In a year marked by unprecedented global temperatures, the climate phenomenon known as El Niño reasserted itself with striking intensity in 2023 and into 2024. This episode, however, departed significantly from classical understandings of El Niño dynamics, presenting scientists with a puzzle that underscores the complexity of the Earth’s coupled ocean-atmosphere system. The 2023–2024 El Niño event was distinguished by exceptionally strong oceanic warming across the tropical Pacific, yet atmospheric indicators traditionally linked to El Niño—such as Southern Oscillation patterns and surface wind anomalies—remained conspicuously subdued. This divergence challenges long-standing paradigms about the intertwined nature of oceanic and atmospheric processes driving these climate phenomena.
Typically, El Niño episodes are characterized by a tightly coupled interaction between sea surface temperature (SST) anomalies in the equatorial Pacific and atmospheric changes known collectively as the Southern Oscillation. This feedback loop, known as the Bjerknes feedback, involves warming of ocean waters leading to shifts in atmospheric pressure and wind patterns, which in turn amplify the oceanic warming. The 2023–2024 event, however, disrupted this linkage. Observations noted strong ocean heat accumulation in the western Pacific following a prolonged La Niña phase, but the expected atmospheric responses in the tropics were unexpectedly weak, suggesting an altered or decoupled mechanism at play.
The uniqueness of this El Niño has prompted extensive modeling and data analysis by climate scientists. Through a series of atmospheric model experiments, researchers isolated the roles of the Atlantic and Indian Oceans in modulating this event. Warming trends in these ocean basins, along with the slow background rise of tropical ocean temperatures over recent decades, appear to have dampened the atmospheric wind responses typically triggered by tropical Pacific warming. In particular, modifications to the Walker circulation—a large-scale atmospheric convective loop critical to tropical climate variability—were implicated in weakening the usual surface wind anomalies associated with El Niño.
By integrating these inter-basin ocean temperature influences, scientists successfully developed a hindcast system that captures 87% of the observed El Niño warming from June to December 2023. Significantly, this predictive framework can replicate the event’s progression even when it excludes wind stress feedback after the spring onset. This finding elevates the role of oceanic preconditioning as a primary driver of the event, highlighting the sustained build-up of heat content beneath the ocean surface during the antecedent La Niña as the critical precursor.
The 2023–2024 El Niño’s independence from the classical Bjerknes feedback mechanism marks a noteworthy shift in the conceptual model of El Niño events. Ocean dynamics, rather than coupled ocean-atmosphere interactions, dominated the genesis of this phenomenon. This has broad implications for climate science, particularly in the context of predictability. Since the ocean’s thermal inertia and subsurface heat accumulation provide a form of "memory," forecasting El Niño events with longer lead times becomes increasingly feasible when ocean heat content is monitored precisely.
This ocean-driven mechanism contrasts with many past El Niño events where atmospheric feedbacks played a central amplifying role. The attenuation of tropical Pacific wind responses in 2023 reflects how changes in atmospheric circulation can be modulated externally by warming anomalies outside the Pacific basin. Enhanced warming in the Atlantic and Indian Oceans appears to have reshaped the Walker circulation’s behavior, effectively suppressing the typical Pacific wind feedback loops, which in turn altered the evolution of El Niño development.
Warming in the Indian and Atlantic Oceans is itself linked to broader trends of climate change. The elevated sea surface temperatures in these basins during 2023 likely represent a manifestation of the ongoing anthropogenic forcing and slow multi-decadal oceanic warming patterns. This interconnectedness among ocean basins lends new insight into the complexity of tropical climate variability and raises questions about the shifting nature of teleconnections under a warming world.
Climate model simulations exploring future scenarios indicate that El Niño events resembling the 2023–2024 episode—marked by strong oceanic warming but muted atmospheric responses—may become more frequent as global temperatures continue to rise. This suggests that the character of El Niño may evolve in the coming decades, with potentially profound impacts on global weather patterns, drought incidence, and ecosystem dynamics.
Given the importance of El Niño in shaping seasonal climate worldwide, from rainfall distribution to hurricane activity, understanding the drivers of these atypical events is critical. The 2023–2024 El Niño case highlights the need to enhance observational networks for subsurface ocean heat and refine coupled climate models to better represent inter-basin interactions and their influence on tropical atmospheric circulation.
Furthermore, the extended predictability afforded by the ocean’s heat memory opens promising avenues for improving seasonal climate forecasts. Reliable early warnings could help mitigate disaster risks in vulnerable regions prone to droughts, floods, and other climate extremes typically associated with El Niño episodes. This long-lead predictability is especially vital as climate change exacerbates the societal impacts of such natural variability.
In laboratories and climate modeling centers worldwide, researchers are now re-evaluating El Niño theories to incorporate these emerging insights. The classic paradigm centered on Bjerknes feedback remains foundational but is increasingly complemented by an appreciation for the ocean’s autonomous role in forcing major climate anomalies. This evolving understanding challenges the climatology community to rethink how coupled ocean-atmosphere systems respond under altered baseline conditions imposed by anthropogenic warming.
The study of Peng, Xie, Miyamoto, and colleagues, recently published in Nature Geoscience, represents a significant advance in this direction. Their detailed analysis of 2023’s strong yet peculiar El Niño unites observational data, atmospheric modeling, and long-term climate simulations to offer a comprehensive narrative of how ocean dynamics alone can generate intense El Niño warming with subdued atmospheric feedback.
Their work emphasizes the importance of the western Pacific’s subsurface ocean heat reservoir and its buildup during a lengthy preceding La Niña. This reservoir effectively set the stage for a strong El Niño to materialize, independent from the classic surface-atmosphere coupled processes. As a result, future climate scientists and forecasters must integrate comprehensive ocean heat monitoring within their predictive frameworks to anticipate similar events.
As the global community confronts the twin challenges of climate change and variable weather extremes, advances in understanding intricate climate phenomena like the 2023–2024 El Niño remain crucial. The findings presented here foreground a shifting climate landscape where multiple ocean basins interact in nuanced ways to influence tropical Pacific variability and, subsequently, global climate impacts.
Ultimately, this ocean-driven El Niño challenges the notion that atmospheric processes dominate these global climate oscillations. It invites a more holistic approach to studying Earth’s climate system—one that transcends basin-specific frameworks and better captures the complex, interlinked nature of ocean and atmosphere under a warming planet.
The story of the 2023 hottest year on record and its unusual El Niño event is far from over. Instead, it marks a turning point in our scientific understanding, setting the stage for more resilient climate prediction models and improved preparedness for the myriad ways in which El Niño touches lives across the planet.
Subject of Research: The 2023–2024 El Niño event and its oceanic dynamics independent of atmospheric feedback mechanisms
Article Title: Strong 2023–2024 El Niño generated by ocean dynamics
Article References:
Peng, Q., Xie, SP., Miyamoto, A. et al. Strong 2023–2024 El Niño generated by ocean dynamics. Nat. Geosci. (2025). https://doi.org/10.1038/s41561-025-01700-9
Image Credits: AI Generated
