HadISST

HadISST, or Hadley Centre Sea Ice and Sea Surface Temperature, is a global, gridded dataset of sea surface temperature (SST) and sea ice concentration (SIC) produced by the UK Met Office Hadley Centre. It provides monthly fields on a 1-degree grid covering from 1870 to the present, enabling long-term analyses of ocean temperature and sea ice conditions.

The dataset combines historical in-situ SST observations from ships and buoys with satellite observations for the later decades, and uses satellite-derived sea ice information to produce a consistent record. An objective analysis method integrates irregular observations onto a regular grid, with bias corrections to maintain continuity across the full time series. HadISST therefore offers a unified view of ocean temperature and sea ice over more than a century.

HadISST has undergone major revisions, with HadISST1 and HadISST2 representing successive improvements. HadISST2 provides enhanced calibration, bias adjustment, and data coverage, aiming to reduce inhomogeneities and numerical biases while extending the record into the recent past. The dataset is widely used in climate research to study long-term SST trends and variability (such as ENSO, the Pacific Decadal Oscillation, and the Atlantic Multidecadal Oscillation), to reconstruct historical climate conditions, and as input or validation data for climate models and reanalysis efforts.

Access to HadISST data is available from the Met Office Hadley Centre and associated data portals, with formats commonly provided in NetCDF on a 1-degree grid.