El Niño and La Niña, explained
These opposing phases of a vast Pacific climate pattern help steer weather across the globe.
Few phenomena influence global weather as profoundly as El Niño and La Niña, the two opposing phases of a vast climate pattern centred in the tropical Pacific Ocean. Understanding them helps explain everything from droughts and floods to hurricane seasons around the world.
The pattern, known formally as the El Niño–Southern Oscillation, revolves around the temperature of the ocean surface in the central and eastern tropical Pacific. During El Niño, those waters are unusually warm; during La Niña, they are unusually cool. A neutral phase sits in between.
These temperature shifts might seem remote, but they ripple across the planet by altering the behaviour of the atmosphere. El Niño tends to bring wetter conditions to parts of the Americas, drought to parts of Asia and Australia, and often suppresses Atlantic hurricane activity. La Niña generally flips many of these effects, and tends to favour a more active Atlantic hurricane season.
Because the pattern influences weather months in advance, forecasters watch Pacific ocean temperatures closely to inform seasonal outlooks, from winter forecasts to hurricane predictions.
El Niño and La Niña are natural cycles that have operated for millennia, typically shifting every few years. But scientists are studying how climate change may affect their frequency and intensity. For now, knowing which phase is in play offers one of the most useful clues to the weather the coming seasons may bring.