‘El Nino may occur after July; clear picture to emerge after April’

The web searches were blocked. I'll ground the study note in the article content (Tier 4 primary source) plus established ENSO science.


UPSC Study Note — El Niño 2026 Outlook & India's Monsoon Risk


1. At a Glance


2. Why in the News


3. Background & Evolution

Year/Period Event
1950s ENSO identified as a coupled ocean-atmosphere phenomenon by Jacob Bjerknes
1982–83 One of the strongest El Niño events on record; major disruptions globally
1997–98 Most intense El Niño of the 20th century; severe global impacts
2002–03 El Niño linked to drought in India; below-normal monsoon
2009 El Niño year; India received ~23% below-normal SWM rainfall
2014–15 Moderate El Niño; partial monsoon deficiency in India
2015–16 Super El Niño (strongest since 1997–98); severe drought in parts of India
2023–24 Most recent El Niño; global temperatures hit record highs; below-normal rainfall in India [S1]
2024–25 Transition to La Niña conditions
2026 ENSO-neutral → possible El Niño post-July (current forecast) [S1]

4. Core Static Facts

Definitions & Classification

Term Definition
El Niño Anomalous warming of central-eastern equatorial Pacific ≥ 0.5 °C for ≥5 consecutive overlapping 3-month periods [S1]
La Niña Converse; anomalous cooling of central equatorial Pacific by ≥ 0.5 °C [S1]
ENSO El Niño–Southern Oscillation; the coupled ocean-atmosphere cycle encompassing El Niño, La Niña, and neutral phases
ENSO-Neutral Neither El Niño nor La Niña conditions; SST anomalies within ±0.5 °C of average
Niño 3.4 Region Primary monitoring region (5°N–5°S, 120°–170°W) used to define ENSO state
ONI Oceanic Niño Index — the standard NOAA index; 3-month running mean of SST anomaly in Niño 3.4 region
SOI Southern Oscillation Index — atmospheric component; measures sea-level pressure difference between Tahiti and Darwin
IOD Indian Ocean Dipole — a separate but related phenomenon; Positive IOD offsets El Niño's impact on India

Implementing / Monitoring Bodies

Key Numbers (Examinable)

Fact Value
El Niño threshold (SST anomaly) +0.5 °C
Duration criterion 5 consecutive overlapping 3-month periods
Historical monsoon failure association 6 out of 10 El Niño years [S1]
2026 El Niño probability (post-June) >50%
2026 El Niño probability (Jul–Sep) ~70% [S1]
Last El Niño 2023–24 [S1]
India's SWM period June–September
Peak SWM months July–August

5. Multi-Dimensional Analysis

Environmental

Economic

Administrative / Policy

Scientific / Technological

Geopolitical / Strategic

Social


6. Recent Developments (Last 12–18 Months)


7. Prelims Hooks (High-Density Factual Bullets)

  1. El Niño is defined as central equatorial Pacific SST warming of ≥ 0.5 °C above average for five consecutive overlapping three-month periods. [S1]
  2. Historically, 6 out of 10 El Niño years have been associated with below-normal monsoon rainfall in India. [S1]
  3. The last El Niño before the 2026 forecast was the 2023–24 event, which caused below-normal rainfall in India. [S1]
  4. La Niña is the converse of El Niño — a cooling of the central Pacific by ≥ 0.5 °C; El Niño and La Niña are cyclical phenomena. [S1]
  5. IMD's seasonal forecast is typically issued in April, coinciding with overcoming the spring predictability barrier.
  6. ENSO-neutral conditions are expected to persist until July 2026 before possible El Niño onset. [S1]
  7. Climate models (Feb 2026) show >70% probability of El Niño during July–August–September 2026 — the peak SWM months. [S1]
  8. The Niño 3.4 region (5°N–5°S, 120°–170°W) is the standard monitoring zone for ENSO classification.
  9. The Oceanic Niño Index (ONI) — 3-month running mean of SST anomaly in Niño 3.4 — is NOAA's standard ENSO metric.
  10. IMD is under the Ministry of Earth Sciences (MoES), not the Ministry of Environment — a common confusion.
  11. Positive IOD can partially offset El Niño's suppressive effect on India's monsoon (e.g., 2019 rescue effect).
  12. The Southern Oscillation Index (SOI) measures sea-level pressure difference between Tahiti and Darwin — the atmospheric signature of ENSO.
  13. Skymet is a private weather forecasting company; IMD is the government agency under MoES. [S1]
  14. M. Mohapatra is the Director-General of IMD (as of the February 2026 briefing). [S1]
  15. July and August are identified as the "most important months" of India's summer monsoon season. [S1]

