Armin Bunde

An orchestra falls out of tune before a storm, then plays in unison again. In the equatorial Pacific, within a rectangle stretching from 5°S to 5°N and from 120°W to 170°W, water temperatures usually change in concert, like musicians playing the same part. This area is called the Niño 3.4 region.

Every day, the ocean in the tropical Pacific carries on a quiet conversation with itself: water temperatures are slightly higher in some places, slightly lower in others, and these patches of warmth and cold slowly drift into one another. This chatter seems random, but it hides a signal.

The Pacific Ocean resembles a vast brass band, where each musician is a point on the weather map. Usually, they play each in their own way: in one place the air warms, in another it cools, and the overall melody seems like random noise. But every few years, the instruments suddenly begin to sound in unison, and then a wave of droughts, floods, and abnormal heat sweeps across the planet.

Two barometers hang on the wall. One reads clear, the other says partly cloudy. Which weather do you trust? That is roughly the question facing a group of climate scientists when two independent methods predicted different futures for the Pacific Ocean in 2026.