Examine the changing relationship between El Niño Southern Oscillation (ENSO) and the Indian Summer Monsoon in the context of climate change.

Q. Examine the changing relationship between El Niño Southern Oscillation (ENSO) and the Indian Summer Monsoon in the context of climate change. (15 marks, 250-350 words)

ENSO — the periodic warming (El Niño) and cooling (La Niña) of the central-east Pacific — has long been the strongest predictor of Indian Summer Monsoon (ISM) rainfall, operating through an altered Walker Circulation that suppresses moisture influx. Under a warming climate, this teleconnection is becoming weaker and less reliable, even as its economic bite remains severe.

The classical linkage and its evidence base - India's severest droughts cluster in El Niño years — 1972, 1982, 2009, 2015 — with El Niño years averaging a 9.7% rainfall shortfall and 5.7% fall in kharif foodgrain output [3]. - IMD's operational forecasting still weights ENSO heavily: its 2026 long-range forecast flagged below-normal monsoon, citing expected El Niño conditions in the Pacific [1], with NOAA confirming El Niño onset in June 2026 [2].

How the relationship is changing - Studies under the Ministry of Earth Sciences' National Monsoon Mission find a monotonic weakening of the ENSO–monsoon teleconnection with rising CO₂ concentrations [4]. - The link has become non-existent over central India (core monsoon zone), where monsoon-trough and depression variability now dominates, while strengthening over north India — a spatial reordering, not a uniform decay [4]. - Rapid Indian Ocean warming and more frequent co-occurring positive Indian Ocean Dipole events increasingly modulate — and mask — the Pacific signal [4]. - Consequence: reduced predictability. El Niño no longer implies drought automatically; only 11 of 15 moderate-to-severe events since 1951 produced agricultural contraction [3].

Why it still matters economically - Food carries roughly two-fifths weight in the CPI basket, so rainfall deficits transmit swiftly into headline inflation and rural demand; the Economic Survey ties the record 357.7 million tonne foodgrain output to a favourable monsoon [5].

The teleconnection is thus weakening as a forecasting anchor while monsoon variability itself widens — a doubly difficult combination. The way forward lies in multi-model ensemble forecasting that internalises Indian Ocean drivers alongside ENSO, district-level contingency crop planning, and expanded micro-irrigation under PMKSY. Building predictive science and on-ground resilience together converts an eroding early-warning signal into durable climate adaptation.

(~320 words)

Sources: 1. IMD Updated Long Range Forecast for Southwest Monsoon 2026, PIB — below-normal 2026 monsoon forecast citing El Niño 2. NOAA Climate Prediction Center, ENSO Diagnostic Discussion — El Niño advisory and onset 3. ICRIER historical analysis of El Niño years and Indian agriculture (since 1951) — 9.7% rainfall drop, 5.7% kharif fall, 11 of 15 years contracting 4. An assessment of the ENSO-monsoon teleconnection in a warming climate, npj Climate and Atmospheric Science (National Monsoon Mission, MoES) — weakening teleconnection, regional divergence, IOD/Indian Ocean warming 5. Economic Survey 2025-26 (PRS summary) — record 357.7 MT foodgrain output, food-price transmission