The Pacific pendulum swings irregularly. Sometimes it barely trembles, and sometimes it makes a giant sweep that disrupts weather across the entire planet. El Niño is a warm current in the equatorial Pacific. It recurs every few years, but truly powerful events happen only every 10–20 years. Scientists have long struggled to understand why. A new study shows that the ocean behaves like a system that first accumulates heat in small increments and then releases it all at once.
The authors used a simple model describing temperature in two parts of the Pacific and the depth of the warm layer. They found that the system has two regimes: a calm one, where temperature barely changes, and an explosive one, where it rises sharply. The transition between regimes occurs through a special point, as if a pendulum passes its highest point and can no longer swing gently. Before a big swing, the ocean makes several small oscillations, and their pattern can hint that a strong El Niño is on the way.
The name 'El Niño' (Spanish for 'boy') was given by Peruvian fishermen who noticed that a warm current sometimes appears around Christmas. In the model, the point of no return for the development of a strong El Niño corresponds to the western Pacific temperature dropping just a few degrees below the climatic norm.
The idea of a critical threshold after which the system irreversibly transitions to an extreme state resonates with the concept of 'tipping points' in climate fiction, for example, in Kim Stanley Robinson's novel 'The Ministry for the Future', where climate tipping points trigger a cascade of events.