European sea surface temperature

All European seas have warmed considerably since 1870 and particularly since the late 1970s, with recent years been among the warmest on record. According to climate projections, sea surface temperature in European basins are expected to increase by 2-6°C by 2100 under the high emissions scenario. The frequency and magnitude of marine heatwaves have increased significantly both globally and in European seas. This is projected to continue, with increasing impacts on climate and ecosystems expected.

Decadal average sea surface temperature anomaly in different European seas

Being the planet’s greatest carbon sink, oceans are absorbing more heat which results in an increase in sea surface temperature (SST) and rising sea levels. This affects species’ metabolism, distribution and phenology, with many marine species and habitats being highly sensitive to changes in SST. Increases in mean SST can also lead to increases in atmospheric water vapour over the oceans, influencing entire weather systems and eventually global climate. The EU is committed to mitigating global warming and its negative impacts, including on oceans, and adapting to climate change .

All five European seas have warmed considerably since 1870, particularly since the late 1970s. Between 1991 and 2022, SST increased by between around 0.3°C per decade in the North Sea and around 0.6°C per decade in the Black Sea.

Over the past century (1925-2016), the increase in SST has been accompanied by an increase in the frequency and intensity of marine heatwaves, both globally and in European seas, with an approximate doubling from 1982 to 2016 . This has had considerable ecological impacts, including promoting harmful algal blooms, with increased risks to human health, ecosystems and aquaculture . For example, recent marine heatwaves led to unprecedented levels of vibriosis infections along the Baltic Sea and North Sea coasts. Marine heatwaves can also affect climate on land, with those in the Mediterranean Sea being thought to have contributed to amplifying heatwaves and heavy precipitation events over central Europe and triggering intense extratropical cyclones.

Ocean temperatures at the surface are expected to increase further in the 21^st century, between 1.3°C (with a 90% spread from 0.2 to 2.5°C, henceforth referred to as a range of SSTs) and 3.5°C (2.2 to 5.8°C) for the Baltic Sea, 1.3°C (0.9 to 2.4°C ) and 3.5°C (2.7 to 5.5°C ) for the Black Sea, 1.1°C (0.6 to 2.1ºC ) and 3.4°C (2.6 to 5.0°C ) for the Mediterranean, and 1.0°C (–0.7 to 1.8°C) and 2.4°C (1.2 to 4.6°C) for the North Sea by 2100 for the ensemble medians under SSP1-2.6 and SSP5-8.5, respectively. Marine heatwaves are also projected to increase in frequency, duration, spatial extent and maximum intensity. Such changes could have widespread effects on marine species and cause the reconfiguration of marine ecosystems.

Projected sea surface temperature anomalies under different SSP scenarios for European seas and global ocean

Supporting information

Definition

This indicator monitors trends in average SST anomalies in Europe’s regional seas and in the global ocean. Care must be taken when comparing the results reported here with previous versions of the indicator, as differences can arise from the choice of underlying data sets.

SST is an important physical characteristic of the oceans. It varies naturally with latitude, being warmest at the equator and coldest in the Arctic and Antarctic regions. As the oceans absorb more heat, 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 (that is, when the daily SST exceeds a locally and seasonally defined threshold).

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 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 oceans 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 and 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.

Methodology

Methodology for indicator calculation

This methodology is extracted from Copernicus Climate Change Service (C3S web).

This indicator primarily uses information from the HadISST1, HadSST4, Extended Reconstruction Sea Surface Temperature version 5 (ERSSTv5) and European Space Agency Sea Surface Temperature Climate Change Initiative (ESA CCI/C3S SST Climate Data Record v2.1) Analysis data sets.

Anomalies are calculated relative to a 1991–2020 average. For the satellite data (ESA CCI/C3S SST), the anomalies are calculated daily based on a daily climatology computed from a five-day mean centered on each day. For the in situ datasets, anomalies are calculated on a monthly basis by subtracting the 1991–2020 mean anomaly (relative to the original baseline used by the dataset) for each month. Daily anomalies were aggregated to monthly anomalies, and the monthly anomalies were aggregated to annual anomalies giving each month an equal weight.

