Global warming is expected to increase the effects of El NiƱo events and may also cause them to grow stronger and extend over wider areas.
An El NiƱo is forecast with an 80 percent likelihood by September, according to current models. Most projections point to a moderate occurrence, though some indicate a very intense episode, sometimes called a super El NiƱo.
The broader outlook remains concerning. Regardless of this eventās scale, future El NiƱos are projected to cause greater harm in coming decades. Even without increased strength, their consequences will be larger in a warmer climate.
A typical El NiƱo in the future will produce bigger regional and worldwide effects, according to Axel Timmermann of Pusan National University.
Research by Timmermann and colleagues indicates that El NiƱo and La NiƱa episodes, collectively known as ENSO, will become more intense and begin influencing weather patterns in the Atlantic, heightening their overall reach.
Recent model runs point to more frequent and powerful El NiƱo-La NiƱa swings, along with stronger effects on distant areas such as Europe, Timmermann notes.
The El NiƱo process centers on Pacific Ocean temperatures and wind patterns. In neutral conditions, trade winds move surface water westward, concentrating warmth in the western Pacific. Cooler water rises near South America, while moist air rises over the western warm pool, bringing heavy rainfall.
When trade winds weaken or reverse, warm water shifts eastward. Rainfall zones move with it, reinforcing the change through feedback and producing droughts in Australia and Indonesia alongside floods in South America.
El NiƱo events also drive rapid global surface warming. Expanded warm water increases evaporation, releasing latent heat into the atmosphere as clouds form.
Event strength depends on the volume and distance of eastward warm-water movement, measured by sea-surface temperature anomalies in the central and eastern Pacific. An El NiƱo is declared above a 0.5Ā°C anomaly. Thresholds above 2Ā°C or 3Ā°C have been informally linked to super or extreme episodes.
Negative feedbacks eventually restore balance. Increased cloud cover over the central Pacific cools the region, returning conditions to neutral or triggering La NiƱa, which strengthens westerly winds and shifts cooler water.
The strongest recorded El NiƱos occurred in 1982-83, 1997-98, and 2015-16, causing widespread damage to communities and marine ecosystems, including extensive coral bleaching.
Each major event produced trillions of dollars in losses, according to a 2023 study by Christopher Callahan. Economic damage scales directly with Pacific temperature anomalies, he states, implying similar costs if a strong episode develops this year.
Future events will inflict still greater harm as the planet warms. Floods linked to ENSO will intensify due to higher atmospheric moisture, while droughts will lengthen and deepen as soils dry more rapidly, says Richard Allan of the University of Reading.
Some models suggest warming will strengthen the feedbacks that drive ENSO, producing larger swings between extremes and faster transitions. This increased variability would create greater challenges for adaptation worldwide.
