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

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.