El Niño Southern Oscillation (ENSO)

Why in News?

The year 2026 is being called an El Niño year due to the extreme summers, which cause heatwaves.

• El Niño Southern Oscillation (ENSO) – It is a climate phenomenon marked by changes in sea temperatures along the eastern Pacific Ocean, coupled with fluctuations in the overlying atmosphere.
• It can alter and interfere with the global atmospheric circulation, which, in turn, influences the weather worldwide.
• Phases of El Niño
  • Warm (El Niño, Spanish for little boy),
  • Cool (La Niña, Spanish for little girl), and
  • Neutral.
• Time Period – It occurs in irregular cycles of 2 to 7 years.

• Warm/El Niño Phase – During El Niño, the surface waters of this region of the Pacific get unusually warm, disrupting the flow of moist winds in India.
• The result is a weak or delayed monsoon for India, as well as dry spells in major agricultural states.
• There is also evidence that the frequency and severity of heatwaves India experiences are linked with the El Niño phenomenon.
• Cool/La Niña Phase – The opposite happens when La Niña is underway, that is, cooling of the surface waters of the eastern Pacific.
• India thus gets stronger, moisture-bearing winds, and typically experiences a boost in its southwest monsoon.
• In extreme situations, the excessive rain has caused flooding and crop damage as well.
• Neutral Phase – The eastern side of the Pacific Ocean (near the northwestern coast of South America) is cooler than the western side (near the Philippines and Indonesia).
• This is due to the prevailing wind systems that move from east to west, sweeping the warmer surface waters towards the Indonesian coast.
• The relatively cooler waters from below come up to replace the displaced water.

Quick Fact

Reference

Indian Express | From Western Disturbance to El Niño: the climate terms we are hearing