What Is El Niño? And why it could cause chaos this year - What in the World, BBC World Service

Key Concepts

• El Niño-Southern Oscillation (ENSO): A recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean.
• El Niño: The "warm phase" of ENSO, characterized by weaker trade winds and warmer sea surface temperatures.
• La Niña: The "cool phase" of ENSO, characterized by stronger trade winds and cooler sea surface temperatures.
• Upwelling: The process where deep, nutrient-rich water rises to the surface; disrupted during El Niño.
• Godzilla/Super El Niño: Informal terms used by scientists to describe exceptionally strong El Niño events.
• Climate Change: The long-term background warming of the planet, which exacerbates the impacts of natural phenomena like El Niño.

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1. The Mechanics of El Niño

El Niño is a natural phenomenon driven by shifts in Pacific Ocean sea surface temperatures.

• Normal Conditions: Trade winds blow west along the equator, pushing warm water from South America toward Asia.
• El Niño Conditions: These trade winds weaken, allowing warm water to pool back toward the west coast of the Americas. This warm water releases heat into the atmosphere, creating warmer and wetter air, which alters global weather patterns.
• Frequency: Episodes typically occur every two to seven years and generally last 12 to 18 months.

2. Global Impacts and Real-World Applications

The video highlights how El Niño disrupts global weather and ecosystems:

• Temperature Extremes: Regions like India, parts of Africa, Europe, and Japan experience increased heat. Conversely, parts of the US and Scandinavia may experience cooler conditions.
• Precipitation Shifts: The Pacific jet stream shifts, causing heavy rain and flooding in the southern US and the Gulf of Mexico, while Southeast Asia, Australia, and Central Africa face drought conditions.
• Marine Life and Food Systems: The disruption of "upwelling" prevents nutrients from reaching the surface. This reduces food availability for marine life (e.g., salmon, tuna, whales), directly impacting global fishing industries and food security.
• Case Study (India): Extreme heatwaves have led to nighttime temperatures reaching 45°C, resulting in heatstroke cases and deaths. Local responses include hospital alerts and public advisories to avoid outdoor activity during peak hours.

3. The "Godzilla" El Niño and Climate Change

Scientists are concerned that the current El Niño could be one of the strongest on record.

• Temperature Projections: While historical strong El Niños raised global temperatures by approximately 2°C, this event could potentially drive an increase of 3°C.
• The "Background" Factor: Experts emphasize that human-induced climate change has already raised global temperatures by 1.5°C. The primary concern is the compounding effect of El Niño occurring on top of this already elevated baseline.
• Perspective: As noted by climate correspondent Georgina Rannard, while we cannot control natural ENSO cycles, we can address the human-induced climate change that amplifies these events.

4. Historical Context and Terminology

• Etymology: The terms were coined in the 1600s by Peruvian fishermen who noticed that warmer ocean temperatures peaked around Christmas. They named the phenomenon "El Niño" (the boy/the Christ child) and its counterpart "La Niña" (the girl).

5. Synthesis and Conclusion

El Niño is a complex, natural climate driver that significantly alters global weather, food security, and public health. While it is a recurring cycle, the current "Godzilla" event is particularly alarming due to its intensity and the context of ongoing global warming. The consensus among experts is that while cities cannot be instantly adapted to extreme weather, long-term planning—such as improved urban cooling, water management, and reforestation—is essential to mitigate the risks posed by both natural climate patterns and the broader, human-driven climate crisis.