Indicator Specification

Sea surface temperature

Indicator Specification
  Indicator codes: CSI 046 , CLIM 013
Published 04 Dec 2019 Last modified 30 Jun 2021
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This indicator monitors trends in average SST anomalies in Europe’s regional seas and in the global ocean.

Assessment versions

Published (reviewed and quality assured)
  • No published assessments


Justification for indicator selection

SST is an important physical characteristic of the oceans. SST varies naturally with latitude, being warmest at the equator and coldest in the Arctic and Antarctic regions. As the oceans absorb more heat, the SST will increase (and heat will be redistributed to deeper water layers). Increases in the mean SST are also accompanied by increases in the frequency and intensity of marine heatwaves.

Increases in SST can lead to an increase in atmospheric water vapour over the oceans, influencing entire weather systems. The North Atlantic Ocean plays a key role in the regulation of climate over the European continent by transporting heat northwards and by redistributing energy from the atmosphere to the deep parts of the ocean. The Gulf Stream and its extensions, the North Atlantic Current and Drift, partly determine weather patterns over the European continent, including precipitation and wind regimes. One of the most visible physical ramifications of increased temperature in the ocean is a reduction in the area of sea ice coverage in the Arctic polar region.

Temperature is a determining factor for the metabolism of species, and thus for their distribution and phenology, such as the timing of seasonal migrations, spawning events or peak abundances (e.g. plankton bloom events). There is an accumulating body of evidence suggesting that many marine species and habitats, such as cetaceans in the North Atlantic Ocean, are highly sensitive to changes in SST. Increased temperature may also increase stratification of the water column. Such changes can significantly reduce vertical nutrient fluxes in the water column, thereby negatively influencing primary production and phytoplankton community structure. Further changes in SST could have widespread effects on marine species and cause the reconfiguration of marine ecosystems.

Scientific references

Indicator definition

  • This indicator monitors trends in average SST anomalies in Europe’s regional seas and in the global ocean.


  • Temperature (°C).

Policy context and targets

Context description

In April 2013, the European Commission presented the EU adaptation strategy package. This package consists of the EU strategy on adaptation to climate change (COM/2013/216 final) and a number of supporting documents. The overall aim of the EU adaptation strategy is to contribute to a more climate-resilient Europe.

One of the objectives of the EU adaptation strategy is to allow 'Better informed decision-making', which will be achieved by bridging knowledge gaps and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘one-stop shop’ for climate adaptation information in Europe. Climate-ADAPT has been developed jointly by the European Commission and the European Environment Agency (EEA) to share knowledge on (1) observed and projected climate change and its impacts on environmental and social systems and on human health, (2) relevant research, (3) EU, transnational, national and subnational adaptation strategies and plans, and (4) adaptation case studies.

Further objectives include 'Promoting adaptation in key vulnerable sectors through climate-proofing EU sector policies' and 'Promoting action by Member States'. Most EU Member States have already adopted national adaptation strategies and many also have prepared action plans on climate change adaptation. The European Commission also supports adaptation in cities through the Covenant of Mayors for Climate & Energy initiative.

In September 2016, the European Commission presented an indicative roadmap for the evaluation of the EU adaptation strategy by 2018.

In November 2013, the European Parliament and the Council of the European Union adopted the EU's Seventh Environment Action Programme (7th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7th EAP is intended to help guide EU action on the environment and climate change up to and beyond 2020. It highlights that ‘Action to mitigate and adapt to climate change will increase the resilience of the Union’s economy and society, while stimulating innovation and protecting the Union’s natural resources.’ Consequently, several priority objectives of the 7th EAP refer to climate change adaptation.


No targets have been specified.

