How the Seasonal Rhythm Pulls the Strings of El Niño
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.