Boy or Girl? The keys to understanding a unique phenomenon in the world
The two episodes are part of the same climatic system and alternate throughout the years
BarcelonaEl Niño is a natural climate phenomenon that occurs when the surface waters of the equatorial Pacific Ocean warm up more than usual. This warming alters the usual circulation of winds and rainfall on a large scale. Normally, trade winds push warm water westward in the Pacific, near Indonesia and Australia. But when these winds weaken, the warm water moves towards the central and eastern Pacific, especially off the coasts of Peru and Ecuador. This increases the sea temperature and alters precipitation.
Where does the name El Niño come from?El Niño is part of a larger climate system called the El Niño-Southern Oscillation (ENSO), which relates ocean temperature changes to variations in atmospheric pressure and winds in the tropical Pacific. El Niño episodes usually appear every two to seven years and can last between nine months and two years. When El Niño is intense, the planet's average global temperature tends to rise temporarily because the ocean releases more heat into the atmosphere. In fact, many of the warmest years on record have coincided with strong El Niño episodes.
El Niño gets its name because fishermen on the coasts of Peru and Ecuador observed centuries ago that, towards the end of December, a warmer-than-normal current of water appeared in this area of the Pacific Ocean. As it coincided with the Christmas season, they named it El Niño, referring to the Child Jesus.
What is La Niña and how does it form?La Niña is the opposite phenomenon to El Niño. In this case, the waters of the equatorial Pacific cool down more than usual. This happens because the trade winds strengthen and push the warm water even further west. As a consequence, cold waters emerge from the seabed in the eastern Pacific, a process known as upwelling.
La Niña is also part of ENSO and often appears after an El Niño episode, although they do not always alternate perfectly. There can also be neutral periods between phenomena. La Niña episodes also tend to occur every few years and, in some cases, last longer than El Niño. As they favor a cooling of the surface waters of the Pacific, they tend to slightly reduce the global temperature of the planet.
Which areas of the planet are most affected?The effects of El Niño and La Niña are not the same everywhere, but the Pacific regions and tropical areas are the most sensitive. During El Niño episodes, the west coast of South America, especially Peru and Ecuador, usually receives very heavy rains and floods. In contrast, Australia, Indonesia, and parts of Southeast Asia tend to suffer droughts and a higher risk of forest fires.
La Niña usually causes the opposite effect: more rain in Australia and Southeast Asia, and more drought on the South American Pacific coast. There are also impacts on other continents. Temperatures, storms, and precipitation can vary in Africa, India, North America, and even Europe. For example, some European winters become milder or wetter depending on the phase of ENSO.
Why do they affect the entire planet so much?The Pacific is the largest ocean on Earth and accumulates an enormous amount of energy in the form of heat. When the temperature of its waters changes, so does the way the atmosphere distributes heat and moisture around the planet. These alterations modify air currents, rain zones, and the trajectories of many storms. It is as if the Pacific acted as a great global climatic engine: any significant change in its functioning has worldwide consequences.
