The 2023-2024 El Niño was one of the five strongest on record. Combined with long-term global warming, it produced the hottest year in recorded history, triggered devastating floods in East Africa and Peru, drove extreme drought in the Amazon, and contributed to a record-breaking Atlantic hurricane season as it faded. This review examines what happened, how strong it actually was, and what we learned.
Timeline and Intensity
NOAA declared El Niño conditions in June 2023. Sea surface temperatures in the Niño-3.4 region rose steadily, reaching the El Niño threshold of 0.5°C above average by April-May. The event peaked in November-December 2023 with Niño-3.4 anomalies around 2.0°C — qualifying as a "strong" El Niño, though short of the 2.3-2.6°C peaks of 1997-98 and 2015-16.
The event then declined through spring 2024, with neutral conditions returning by May 2024. Total duration: approximately 11 months, a fairly typical El Niño lifespan. By June 2024, forecast models were already pointing toward a potential La Niña transition by late 2024.
Global Temperature Records
2023 was the hottest year in the instrumental record, with a global average temperature approximately 1.45°C above pre-industrial levels. Every month from June 2023 through May 2024 set a new monthly temperature record. The combination of strong El Niño and background warming pushed the planet into territory never before observed. July 2023 was the hottest month ever recorded, with July 6 becoming the hottest single day ever (global average 17.23°C).
What made this event notable: even before El Niño fully developed, global temperatures were already breaking records. April, May, and June 2023 — before El Niño was officially declared — each set new monthly records, suggesting the background warming trend is accelerating independent of ENSO variability.
Regional Impacts
East Africa: Catastrophic floods in Kenya, Somalia, and Ethiopia killed over 500 people and displaced 1.5 million during October-November 2023, the "short rains" season amplified by El Niño.
Peru and Ecuador: Heavy rains and flooding hit coastal regions in early 2024. Dengue outbreaks surged as floodwaters created mosquito breeding grounds — Peru declared a health emergency.
Amazon Rainforest: Severe drought gripped the northern Amazon. The Rio Negro in Manaus, Brazil fell to its lowest level in 121 years of record-keeping. River dolphins died from heat stress as water temperatures exceeded 39°C.
Southeast Asia: Delayed monsoon onset and below-average rainfall in Indonesia and the Philippines reduced rice yields and drove up global rice prices.
Southern United States: A wet winter across the Gulf Coast and California brought drought relief but also localized flooding. Los Angeles received nearly double its annual average rainfall.
How It Compared to Previous Events
The 2023-24 El Niño was somewhat weaker in ocean temperatures than 1997-98 and 2015-16, but it produced larger global temperature anomalies because the underlying planet is warmer. The event itself was unremarkable by "Super El Niño" standards, but its effects were amplified by an atmosphere already primed by 1.2°C of global warming.