About ENSO Monitor

El Niño-Southern Oscillation (ENSO) is the swing in tropical-Pacific sea surface temperatures and overlying atmospheric pressure that drives most of the world's biggest annual climate variability. This dashboard reads NOAA's official indices and pairs them with live signals from related monitors.

What the metrics mean

Niño-3.4 SST anomaly — central Pacific temperature departure from the 1991-2020 baseline. The benchmark single number for ENSO state.

ONI (Oceanic Niño Index) — 3-month running mean of Niño-3.4 anomaly. NOAA's official classification rule: El Niño = ONI ≥ +0.5 °C for 5+ consecutive 3-month seasons; La Niña = ONI ≤ −0.5 °C for 5+; otherwise Neutral.

Niño-1+2 — eastern Pacific, off Peru and Ecuador. Tends to warm first in developing El Niños and is the most directly relevant region for Peruvian fisheries and South American climate impacts.

SOI (Southern Oscillation Index) — standardized Tahiti-minus-Darwin sea level pressure anomaly. The atmospheric counterpart. Negative SOI = El Niño-like atmosphere; positive = La Niña-like.

Intensity bins (informal)

NOAA classifies events only as El Niño / La Niña / Neutral. Strength labels here are common informal conventions:

• Weak: |ONI| 0.5-1.0
• Moderate: |ONI| 1.0-1.5
• Strong: |ONI| 1.5-2.0
• "Super" (informal): |ONI| ≥ 2.0 at peak — only 4 events since 1950

Sources

NOAA CPC Niño SST indices, ONI, SOI (all no-auth, monthly cadence). Cross-tool reads from coral bleaching, marine heatwave, crop stress, climate tipping points monitors.