ENSO sonification · 1950 – present

Hear the Pacific

Each note is one season of tropical Pacific sea-surface temperature. El Niño warmth rises in pitch; La Niña cold falls. Underneath, atmospheric CO₂ measured at Mauna Loa slowly brightens a low drone.

Season—
Niño-3.4 anomaly—
Phase—
CO₂ (Mauna Loa)—

Loading NOAA data…

Jump to
Warm season (≥ +0.5 °C) Cool season (≤ −0.5 °C) Neutral CO₂ (right axis)

How it works, in four steps

1

The Pacific swings between warm and cool

Every 2–7 years, the surface of the tropical Pacific Ocean turns unusually warm (El Niño) or unusually cool (La Niña). These swings move rain, drought and heat waves around the whole planet.

Niño-3.4 Asia Americas
Simplified sketch, not to scale.
2

Scientists take its temperature in one spot

NOAA watches a patch of ocean in the middle of the Pacific called Niño-3.4 (the dashed box above). Each season they compare its temperature with what is normal for that time of year. The difference is the anomaly, the number this whole project is built on.

28.9 °Cthis season
−
26.9 °Cnormal
=
+2.0 °Canomaly
Illustrative numbers. +2.0 °C means "two degrees warmer than usual".
3

Warmer means a higher note

Each season becomes one note. The warmer the anomaly, the higher the note, like climbing stairs. The notes come from a pentatonic scale, so any sequence sounds pleasant. Drag the slider to try it.

−3 °C0+3 °C

4

Three voices and a hum

Warm, cool and normal seasons each get their own instrument, so you can hear which kind of season you're in. The low hum underneath is carbon dioxide in the air, measured on Mauna Loa in Hawaiʻi since 1958. As CO₂ rises, the hum gets brighter.

Warm seasonbright, plucky
Cool seasonsoft, round
Normal seasonquiet
——
CO₂ hum: darker → brighter

For musicians: how the sound is made

No samples. Every sound is synthesized live in your browser with Tone.js 14.8.49 on the Web Audio API. The waveform pictures below are rendered offline by the same engine with the same settings the player uses, so what you see is exactly what plays.

Signal chain

The voices

Scale and tuning

C major pentatonic (C D E G A) over three octaves, C3 to C6: 16 notes in 12-tone equal temperament with A4 = 440 Hz. Each note covers a 0.4 °C band of temperature anomaly.

NoteMIDIFrequencyAnomaly bandVoice

Timing and dynamics

What the music can't tell you

  • Notes are 0.4 °C apart, so seasons with similar temperatures can share a note. Hover the chart for the exact number.
  • One warm season doesn't make an El Niño. NOAA only declares one when warm conditions last for about five overlapping seasons in a row.
  • The newest numbers are early estimates and can change a little.
  • The music helps you feel the pattern. For real conclusions, use the numbers.
Technical details
  • Data: Oceanic Niño Index (ONI): 3-month running mean of ERSSTv5 sea-surface temperature anomalies in Niño-3.4 (5°N–5°S, 170°W–120°W), using NOAA's centered 30-year base periods.
  • Pitch: linear map from −3 °C to +3 °C onto a 16-note, three-octave C-major pentatonic scale (C3–C6); 0.4 °C per step. Values outside the range are clipped and flagged.
  • Timbre: NOAA's ±0.5 °C thresholds applied to each season individually (not an episode classification).
  • Drone: Mauna Loa monthly mean CO₂ (NOAA GML), scaled over the record's minimum to maximum, controls a low-pass filter. Silent before March 1958.
  • Full methods: docs/SCIENCE.md.