Sea surface temperature (HadISST1)



This data set is only available for a restricted user group, please contact us if you want to access these data.

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Data access via file system: /data/icdc/ocean/hadisst1/


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The HadISST1 data set is a blend of historical SST and modern SST observations from ships, buoys, drifters, etc. and sea ice observations, partly from historical ship- and air-borne and partly from satellite data.

The SST data are taken from the Met Office Marine Data Bank (MDB), which from 1982 onwards also includes data received through the Global Telecommunications System (GTS). In order to enhance data coverage, monthly median SSTs for 1871-1995 from the Comprehensive Ocean-Atmosphere Data Set (COADS) (now ICOADS) were also used where there were no MDB data. The sea ice data are taken from a variety of sources including digitized sea ice charts and passive microwave retrievals.

For a detailed description of the dataset, see the web page at the Hadley Centre and the paper by Rayner et al. (see references).

The top right figure shows the time series of the global mean HadISST SST. We NOTE EXPLICITELY, that this time-series is based on a SIMPLE ARITHMETIC MEAN of the SST of the ice-free grid cells WITHOUT ANY WEIGHING with information about data density and quality - like is used to create the global SST and temperature anomalies of the HadCRUT and CRUTEM data sets.

Last update of this data set at ICDC: October 10, 2019

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Name Unit
Sea ice cover %

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Coverage, temporal and spatial resolution

Period and temporal resolution:

  • 01/1870 to 07/2019
  • Monthly

Coverage and spatial resolution:

  • Global
  • Spatial resolution: 1.0° x 1.0°, cartesian grid
  • Geographic latitude: -89.5°N to 89.5°N
  • Geographic longitude: -179.5°E to 179.5°E
  • Dimension: 360 columns x 180 rows
  • Altitude: 0.0 m


  • NetCDF

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Data quality

The offered data set does not include uncertainty estimates. Information about uncertainties are, however, given in the two publications listed in the references section.

Recent investigations have revealed some inconsistencies which are discussed and summarized in this report.

We (the ICDC team) recommend users of the HadISST1 data set to NOT use the sea ice concentration for quantitative investigations but only for qualitative purposes - e.g. for the delineation of the ice edge. Reasons for this are as follows:

- The sea ice concentration data is based on an inhomogeneous number and type of data; only with begin of the satellite era in 1978/79 data for sea ice concentration retrieval have been available quasi-daily. This applies in particular for the Southern Ocean.

- The Arctic sea ice concentrations contains artifacts. 1) Between November 1973 and February 1974 there is an inconsistency across the entire Arctic Ocean with unrealistic patches of around 90% and 100% sea ice concentration. 2) During late spring to early winter there is an unrealistic sea ice concentration gradient in the marginal ice zone. First the sea ice concentration increases from the ice edge towards the pack ice and eventually reaches 100%. But then there is a jump to values of 90% to 92% over large areas along the marginal ice zone before further to the north the sea ice concentration again increases towards 100%.

An alternative sea-ice concentration data set has been released: HadISST2; this data set can be downloaded here.

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Nick Rayner
Met Office Hadley Centre, FitzRoy Road, Exeter, Devon EX1 3PB
United Kingdom
email: nick.rayner (at) metofffice.gov.uk

John Kennedy
Met Office Hadley Centre, FitzRoy Road, Exeter, Devon EX1 3PB
United Kingdom
email: john.kennedy (at) metoffice.gov.uk

Stefan Kern
ICDC / CEN / University of Hamburg
email: stefan.kern (at) uni-hamburg.de

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Data citation

Please cite

Rayner, N. A., Parker, D. E., Horton, E. B., Folland, C. K., Alexander, L. V., Rowell, D. P., Kent, E. C., and Kaplan, A. (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century, J. Geophys. Res., 108(D14), 4407, doi: 10.1029/2002JD002670

when using the data.

Plus: Distributed in netCDF format (last access date: 2019-09-30) by the Integrated Climate Data Center (ICDC, http://icdc.cen.uni-hamburg.de) University of Hamburg, Hamburg, Germany.

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