The extended reconstructed sea surface temperature (ERSST) was constructed using the most recently available International Comprehensive Ocean-Atmosphere Data Set (ICOADS) SST data and improved statistical methods that allow stable reconstruction using sparse data. This monthly analysis begins January 1854, but because of sparse data the analyzed signal is heavily damped before 1880. Afterwards the strength of the signal is more consistent over time. The ERSST analysis will be updated as new data become available.
Currently, the ERSST V3 and ERSST version 2 (ERSST.v2) are available. ERSST.v2 is an improved extended reconstruction. In the reconstruction the high-frequency SST anomalies are reconstructed by fitting to a set of spatial modes. Compared to the earlier reconstruction, version 1 (v1), the improved reconstruction better resolves variations in weak-variance regions. It also uses sea-ice concentrations to improve the high-latitude SST analysis, a modified historical bias correction for the 1939-1941 period, and it includes an improved error estimate.