Sophie Cravatte

Water remembers. Every current, every eddy, every degree of temperature in the ocean's depths does not vanish without a trace; it leaves a mark that can be read. But until recently, that mark was read only by bulky physical models that spent weeks on supercomputers and still got the details wrong.

An artist painting the ocean does not limit themselves to two colors: warm and cold. Likewise, climatologists studying El Niño increasingly speak of a whole palette of shades. El Niño is a warm current off the coast of Peru that, every few years, alters weather across the planet. Its counterpart, La Niña, brings cold.