My Mother Thinks El Niño Comes From the Sky. She’s Only Wrong About the Direction.

Mother has the TV on with the sound off, the way she likes it, and the map on the screen has a fat red smear across the Pacific. The kettle is still going while she nods at the screen.

“Hmmm, this El Niño again. They’re saying it’s goingo to be enormous”

“It is.”

“So it’ll rain here.” A statement, with a question folded inside it. She wants to know about her garden.

“Probably. That’s roughly what the models say.”

“And where does it come from, this thing? Is it like a storm that gets stuck? Something up there,” she waves her hands at the ceiling, “that just sits over us for months?”

I open my mouth to say no, and then I stop, because I don’t want to explain it the way I’d explain it to a colleague, and I’m not sure I can explain it any other way. The kettle clicks off.

“It’s not in the sky,” I say. “It’s in the water.”

“What water? We’re eight hundred kilometres and a mountain range away from the sea.”

Which caught me off guard because it is the right question, one that took science until the 1960s to answer.

So, after pouring the coffee and pausing the TV, here is the version I gave her, with the parts I looked up afterwards to make sure my explanation was accurate.

The rain in her garden

There’s a map I keep coming back to, made by the climate scientist Zeke Hausfather, that shows where on Earth this El Niño is expected to bite. Brown blobs where it dries things out. Blue where it soaks them. Each one carries two small numbers: one shows how often the same thing happened during the eight strongest El Niños since 1957, and the other shows how many of this year’s thirteen forecast models agree.

Southeastern South America is covered by one big blue patch. It stretches across Uruguay, southern Brazil, Paraguay and northeastern Argentina. Seven of the past eight strong El Niños brought more rain than usual from September to February, and all thirteen models expect the same this year for the soybean belt that brings a good share of the country’s income. But my mother’s garden, a.k.a. where I live in Patagonia, sits between that blue patch and a smaller one on the other side of the Andes, in Central Chile.

So what do I tell her? Rain is more likely, but I can’t promise it. Every El Niño plays out differently, so the exact same impacts don’t happen every time. Likelihoods, but not guarantees. NOAA’s Climate Prediction Center says the same thing in its current ENSO discussion: “With an event of this magnitude, the chances of experiencing impacts consistent with El Niño are larger, but they are not guaranteed.”

Fine. That tells her what may happen, but not where El Niño comes from. The map shows the end of the story. To find the beginning, you have to follow the rain back to its source.

The rain over her town this spring will come, mostly, from storms carried by the subtropical jet, a fast-moving river of air several kilometres above us. During El Niño, that jet grows stronger and shifts position, pulling more storms than usual across the southern half of the continent.

And what strengthens the jet? Heat. Jet streams feed on the difference in temperature between the tropics and the poles, and this year there’s an unusual amount of extra heat sitting in the tropics. Where? In the Pacific. A patch of ocean the size of the United States, off Peru and Ecuador and stretching west for thousands of kilometres, is running far warmer than it should.

So the chain goes like this: warm water in the Pacific adds heat to the air, that heat strengthens the jet, the jet carries more storms across South America, and those storms will (likely) water my mother’s garden.

It all starts in an ocean 10,000 miles away. Now the only question left is why the ocean is hot.

The two ends of a seesaw

This is the part my mother had backwards, and it’s the part almost everyone has backwards, so she’s in good company.

Most years, the trade winds blow steadily from east to west across the tropical Pacific. They push warm surface water toward Indonesia and the Philippines, much like a fan blowing across a bathtub and piling the water up at one end. The sea surface there ends up about half a metre higher and several degrees warmer than off South America, where cold water rises from the deep to replace what the wind pushed away. That cold, nutrient-rich upwelling is why Peru has one of the richest fisheries on Earth.

Warm water heats the air above it. Hot, wet air rises. So over that western pool, a permanent column of rising air builds huge thunderstorms that soak Indonesia and New Guinea. Higher up, the air moves east, sinks over the cooler eastern Pacific, and returns west along the surface as the trade winds, forming a giant loop. Scientists call it the Walker circulation, after Gilbert Walker, who in the 1920s noticed that air pressure in Darwin and Tahiti rose and fell in opposite directions, like two ends of a seesaw. He called this pattern the Southern Oscillation, though he didn’t yet know what was driving it.

Every few years, the trade winds weaken, and no one knows for sure what sets that off. When it happens, the warm water piled up in the west starts moving east along the equator, toward the Americas. As it moves, the column of rising air moves with it, because the rising air goes wherever the warmest water is. Now the thunderstorms sit in the middle of the Pacific instead of over Indonesia. Indonesia dries out. The Peruvian coast, normally a desert next to a cold sea, suddenly finds itself beside warm water, and it rains there like it hasn’t in years.

Then the cycle feeds itself: weaker winds let more warm water move east, and that warm water weakens the winds even more. In the 1960s, Norwegian meteorologist Jacob Bjerknes worked out that the fishermen’s warm current and Walker’s pressure seesaw were two sides of the same system: the ocean and the atmosphere pushing each other.

Put El Niño and the Southern Oscillation together, and you get ENSO: El Niño Southern Oscillation.

The name came long before the science. For centuries, Peruvian fishermen had noticed that the warm current often arrived around Christmas, so they named it after the newborn Christ: El Niño de Navidad. When it eventually became obvious that the whole system swings the other way too, with colder-than-normal water and fiercer trade winds, scientists needed a name for the opposite phase and, with a straight face, chose La Niña, “the girl.” The quiet middle state is called Neutral.

