The ocean's pulse can shift global weather in months

Science · Published 25 October 2026 Swipe more like this →

In short: A massive heat engine in the Pacific Ocean dictates everything from your local rainfall to global food prices. Known as El Niño, this natural cycle disrupts the planet's atmospheric circulation, acting as a dominant driver of climate variability that can alter life across every continent.

El Niño is a significant climate phenomenon characterized by unusually warm sea surface temperatures in the central-east equatorial Pacific. It occurs irregularly every two to seven years and typically lasts about one year, though some episodes can persist for several years. An event is officially declared when these tropical waters rise at least 0.5°C above the long-term average. During normal conditions, trade winds push warm water westward toward Asia, allowing cold, nutrient-rich water to rise from the depths in the east—a process known as upwelling.

When El Niño develops, these trade winds weaken, allowing the warm water to shift eastward toward the Americas. This shift acts like a giant heat source in the tropics, moving the Pacific jet stream and altering large-scale atmospheric circulation. The consequences are global: while it can suppress rainfall over most tropical land—leading to drier monsoons in Asia, Africa, and South America—it simultaneously drives severe flooding in regions like the southern United States, Peru, Argentina, and East Africa. Stronger events can warm the planet by approximately 0.2°C on average over a year.

Beyond weather, El Niño impacts human infrastructure, health, and economies by influencing global food supplies and prices through drought or extreme weather. It even affects marine ecosystems; by weakening upwelling, it reduces nutrient availability for phytoplankton, disrupting entire food chains off the Pacific coast. While its effects are less severe in places like the UK, it still influences winter patterns and storm tracks via global supply chains.

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