The International Research Institute (IRI) provides historical Niño 3.4 sea-surface-temperature anomaly data.
Notes on verification
Confirmed via IRI's own ENSO monitoring page plus independent corroboration from NOAA Climate.gov and a third-party weather site listing IRI as a data source. [tier=gold indep_score=0.95 clusters=3 claim_tier=everyday]
Sources
- El Niño Today | El Nino Theme Page - A comprehensive Resource (seed:science_and_space)
- https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/ (corroboration)
- https://www.climate.gov/news-features/understanding-climate/climate-variability-oceanic-nino-index (corroboration)
- https://www.webberweather.com/ensemble-oceanic-nino-index.html (corroboration)