Water in the equatorial Pacific heats up, then the warm current moves west, and a few months later it returns and cools the surface. This is like a pendulum that swings with a delay. There are two such pendulums in the ocean, and they are connected as if by a spring.

Scientists built a model of two pendulums with different delays. It turned out that if the spring is too stiff, both pendulums stop, and temperature oscillations disappear. But if the spring is weak, one pendulum can swing the other, even if the latter would have long since stopped on its own. That is why El Niño arrives irregularly: sometimes after two years, sometimes after seven.

This knowledge helps climatologists better understand which parts of the Pacific Ocean influence each other most strongly, and to read water temperature data more accurately.