What is the ‘El Niño’ effect?

El Niño is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean.

  • El Nino is the “warm phase” of a larger phenomenon called the El Nino-Southern Oscillation (ENSO).
  • El Niño and La Niña are considered the ocean part of ENSO, while the Southern Oscillation is its atmospheric changes.
  • La Nina, the “cool phase” of ENSO, is a pattern that describes the unusual cooling of the region’s surface waters.

How El Niño get Initiated?

  • Change in surface water of eastern tropical Pacific Ocean is intimately tied to the atmosphere and to the winds blowing over the vast Pacific.
  • Easterly trade winds (which blow from the Americas toward Asia) loose strength and momentum and can even turn around into westerlies.
  • This allows great masses of warm water to slosh from the western Pacific toward the Americas.
  • It reduces the upwelling of cooler, nutrient-rich waters from the deep—shutting down or reversing ocean currents along the equator and along the west coast of South and Central America.
  • The circulation of the air above the tropical Pacific Ocean responds to this tremendous redistribution of ocean heat.
  • The strong high-pressure systems of the eastern Pacific weaken, thus changing the balance of atmospheric pressure across the eastern, central, and western Pacific.
  • The vastness of the Pacific basin—covering one-third of the planet—these wind and humidity changes get transmitted around the world, disrupting circulation patterns such as jet streams (strong upper-level winds).
  • These large-scale shifts in Pacific winds and waters initiate El Niño.


Effects of El Niño:Primary effects: These effects are directly caused.

  1. Alteration of weather patterns which include:
  • Temperature changes
  • Precipitation changes
  • Storm track changes and intensity
  1. Alteration of currents and ocean temperature

Secondary effects: These are some consequences.

  • Fires
  • Drought
  • Flooding
  • Crash of fisheries
  • Famine
  • Plagues (hanta virus)
  • Insect population explosion leading to disease and plagues.
  • Crop failure

Benefits of El Niño:

  • Fewer hurricanes and other tropical cyclones in the north Atlantic
  • Milder winters in southern Canada and the northern continental United States.
  • Replenishment of water supplies in the southwestern U.S.
  • Less disease in some areas due to drier weather (like malaria in southeastern Africa)

Also Read more Article like this for UPSC Preparation on : EDEN IAS GS Articles

Source: @nationalgeographic.org, @earthobservatory.nasa.gov, @earthobservatory.nasa.gov

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