Oceanic Niño Index (ONI). The standard ENSO index: Niño-3.4 sea-surface temperatures against a fixed 30-year baseline, tracking the Pacific signal that drives El Niño and La Niña.
Central Pacific. The headline region — best single predictor of global ENSO impacts.
El Niño ≥ +0.5°C · La Niña ≤ −0.5°C; the shaded bands mark those thresholds. Switch on the trendline to see the 10-year rolling average and how the baseline itself drifts over the decades.
Historical distribution of every recorded ASO value. The red line marks where the current reading (2.50°C) sits in the record.