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El Niño Then and Now

✇NASA Breaking News
23 October 2026 at 00:00
october 13, 1997
october 12, 2026
Side-by-side maps of the Pacific Ocean compare sea surface height anomalies in October 1997 (left) and October 2026 (right). In both, red areas of higher-than-normal sea surface height stretch across the central and eastern Pacific and reach South America.
Sea levels are higher than normal across the central and eastern equatorial Pacific in October 2026 (right), a hallmark of El Niño. The pattern closely resembles October 1997 (left), during another one of the strongest El Niño events in the satellite altimetry record.
NASA Earth Observatory / Lauren Dauphin
Side-by-side maps of the Pacific Ocean compare sea surface height anomalies in October 1997 (left) and October 2026 (right). In both, red areas of higher-than-normal sea surface height stretch across the central and eastern Pacific and reach South America.
Sea levels are higher than normal across the central and eastern equatorial Pacific in October 2026 (right), a hallmark of El Niño. The pattern closely resembles October 1997 (left), during another one of the strongest El Niño events in the satellite altimetry record.
NASA Earth Observatory / Lauren Dauphin
Side-by-side maps of the Pacific Ocean compare sea surface height anomalies in October 1997 (left) and October 2026 (right). In both, red areas of higher-than-normal sea surface height stretch across the central and eastern Pacific and reach South America.
Sea levels are higher than normal across the central and eastern equatorial Pacific in October 2026 (right), a hallmark of El Niño. The pattern closely resembles October 1997 (left), during another one of the strongest El Niño events in the satellite altimetry record.
NASA Earth Observatory / Lauren Dauphin
Side-by-side maps of the Pacific Ocean compare sea surface height anomalies in October 1997 (left) and October 2026 (right). In both, red areas of higher-than-normal sea surface height stretch across the central and eastern Pacific and reach South America.
Sea levels are higher than normal across the central and eastern equatorial Pacific in October 2026 (right), a hallmark of El Niño. The pattern closely resembles October 1997 (left), during another one of the strongest El Niño events in the satellite altimetry record.
NASA Earth Observatory / Lauren Dauphin
october 13, 1997
october 12, 2026

October 13, 1997 – October 12, 2026

Sea levels are higher than normal across the central and eastern equatorial Pacific in October 2026 (right), a hallmark of El Niño. The pattern closely resembles October 1997 (left), during another one of the strongest El Niño events in the satellite altimetry record. Maps by NASA Earth Observatory/Lauren Dauphin using altimetry data provided by NASA/JPL-Caltech.

El Niño is part of a natural climate pattern that occurs roughly every two to seven years, bringing warmer-than-normal water to parts of the equatorial Pacific. The most recent very strong El Niño events, in 1997-98 and 2015-16, upended weather patterns. Impacts spanned the planet, from fires in Indonesia and the Amazon, to crop failures due to drought in southern Africa, to heavy rain and coastal flooding in Southern California. The current El Niño rivals these past heavyweights.

Every El Niño grows from a feedback loop between the atmosphere and the ocean. 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.

But each El Niño has its own character, shaped by where in the Pacific the warmth builds and how the atmosphere responds. “The search for the ‘typical’ El Niño is very elusive,” said Josh Willis, project scientist for sea level missions at NASA’s Jet Propulsion Laboratory (JPL). “They’re all different in terms of where they land and how their impacts play out.”

Altimetry satellites can track those differences by measuring the height of the sea surface. Because water expands as it warms, higher-than-normal sea levels in the central and eastern equatorial Pacific signal the buildup of heat associated with El Niño. The maps above depict sea surface height anomalies across the Pacific Ocean on October 13, 1997 (left), and on October 12, 2026 (right). Data are from the TOPEX/Poseidon satellite and the Sentinel-6 Michael Freilich satellite, respectively, and were processed by scientists at JPL.

Shades of red indicate where sea levels were higher than average. Normal sea level conditions appear white, and lower areas are blue. Signals related to seasonal cycles and long-term trends have been removed to highlight sea level anomalies associated with El Niño and other short-term natural phenomena.

“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,” Willis said. “That lets us look back in time and compare this El Niño to what happened in 1997. And right now, this one is on track to be even bigger.”

Compared with the 1997-98 event, El Niño in 2026 came on much more suddenly. But as of October, the two events appear similar in character—the tilt of sea level (low in the west and high in the east) and high, warm water extending all the way to South America—so Willis thinks the impacts could be similar as well. In 1997-98, that meant, for instance, lots of rain in California and across the southern tier of the U.S.

