📌 Topic 05 of 6 · Chapter 03 · Climate of India
El Niño, La Niña & India’s Climate
ENSO, Indian Ocean Dipole, impact on Indian monsoon — complete notes for UPSC & PSC exams.
🌊 El Niño — What is it?
El Niño (Spanish for “The Boy/Christ Child”) is the abnormal warming of the central and eastern Pacific Ocean near the coast of Peru and Ecuador. It occurs every 2–7 years and disrupts global weather patterns.
| Feature | El Niño | La Niña |
|---|---|---|
| Pacific Ocean | Warming of central/eastern Pacific | Cooling of central/eastern Pacific |
| Indian Monsoon | Weakens SW monsoon → drought in India | Strengthens SW monsoon → good/excess rainfall |
| Australia | Drought in Australia | Heavy rainfall/floods in Australia |
| Peru/South America | Heavy rainfall, floods | Drought |
| Frequency | Every 2–7 years | Often follows El Niño |
⭐ ENSO = El Niño Southern Oscillation:
The combined phenomenon of El Niño + Southern Oscillation (pressure changes in Pacific). Southern Oscillation = seesaw of atmospheric pressure between eastern and western Pacific. When pressure is high in eastern Pacific (normal), monsoon is good. When pressure is low in eastern Pacific (El Niño), monsoon weakens.
The combined phenomenon of El Niño + Southern Oscillation (pressure changes in Pacific). Southern Oscillation = seesaw of atmospheric pressure between eastern and western Pacific. When pressure is high in eastern Pacific (normal), monsoon is good. When pressure is low in eastern Pacific (El Niño), monsoon weakens.
🌊 Indian Ocean Dipole (IOD)
- IOD = difference in sea surface temperature between western and eastern Indian Ocean
- Positive IOD = western Indian Ocean warmer than eastern = good monsoon for India
- Negative IOD = eastern Indian Ocean warmer = weak monsoon for India
- IOD can sometimes counteract El Niño’s negative effect on Indian monsoon
- 2019: El Niño year but positive IOD → India had normal monsoon
🌡️ Climate Change & India
- Rising temperatures: India’s average temperature has risen ~0.7°C since 1901
- Erratic monsoon: More intense but shorter rainfall events; longer dry spells
- Glacial retreat: Himalayan glaciers retreating — threatens river flows
- Sea level rise: Threatens coastal cities (Mumbai, Chennai, Kolkata)
- Extreme events: More frequent cyclones, floods, droughts, heat waves
- India’s commitments: Net zero by 2070; 500 GW renewable energy by 2030 (Paris Agreement)
📌 Key Exam Points:
• El Niño = warming of Pacific = weakens Indian monsoon = drought risk
• La Niña = cooling of Pacific = strengthens Indian monsoon = good rainfall
• Positive IOD = good monsoon for India
• ENSO = El Niño + Southern Oscillation = combined phenomenon
• Major El Niño years: 1982-83, 1997-98, 2015-16, 2023
• El Niño = warming of Pacific = weakens Indian monsoon = drought risk
• La Niña = cooling of Pacific = strengthens Indian monsoon = good rainfall
• Positive IOD = good monsoon for India
• ENSO = El Niño + Southern Oscillation = combined phenomenon
• Major El Niño years: 1982-83, 1997-98, 2015-16, 2023