So when my mother waves at the ceiling, she’s pointing at the delivery truck. The warehouse is the sea. The warm ocean stores heat for years, like a giant battery, and El Niño is the ocean discharging it into the sky all at once.

A few weeks and several thousand kilometres later, some of it falls as rain on her garden.

A bent highway

Which brings us to why this year’s map is covered in blobs.

The heat released by a warm tropical Pacific doesn’t stay put. It bends the jet streams, which are the highways weather travels on, and a bent highway delivers storms to different addresses. Scientists call these long-distance effects teleconnections, which is a fancy word for a simple idea: what happens in one place can affect the weather somewhere far away.

And this year, the Pacific is warmer than models have ever measured before. They put the central Pacific’s peak warmth at about 4.1°C (7.4°F) above normal. The previous record, during the monster El Niño of 2015–16, was 2.75°C. Think of it as a swimming pool in spring rather than in summer.

NOAA’s forecasters gave it a better than 90% chance of reaching “very strong,” their top tier, and the World Meteorological Organization has called its own outlook the most unequivocal it has ever issued. The event should peak around Christmas, on schedule, and hang on into the southern autumn of 2027.

Now let’s follow the effects out from that warm patch.

To the west, Indonesia is left with less of the rising air that brings rain. In all eight past strong events, the islands got roughly three quarters of their normal rain from September to December, and the risk isn’t thirst so much as fire. Indonesia’s lowlands are drained peat, ancient bog that burns underground once it dries, and in 1997 the fires released somewhere between 0.8 and 2.6 billion tonnes of carbon, as much as 40% of what every car, power plant and factory on Earth emitted that year. The haze from the 2015 fires, a milder event, has been linked to around 100,000 early deaths across Indonesia, Malaysia and Singapore. All thirteen models show drought there this spring.

To the east, the Peruvian coast is where the violence can be worst. Two past events, in 1982–83 and 1997–98, brought catastrophic floods. In both cases, the water right along the coast was unusually warm. In mid-September, the water off Peru was 4.6°C above normal. At the same point in 1997, it was only 3.5°C.

Farther south, southern Africa depends on summer rain to grow maize, a staple for tens of millions of people. That rain tends to fall short during El Niño: six of the past eight events ran dry. The most recent one, in 2023–24, brought the region’s driest season on record and prompted a humanitarian appeal for 61 million people. That’s nearly the combined population of Argentina and Chile. All thirteen models show the region drying again.

Some places are harder to predict.

Europe is blank because, across most of the continent, we can’t say what a strong El Niño does in winter. The eight past events split evenly, with four wetter and four drier outcomes. Northern California is a coin flip. India’s monsoon, often blamed on El Niño, was close to normal in the year after seven of those eight outstanding events, because by then the system is often swinging back toward La Niña.

El Niño loads the dice, but it doesn’t roll them.

What it does with certainty is heat the whole planet. The ocean is exhaling heat it stored for years, and global temperatures tend to follow the Pacific by a few months. That’s why 2027 has a 95% chance of being the warmest year ever recorded — something my mother wasn’t expecting to hear.

Back at the table

“So that’s it,” she said when I got to that part. “That’s climate change? The thing everyone’s always talking about these days? This ocean-and-sky seesaw turning the planet into a pressure cooker?”

And there it was: the second misunderstanding, and the one that worries me the most.

El Niño has been around for centuries. Peruvian fishermen were watching it back in the 1600s, long before anyone burned coal. It made the planet’s temperature rise and fall then, and it will keep doing that even if we ever stop burning fossil fuels. A strong El Niño can raise global temperatures by about 0.2°C for a year or so, then temperatures drop again. That’s the swing, and it has nothing to do with climate change.

What’s changed is the floor the swing starts from. Human-induced warming has raised the planet’s temperature by about 1.3°C since the 1800s, six or seven El Niños stacked on top of each other without letting the temperature fall back down. So the 2023–24 event, the last big one, arrived on a floor already so high that 2024 became the first calendar year to pass 1.5°C above the pre-industrial world. With the old starting point, the same El Niño would have meant a warm year nobody remembered, and then things would have cooled again. On the new one, it broke every record we have and bleached most of the world’s coral. This year’s swing is bigger, and the floor hasn’t moved back an inch.

This is what worries me most.

Every strong El Niño hands the world a story: it’s the Pacific, it’s natural, it comes and goes. And when a story makes the cause sound like nobody’s responsibility, someone benefits. The most successful of those stories is one you’ve most definitely used yourself. “Carbon footprint” wasn’t coined by an environmentalist; the oil company BP paid an advertising agency to popularize it in 2004, along with a calculator so you could work out how much of the problem came from your commute and your plastic bags. It even won a design award, and the company selling the fuel and cashing the billions got to watch its customers weigh their guilt.

Focus on what individuals do, while leaving the bigger system alone. Change the players, never the game. A drought in southern Africa becomes a question of what farmers planted. A record-hot year becomes El Niño’s fault, as if no one could do anything about it. Meanwhile, the starting point keeps rising, one coal plant and one drilling permit at a time, feeding the universal religion of endless growth.

The people who own the floor would very much like you to keep looking at the sky.

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Mother puts the cups in the sink.

“So it’s the water,” she says. “And the water’s warmer than it used to be because of us. Well, not us-us, but the carbon cartel, the owners of the system, the corporations and governments and greedy, uberbillionaires that just want to see another zero in their bank accounts. And this year, the warm water is moving the wrong way, so we’ll get rain and Indonesia will get fires.”

“That’s it.”

“That’s it.”

“And the sky just delivers it?”

“The sky just delivers it.”