Area-averaged anomalies were calculated using an area-weighted average of non-missing grid cells within the chosen region. A grid cell was assumed to be within a region if its center was within the region. Ocean area in the in situ products was estimated based on the high-resolution C3S satellite product, assigning 100% ocean area to grid cells populated in the satellite product and 100% land area to grid cells that are missing in that product. A 10-year rolling mean centered on right edge of the window is applied to the annual times series.

Due to lack of observations during some periods of 19th century and first half of 20^th, Black Sea is only represented from the 1950s onward.

Uncertainty information in large scale aggregates is not available for the L4 satellite data, so uncertainties in this product were not computed.

Uncertainties in the HadSST4 product were calculated following Kennedy et al. (2019). Correlated uncertainties were assumed to be correlated within a year and uncorrelated between years where appropriate. Uncertainties were not calculated for the ERSSTv5 and HadISST1 datasets. No uncertainty information is available for HadISST1. Pre-computed uncertainties in the ERSSTv5 data are available for the global mean but not for the European seas and other regional SST averages. Uncertainty in ERSSTv5 is represented by an ensemble, but the ensemble is not regularly updated. Final uncertainty (shown in figure) is based on maximum and minimum values of HadISST1, ERSSTv5 and higher and lower boundaries of HadSST4.

The areas used for the regional seas are the following:

· Europe: 35°-70°N, 25°W-40°E

· Baltic Sea: 52.5°-67.5°N, 8.5°-30.5°E

· Black Sea: 39.5°-48.5°N, 27.5°W-42.5°E

· Mediterranean: 30.5°-46.5°N, 6.5°W-38.5°E

Methodology for gap filling

Not applicable.

Policy/environmental relevance

In February 2021, the European Commission adopted a new EU strategy for adaptation to climate change. The new strategy sets out how the European Union can adapt to the unavoidable impacts of climate change and become climate resilient by 2050. It has four principle objectives: to make adaptation smarter, swifter and more systemic, and to step up international action on adaptation to climate change. The strategy builds on the 2018 evaluation of the 2013 EU adaptation strategy accompanied by a Commission staff working document . An open public consultation was conducted in preparation for the new strategy between May and August 2020.

Targets

No targets have been specified.

Accuracy and uncertaintiesData sources and providers

CMIP6 models- Sea Surface Temperature - SSP5-8.5, CMIP coupled model intercomparison project
CMIP6 models- Sea Surface Temperature - SSP2-4.5, CMIP coupled model intercomparison project
CMIP6 models- Sea Surface Temperature - SSP1-2.6, CMIP coupled model intercomparison project
HadISST, Met Office Hadley Centre observations datasets
ESA SST CCI: Level 4 Analysis Climate Data Record, European Space Agency (ESA)
NOAA Extended Reconstructed Sea Surface Temperature (ERSST), Version 5, National Oceanic and Atmospheric Administration (NOAA)
HadSST.4.0.1.0, Met Office Hadley Centre observations datasets

Metadata

DPSIRTopicsTagsTemporal coverageGeographic coverage

TypologyUN SDGsUnit of measureFrequency of dissemination

References and footnotes

European Commission, 2021, 'A European Green Deal', European Commission - European Commission (
https://ec.europa.eu/info/strategy/priorities-2019-2024/european-green-deal_en)
accessed May 17, 2022.

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EC, 2020, Adaptation to climate change: blueprint for a new, more ambitious EU strategy, European Commission, Brussels.

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Oliver, E. C. J., Donat, M. G. and Burrows, M. T., 2018, 'Longer and more frequent marine heatwaves over the past century', Nature Communications 9, 1324.

