Every few years the largest body of water on Earth performs the same slow act of release. The trade winds that normally hold a great pool of warm water pressed against Indonesia and Australia slacken, and the heat that had been dammed in the western Pacific slides eastward across the equator like a tide with no shore to stop it. The ocean, in effect, breathes out. That exhalation has a name — El Niño — and in 2026 the forecasters watching the Pacific are using a word they reserve for the rare and the violent: super.

As of the eleventh of June, it is no longer a forecast. The United States' Climate Prediction Center has declared an El Niño Advisory — its signal that the warm phase has actually arrived. The central-Pacific index it watches most closely now stands at +0.7°C, past the half-degree threshold, and the ocean and atmosphere have coupled in El Niño's signature pattern; the brief La Niña of 2025–26 is spent. The agency's language is unhedged: conditions are present and expected to strengthen into the heart of next winter. The question is no longer whether the Pacific will exhale. It is how hard.

I

To understand why a warming of a few tenths of a degree in one ocean basin can reorder weather on six continents, it helps to think of El Niño as a release valve. The tropical seas between Australia and Indonesia are the warmest large expanse of water on the planet, covering an area several times the size of the continental United States. In normal years the trade winds keep that warmth penned in the west. When the winds fail, the warm pool migrates east, upwelling of cold water off South America shuts down, and an enormous reservoir of stored ocean heat is handed back to the atmosphere.

The threshold for declaring an El Niño is modest — sea-surface temperatures about half a degree Celsius above the long-term average in the central Pacific. A super El Niño is something else: a surface anomaly of two degrees or more, an event that arrives roughly once a decade and has crossed that line only a handful of times in the instrumental record. The last one, in 2015–16, helped make that year the hottest then measured. The El Niño of 2023–24 touched the two-degree mark exactly and still ranked among the five strongest ever logged.

II

The arresting number — the one circulating as “the strongest in a hundred years” — first came from a specific source: forecast models run by the European Centre for Medium-Range Weather Forecasts pushed the projected central-Pacific anomaly into territory not seen in well over a century, prompting the atmospheric scientist Paul Roundy to raise the possibility of the largest El Niño since the 1870s. American forecasters, once more conservative, have now moved sharply in the same direction. In its June update the Climate Prediction Center put the chance of a very strong El Niño at the November-to-January peak at 63 percent — better-than-even odds on an event that would rank among the largest in the record since 1950. The “very strong” tier that earns the prefix super is no longer a tail risk in the forecast; it is the single most likely outcome.

Layered over all of this is a trend the ocean did not used to carry. El Niño has always been a natural fluctuation; what is new is the baseline it now rides upon. Each event releases its heat into an atmosphere already warmed by more than a century of emissions, so the spike lands higher than the one before. The plain consequence is that a strong event arriving now loads the dice toward 2026 or 2027 becoming the warmest year humanity has recorded.

A natural fluctuation, riding higher each time on a baseline that no longer returns to where it began.

III

Here the honest account still marks its uncertainties — but they have narrowed. The aggressive projections first landed in spring, the season forecasters trust least, when the coupling between ocean and atmosphere is loose and models disagree. That is the spring predictability barrier, and not long ago the prudent caveat was that the hundred-year headline might be trimmed as the season matured. It has not been trimmed: as the barrier passed, the official numbers firmed and rose rather than faded. What remains genuinely uncertain is not whether an El Niño is coming — it is here — but how strong it grows, and whether the ocean–atmosphere coupling holds through the summer the way the record's biggest events did. Even a very strong event, the forecasters are careful to add, does not guarantee strong impacts everywhere.

This is the part that tends to fall out of the retelling. “Strongest in a hundred years” is still a scenario, not a certainty — the distance between a likely large event and a measured record. But the disciplined version is no longer that an El Niño is probably coming. It is here; a big one is now the forecast's central expectation rather than its upper edge; and the question has narrowed from whether to how much. The numbers sharpened, as they always do once spring lets go — and this time they sharpened upward.

IV

What is not in doubt is what a strong event does when it lands, because the historical ledger is long and consistent. A super El Niño redistributes the planet's rain. It tends to dry out Indonesia, eastern Australia, southern Africa and the Amazon, weaken the Indian monsoon, and at the same time drown parts of East Africa, coastal Peru and the southern United States. It warms the surface ocean enough to bleach coral reefs across whole basins. It rearranges the hurricane map — suppressing storms across the Caribbean and tropical Atlantic while energising the eastern Pacific.

The human cost of the largest events is not abstract. The catastrophic El Niño of 1877–78 is bound up with famines that killed tens of millions across India, China and Brazil. The 1997–98 event, the most powerful in the modern instrumental record before this decade, has been associated with global economic losses on the order of trillions of dollars within a few years, alongside cholera outbreaks, mass coral mortality and floods that turned arid regions to mud. Even the comparatively recent 2023–24 event pushed staple food prices sharply higher. These are not edge cases. They are what the warm phase has reliably done at full strength.

V

The newest concern is also the quietest, and it is the one most worth carrying out of this piece. A study published in Nature Communications in December 2025 examined all three super El Niños on record alongside climate-model projections and found that events of this magnitude sharply raise the likelihood of what the authors call climate regime shifts — abrupt, persistent jumps between stable states in temperature, sea-surface conditions and soil moisture that can hold for years or even decades after the Pacific itself has cooled. Under continued warming, the study concludes, that effect is greatly amplified.

The implication unsettles the usual mental model of El Niño as a passing weather season. Some of what a super event sets in motion may not simply reverse when the ocean exhales its last and the surface cools. The researchers point to the central North Pacific, the Gulf of Mexico, East Africa, the Amazon, central Australia and the Indonesian Maritime Continent as the regions most exposed — and note that after 2015–16 the Gulf of Mexico settled into a new, sustained warmth that may have fed the stronger hurricanes of the years that followed. A footprint, in other words, deeper than the event that made it.

VI

So there are two stories braided together in the Pacific this year, and they pull in opposite directions. One is loud, round-numbered and already everywhere: the strongest in a century, chaos incoming. The other is slower and harder to compress: a probable strong event on a rising baseline, its precise size still inside the spring fog, its longest shadow falling not on next winter's weather but on whatever the climate decides to keep afterward.

The temptation is to pick the dramatic version, because it travels. The more useful discipline is to hold the uncertainty and the gravity at once — to say that the ocean is about to breathe out, that it may breathe out hard, and that we will know how hard soon enough, without pretending we know it yet. The Pacific will settle the question on its own schedule. The least we can do is report it on the science's terms rather than the forecast's loudest.

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