Version 3b (v3b) of the Extended Reconstructed Sea Surface Temperature (ERSST) dataset is a monthly SST analysis on a 2-degree global grid based on the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) Release 2.4. ERSST v3b is generated using in situ SST data and improved statistical methods that allow stable reconstruction using sparse data throughout the 150 year record. The monthly SST analysis extends from January 1854 to the present month, but because of sparse data coverage in the early years, the analyzed signal is damped before 1880. After 1880, the strength of the signal is more consistent over time. The ERSST analysis is updated monthly with the available Global Telecommunication System (GTS) ship and buoy data for that month. The data from January 1985 to the previous month are recalculated every month, yet the data before Jan 1985 are not updated. SST anomalies are computed with respect to a 1971-2000 monthly climatology. ERSST is suitable for long-term global and basin-specific SST studies as short-term and local variations have been smoothed in the analysis. The previous ERSST Version 3 (v3) analysis used satellite-derived (AVHRR) SST data, however the satellite data are not included in v3b due to resulting residual biases. No satellite data were used in the earlier ERSST v2. ERSST is used as an input to the NCDC Merged Land-Ocean Surface Temperature (MLOST) dataset.