El Niño Is Stronger Than Any Time in 1,000 Years, Galápagos Corals Show

TL;DR: El Niño variability in the eastern Pacific over the past 40 years is stronger than at any point in the past 1,000 years, according to fossil Galápagos corals analyzed in a study published August 27, 2026.

El Niño in the eastern Pacific Ocean has never been as violent as it is now, according to a thousand-year temperature reconstruction built from fossilized Galápagos corals. Temperature variability since 1984 runs 36.5 percent higher than during the preindustrial stretch from 1000 to 1850 CE, and researchers found no comparable swing in climate models run without human greenhouse gases, according to Ars Technica.

The work, led by University of Michigan environmental scientist Julia Cole, was published in the journal Science on August 27, 2026, as “Recent strengthening of eastern Pacific ENSO in the last millennium paleorecord.” The team reports that stronger El Niño warm events, not its cool La Niña counterpart, drive the increase, and that the rise parallels rising global temperature, according to Science and the University of Michigan.

What the corals found

Every few years, El Niño or its cool counterpart, La Niña, shifts rainfall across the tropics, dries out Australia, floods parts of Peru, and rearranges weather on most of the planet, according to Ars Technica. The two are the warm and cold swings of a single system, the El Niño–Southern Oscillation, or ENSO, and that system is the largest source of year-to-year climate variation on Earth.

The central question was whether global warming was making those swings more dramatic, because models disagree with one another and the instrumental data are too short to separate a trend, according to Ars Technica. Detailed observational records only began in the 1980s, a much shorter timescale than needed to tease out a trend from natural variability, according to New Scientist.

To extend the view, Cole’s team reconstructed a thousand-year-long ocean surface temperature record by analyzing fossilized Galápagos corals, according to Ars Technica. In records preserved by living and ancient fossil corals, the researchers found that, on average, El Niño events have been stronger in the past 40 years than at any time in the past millennium, with higher temperatures that lead to more powerful effects on weather, according to The Conversation.

Why the Galápagos are the bullseye

The Galápagos sit in the bullseye of the eastern Pacific ENSO pattern, where the biggest events have their strongest impact, according to Ars Technica. The islands at 90 degrees west require going all the way to 160 degrees west to find another island in that near-equatorial zone, making them one of the few options to look for fossilized corals in the region.

The team collected living and dead corals from around the Galápagos Islands in the eastern Pacific Ocean, where El Niños first develop, according to New Scientist. The researchers sampled cores from 13 corals, including living colonies and boulders of ancient coral, from the Galápagos Islands, according to the University of Michigan.

The largest living corals in the Galápagos grow in the northern islands of Wolf and Darwin, in water 20 to 50 feet deep, according to The Conversation. To study their history, divers took core samples from long-lived corals, some 8 to 10 feet tall.

A limestone thermometer with monthly resolution

Corals there grow one to two centimeters a year, laying down a calcium carbonate skeleton with a chemistry that depends on the water it formed in, according to Ars Technica. Like trees that produce annual growth rings, corals add skeletal layers of calcium carbonate year after year, and the alternating bands of higher and lower density reveal changes in growth rate and can serve as a timekeeper, according to The Conversation.

In these skeletons, Cole and her colleagues looked at the strontium-to-calcium ratio and at different isotopes of oxygen because both track temperature, according to Ars Technica. To track water temperatures, the team measured two chemical parameters — the ratio of heavy to light oxygen isotopes and the ratio of strontium to calcium — both of which reflect the seawater temperature in which the coral grew, according to The Conversation.

As temperatures get warmer, corals incorporate less strontium, according to Ars Technica. The University of Michigan explains that researchers analyzed the ratio of strontium to calcium, which depends on temperature, and supplemented results with analysis of oxygen isotopes, also a measure of temperature at this site.

Sampling extracted cores millimeter by millimeter yields more than a dozen measurements per year — a monthly temperature log for the life of the colony, according to Ars Technica. Because El Niño extremes occur every few years, researchers focused on core samples that spanned at least 20 years, according to the University of Michigan.

How 1,000 years were pieced together

Living colonies cover recent decades and can be checked against instrument data, while deeper history comes from dead coral heads dated using uranium-thorium methods to within a few years, even as far back as 500 years, according to Ars Technica. The team used uranium and thorium dating to identify the age of corals, then analyzed skeleton chemistry to track sea temperatures during their lifetime, according to New Scientist.

Dead corals washed up on beaches extended the record further. According to Ars Technica, the team also found corals dead and washed up on beaches that may be 100 years old, 200 years old, or 900 years old, or even older.

The result was a patchy but long temperature log — 28 time-separated series from five islands, covering scattered years back to around 1100 CE, according to Ars Technica. El Niño and La Niña events are measured by changes to sea surface temperatures in the Pacific, so by building this time series, Cole and colleagues could track the fluctuating ENSO cycle through the centuries, according to New Scientist.

The corals collected covered about half the 1,000-year period, according to New Scientist. The researchers noted that adding records did not complicate the pattern, with Cole saying the team kept adding records thinking it would get more complicated, but it really did not, according to the University of Michigan.

