El Niño and La Niña — Earth science, 14–17 years
How unusual Pacific Ocean temperatures can change weather far away. Earth science, 14–17 years.
A Pacific Ocean rhythm
El Niño and La Niña are opposite phases of a recurring ocean-atmosphere pattern in the tropical Pacific. During El Niño, surface water in the central and eastern Pacific becomes unusually warm; during La Niña, it becomes unusually cool. The changed ocean temperature affects air movement and rainfall across distant regions.
The problem it helps solve
A puzzle for weather scientists was why rainfall and temperature could shift across continents even when the local sky gave no early warning. El Niño and La Niña connect those distant changes to a measurable Pacific pattern. They do not predict every storm, but they improve seasonal forecasts and explain broad probabilities.
Following one event
Suppose Pacific monitoring shows sea-surface temperatures 1.2 °C above the long-term average for several months. Scientists check wind, pressure and ocean heat, then classify the pattern as El Niño if the wider evidence agrees. They compare climate records to estimate likely effects, such as wetter conditions in one region and drought risk in another.
Not every unusual season is El Niño
It is reasonable to blame any hot, wet or dry season on El Niño because the pattern is famous for changing weather. In reality, local weather has many causes, and El Niño is identified from ocean and atmosphere measurements across a region. It changes chances and averages, not a guaranteed result for every town.
Where it appears outside school
Seasonal forecasts use El Niño and La Niña information to help farmers choose crops, water managers plan supplies and emergency services prepare for flood or drought risks. Fisheries also track the pattern because warmer or cooler surface water can move nutrients and fish. These are planning tools, not promises about one person’s weather.
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