Samuel Bolduc-St-Aubin

Imagine a pendulum that is pushed in time with the seasons: harder in winter, softer in summer. But this pendulum has a quirk: a switch that operates with a delay. When the pendulum passes through zero, the switch clicks and changes the direction of the push. That is exactly how the simplified El Niño model built by mathematicians works.

Every year, as December approaches, the water off the coast of Peru becomes anomalously warm or anomalously cold. This is El Niño and La Niña, two phases of the same climate pendulum that swings in the equatorial Pacific. The pendulum is not a simple one: it remembers what happened to it several months earlier, and this memory determines which way it will swing next.