Three stacked maps of the Pacific Ocean compare sea surface height anomalies in October 1997 (top), October 2015 (middle), and October 2026 (bottom). In 1997 and 2026, dark red areas of exceptionally high sea surface height extend across the eastern Pacific and pile up against the coast of South America. In 2015, the dark red stays farther offshore and does not reach the coast.
The 2015-16 El Niño was also very strong, as elevated sea levels in October 2015 (middle) show. But its pattern differed from those in October 1997 (top) and October 2026 (bottom): less of the elevated water reached the coast of South America, which contributed to different weather patterns that year.

The 2015-16 El Niño was another heavy hitter but differed in its character. Sea surface height anomalies on October 12, 2015, based on altimetry data from the Jason-2 satellite, are shown above in context with maps from around the same time in 1997 and 2026. In 2015, the exceptionally warm, high water along the equator didn’t push up against South America to the extent it did in the other years. Rainfall impacts that winter concentrated more over Central America and the southeastern U.S., with significant flooding in Mexico.

NOAA’s El Niño outlook on October 8, 2026, called for an 83 percent chance of a strong-to-very strong El Niño through the first three months of 2027. But exactly how the impacts will play out in winter 2026-27 and beyond remains to be seen. Willis noted that El Niño’s influence propagates through a chaotic atmosphere, and the signal can get muddled as it extends beyond the tropics. “There’s always a bit of a dice roll here,” 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.”

NASA Earth Observatory maps by Lauren Dauphin, using NASA-SSH altimetry data provided by Josh Willis, Severine Fournier, and Kevin Marlis, NASA/JPL-Caltech. Story by Kathryn Hansen.

Downloads

Side-by-side maps of the Pacific Ocean compare sea surface height anomalies in October 1997 (left) and October 2026 (right). In both, red areas of higher-than-normal sea surface height stretch across the central and eastern Pacific and reach South America.

October 13, 1997

JPEG (1.22 MB)

The 2015-16 El Niño was also very strong, as elevated sea levels in October 2015 show.

October 12, 2015

JPEG (1.21 MB)

Side-by-side maps of the Pacific Ocean compare sea surface height anomalies in October 1997 (left) and October 2026 (right). In both, red areas of higher-than-normal sea surface height stretch across the central and eastern Pacific and reach South America.

October 12, 2026

JPEG (1.24 MB)

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NASA Satellites Observe Historic 2026 El Niño

✇NASA Breaking News
15 October 2026 at 13:59
6 Min Read

NASA Satellites Observe Historic 2026 El Niño

This visualization compares three ocean data products, sea surface temperature anomaly, apparent visible wavelength, and sea surface height anomaly, over the same months in 2025 and 2026. Signals of El Niño in each map are highlighted with pop-up labels.
Credits:
NASA’s Scientific Visualization Studio

A phenomenon rarer than a solar eclipse and more powerful than any single storm system is unfolding this fall, and NASA is tracking it closely.

El Niño is a natural climate pattern that emerges roughly every two to seven years marked by warmer-than-normal water temperatures in parts of the equatorial Pacific. NASA scientists are keeping watch as it flips trade winds, redistributes ocean heat, scrambles rain patterns, and raises sea surface height across parts of the Pacific.

As of October, the National Oceanic and Atmospheric Administration (NOAA) has said that there’s an 83% chance that the strongest El Niño since 1950 is currently unfolding. People around the world, including farmers, firefighters, and coastal communities, are already experiencing the effects in different ways.

Follow along with these maps as NASA tracks El Niño from its epicenter in the equatorial Pacific Ocean.

Sea surface height in flux 

Lower-than-normal sea level conditions appear blue, and higher areas are orange and red in this map, which compares the ocean in 2025 (a weak La Niña year) and 2026. The map was created using altimetry data from the Sentinel-6 satellites, which measure water height for the entire ocean every 10 days, down to fractions of an inch.
Credit: NASA’s Scientific Visualization Studio

One of the first clues appeared in satellite imagery in January 2026, when a swell of warm water called a Kelvin wave was spotted near Micronesia in the western Pacific. Kelvin waves are slow-moving pulses of water thousands of miles long. Like underwater freeways, they transfer heat from west to east across the Pacific. The warm water heats the air directly above it, making it rise. The change in air pressures weakens or even reverses the trade winds that typically blow in the opposing direction, from the Americas toward Asia, causing sea levels in the eastern Pacific to rise further, and waters to warm even more. This chain reaction signifies the start of an El Niño.

