Explainer: How the ‘super El Niño’ will reshape the world’s weather

The World Meteorological Organization has classified this year's El Niño event as a "super El Niño," marking one of the strongest occurrences of this climate phenomenon in recent decades. The impact of such an event extends beyond the Pacific, influencing global weather patterns and potentially altering ecosystems, agriculture, and human activities worldwide. An El Niño event begins with a disruption in the typical trade wind patterns that dominate the tropical Pacific. Under normal conditions, these winds blow from east to west, pushing warm surface water toward Asia while drawing up cold, nutrient-rich water from the deep ocean near South America. This process, known as upwelling, supports some of the most productive fisheries in the world, including Peru’s vast anchovy fishery. Rainfall follows similar patterns, with increased precipitation in the western Pacific and reduced rainfall along the coasts of South America. During an El Niño, the trade winds weaken or even reverse direction, allowing warm surface waters to move back toward South America. This disrupts the upwelling process, reducing the availability of nutrients for marine life and impacting fisheries. As the warm waters shift, so too does the distribution of rainfall. Typically, this leads to heavy rains along the west coast of South America, while Southeast Asia experiences unusually dry conditions. The changes in sea surface temperatures also affect the Southern Oscillation, a seesaw pattern of air pressure variations between the Pacific islands of Tahiti and Darwin in northern Australia. The opposite effect is observed during a La Niña event, where trade winds strengthen, pushing warm water further west and enhancing upwelling. This results in cooler surface waters extending farther into the Pacific, leading to stronger rainfall patterns in Southeast Asia and drier conditions along the west coast of South America. Both El Niño and La Niña are part of the broader El Niño-Southern Oscillation (ENSO) cycle, which has influenced global climate for thousands of years. Evidence of ENSO variability dates back at least 130,000 years, according to studies of coral proxies. Historical records indicate that Peruvian fishermen recognized El Niño events as early as the 1600s, noting the arrival of warm currents that disrupted their fishing practices. They referred to this phenomenon as "El Niño de Navidad," meaning "the Christ Child," due to its frequent occurrence around Christmas. It wasn’t until the early 20th century that scientists began systematically studying these patterns. In 1926, British meteorologist Gilbert Walker introduced the term "Southern Oscillation" to describe the periodic shifts in atmospheric pressure across the Pacific. Decades later, in the 1960s, Swedish-born meteorologist Jacob Bjerknes connected El Niño with the Southern Oscillation, laying the foundation for modern understanding of the ENSO phenomenon. To determine the strength of an El Niño or La Niña event, scientists monitor sea surface temperatures in specific regions of the Pacific. The Niño3.4 region, a large area centered on the equator, is often the primary focus. Data from ships, buoys, and satellites help track deviations from average temperatures, measured using the Oceanic Niño Index (ONI). Sustained ONI values above certain thresholds confirm the onset of an El Niño or La Niña event. These indices provide critical insights into the potential global impacts of each phase of the ENSO cycle.