While El Niños occur every two to seven years, this year's climate event is shaping up to be the most intense one we've ever seen.

NASA has released satellite images of two previous El Niños – in 1997 and 2015 – alongside an image of this year's event, to compare their build–ups.

Compared with the 1997 event, this year's El Niño came on much more suddenly, NASA says.

And looking ahead, it's on track to be even more powerful than both the 1997 and 2015 events, which sparked fires in Indonesia and the Amazon, drought in southern Africa, and coastal flooding in Southern California.

'[Satellites let] us look back in time and compare this El Niño to what happened in 1997,' explained Josh Willis, project scientist for sea level missions at NASA's Jet Propulsion Laboratory.

'And right now, this one is on track to be even bigger.'

El Niño is part of a naturally occurring climate pattern that takes place roughly every two to seven years, bringing warmer–than–normal water to parts of the equatorial Pacific.

'Every El Niño grows from a feedback loop between the atmosphere and the ocean,' NASA explained.

'Trade winds normally keep warm water piled up in the western Pacific, where it stands higher than in the east.

'When those winds weaken, that warm water begins to pulse eastward, which further weakens and sometimes reverses the winds, allowing even more warm water to move east.

'The cycle intensifies as waters continue to warm and pile up in the central and eastern Pacific.'

While El Niños all form in the same way, each one has its own character.

Mr Willis said: 'The search for the "typical" El Niño is very elusive.

'They're all different in terms of where they land and how their impacts play out.'

To understand just how strong this year's El Niño is shaping up to be, NASA studied altimetry satellite images of the 1997–98 and 2015–16 events, which it describes as 'past heavyweights'.

Altimetry satellites track the height of the sea, which expands as the water warms.

In the images, shades of red indicate areas where sea levels are higher than normal, while normal conditions appear white, and lower areas are blue.

'What's unique about altimetry is that we have a 35–year record from nearly identical satellites flying almost the same ground track, with each mission overlapping the next,' Mr Willis said.

The images show that, as of October, the 1997 and 2026 El Niños appear similar in character.

The tilt of sea level – low in the west and high in the east – and the high, warm water extending all the way to South America are both very alike.

In contrast, in 2015, the warm water along the equator didn't push up against South America to the extent it did in the other years.

As for what this means for this year's event, NASA says the true extent of the impacts this winter remains unclear.

'There's always a bit of a dice roll here,' Mr Willis said.

'Just because this El Niño looks like 1997 doesn't mean it will be exactly the same—it's just our best guess at the moment.'

The images come shortly after the World Meteorological Organisation (WMO) revealed that the Super El Niño is becoming 'unprecedented in strength'.

According to the latest Global Seasonal Climate Update, sea surface temperatures in the tropical Pacific – the epicentre of El Nino – could rise by as much as 3.8°C above average during November 2026 to January 2027. 

For reference, the WMO declares an El Niño when the sea surface temperature anomaly in this region is just 0.5°C.

'This is literally off the monitoring charts that we have used for the past four decades,' WMO Secretary–General Celeste Saulo said.

'El Niño will peak towards the end of 2026 but its impacts will be felt long after that.'