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. This coordinated roar is El Niño, the warm phase of the Pacific climate cycle that disrupts weather worldwide.
Scientists have long tried to hear the opening notes of this concert in advance, but they hit a wall known as the 'spring barrier.' Every spring, forecast models lost confidence: they could not see further than six months ahead. Then at the Potsdam Institute for Climate Impact Research, they decided not to listen to each instrument individually, but to monitor how harmoniously they play together. They built a network of 207 points, 14 in the equatorial Pacific where El Niño is born, and 193 around it. For each pair of points, they calculated how synchronously their temperatures changed over the past year, and reduced everything to a single overall indicator, something like the volume of the orchestra.
Since 2012, this method has been operating in real-time forecast mode, and its results are impressive. It correctly predicted that El Niño would not occur in 2012, 2013, and 2017, but would occur in 2014 and 2018. Over seven years, the algorithm issued ten warnings, and eight of them were correct. That is an 80% success rate, whereas random guessing of such a sequence would yield only one and a half percent. In September 2019, the orchestra again sounded in unison, and the algorithm announced that El Niño would return in 2020.
Previously, forecasters could only throw up their hands: in spring, ocean temperature data become unreliable, and models go blind. The new approach bypasses this wall because it listens not to the ocean but to the atmosphere above it. The air over warm water begins to behave coherently long before the ocean itself shows obvious signs of overheating. It is like hearing the musicians tuning their instruments before they start to play.
The practical benefit is obvious: farmers will have time to choose different crops, water agencies can reallocate supplies, and rescue teams can prepare for floods. However, the method cannot yet predict the strength of a future event, and scientists are already thinking about how to measure the volume of the orchestra, not just the moment it starts playing. If they succeed, humanity will for the first time be able to prepare for the whims of the Pacific a year in advance, rather than a couple of months. And then, perhaps, the roar of the elements will no longer catch us off guard.
An average El Niño raises the global temperature anomaly by about 0.1°C. If a strong event develops in late 2020, 2021 could become a new record year for temperature, since the atmospheric response lags by three months.
The idea of predicting global catastrophes from barely perceptible signs echoes Kim Stanley Robinson's novel "Forty Signs of Rain," where scientists try to convince politicians of an impending climate shift based on early indicators.