h/t to SpaceWeather.com Headlines are announcing the formation of a significant El Niño in the Pacific Ocean, and at least one solar physicist says he saw it coming three years ago.
Robert Leamon of NASA and the University of Maryland (Baltimore County) published a 2023 paper predicting that the next El Niño would arrive in 2026. His forecast wasn’t based on ocean models or climate simulations. It was based on the sun.
Specifically, it was based on a solar phenomenon he and colleague Scott McIntosh call the “Terminator”: a magnetic event that marks the end of one solar cycle and the ignition of the next. By averaging the past five solar cycles into a composite “standard cycle” and projecting it forward, Leamon identified a recurring pattern. El Niños tend to follow Terminator events by roughly five years. The most recent Terminator occurred in December 2021. Do the math: that puts the next El Niño squarely in 2026. His model doesn’t speak to the strength of the event, but on timing, it appears to be spot-on.
This isn’t the first time the Leamon-McIntosh framework has made a successful call. The pair previously demonstrated that every Terminator since the 1960s coincided with a flip from El Niño to La Niña conditions. That framework correctly predicted the onset of the triple-dip La Niña that began in 2020, and it revealed what may be a meaningful physical connection between solar variability and the ENSO (El Niño-Southern Oscillation) cycle.
What’s the mechanism?
That remains an open question, and an honest one. Most researchers working in this space favor “top-down” models, where solar activity modifies the upper atmosphere in ways that eventually propagate down to surface weather. But the specific physical pathway hasn’t been pinned down.
Leamon and McIntosh initially suspected (in their 2021 work) that galactic cosmic rays were the link. Cosmic ray flux varies with the solar cycle and affects atmospheric ionization. But by 2023, Leamon had reconsidered, as the timing didn’t fit well enough, and he now leans toward geomagnetic activity as a more plausible driver.
It’s worth noting that the search for a solar-ENSO connection is not new. Sir Gilbert Walker, who first identified the Southern Oscillation (the “SO” in ENSO) in the early 1900s, explicitly looked for a sunspot connection and came up empty. Researchers throughout the 20th century made similar attempts with similarly inconclusive results.
What’s different here is the Terminator concept itself, a relatively new framework that McIntosh and Leamon began developing about a decade ago. It offers a more precise solar marker than sunspot counts, and it appears to do a better job of both hindcasting solar cycles and anticipating ENSO transitions.
A possible geomagnetic-stratosphere-ENSO chain
The Terminator marks a rapid reorganization of the sun’s magnetic field at solar cycle boundaries. This reconfiguration produces a measurable shift in the solar wind and the interplanetary magnetic field, which in turn modulates Earth’s geomagnetic activity. That’s the entry point.
From there, geomagnetic disturbances are known to affect the distribution of electrical currents in the upper atmosphere. Those currents influence the stratospheric circulation, particularly the polar vortex and the quasi-biennial oscillation (QBO), both of which are established modulators of tropospheric weather patterns.
The tropical Pacific is particularly sensitive to stratospheric forcing because the deep convective systems there, the engines of ENSO, respond to even small changes in the temperature gradient between the equatorial stratosphere and the surrounding atmosphere. A Terminator-driven nudge to the stratospheric circulation could plausibly tip the balance between the trade wind patterns that sustain La Niña and the weakening that triggers El Niño onset.
Why the five-year lag?
This is where it gets interesting. The Terminator doesn’t flip a switch instantly. The post-Terminator solar cycle ramps up gradually, and the cumulative geomagnetic forcing takes time to work its way through the stratosphere and into the ocean-atmosphere coupling of the tropical Pacific. Five years is roughly consistent with the timescales of both stratospheric adjustment and the oceanic heat content buildup that precedes a major El Niño.
Caveats
This is a plausible chain, not a proven one. Each link, from solar magnetic reorganization to geomagnetic activity, to stratospheric circulation, to tropical convection, to ENSO, is individually uncertain, and the compounding of those uncertainties is substantial. The honest position is that this mechanism is testable in principle, which is exactly what makes the Leamon-McIntosh prediction record worth watching closely.
Bottom line
Two successful predictions, the 2020 La Niña onset and now apparently the 2026 El Niño, is not proof of a causal mechanism, but it is more than coincidence deserves to be called. Science advances on exactly this kind of pattern recognition followed by mechanism-hunting. The Terminator hypothesis is young, the mechanism is unknown, and confidence should remain appropriately provisional.
But the prediction was made. It’s on record. And the El Niño appears to be arriving right on schedule.
