Three-month running mean of the Niño 3.4 sea-surface temperature anomaly, the NOAA measure of El Niño and La Niña. The instrumental counterpart of the reconstruction in enso_nino34.
Format
A data frame with 920 rows: year, season (three-month window,
e.g. "DJF"), sst (degrees Celsius), anomaly (degrees Celsius).
Source
NOAA Climate Prediction Center, https://www.cpc.ncep.noaa.gov/data/indices/oni.ascii.txt, accessed 2026-10-17. A work of the US Government, public domain.