When Volcanoes Strike a Chord, El Niño Doesn't Always Follow the Script

A long-held, seemingly straightforward notion in climate science suggested a clear chain reaction: a major volcanic eruption injects aerosols into the stratosphere, leading to planetary cooling, which in turn reliably triggers a classic El Niño event in the Pacific Ocean one to two years later.

However, new research published in Scientific Reports reveals a far more intricate planetary mechanism at play. By analyzing climate simulations spanning the last millennium alongside data extracted from ancient corals, scientists have demonstrated that El Niño is not obligated to appear following every significant eruption—a finding that challenges textbook expectations.

Volcanoes and El Niño: A Deeper, More Nuanced Connection

The research team, led by Verona and collaborators, utilized multi-model experiments from the PMIP4/past1000 project. Their goal was to examine how the tropical Pacific and Atlantic Oceans responded to major volcanic events over the last thousand years.

The resulting picture proved multifaceted:

• Volcanic eruptions can indeed set the stage for an El Niño, particularly if the eruptions occur late in the calendar year.

The key scientific takeaway is that while volcanoes provide a significant initial jolt to the system, the fundamental rhythm of the El Niño-Southern Oscillation (ENSO) is dictated primarily by the ocean and atmosphere's internal dynamics, rather than a simple, linear cause-and-effect sequence. The volcano strikes a key, but it is not the composer of the entire piece.

The Atlantic Niño: The Ocean Choir's Second Voice

Simultaneously, climatologists are paying closer attention to the Atlantic Niño, which represents the equatorial Atlantic’s own version of El Niño. As early as 2009, work by Rodríguez-Fonseca and colleagues indicated that summer Atlantic Niño or La Niña events could influence the Pacific, thereby increasing the likelihood of an El Niño or La Niña developing the following winter.

Since then, the complexity has only deepened:

• Two distinct types of Atlantic Niño have been identified—the central and the eastern—each possessing a unique atmospheric signature and varying influence on ENSO.

This suggests the tropical oceans are engaged not in a simple leader-follower dialogue, but in a complex, multilateral conversation involving three major basins: the Pacific, the Atlantic, and the Indian Ocean.

Atlantic Niño and Tropical Cyclones: More Than Just El Niño in Play

A separate line of inquiry focuses on the Atlantic Niño’s impact on tropical cyclones. Research by Kim and colleagues in 2023 demonstrated that a warm phase of the Atlantic Niño can intensify activity among so-called Cape Verde hurricanes—those storms that originate off the coast of Africa and have time to develop into the season's most formidable systems. Conversely, in different configurations involving the Atlantic Meridional Mode (AMM), the same Atlantic Niño has been linked to suppressed activity.

Newer findings indicate that the Atlantic Niño/Niña affects not only Atlantic storm genesis but also early-season typhoon activity in the western Pacific, mediated through changes in circulation, moisture, and atmospheric vorticity. This leads to a cautious forecast for 2025: the current state of the Atlantic Niño may alter the probability and character of tropical storms—potentially dampening the most extreme trajectories in some areas while shifting the birth zones of cyclones elsewhere. This is not a simple 'fewer hurricanes' switch, but a fine-tuning of the entire tropical circulation involving ENSO, the Atlantic Niño, the AMM, and the overarching background of warming.

The latest investigations into volcanoes, ENSO, and the Atlantic Niño converge on a single message: Oceans are not merely passive screens reflecting external shocks. Even a massive impulse like the eruption of Mount Pinatubo does not guarantee a specific El Niño outcome. The ocean's inherent dynamics remain the primary author of the climate score.

The basins are interconnected. Thermal anomalies in the Atlantic can alter the rhythm of ENSO, which in turn influences the Atlantic Niño, and together they can recalibrate the genesis of hurricanes and typhoons across the tropical belt.

Our familiar understanding of causality is breaking down. Instead of a simple 'volcano → El Niño → hurricanes' sequence, we are observing a vibrant network of feedback loops where no single factor is solely responsible; rather, it is the planet acting as a single, harmonized organism.

What This Adds to the Planet's Soundscape

This narrative shifts the tone with which we approach climate science. We stop viewing the ocean as a mere object of prediction and begin to perceive it as a unified instrument, where the Pacific, Atlantic, and Indian Oceans function as three voices in a single planetary melody.

The volcanic impulse is not just a catastrophe; it is a powerful signal emanating from the planet's depths. The oceans absorb this impulse and act as giant harmonizers, redistributing heat, reconfiguring winds and currents, and helping the system gradually return to its internal rhythm—albeit on a new baseline.

This adds a new register to the Planet's soundscape. For us humans, it serves as a reminder: 'Music is not in the notes, but in the silence between them,' as W. A. Mozart famously said.

It is the same in climate science. What matters is not just when El Niño or the Atlantic Niño sounds, but what happens in the intervals between events: the quiet years, the transitional phases, and the subtle shifts in temperature and wind. New studies on volcanoes and oceans underscore this point: the planet operates not through a series of discrete 'disaster notes,' but through a continuous music of interconnectedness. Our task is learning to hear not only the loud chords but also the silence that frames them.