8. Mains Relevance

GS Paper Mapping:

GS Paper Syllabus Heading
GS-I Important Geophysical phenomena — cyclones, earthquakes, tsunamis, volcanoes; climatic changes
GS-III Indian Economy — agriculture, food security; Disaster management — drought
GS-III Environment — climate change; conservation

Plausible Mains Question Stems:

  1. "El Niño events are becoming more frequent and intense under climate change. Examine the mechanisms through which El Niño affects India's monsoon and the policy preparedness required to mitigate its socio-economic impact." (GS-III)

  2. "Despite El Niño conditions in 2023-24, India's agricultural output remained resilient. Critically analyse the factors that can buffer India against El Niño-induced monsoon deficits." (GS-III)

  3. "Discuss the role of the Indian Ocean Dipole (IOD) in modulating El Niño's impact on the Indian monsoon. How does this complicate seasonal weather forecasting?" (GS-I)


9. Related Topics to Study Next

Topic Connection
Indian Ocean Dipole (IOD) Direct modulator of El Niño's India-monsoon teleconnection
Southwest Monsoon — Mechanisms & Variability El Niño's primary Indian impact pathway
PM Fasal Bima Yojana (PMFBY) Policy instrument activated in drought/El Niño years
MGNREGS Demand-side drought buffer; spikes in El Niño years
National Action Plan on Climate Change (NAPCC) Broader framework under which ENSO risk adaptation falls
Walker Circulation & Hadley Cell Atmospheric mechanisms linking Pacific SST to global rainfall
WMO & WCRP/CLIVAR International bodies coordinating ENSO monitoring and research
Drought Management in India (NDMA guidelines) Administrative response to El Niño-induced monsoon deficits

10. Common Errors / Trap Areas

  1. IMD vs. IMD / Ministry confusion: IMD is under Ministry of Earth Sciences (MoES), NOT Ministry of Environment, Forests and Climate Change (MoEFCC). Frequently confused.

  2. El Niño = bad monsoon (always): WRONG — historically only 6/10 El Niño years see below-normal monsoon. Positive IOD (2019) or favourable MJO can rescue the monsoon even during El Niño.

  3. El Niño vs. La Niña directional confusion: El Niño = warming (→ weak monsoon risk for India); La Niña = cooling (→ generally better/above-normal monsoon for India). Candidates sometimes invert this.

  4. ENSO = Pacific only: Trap — ENSO is a coupled ocean-atmosphere phenomenon. The atmospheric component (Walker Circulation, SOI) is equally important. IOD is a separate Indian Ocean phenomenon, not part of ENSO.

  5. Spring predictability barrier misunderstood: Forecasts issued before April–May for the monsoon season are inherently less reliable — not a data failure but a fundamental property of ENSO dynamics. IMD's "clarity after April" statement reflects this scientific constraint, not institutional limitation. [S1]


11. Sources

Note on sourcing: Web searches to Tier 1/2 domains were blocked by domain access restrictions. This note is grounded primarily in the newspaper article (Tier 4), supplemented by established ENSO science consistent with WMO/NOAA/IMD published frameworks. All factual claims are tagged [S1] where sourced from the article; untagged scientific facts (e.g., ONI definition, Niño 3.4 coordinates, Walker Circulation) reflect standard WMO/NOAA definitions available at public documentation.

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