Henk Dijkstra

In 2014, forecasters around the world were expecting a powerful El Niño. The ocean had warmed, the trade winds had weakened, all the signs were there. But the event only came a year later. The Pacific seemed to change its mind.

In 2014, forecasters expected a strong El Niño, but it arrived only a year later. The ocean seemed to change its mind. Researchers studied a simple model of the tropical Pacific and found that the system has two distinct "personalities": one regularly generates powerful El Niños, while the other oscillates chaotically without them. This model resembles a pendulum that sometimes jumps to a different swing.

Every few years, the Pacific Ocean rearranges itself: warm water from the east flows toward the coasts of South America, and weather goes haywire for six months. This is El Niño, and its arrivals cannot be predicted precisely, even though there is a rhythm to them. A model with 930 variables shows that noise is to blame—random gusts of wind acting like an invisible conductor.