The map above shows that by early April, those Kelvin waves had reached the eastern Pacific, and sea surface temperatures had begun to warm. Warm water expands in volume, elevating local sea levels in some areas by as much as 1 to 1.3 feet (30 to 40 centimeters). The higher-than-normal water can be seen sloshing toward South America then moving up the coast to California. Sea levels that are six to eight inches (15 to 20 centimeters) lower than normal are visible around Indonesia and northern Australia.

“Kelvin waves are like the heartbeat of El Niño,” said Josh Willis, project scientist for sea level missions at NASA’s Jet Propulsion Laboratory in Southern California. “And our sea level satellites let us peer into the ocean and watch every beat.”

Scientists have used satellite altimetry to track the height of the ocean with ultraprecision since 1993. That unbroken data record continues today with the Sentinel-6 satellites. State-of-the-art radar altimeters aboard these satellites survey millions of square miles of ocean in a single day, complementing NOAA’s fleet of ocean sensors and buoys drifting and diving through the water below.

Warming Pacific waters 

The map above compares sea surface temperatures in 2025 (a weak La Niña year) and 2026. Data are acquired from satellite instruments, buoys, and ship sensors.
Credit: NASA’s Scientific Visualization Studio

Warmer-than-normal seawater is one of the best-known indicators of El Niño. Already, sea surface temperatures in the eastern Pacific are about 3 degrees Fahrenheit (1.7 degrees Celsius) warmer than the long-term average and could jump another fraction of a degree in the coming months, Willis said. 

Satellites carrying microwave and infrared radiometers can see through and around clouds to measure heat energy at the sea surface. Satellites in 2026 mapped the band of warmer-than-normal water as it expanded throughout the spring. The band, seen in dark red, stretches for millions of square miles from the heart of the Pacific to the coast of South America.  Ocean temperatures can influence weather patterns around the world. Air above the water’s surface carries heat and moisture into the atmosphere, seeding rainstorms and rearranging weather patterns across the globe.

Ocean gets bluer

The map above compares Apparent Visible Wavelength from 2025 (a weak La Niña year) and 2026. Apparent Visible Wavelength is a data product from NASA’s PACE satellite utilizing ocean color data from the Ocean Color Instrument.
Credit: NASA’s Scientific Visualization Studio

El Niño’s warm waters also change the color of the ocean. A NASA satellite is tracking these subtle shifts in hues, as equatorial Pacific waters have become measurably more blue over the last several months.

“Some people think of water as being just blue, but it’s amazing the multitude of colors the ocean can be,” said Matthew Kehrli, a lead research scientist for the PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) satellite team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

This spectrum is in part thanks to microscopic plants called phytoplankton, which form the basis of the marine food web. There are thousands of different species of phytoplankton, which come in shades like teal, brown, or green. This year, in areas of the Pacific Ocean along the equator that are typically lush with phytoplankton and greener as a result, these hues are waning.

This is an expected effect of El Niño. Phytoplankton thrive in cool, nutrient-rich waters, but during an El Niño, the weakening trade winds reduce the upwelling of nutrient-rich deep water to the ocean surface. With limited food supply, phytoplankton abundance drops. This decline can trigger cascading effects across the marine food web, forcing other marine life to relocate to new feeding grounds.

This year’s El Niño is the first since PACE launched in 2024, providing new views of the phenomenon. The Ocean Color Instrument aboard PACE observes the ocean in hyperspectral color — across several hundred different wavelengths of visible, near-infrared, and ultraviolet light — monitoring phytoplankton and other ocean-color changes in near-real time. With PACE data, researchers calculate the average color of the ocean, simplifying spectra of light into a single number, known as apparent visible wavelength.

The 2026 map above shows the green area along the equator in the western Pacific Ocean shrink as a bluer shade fills in, indicating fewer phytoplankton. In contrast, the map from 2025 shows how the green-hued section stays steady over time.

“You have expectations of what you would think would happen,” Kehrli said. “But to visually see the results with the data products that you’re working with in real time is gratifying.”

NASA scientists will continue to monitor the signs and impacts of this El Niño with its fleet of Earth-observing satellites.

“El Niño touches almost all of us in some way every time it occurs,” Willis said. “While many have seen what it can do, we look to the ocean to understand why.”

View and download these data visualizations here.

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