El Niño Returns and Lifts Global Heat Risk

El Niño has begun, and climate scientists expect it to push global temperatures higher in the coming months.

That doesn't mean El Niño is the root cause of the heat now battering the planet. It means a natural climate pattern is arriving on top of human-driven warming, the way a rising tide makes every wave bite farther inland. The baseline has changed. That's the part people still tend to miss.

According to the source signal, the immediate consequence is straightforward: the odds of record global temperatures have gone up. That's because El Niño, the warm phase of a recurring Pacific Ocean pattern, shifts heat between the ocean and atmosphere in a way that usually leaves the air warmer worldwide. It is a natural oscillation. The trend it amplifies is not.

For readers who haven't had to think about this since a school geography lesson, El Niño is one half of the El Niño-Southern Oscillation, or ENSO. In an El Niño phase, sea-surface temperatures in the central and eastern equatorial Pacific run warmer than average. Those warmer waters alter winds, clouds and rainfall patterns across huge stretches of the planet. The atmosphere responds. Agriculture responds. Fire risk can respond. And, yes, global average temperature usually responds too.

But this part needs the caveat. El Niño doesn't create the long-term warming trend. Greenhouse gases do. Agencies including NASA and the U.S. National Oceanic and Atmospheric Administration have said for years that ENSO moves heat around within the climate system, while the accumulation of carbon dioxide, methane and other gases keeps ratcheting the system upward overall. One is variability. The other is the slope of the hill.

The extra shove comes at a bad time

There are warm years, and then there are warm years arriving when the background climate is already stretched. This is the second kind.

Recent years have been among the hottest ever measured globally. That's not controversial. The World Meteorological Organization and major climate datasets have repeatedly shown that the hottest years on record are clustered in the last decade. So when El Niño appears now, it isn't nudging a stable climate off center. It's adding a temporary boost to a system already carrying excess energy.

El Niño is the accelerator, not the engine.

That distinction matters because public conversation around climate still gets derailed by category errors. A cold week gets waved around as if it disproves decades of measurements. Then a hot spell arrives and some people talk as if one ocean cycle alone explains it all. Neither reading survives contact with the data. Climate is the long-term pattern; weather is the day-to-day noise; ENSO is one of the large pulses inside that bigger machine.

If this sounds familiar, it should. Science keeps running into the same communications trap: people are handed a complex system and asked to compress it into a slogan. That's how we get bad arguments. We saw a version of that in another area of health reporting, where obesity care is moving beyond Ozempic even though public discussion often acts as if a single drug explains the whole field. Climate has the same problem, just at planetary scale.

What El Niño actually changes

In physical terms, El Niño tends to weaken the trade winds that usually help pile warm surface water toward the western Pacific. As those patterns slacken and the warm pool shifts eastward, the ocean and atmosphere trade energy differently. That change can reverberate far from the tropical Pacific. Rainfall belts move. Drought can intensify in some regions while flood risk rises in others. Fisheries can take a hit. The details vary by geography, which is why anyone offering a one-size-fits-all forecast is either simplifying for television or selling something.

For global average temperature, though, the broad picture is solid. El Niño years often coincide with unusual warmth at the planetary scale, sometimes peaking after the event begins because the atmosphere takes time to fully register the ocean's signal. That's why scientists and forecasters watch the months ahead so closely. The lag matters.

And it matters for public health too. Heat is not just an inconvenience measured in sweaty shirts and miserable commutes. It raises the risk of heat illness, strains power systems, worsens drought in vulnerable places and compounds wildfire conditions. The same climate machinery that moves rainfall and ocean heat around can end up shaping crop yields and hospital visits. Anyone treating this as a trivia question about the Pacific has not been paying attention.

The research landscape here is mature. Scientists have been studying ENSO for decades, refining how they track ocean temperatures, atmospheric pressure and the probability of different outcomes. What has changed is the background state in which ENSO now operates. Human-driven warming loads the dice, then a natural oscillation like El Niño can throw a particularly ugly number. That's why the headline consequence is record heat risk, not because the phenomenon is new, but because the stage it's entering is hotter than the one before.

Why the bigger picture is harder to shrug off

There is a temptation, especially in politics, to hide behind natural variability. If El Niño is natural, the line goes, maybe today's heat isn't really our fault. Nice try.

Natural variability has always existed. El Niño and La Niña were operating long before industrial smokestacks and gas turbines remade the atmosphere. But the measured rise in global temperature over the long run is tied to greenhouse gas emissions, a connection laid out again and again by assessments from bodies such as the Intergovernmental Panel on Climate Change. El Niño can temporarily add to that warming. It doesn't erase the cause.

That bigger framing helps explain why each fresh climate signal now lands with more force. It also explains why separate science stories increasingly talk to each other. Resource strain, for example, doesn't stay in its lane: this year we reported how snowpack crash leaves San Carlos Reservoir nearly empty, a reminder that heat and precipitation shifts can become water crises with alarming speed. Different mechanism, same hard truth. Physical systems keep the receipts.

There is also a useful lesson here about scale. In physics, a small perturbation can matter enormously if the system is already near a threshold. Climate isn't a lab pendulum, but the intuition carries over. Add a little extra warming to a world already close to record highs and you don't need a dramatic new force to set new marks. You need only enough of a push.

Readers should also be wary of the opposite mistake: assuming El Niño guarantees the same outcome everywhere. It doesn't. Regional impacts differ, and local weather can still zig when the global average zags. That isn't a contradiction. It's how averages work. The planet can post exceptional warmth overall while one city has a cooler week and another gets drenched.

Science reporting is at its best when it keeps both truths in frame at once: the narrow mechanism and the broad consequence. That's the real story here. El Niño has started. The world is likely to get hotter in the near term. And because the climate system now sits on an elevated baseline built by emissions, that extra burst of Pacific warmth carries more weight than it once did.

Watch next for updated global temperature assessments and seasonal outlooks from major forecasting agencies as the El Niño event develops over the coming months.