Quick Facts
Explore El Niño
What Is El Niño
From the Walker Circulation to the thermocline — understand the physics of El Niño, the three phases of the ENSO cycle, and how it differs from La Niña.
Global Impacts
From Peru's fisheries to Australia's droughts, from the Indian monsoon to North American hurricane seasons — trace El Niño's cascading effects worldwide.
Historical Events
1982–83, 1997–98, 2015–16 — revisit the strongest El Niño events of the past century and how they reshaped societies and scientific understanding.
Monitoring & Prediction
TAO buoy arrays, satellite remote sensing, climate models — how scientists track Pacific Ocean temperature changes and predict El Niño months in advance.
The Three Phases of ENSO
ENSO (El Niño-Southern Oscillation) is the dominant mode of variability in the tropical Pacific ocean-atmosphere coupled system. It has three phases:
Sea surface temperatures in the central and eastern equatorial Pacific warm to ≥ +0.5°C above average, persisting for 5+ months. Trade winds weaken or reverse, warm water spreads eastward, and the Walker Circulation collapses.
Equatorial Pacific sea surface temperatures near the long-term average, fluctuating within ±0.5°C. Trade winds and the Walker Circulation operate normally. ENSO is in a neutral state roughly half the time.
Sea surface temperatures in the central and eastern equatorial Pacific cool to ≤ -0.5°C below average. Trade winds strengthen abnormally, upwelling intensifies. Often follows strong El Niño events.