technical Assessment),” in Climate Change 2013: The Physical Science Basis (Intergovernmental Panel on Climate Change (IPCC), 2013), Chapter 13
Ablain et al. (2009): A new assessment of the error budget of global mean sea level rate estimated by satellite altimetry over 1993-2008 Ablain, M., A. Cazenave, G. Valladeau, and S. Guinehut. 2009: A new assessment of the error budget of global mean sea level rate estimated by satellite altimetry over 1993-2008. Ocean Sci, 5, 193-201
Ssalto/Duacs User Handbook (2013) Ssalto/Duacs User Handbook, 2006: (M)SLA and (M)ADT Near-Real Time and Delayed Time Products, SALP-MU-P-EA-21065-CLS, Edition 3.6.

Uncertainties

Methodology uncertainty

A paper describing the methodology and the estimation error was published in the Ocean Science journal:

Ablain, M., A. Cazenave, G. Valladeau, and S. Guinehut. 2009: A new assessment of the error budget of global mean sea level rate estimated by satellite altimetry over 1993-2008. Ocean Sci, 5, 193-201. Available at http://www.ocean-sci.net/5/193/2009/os-5-193-2009.pdf.

Data sets uncertainty

Changes in global average 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 large Greenland and West Antarctic ice sheets. Further contributions may come from changes in the storage of liquid water on land, either in natural reservoirs such as groundwater or man-made reservoirs.

The locally experienced changes in sea level differ from global average changes for various reasons. Changes in water density are not expected to be spatially uniform, and changes in ocean circulation also have regionally different impacts. At any particular location there may also be a vertical movement of the land in either direction, for example due to the post-glacial rebound (in northern Europe) or to local groundwater extraction.

Projections from process-based models with likely ranges and median values for global-mean sea level rise and its contributions in 2081–2100 relative to 1986–2005 have been made for the four RCP scenarios and scenario SRES A1B used in the AR4. The contributions from ice sheets include the contributions from ice-sheet rapid dynamical change. The contributions from ice-sheet rapid dynamics and anthropogenic land water storage have been treated as having uniform probability distributions, and as independent of scenario (except that a higher rate of change is used for Greenland ice-sheet outflow under RCP8.5).

Further information on uncertainties is provided in Section 1.7 of the EEA report on Climate change, impacts, and vulnerability in Europe 2012(http://www.eea.europa.eu/publications/climate-impacts-and-vulnerability-2012/).

Rationale uncertainty

No uncertainty has been specified

Data sources

Coupled Model Intercomparison Project Phase 5 - CMIP5
provided by Lawrence Livermore National Laboratory (LLNL)
RCP4.5 total sea level rise projections
provided by Integrated Climate Data Centre (ICDC)
Permanent Service for Mean Sea Level (PSMSL)
provided by Natural Environment Research Council (NERC)
Sea-Level Rise from the Late 19th to the Early 21st Century
provided by Commonwealth Scientific and Industrial Research Organisation (CSIRO)

Other info

DPSIR: Impact
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)

Indicator codes

CSI 047
CLIM 012

Frequency of updates

Updates are scheduled once per year

EEA Contact Info

Permalinks

Permalink to this version: deeb87e2a90a46ada0b1143acea8dded
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Older versions

11 Dec 2013 - Storm surges

21 Nov 2012 - Storm surges

19 Nov 2012 - Global and European sea-level rise

08 Sep 2008 - Storms and storm surges in Europe

08 Sep 2008 - Sea level rise

Geographic coverage

Austria Belgium Bulgaria Croatia Cyprus Czechia Denmark Estonia Finland France Germany Greece Hungary Iceland Ireland Italy Latvia Lithuania Luxembourg Malta Netherlands Norway Poland Portugal Romania Slovakia Slovenia Spain Sweden United Kingdom Arctic Ocean Atlantic Ocean Baltic Sea Bay of Biscay Black Sea Earth Indian Ocean Marine Arctic Ocean Marine Baltic sea Marine Black sea Marine Macaronesian/Atlantic ocean Marine Mediterranean sea Marine North sea Marine North-east Atlantic ocean Mediterranean Sea North Atlantic Ocean North Sea Norwegian Sea Pacific Ocean South Atlantic Ocean South Pacific Ocean (Tonga) Southern Ocean

Temporal coverage

1880-2013 2081-2100

For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/sea-level-rise-3/assessment or scan the QR code.

PDF generated on 25 Apr 2024, 04:31 PM

Dates

First draft created:

05 Feb 2014, 05:38 PM

Publish date:

28 Jul 2014, 11:52 AM

Last modified:

11 May 2021, 11:50 AM

Topics

Topics: Climate change adaptation Water and marine environment