What Is El Niño? Here’s What It Means for Weather, Water, and Global Economy
This year’s El Niño is shaping up to be the strongest on record. This is what impacts to expect and how bad it could get.
El Niño is a weather phenomenon characterized by unusually warm sea surface temperatures in the equatorial Pacific. It occurs approximately every few years and can impact global weather patterns, water availability, and the economy. Meteorological agencies closely monitor the NINO3.4 region in the eastern-central tropical Pacific to determine the presence of El Niño.
This region is defined by a three-month average sea surface temperature threshold of 0.5 degrees Celsius (0.9 degrees Fahrenheit) above normal for three consecutive overlapping three-month periods.
During an El Niño event, the trade winds that normally blow from east to west weaken, causing seawater to accumulate on the eastern side of the Pacific. This can lead to shifts in rainfall patterns, with increased precipitation in the Southwest and decreased precipitation in the Pacific Northwest. Atlantic hurricane season tends to be milder, while Indonesia and parts of southern Africa face increased drought risks.
Warmer temperatures can also result in milder winter conditions in some areas, such as Japan, parts of Australia, and parts of Brazil.
El Niño events are generally classified as either moderate or strong, with a "super" designation reserved for events where temperatures are at least 2 degrees Celsius above average. Four notable super El Niños have occurred in recent history: 1982–83, 1997–98, 2015–16, and 2023–24. The ongoing 2023–24 super El Niño is particularly significant, with a greater than 90% probability of becoming "very strong" this fall and winter.
Modeling suggests that median temperatures in the NINO3.4 region could reach 3.6 degrees Celsius above normal, surpassing the all-time high recorded during the 2015–16 El Niño by approximately 0.8 degrees Celsius.
The economic consequences of such a powerful El Niño can be substantial. The 1997–98 El Niño, for example, resulted in a cumulative loss of approximately $5.7 trillion over the following five years. Although some impacts of El Niño may be beneficial, such as increased winter warmth in certain regions, the overall effects can be detrimental. For instance, the 1982–83 super El Niño led to record-breaking heavy snowfall in the Colorado River basin, overwhelming reservoirs and causing significant flood damage.
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