How much stronger recent decades look

Temperature variability since 1984 runs 36.5 percent higher than during the preindustrial stretch from 1000 to 1850 CE and is still 16.2 percent higher than during the period from 1851 to 1982, according to Ars Technica. All three intervals are statistically distinct, and the trend only goes up.

In practical terms, those figures mean events that once ran a degree or two above normal in the Galápagos now run three or four, according to Ars Technica. The University of Michigan summarized the same shift as El Niño variability becoming nearly 40 percent stronger in the last 40 years than in the preindustrial era.

The corals also record a shift in skewness — whether swings were lopsided in the warm or cold direction, according to Ars Technica. The skewness turned positive, and positive skewness indicates it is the warmer events that got stronger.

The extra variability is due to El Niño specifically, according to Ars Technica. Strong El Niños occurred in the last 40 to 50 years, whereas earlier El Niños showed a pretty consistent pattern of lower intensity El Niños, according to the University of Michigan.

No precedent in Medieval warmth or Little Ice Age

Nothing comparable shows up elsewhere in the record, according to Ars Technica. Neither the Little Ice Age nor the Medieval warm period left such a distinct fingerprint on ENSO variability.

The study found that El Niño events in the last four decades were stronger than any in the 1,000 years prior to about 1850, when humans began impacting the climate with greenhouse gases, according to the University of Michigan. That intensification also coincides with human-caused global warming, according to The Conversation.

Cole said the events do not look anything like what is seen in the pre-industrial era, describing the result as exciting and a little surprising, according to Ars Technica. The University of Michigan quoted Cole saying researchers do not see a time in the past where El Niños have been as strong as today, and that strength changes in parallel with warming of global temperature.

Testing whether nature alone could do this

ENSO fluctuates on its own, with quiet decades followed by wild ones with no external push required, according to Ars Technica. To understand whether recent decades were really special or researchers just caught the cycle in a more energetic period, the team needed a reference point.

The researchers examined whether natural processes could have caused similar intensifications over the past thousand years by using climate models that simulate the last thousand years using histories of volcanic eruptions and solar variability, according to the University of Michigan. The models incorporated only natural factors like volcanoes or solar variability, with changes in greenhouse gas concentrations left out, according to Ars Technica.

The team tried to see if there was evidence for this scale of change in climate models, and found none, according to Ars Technica. The models found no large shifts suggesting natural processes could create such large changes, according to the University of Michigan.

The actual increase from coral records sits outside the models’ internal variability at a confidence level approaching 99 percent, which the team interpreted as evidence that what is happening with ENSO would not be happening without human influence, according to Ars Technica. The findings add to emerging evidence that the ENSO cycle is changing in response to rising temperatures, according to New Scientist.

Central Pacific picture is murkier

The picture in the central Pacific is murkier, according to Ars Technica. Line Islands corals show a similar mean increase but far wider scatter, which researchers partly attribute to reliance on oxygen isotopes alone.

Heavy El Niño rainfall there can account for half or more of the signal by changing oxygen levels in water, according to Ars Technica. Central Pacific coral data also show increased variability, although less distinctly than in the Galápagos, according to Science.

The researchers noted they do not have a direct source of long observational data to compare records to in the eastern Pacific, with Cole saying if the team had another long record, it would not be publishing this in Science, according to Ars Technica.

Why stronger El Niños matter for people

Under normal conditions, trade winds blow along the equator from east to west, pushing warm water from South America toward Australia, according to the University of Michigan. But when trade winds weaken, warm water spreads eastward back toward South America, kicking off an El Niño event.

The atmospheric circulation responds as strong rainfall shifts from Indonesia into the central Pacific, leaving the western Pacific in drought, which weakens trade winds further and locks in El Niño conditions that can persist for one to two years, according to the University of Michigan. These temperature and precipitation fluctuations originate in the tropical Pacific, but they affect weather all over the world.

Storm tracks over the United States shift southward, bringing more rain to the desert Southwest and less to the Northwest, according to the University of Michigan. Similar shifts around the world lead to droughts and flooding that bring disease, crop failure, wildfires and other crises that impact health and well-being.

Past strong events illustrate the scale. One of the strongest El Niños hit in 1982, triggering a marine heat wave in which exceptionally warm surface water blocked upwelling of cool, nutrient-rich water, and more than 95 percent of Galápagos corals died, according to The Conversation. The 1982-83 El Niño contributed to climate extremes worldwide, from flooding in Kenya and Peru to drought in Indonesia and Brazil, costing the global economy as much as US$4 trillion by some estimates, while the similarly strong 1997-98 event resulted in 23,000 deaths from disease and climate disasters, according to The Conversation.

The study suggests the 1982-83 and 1997-98 El Niños — two of the strongest in recent memory — may be harbingers of more extreme events to come as the planet warms, according to The Conversation. The research itself does not include the recent El Niños in 2015, 2023 and 2026, but Cole said they are consistent with the trend identified by corals, according to New Scientist.

Temperatures warmed dramatically across the equatorial Pacific in 2026, signaling onset of a strong and potentially historic El Niño, according to The Conversation. When the current El Niño peaks at the end of this year, sea surface temperatures in the east-central Pacific are projected to reach 4 degrees Celsius above normal, a 60 percent increase over the old record, according to New Scientist.

Sources referenced