Related policy documents

  • 7th Environment Action Programme
    DECISION No 1386/2013/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 20 November 2013 on a General Union Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. In November 2013, the European Parliament and the European Council adopted the 7 th EU Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. This programme is intended to help guide EU action on the environment and climate change up to and beyond 2020 based on the following vision: ‘In 2050, we live well, within the planet’s ecological limits. Our prosperity and healthy environment stem from an innovative, circular economy where nothing is wasted and where natural resources are managed sustainably, and biodiversity is protected, valued and restored in ways that enhance our society’s resilience. Our low-carbon growth has long been decoupled from resource use, setting the pace for a safe and sustainable global society.’
  • 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.
  • Evaluation of the EU Adaptation Strategy Package
    In November 2018, the EC published an evaluation of the EU Adaptation Strategy. The evaluation package comprises a Report on the implementation of the EU Strategy on adaptation to climate change (COM(2018)738), the Evaluation of the EU Strategy on adaptation to climate change (SWD(2018)461), and the Adaptation preparedness scoreboard Country fiches (SWD(2018)460). The evaluation found that the EU Adaptation Strategy has been a reference point to prepare Europe for the climate impacts to come, at all levels. It emphasized that EU policy must seek to create synergies between climate change adaptation, disaster risk reduction efforts and sustainable development to avoid future damage and provide for long-term economic and social welfare in Europe and in partner countries. The evaluation also suggests areas where more work needs to be done to prepare vulnerable regions and sectors.

Key policy question

What are the trends in surface water temperature across European seas?



Methodology for indicator calculation

The current indicator primarily uses information from the HadISST1 (Rayner et al., 2003), HadSST4 (Kennedy et al., 2019), ERSSTv5 (Huang et al., 2017), ESA SST CCI Analysis (Merchant et al., 2019) and the OSTIA (Stark et al., 2007) data sets.

Each data set was averaged on to a common 5° latitude by 5° longitude monthly grid. These averaged data sets were used to calculate the regional area averages. Regional area averages were calculated by a weighted average of grid cell values where the weights were equal to the area of ocean in that grid cell (determined using the SST CCI analysis land mask). The OSTIA real-time updates include some lakes not considered in the SST CCI Analysis and other data sets. These lakes were masked out of the OSTIA analysis.

There is a small, geographically varying offset between the OSTIA and SST CCI Analysis data sets. The OSTIA data set represents the 'foundation' SST and the SST CCI Analysis data set represents SST at a depth of 0.2 m; at least part of the variability is due to these differences in definitions.

A monthly time series was calculated for each of the seas and regions. A trailing 120-month (i.e. decadal) mean was calculated from the monthly series. Consequently, the first available decadal mean for a series is 120 months after the start date of that series.

Uncertainty in the long-term data sets is assessed as the range of the three data sets (HadISST1, Rayner et al., 2003; ERSSTv5, Huang et al., 2017; and HadSST4, Kennedy et al., 2019), including the estimated uncertainty range from HadSST4. This therefore covers uncertainties arising from measurement, sampling, bias adjustment and spatial infilling, as well as structural uncertainty. The HadSST4 uncertainty range was calculated as described in the HadSST4 paper (Kennedy et al., 2019). Correlated errors were assumed to be correlated within a year and uncorrelated between years.

Methodology for gap filling

Not applicable.

Methodology references



Methodology uncertainty

Not applicable.

Data sets uncertainty

Systematic observations of SST began around 1850. More recently, these manual measurements have been complemented by satellite-based observations that have a high resolution in terms of time and a wide geographical coverage, as well as by measurements from drifting buoys and Argo floats that automatically measure temperature and salinity below the ocean surface.

Rationale uncertainty

No uncertainty has been specified

Further work

Short term work

Work specified here requires to be completed within 1 year from now.

Long term work

Work specified here will require more than 1 year (from now) to be completed.

General metadata

Responsibility and ownership

EEA Contact Info

Hans-Martin Füssel


European Environment Agency (EEA)


Indicator code
CSI 046
CLIM 013
Version id: 4

Frequency of updates

Updates are scheduled every 2 years


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