Global and European sea-level rise

Assessment versions

Published (reviewed and quality assured)

• No published assessments

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.

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)

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.

Related policy documents

• Climate-ADAPT: Adaptation in EU policy sectors
  Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored
• Climate-ADAPT: Country profiles
  Overview of activities of EEA member countries in preparing, developing and implementing adaptation strategies
• DG CLIMA: Adaptation to climate change
  Adaptation means anticipating the adverse effects of climate change and taking appropriate action to prevent or minimise the damage they can cause, or taking advantage of opportunities that may arise. It has been shown that well planned, early adaptation action saves money and lives in the future. This web portal provides information on all adaptation activities of the European Commission.
• EU Adaptation Strategy Package
  In April 2013, the European Commission adopted an EU strategy on adaptation to climate change, which has been welcomed by the EU Member States. The strategy aims to make Europe more climate-resilient. By taking a coherent approach and providing for improved coordination, it enhances the preparedness and capacity of all governance levels to respond to the impacts of climate change.

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.

Data specifications

EEA data references

• No datasets have been specified here.

External data references

• Coupled Model Intercomparison Project Phase 5 - CMIP5
• RCP4.5 total sea level rise projections
• Permanent Service for Mean Sea Level (PSMSL)
• Sea-Level Rise from the Late 19th to the Early 21st Century

Data sources in latest figures

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