Syllabus: GS1/Geography
Context
- Recently, the National Oceanic and Atmospheric Administration (NOAA) has forecasted that neutral conditions will dominate the Pacific Ocean until October 2025.
- It highlights the absence of El Niño or La Niña phenomena, collectively known as the El Niño-Southern Oscillation (ENSO).
About El Niño-Southern Oscillation (ENSO)
- It is a naturally occurring climate phenomenon resulting from interactions between the ocean and atmosphere in the equatorial Pacific Ocean. It has three distinct phases:
- El Niño: It is a naturally occurring climate pattern associated with the warming of the ocean surface temperatures in the central and eastern tropical Pacific Ocean.
- It occurs irregularly at two to seven year intervals.
- La Nina: It is characterised by cooler than average ocean surface temperatures in the central and eastern tropical Pacific Ocean.
- During La Niña events, trade winds are even stronger than usual, pushing more warm water toward Asia.
- Neutral: Neither El Niño nor La Niña conditions dominate.
- Neutral conditions occur when sea surface temperatures in the equatorial Pacific Ocean remain close to the long-term average.
| Key Components of ENSO | ||
| El Niño | La Niña | Southern Oscillation |
| – Suppresses rainfall in Australia, Indonesia, and India. – Increases rainfall and flooding in the southern US and Peru. – Typically weakens the Indian Monsoon and increases hurricane activity in the Pacific. | – Strengthens monsoons in South Asia. – Brings drought to the U.S. Southwest. – Causes increased Atlantic hurricane activity. | – Refers to the atmospheric component of ENSO. – Measured via the Southern Oscillation Index (SOI), which tracks pressure differences between Tahiti and Darwin, Australia. |
Recent Trends
- The NOAA report indicates that the short and weak La Niña observed earlier this year has transitioned into neutral conditions.
- Sub-surface temperatures in the Pacific have normalized, signaling the end of La Niña.
Impact on Global Weather
- Global Implications: Neutral conditions reduce the likelihood of extreme weather events linked to El Niño or La Niña, such as droughts or floods.
- However, localized weather anomalies may still occur due to other climatic factors.
- India’s Southwest Monsoon: ENSO-neutral conditions are generally associated with normal or above-normal rainfall during India’s monsoon season.
- It is a positive development for agriculture, as nearly 70% of India’s annual rainfall occurs between June and September.
| Global Impacts of ENSO | ||
| Region | El Niño Effects | La Niña Effects |
| India | – Weaker monsoon, droughts | – Stronger monsoon, flooding |
| USA | – Wetter South, drier North | – Drier South, colder North |
| South America | – Heavy rains and floods (Peru, Ecuador) | – Drier west coast |
| Africa | – Drought in southern Africa | – Flooding in parts of East Africa |
| Australia | – Droughts and bushfires | – Cooler, wetter weather |
Future Outlook
- Forecast Accuracy: NOAA predicts a 50% chance of ENSO-neutral conditions persisting through August-October 2025.
- IMD is expected to release its Long Range Forecast for the monsoon season soon, incorporating these findings.
- Monitoring ENSO: Continuous monitoring of sea surface temperatures and atmospheric patterns is essential for early detection of any shifts toward El Niño or La Niña.
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