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Extended Reconstructed Sea Surface Temperature (ERSST) v3b

The Extended Reconstructed Sea Surface Temperature (ERSST) dataset is a global monthly sea surface temperature analysis derived from the International Comprehensive Ocean–Atmosphere Dataset with missing data filled in by statistical methods. This monthly analysis begins in January 1854 continuing to the present and includes anomalies computed with respect to a 1971–2000 monthly climatology. The newest version of ERSST, version 3b, is optimally tuned to exclude under-sampled regions for global averages. In contrast to version 3, ERSST v3b does not include satellite data, which were found to cause a cold bias significant enough to change the rankings of months.

Annual ERSST v3b anomaly from 1880–2010 from 60°S and 60°N (red solid line). Note that the data are more reliable after the 1940s. The magnitude of the temperature increase in recent decades is much greater than the uncertainty in the data.

Background Information

The paper, "Improvements to NOAA's Historical Merged Land-Ocean Surface Temperature Analysis (1880–2006)," describes the update from ERSST v2 to ERSST v3, and both in situ and satellite Advanced Very High Resolution Radiometer SST data are included. The current version (ERRST v3) has satellite SST data not included in previous versions. However, the addition of satellite data led to residual biases. The ERSST v3b analysis is exactly as described in the ERSST v3 paper with one exception: ERSST v3b does not use satellite SST data. The ERSST v3 improvements are justified by testing with simulated data.

ERSST v3 has improved low frequency tuning that reduces the SST anomaly damping before 1930 using the optimized parameters. However, the addition of satellite SSTs introduced a small residual cold bias (in the order of 0.01°C). The Advanced Very High Resolution Radiometer is an infrared-based instrument. There must be clear-sky conditions to obtain infrared measurements, and cloud contaminated data are often difficult to identify. This contamination leads to a cold SST bias in the retrievals. There were attempts to correct these biases as mentioned in "Improvements to NOAA's Historical Merged Land-Ocean Surface Temperature Analysis (1880–2006)," but the adjustment did not fully compensate for the cold bias. While this small difference did not strongly influence the long-term trend, it was sufficient to change the rankings of the warmest months in the time series. Therefore, use of satellite SST data was discontinued. Except for the removal of the satellite aspect, ERSST v3b processing is identical to version 3.

Analysis Description

Generation of ERSST v3b uses in situ SST data and improved statistical methods that allow stable reconstruction using sparse data. The monthly analysis extends from January 1854 to the present, but because of sparse data in the early years, there is damping of the analyzed signal before 1880. After 1880, the strength of the signal is more consistent over time. ERSST is suitable for long-term global and basin-wide studies, and smoothed local and short-term variations are used in the dataset. The Merged Land-Ocean Surface Temperature product uses ERSST as input.

Data Access

To receive email notifications for ERSST update, please register online at NCDC ERSST Data Optional Registration. For information about the data status, changes to processes, and corrections, visit ERSST status.

References

Contact Information

Boyin Huang
boyin.huang@noaa.gov

Tom Smith
tom.smith@noaa.gov

Ron Ray
ron.ray@noaa.gov