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Hadley Centre Sea Ice and Sea Surface Temperature data set (HadISST)

05/JUNE/2025: We have replaced the sea-surface temperature field previously released for January 2025 as it contained an error. Please redownload the data for January 2025 if you downloaded it prior to 05/June/2025.

Within the next year (2025), we will replace HadISST1 with a new dataset. If you are a regular HadISST1 user and would like a preview of this new dataset when it is available, please contact us.

The Met Office Hadley Centre's sea ice and sea surface temperature (SST) data set, HadISST1 is a combination of monthly globally-complete fields of SST and sea ice concentration on a 1 degree latitude-longitude grid from 1870 to date.

Previous service notes are available here

Fields for the month-before-last (see image below) are added to the data set soon after the start of every new month. In the picture white areas represent land and 100% ice cover.

Brief description of the data

The SST data are taken from collections of measurements from ships, drifting and moored buoys and satellite data. The sea ice data are taken from a variety of sources including digitized sea ice charts and passive microwave retrievals.

HadISST1 temperatures are reconstructed using a two stage reduced-space optimal interpolation procedure, followed by superposition of quality-improved gridded observations onto the reconstructions to restore local detail. The sea ice fields are made more homogeneous by compensating satellite microwave-based sea ice concentrations for the impact of surface melt effects on retrievals in the Arctic and for algorithm deficiencies in the Antarctic, and by making the historical in situ concentrations consistent with the satellite data. SSTs near sea ice are estimated using statistical relationships between SST and sea ice concentration.

For a detailed description of the dataset and its production process, see the cited paper (in references section). We recommended you read this before using the data.

Data are available from the download page without charge for the purposes of private study and scientific research, but please read the terms and conditions.

Commercial and media enquiries

You can access the Met Office Customer Centre, any time of the day or night by phone, fax or e-mail. Trained staff will help you find the information or products that are right for you.
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References

When using the data set in a paper, the following is the correct citation to use:

Rayner, N. A.; Parker, D. E.; Horton, E. B.; Folland, C. K.; Alexander, L. V.; Rowell, D. P.; Kent, E. C.; Kaplan, A. (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century J. Geophys. Res.Vol. 108, No. D14, 4407 10.1029/2002JD002670 (pdf ~9Mb)

Other information

Various diagnostics are produced from the monthly gridded fields.

Dataset produced in collaboration with: