Why El Niño and Climate Change Are Multiplying Each Other

The Number on the Screen That Started This

On September 23, 2026, a satellite feed logged a weekly sea surface temperature anomaly of +3.1 °C in a stretch of the tropical Pacific called the Niño 3.4 region. Not 3.1 °C above last Tuesday. Above the long-term average for that week of the year. Hold that number for a moment.

The Niño 3.4 region is a rectangle of ocean roughly the size of the continental United States, straddling the equator west of Ecuador. It is the thermometer scientists watch most closely when they want to know whether El Niño is arriving, intensifying, or fading. Right now, that thermometer is reading fever. The Oceanic Niño Index, which smooths the signal by averaging three-month windows, registered +1.8 °C for June through August 2026. That is not a spike. That is a sustained roar.

Zoom out from the Niño 3.4 box and the picture gets larger and stranger. Tropical Pacific sea surface temperatures across vast swaths of the basin are sitting 2 to 3 °C above long-term averages, a warm tongue stretching thousands of kilometers from the South American coast toward the open ocean. NASA satellite maps make it impossible to miss. It looks less like a weather pattern and more like the ocean is running a planetary-scale fever.

WMO and NOAA have both confirmed what the numbers have been quietly insisting: this is a very strong El Niño event. The probability it persists through the 2026-27 Northern Hemisphere winter sits at 90%, and WMO projections from September 2026 push that figure close to 100% through early 2027. Something significant is happening in the Pacific. The question is what, exactly, the convergence of climate change and El Niño means for the rest of us.

How the Pacific Breathes: Kelvin Waves, Upwelling, and the Engine Behind the Number

Start with the trade winds. Normally they blow westward across the tropical Pacific, piling warm surface water up near Indonesia and Australia like water pushed to one end of a bathtub. That pile is real: sea level on the western side of the Pacific sits roughly half a meter higher than on the east. The warm water follows.

When those winds weaken, the system relaxes. The piled-up heat doesn't stay put. It travels east as Kelvin waves, subsurface pulses of warm water moving along the equator at roughly two to three meters per second, invisible from the surface but detectable by the network of Argo floats and satellite altimeters watching the ocean's topography. Right now, those waves are feeding the warm tongue that stretches thousands of kilometers westward from the South American coast. That tongue is not a metaphor – it is a physical intrusion of heat into waters that are supposed to be cold.

Here is the strange part. The east Pacific should be cold. Off the coast of Peru, wind-driven upwelling normally draws frigid, nutrient-rich water up from several hundred meters depth. During El Niño, that cold water gets capped. The warm layer is too thick, and the deep cold cannot push through. The anchovy disappear. The fishery collapses. A continent's worth of cloud patterns shifts with it.

To track all of this without being fooled by a single hot week, scientists use the Oceanic Niño Index (ONI): a three-month running average of temperature anomaly in the Niño 3.4 region, a box of ocean straddling the central equatorial Pacific. For June through August 2026, it read +1.8 °C. A three-month average smooths out the noise and leaves the signal. Right now, the signal is loud.

Thirty-Six Percent More Powerful Than It Used to Be

Julia Cole at the University of Michigan went looking for El Niño in coral records – chemical archives of ancient ocean temperatures – and found something uncomfortable. El Niño events over the last forty years have been 36.5% more intense than those in the pre-industrial era. Not a little stronger. Substantially, measurably, persistently stronger.

That number needs a floor beneath it to mean anything. Here is the floor: 2024 was the warmest year ever recorded, with global average temperatures sitting 1.55 °C above pre-industrial levels. That threshold, the one the Paris Agreement asked humanity not to cross, fell for the first time as a full calendar year. El Niño no longer rises from the cool, stable baseline of a nineteenth-century ocean. It rises from this one.

El Niño no longer rises from the cool, stable baseline of a nineteenth-century ocean. It rises from this one.

Carlo Buontempo at Copernicus puts a number on what that layering costs us: El Niño adds roughly 0.2 °C to the global mean temperature on top of whatever warming already exists. That sounds small. It is not. Think of a fever – a single degree separates discomfort from something that shuts down your body. Global climate systems are similarly sensitive to what looks, on paper, like a rounding error.

And then there is the rain. Celeste Saulo at the WMO points to a physical law that is as reliable as arithmetic: each degree Celsius of warming loads roughly 7% more moisture into the atmosphere. One degree, 7% more water in the air, waiting to fall somewhere. El Niño already redirects where storms hit. Climate change hands those storms a heavier cargo before they arrive.

This is what scientists mean when they call climate change and El Niño a "dangerous team." One is a permanent shift in the ground state. The other is a natural spike on top of it. The distinction matters because neither is going away.

The Arithmetic of Ruin: Droughts, Floods, and a Bill That Keeps Growing

Start with a number that has already been counted: $103.3 billion. That is the estimated economic damage left behind by the 2023-24 El Niño, tallied mostly from agriculture and fisheries – the quiet industries that convert ocean temperatures into food on tables ten thousand kilometers away. It is not a projection or a model output. It is a settled invoice.

The geography of that damage follows a cruel logic. Southeast Asia and Australia crack dry, their monsoon moisture rerouted elsewhere by the warm Pacific tongue. On the opposite side, the Pacific coast of South America drowns. Peru and Ecuador receive months of rain compressed into days, rivers detach from their channels, and topsoil that took centuries to build washes into the sea inside a week. The same event, two opposite disasters.

Then there is the cost that does not appear in insurance spreadsheets. Researchers projected that a strong El Niño event could drive more than 450,000 premature heat-related deaths inside a six-month window. That figure carries the word "projected," which is worth holding carefully – it depends on infrastructure, on cooling access, on how quickly governments move. But even as an upper bound, the number asks to be translated: it is roughly the population of Lyon, or Tallinn and Tartu combined, gone in half a year.

The cascade does not stop at the borders of the affected regions. When harvests fail in Southeast Asia or the Peruvian anchovy fishery collapses, the price signal travels. A shopper in Riga or Helsinki pays more for cooking oil or fishmeal without ever knowing that a band of warm water in the Pacific wrote the price tag.

The Signal and the Noise: How Climate Change Rewrote the El Niño Rulebook

For decades, measuring El Niño was straightforward: compare this year's Pacific temperatures to a long-term average, and you have your anomaly. Then the average itself started moving. NOAA's recent adjustment to its measurement criteria was not a bureaucratic tweak. It was an admission that the old ruler had stretched.

To isolate what El Niño is actually doing, scientists now strip out the anthropogenic warming signal from the baseline before calculating the anomaly. Otherwise, every event looks artificially stronger than it is, not because the oscillation changed, but because the floor beneath it rose. Think of measuring a jump on a platform that is itself being slowly lifted. The jump did not get higher; the room got taller.

This is the methodological tension at the heart of modern ENSO science. The phenomenon is natural, but it no longer occurs against a fixed backdrop. And that creates a genuine puzzle: is climate change making El Niño events more frequent, or only more severe when they do arrive? The honest answer is that nobody knows. Julia Cole's coral records confirm that events have grown 36.5% more intense compared to the pre-industrial era. Whether they are arriving more often remains stubbornly unclear.

What scientists can say with confidence is narrow but important. The current event has a 90% probability of persisting as very strong through the 2026-27 winter. Beyond that window, the forecast dissolves into exactly the kind of uncertainty science is supposed to produce, and too rarely admits.

Estonia at the Far End of the Butterfly's Wing

Estonia sits at the wrong end of the atmosphere for El Niño to reach directly. The Baltic weather engine runs on Atlantic pressure oscillations, not Pacific ones, and the warm tongue stretching from South America might as well be on another planet in terms of immediate meteorological grip. That is the honest baseline, and Ain Kallis at the Estonian Environment Agency and Velle Toll at the University of Tartu have both said as much.

But weak direct impact is not the same as no impact. Two channels carry the signal north. The first is statistical: strong El Niño events produce a measurable lean toward warmer winters across Northern Europe, not a guarantee, just a tilted probability. The second is economic. When tropical harvests collapse under El Niño-driven drought, food prices ripple outward along supply chains that have no regard for Baltic geography. An Estonian family paying more for cooking oil in February 2027 is, in a roundabout way, feeling the Pacific.

Precisely to translate that roundabout into something actionable, the University of Tartu is producing 12 climate projection sheets under the LIFE-SIP AdaptEST project, running from September 2026 through February 2027. Each sheet converts global signals into local language: what this event probably means for Estonian agriculture, infrastructure, and public health.

The first results will arrive while the current El Niño event, sharpened by climate change, is still unfolding. That is not a flaw in the timing. That is what it means to do science on a planet that does not wait.