Kathmandu | Ecosphere News
A new data visualization published by environmental data platform Visual Capitalist, created by Julie R. Peasley using historical records from Golden Gate Weather Services and the U.S. National Oceanic and Atmospheric Administration (NOAA), provides a comprehensive view of the El Niño–Southern Oscillation (ENSO) cycle from the 1979-1980 winter through the projected 2026-2027 season.
The circular climate timeline illustrates how ENSO phases-El Niño, La Niña, and Neutral conditions-have alternated over nearly five decades, helping place current climate developments and future projections into a broader historical context.
ENSO is one of the world's most influential climate patterns, affecting rainfall, droughts, floods, tropical cyclones, agricultural production, marine ecosystems, and global temperatures. Changes in sea surface temperatures across the tropical Pacific Ocean influence weather systems far beyond the Pacific region, including South Asia.
According to the analysis, El Niño develops when sea surface temperatures in the central and eastern equatorial Pacific rise at least 0.5°C above the long-term average. The warming weakens the easterly trade winds, shifts rainfall eastward across the Pacific, and is often associated with warmer global temperatures and altered precipitation patterns in many regions.
Conversely, La Niña occurs when sea surface temperatures fall 0.5°C or more below average, strengthening the trade winds and increasing the upwelling of cold, nutrient-rich water along the eastern Pacific. Neutral conditions prevail when ocean temperatures and atmospheric circulation remain close to long-term averages.
Meteorologists classify the strength of ENSO events using the Oceanic Niño Index (ONI), which measures three-month average sea surface temperature anomalies in the Niño 3.4 region of the Pacific Ocean. Events are categorized as weak, moderate, strong, or very strong ("Super") depending on the magnitude of the temperature anomaly.
The historical timeline identifies several of the most powerful El Niño events on record, including the 1982-1983, 1997-1998, and 2015-2016 episodes, all of which had far-reaching impacts on global weather, agriculture, fisheries, water resources, and disaster risk.
The visualization also shows that ENSO does not follow a fixed schedule. Instead, El Niño and La Niña events typically alternate every two to seven years, although multi-year La Niña episodes can persist longer than individual El Niño events.
Looking ahead, climate model projections indicate a possible transition toward El Niño conditions during the 2026-2027 season. Some forecast models suggest the event could strengthen into a very strong ("Super") El Niño, although scientists emphasize that seasonal climate forecasts carry uncertainty and should be interpreted as evolving projections rather than confirmed outcomes.
Climate experts note that continued monitoring of Pacific Ocean conditions will be essential in the coming months, as the eventual strength and timing of any El Niño event could significantly influence weather patterns, food production, water availability, disaster preparedness, and climate adaptation efforts across many parts of the world, including Nepal.
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