The 2023-24 El Niño: The Event That Pushed Earth Past 1.5°C

For three years, the Pacific had leaned cold. From 2020 to early 2023, La Niña conditions persisted through a rare "triple-dip" — three consecutive cold winters — even as the world's oceans quietly accumulated record amounts of heat. When the cold phase finally broke in early 2023, the rebound was swift and emphatic. By mid-year an El Niño was declared; by the November 2023-January 2024 season it had peaked at an Oceanic Niño Index of about +2.0, and the World Meteorological Organization was ranking it among the five strongest events on record.

By the raw index it fell short of the giants of 1997-98 and 2015-16. But the 2023-24 El Niño arrived on the warmest ocean ever measured, and the combination produced something no previous event had: a planet, briefly, beyond 1.5°C.

The year the records fell

The global temperature response was immediate and stunning. Every single month from June to December 2023 set a new monthly record. When the year's accounts were closed, the WMO's consolidated six-dataset figure showed 2023 at 1.45±0.12°C above the 1850-1900 baseline — smashing the previous annual record.

Then 2024 went further. At roughly 1.55°C above pre-industrial levels, it became the first calendar year to exceed 1.5°C — the figure enshrined in the Paris Agreement as the aspirational limit for long-term warming. A single El Niño-boosted year does not breach that long-term threshold, but the symbolism was unmistakable, and the arithmetic sobering: the decade 2015-2024 now comprised the ten warmest years on record, bracketed by the two most recent super-class El Niños.

Familiar impacts, modern response

Around the tropics, the event followed the classic script with regional twists. The Amazon basin fell into exceptional drought, with major rivers dropping to record-low levels — isolating communities and stressing an ecosystem already under pressure. In southern Africa, failed rains devastated harvests; Zambia, Zimbabwe and Malawi all declared national drought disasters in early 2024. Central America faced drought and deepening food insecurity, and patches of Southeast Asia saw a weakened monsoon.

The ocean bore its now-familiar share. With marine heat at record levels, NOAA declared the fourth global coral bleaching event in April 2024 — the most widespread ever recorded, surpassing even the 2014-17 catastrophe that accompanied the Godzilla El Niño of 2015-16.

The event faded in the northern spring, dissipating around May-June 2024 — though the WMO's parting message, "El Niño weakens but impacts continue," captured a truth every event in this series has taught: the human consequences of a warm phase outlast the warm water.

An atypical anatomy

As researchers dissected the event, it proved structurally unusual. A 2025 study in Communications Earth & Environment found the 2023-24 El Niño followed an atypical pattern: its warming leaned toward the central Pacific, with only modest warming along the South American coast — the region where the phenomenon was first named. Yet this comparatively coast-sparing, central-Pacific-flavored event still helped push global temperature past 1.5°C.

That dissonance — a not-quite-record El Niño producing record planetary heat — is the event's defining scientific lesson. The ENSO cycle no longer plays out against a stationary background. Each warm phase now stacks on a higher baseline, so the global-temperature consequences of a given ONI value grow decade by decade. The mechanics of how El Niño releases stored ocean heat to the atmosphere are explored in the science of El Niño.

History's newest chapter

Viewed against the long record, 2023-24 completes a striking 150-year arc. The 1877 event killed tens of millions in famines no one could predict, in an era when the phenomenon itself was unnamed. The 2023-24 event was forecast months in advance, tracked by buoy arrays and satellites, and met with early-warning systems and coordinated humanitarian response; its droughts brought hardship and emergency declarations, not Victorian-scale mortality.

Yet the newest chapter carries its own warning. The observing and forecasting triumphs of the past four decades solved the problem of surprise — no El Niño will again "keep itself a secret" as 1982-83 did. What they cannot solve is the rising floor. When the next major event arrives, it will start from an ocean warmer than the one 2023 inherited, on a planet where a moderate-to-strong El Niño was enough to touch 1.55°C. The history of El Niño, which began with fishermen naming a Christmas current, is now inseparable from the history of a warming world.