Source: DTE
Subject: Geography
Context: Climate models and ocean observations show early signals of a possible El Niño return in 2026, as warming in the equatorial Pacific weakens La Niña conditions.
About El Niño:
- What it is?
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- El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO), marked by abnormal warming of surface waters in the eastern and central equatorial Pacific Ocean.
- It occurs irregularly every 2–7 years and tends to raise global average temperatures.
- How it forms?
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- Trade winds weaken along the equator, allowing warm surface waters to shift eastward from the western Pacific toward South America.
- The thermocline deepens in the eastern Pacific, suppressing upwelling of cold, nutrient-rich water.
- This alters atmospheric circulation, linking oceanic warming with pressure changes known as the Southern Oscillation.
- Indicators:
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- Sea Surface Temperature (SST) anomalies in the Niño regions.
- Subsurface ocean heat build-up (warm water pools at 100–250 m depth).
- Oceanic Niño Index (ONI): SST anomalies of ≥ +0.5°C (or +0.9°F) for at least five consecutive three-month periods.
- Weakening or reversal of Walker Circulation and trade winds.
- Factors affecting El Niño:
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- Strength and persistence of trade winds.
- Subsurface heat content of the Pacific Ocean.
- Interaction between ocean temperatures and atmospheric pressure systems.
- Natural climate variability and long-term global warming, which can amplify impacts.
- Implications:
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- Global warming boost, often making El Niño years among the hottest on record.
- India: Increased risk of weaker monsoons and droughts.
- South America: Heavy rainfall, floods and coastal erosion.
- Australia & Southeast Asia: Droughts, heatwaves and wildfires.