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Smale, D. A., Wernberg, T., Oliver, E. C. J., Thomsen, M., Harvey, B. P., Straub, S. C., Burrows, M. T., Alexander, L. V., Benthuysen, J. A., Donat, M. G., Feng, M., Hobday, A. J., Holbrook, N. J., Perkins-Kirkpatrick, S. E., Scannell, H. A., Sen Gupta, A., Payne, B. L. and Moore, P. J., 2019, 'Marine heatwaves threaten global biodiversity and the provision of ecosystem services', Nature Climate Change 9(4), pp. 306–312 (
https://www.nature.com/articles/s41558-019-0412-1)
accessed January 12, 2022.

^a^b
Baker-Austin, C., Trinanes, J. A., Salmenlinna, S., Lofdahl, M., Siitonen, A., Taylor, N. G. H. and Martinez-Urtaza, J., 2016, 'Heatwave-associated vibriosis, Sweden and Finland, 2014', Emerging Infectious Diseases 22(7), pp. 1216–1220 (
http://wwwnc.cdc.gov/eid/article/22/7/pdfs/15-1996.pdf).</div>

^↵
Collins, M., Sutherland, M. and Bouwer, L., 2019, 'Extremes, abrupt changes and managing risk', in: Pörtner, H.-O., Roberts, D. C., and Masson-Delmotte, V. (eds), IPCC Special Report on the Ocean and Cryosphere in a Changing Climate, Cambridge University Press, Cambridge, UK.

^a^b
IPPC, 2019, Summary for Policymakers. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. Potner, H.O., Roberts, D.C., Masson-Delmotte, V., Zhai, P., Tignor, M., Poloczanska, E., Mintebeck, K., Nicolai, M., Okem, A., Petzold, J., Rama, B. and Weyer, n. (eds.).,

^↵
Baker-Austin, C., Trinanes, J. A., Salmenlinna, S., Löfdahl, M., Siitonen, A., Taylor, N. G. H. and Martinez-Urtaza, J., 2016, 'Heat Wave–Associated Vibriosis, Sweden and Finland, 2014', Emerging Infectious Diseases 22(7), pp. 1216–1220 (
http://wwwnc.cdc.gov/eid/article/22/7/15-1996_article.htm)
accessed July 22, 2020.

^↵
Rayner, N. A., Parker, D. E. and Horton, E. B., 2003, 'Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century', Journal of Geophysical Research 108(D14), 4407.

^↵
Kennedy, J. J., Rayner, N. A. and Atkinson, C. P., 2019, 'An ensemble data set of sea‐surface temperature change from 1850: the Met Office Hadley Centre HadSST.4.0.0.0 data set', Journal of Geophysical Research: Atmospheres 124(14), pp. 7719–7763.

^a^b
Huang, B., Thorne, P. W. and Banzon, B. F., 2017, 'Extended Reconstructed Sea Surface Temperature, Version 5 (ERSSTv5): Upgrades, validations, and intercomparisons', Journal of Climate 30(20), pp. 8179–8205.

^↵
Good, S. A., Embury, O. and Bulgin, C. E., 2019, 'ESA Sea Surface Temperature Climate Change Initiative (SST_cci): Level 4 Analysis Climate Data Record, version 2.1', Centre for Environmental Data Analysis, 22 August 2019 (
https://catalogue.ceda.ac.uk/uuid/62c0f97b1eac4e0197a674870afe1ee6)
accessed March 21, 2021.

^↵
EC, 2018, Commission Staff Working Document — Evaluation of the EU Strategy on adaptation to climate change accompanying the document ‘Report from the Commission to the European Parliament and the Council on the implementation of the EU strategy on adaptation to climate change’, SWD(2018) 461 final., SWD(2018) 461 final

^↵
EC, 2018, Commission Staff Working Document — Adaptation preparedness scoreboard country fiches accompanying the document ‘Report from the Commission to the European Parliament and the Council on the implementation of the EU Strategy on adaptation to climate change’, SWD(2018) 460 final.

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European sea surface temperature

Figure 1. Decadal average sea surface temperature anomaly in different European seas

Figure 2. Projected sea surface temperature anomalies under different SSP scenarios for European seas and global ocean

Supporting information

Methodology for indicator calculation

Methodology for gap filling

Targets

Data sets uncertainty

Rationale uncertainty

Metadata

References and footnotes