ERSST v5¶

NOAA Extended Reconstructed Sea Surface Temperature (ERSST), Version 5

Being replaced

At a glance¶

Note on period: As of 2026-10-11, the NOAA PSL v5 file runs through September 2026. Discontinuation has been announced, so updates may stop. Early values (when observations were sparse) are highly uncertain; the official product page notes that data are more reliable after the 1940s.

Overview¶

ERSST is a global monthly analysis of SST derived from the International Comprehensive Ocean–Atmosphere Dataset (ICOADS), with Argo float data added. It is produced on a 2° × 2° grid with spatial completeness enhanced using statistical methods, beginning in January 1854. It uses in situ data only (no satellite data), and for many years has been the basis of NOAA's ENSO index (ONI) and the ocean component of the NOAA global temperature dataset (NOAAGlobalTemp).

What changes with the successor¶

ERSST v5 → ERSST v6¶

Transition: 2025-12

v6 keeps the 2° monthly grid and the in situ basis, but replaces the EOT-based gap filling with artificial neural network (ANN) interpolation. Ship-observation quality control, a large-scale filter and the ice-SST proxy were revised too, improving agreement with observations in data-sparse periods and regions and since the 1970s. The anomaly climatology moved to 1991–2020, and in 2026 NOAA's ENSO monitoring and NOAAGlobalTemp switched to v6.

Sources: Huang et al. (2025) ERSSTv6 Part I · Huang et al. (2025) ERSSTv6 Part II · NCEI Extended Reconstructed SST product page · NCEI news — Key NOAA Dataset Upgraded Using AI (2025-12-04) · NCEI news — AI Supercharges Key NOAA Dataset, Ensuring Peak Accuracy (NOAAGlobalTemp 6.1.0, 2026-04-13) · NOAA PSL Data Notices · NCAR Climate Data Guide — ERSSTv6

Compare the two side by side

Available variables¶

Variable names are those in the original NCEI NetCDF files. The NOAA PSL single-file version (sst.mnmean.nc) contains only sst.

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

Sea surface temperature¶

The full variable list is in the official documentation.

How to get the data¶

• NCEI direct download (monthly NetCDF) — HTTPS (wget / curl) No login needed
  • One file per month, named ersst.v5.YYYYMM.nc. ASCII files are in the ascii/ folder alongside.
• NOAA PSL (full record in one file) — Web download / THREDDS / OPeNDAP No login needed
  • The full record is in a single file, sst.mnmean.nc, which is convenient to use directly. Climatology files (e.g. 1991–2020) are also provided.
• NOAA CoastWatch ERDDAP (nceiErsstv5) — ERDDAP (choose region and period, then NetCDF, CSV, etc.) No login needed
  • A mirror that re-downloads the NCEI files each month, so new months appear a few days later.

Practical tips¶

• For new work, use ERSST v6. NOAA's ENSO monitoring, the RONI index and NOAAGlobalTemp have already moved to v6.
• v5 and v6 use different anomaly climatologies (v5 1971–2000, v6 1991–2020). Do not compare their ssta fields directly.
• Do not splice v5 and v6 into one time series. The interpolation methods differ, so values differ even for the same month.
• If you need v5, for example to reproduce a paper, download the full record now. Distribution locations may change once updates stop.

Notices and change history¶

References for your paper¶

Dataset citation¶

NCEI dataset DOI (v5) — DOI 10.7289/V5T72FNM

@misc{ersst_v5_dataset,
  author    = {Huang, Boyin and Thorne, Peter W. and Banzon, Viva F. and Boyer, Tim and Chepurin, Gennady and Lawrimore, Jay H. and Menne, Matthew J. and Smith, Thomas M. and Vose, Russell S. and Zhang, Huai-Min},
  title     = {{NOAA} Extended Reconstructed Sea Surface Temperature ({ERSST}), Version 5},
  year      = {2017},
  publisher = {NOAA National Centers for Environmental Information},
  doi       = {10.7289/V5T72FNM},
  note      = {Accessed DD MMM YYYY}
}

Reference papers¶

ERSST v5 paper — DOI 10.1175/JCLI-D-16-0836.1

@article{huang2017ersstv5,
  author  = {Huang, Boyin and Thorne, Peter W. and Banzon, Viva F. and Boyer, Tim and Chepurin, Gennady and Lawrimore, Jay H. and Menne, Matthew J. and Smith, Thomas M. and Vose, Russell S. and Zhang, Huai-Min},
  title   = {Extended Reconstructed Sea Surface Temperature, Version 5 ({ERSSTv5}): Upgrades, Validations, and Intercomparisons},
  journal = {Journal of Climate},
  volume  = {30},
  number  = {20},
  pages   = {8179--8205},
  year    = {2017},
  doi     = {10.1175/JCLI-D-16-0836.1}
}

Successor ERSST v6 paper, Part I (when using v6) — DOI 10.1175/JCLI-D-23-0707.1

Successor ERSST v6 paper, Part II (when using v6) — DOI 10.1175/JCLI-D-24-0185.1

Acknowledgements¶

NCEI asks that publications cite the dataset DOI and also reference the Huang et al. (2017) journal article. If you obtained the data from NOAA PSL, also include the acknowledgement wording requested on the PSL page.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• NCEI Extended Reconstructed SST product page (v6 and v5)
• NCEI ERSST v5 metadata and citation page
• NOAA PSL ERSST v6
• NCAR Climate Data Guide — ERSST v5
• NCAR Climate Data Guide — ERSST v6