Jan Sieber

The Pacific Ocean does not breathe evenly but in bursts. Every few years, its warm waters stir, and then Australia suffocates from drought while Peru is flooded with rain. This phenomenon is called El Niño, and it resembles a traveler wandering along an invisible road map.

A wave travels westward, reflects off the coast, and returns six months later to alter temperatures along the eastern Pacific. This journey of Rossby and Kelvin waves Mori-Zwanzig formalism turns into an equation with memory. Previously, climatologists added delays to El Niño models by intuition, relying on physical insight.

The ocean remembers its past. Heat given to the water off the coast of Norway does not vanish without a trace: it embarks on a long journey across the Atlantic, only to return decades later and alter the temperature at those same shores once again.

A cartographer charting a route through a mountain range notes not only peaks and valleys but also passes where the trail sharply changes direction.