Daily Mains Question - 11th June 2025
- TPP
- 6 days ago
- 3 min read
Welcome to your daily Mains Model Answer — designed to bridge the gap between current affairs and conceptual clarity, just the way UPSC tests in GS Papers. Today’s answer focuses on La Niña — a key component of the El Niño Southern Oscillation (ENSO) that significantly affects global weather systems. With recent deviations in predicted La Niña emergence during late 2024 and early 2025, this topic has gained importance in climate discussions.
Given its direct impact on monsoons, tropical cyclones, and ocean-atmosphere interactions, questions on La Niña could appear in GS Paper I (Geography and Physical Phenomena) and GS Paper III (Environment, Climate Change, and Disaster Management). Use this answer to understand the scientific basis of ENSO variability and its forecasting challenges.
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QUESTION
Examine the influence of La Niña on global weather systems and its implications for climate forecasting. Why do global climate models sometimes struggle to accurately predict La Niña events?
(15 Marks, 250 Words)
Answer: La Niña, meaning “Little Girl” in Spanish, is a cool phase of the El Niño Southern Oscillation (ENSO), which represents natural ocean-atmosphere climate variability in the tropical Pacific. It is the opposite of El Niño and is marked by stronger trade winds, cooler-than-average sea surface temperatures (SSTs) in the central and eastern Pacific, and enhanced upwelling of nutrient-rich waters off South America.
La Niña significantly influences global weather systems, including rainfall patterns, temperature anomalies, and storm intensity, while also presenting challenges for seasonal climate forecasting due to its erratic behaviour.
I. Influence of La Niña on Global Weather Systems
1. Impact on Global Weather Patterns:
Stronger Trade Winds: These push warm water westward toward Asia, enhancing upwelling of cool water in the eastern Pacific.
Jet Stream Disruption: La Niña typically pushes the jet stream northward, leading to:
Drought in the southern U.S.
Heavy rainfall and flooding in the Pacific Northwest and Canada
Colder winters in the northern U.S. and warmer winters in the south
Hurricane Activity: Can lead to more intense Atlantic hurricanes, as wind shear decreases.
2. Impact on Indian Weather:
La Niña is associated with:
Increased monsoon rainfall
Lower-than-normal temperatures
Better kharif crop prospects due to stronger monsoonal circulation
Example: The 2020–2023 La Niña phase supported multiple above-average monsoon years in India.
II. Current La Niña Trends and 2024–25 Scenario
According to NOAA (December 2024):
Sea surface temperatures in the central and eastern Pacific were near-to-below average
ENSO conditions were neutral, despite being in a La Niña ‘watch’ phase
The Oceanic Niño Index (ONI) in the Nino 3.4 zone was –0.3°C, below the La Niña threshold of –0.5°C.
ONI measures the 3-month average sea surface temperature anomaly in the equatorial Pacific.
A La Niña is officially declared when ONI is ≤ –0.5°C for five consecutive overlapping seasons.
Experts predicted a brief and weak La Niña in December 2024 to February 2025, likely returning to ENSO-neutral by March–May 2025.
Implication: Minimal impact on Indian winter, with La Niña conditions too mild to produce major weather anomalies.
III. Why Do Climate Models Struggle to Accurately Predict La Niña?
1. Minor SST Variations:
Climate models are more accurate during strong El Niño or La Niña events when SST deviations are large.
Small temperature changes, like in 2024, lead to forecasting errors, as models fail to detect subtle inputs.
2. Ocean-Atmosphere Coupling Issues:
In 2024, expected ocean-atmosphere interaction did not manifest strongly.
Persistent El Niño warmth lingered, suppressing La Niña development.
3. Westerly Wind Anomalies:
In September–October 2024, westerly winds dominated instead of the easterly trade winds needed for La Niña onset.
These anomalies disrupted SST cooling required for La Niña formation.
4. Monsoon-ENSO Interaction:
A strong Indian monsoon (June–September 2024) influenced atmospheric circulation.
The robust monsoon may have inhibited La Niña by affecting wind anomalies across the Pacific.
Conclusion:
La Niña is a critical climatic driver with far-reaching implications, from agricultural output in India to hurricane activity in the Atlantic. However, its inconsistent onset, weak signatures, and interference from other atmospheric phenomena make it difficult to model accurately.
Climate forecasting agencies must improve data resolution, understand multi-factor interactions, and refine coupled models to better predict ENSO events. As climate variability becomes more complex under global warming, early warning systems and region-specific strategies will be essential to mitigate its impacts.
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