Thirteen Galápagos corals put recent El Niños about 40% above their preindustrial strength
Coral chemistry from the eastern tropical Pacific has finally put a number on how much warming has strengthened El Niño. The natural-forcing alternative fails the test the same authors ran.
The Scientist · Science desk
What happened
- A University of Michigan team led by Julia Cole reports in Science that El Niño events of the last 40 years have run nearly 40 percent stronger than their preindustrial counterparts.
- The evidence comes from cores through 13 Galápagos corals, living colonies alongside boulders of ancient coral that had washed up on the islands' beaches.
- Nothing in the 1,000 years before about 1850, when greenhouse gas emissions began to matter, reaches the intensity the corals record for the recent four decades.
- Kim Cobb of Brown University, who had no part in the work, calls the coral evidence a critical piece of the puzzle in understanding how warming alters the cycle.
Why it matters
- Who has to decide decision Anyone who logged ENSO amplitude as an unresolved model question in a risk register now has to defend the size they assign the extreme; the direction is no longer in doubt.
- What doesn't add up contradiction Simulations could not agree on whether warming strengthens El Niño, yet simulations are the instrument used to rule out volcanoes and the sun, so the attribution asks you to trust models for one task while the coral work exists because they failed another.
- What it limits constraint Because the millennium is sampled as discrete coral windows rather than a continuous series, a planner hunting a specific pre-1850 analogue year to stress-test against will not find one here.
- Who's exposed exposure The June 2023 to April 2024 event was enough on its own to make 2024 the hottest year on record, so whoever prices heat exposure is now adding a larger El Niño to a baseline that keeps moving.
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The Galápagos is the right place to take this measurement, and the reason is signal size. Earlier fossil-coral reconstructions came from the western and central Pacific [21]; Cole's team worked in the eastern tropical Pacific, which she describes as the heart of where El Niño has some of its strongest impacts [22]. In an ordinary event the water there runs one to two degrees C above normal, and above two degrees in a strong year [3]. A proxy sited where the swing is largest has the easiest job.
The chemistry is two thermometers rather than one. Corals build calcium carbonate skeletons and substitute strontium for calcium more readily when the water is cooler; separately, the ratio of oxygen isotopes in the skeleton varies with temperature [6]. Measuring both is the internal control, since an artifact in one system is unlikely to be mimicked by the other. Resolution follows from growth rate: the colonies add one to two centimetres a year [2] and the team sampled every millimetre [4], which comes to roughly ten to twenty samples per year [23], fine enough to catch a seasonal peak. That matters, because intensity is a peak measurement.
Now the limit. Thirteen cores [1], each chosen to span at least twenty years because extremes arrive only every few years [5], gives at least 260 coral-years of record; set against a thousand-year interval that is 26 percent even if no two cores overlap in time [24]. Cole calls them windows into points in the past [15]. The claim the design supports is correspondingly precise: no sampled window resembles the last forty to fifty years [27], which is how the team can speak about the preindustrial period with confidence for the first time [10].
What will get argued is the attribution, so it is worth separating which model does what. Simulations have given mixed signals on whether warming should strengthen El Niño at all [11], which is precisely why a coral record was worth years of beach-combing. The same class of tool then supplies the exclusion: last-millennium runs forced with volcanic eruption and solar variability histories show no comparable change [12]. Those two jobs are not equally hard. Asking whether known natural forcings can manufacture an amplitude jump of the observed size is bounded; asking a model to get ENSO's greenhouse response right is not. The exclusion is the more defensible half of the argument, and it is the half doing the work here.
The mechanism remains open. Cole points to ocean stratification, in which a warmer and rainier surface layer becomes less dense, more isolated from the cool water beneath, and more responsive when the trade winds slacken, while allowing that how warming strengthens the cycle is not yet clear [14].
The figure is amplitude at one location, and it doesn't speak to frequency. The published accounts still describe events arriving every two to seven years [16] without reporting a change in that spacing. Teleconnection strength is a separate matter that a Galápagos temperature series leaves untouched; the southward shift in US storm tracks, with a wetter desert Southwest and a drier Northwest [18], follows from the tropical signal through a chain this record does not close by itself.
My read: eastern Pacific El Niño amplitude now belongs in the observed-trend column, with two conditions attached. The trend is documented in the size of the extremes, not in their count, and the headline forecasts quoted alongside the study, three degrees above normal near the islands [3] and a global anomaly of 1.7 to 1.8 degrees C [8], are forecasts rather than paleorecord.
What to watch
- Whether the peak of the current event, forecast near three degrees above normal around the Galapagos, lands inside or above the amplitude range the corals reconstruct.
- Whether other eastern Pacific sites, or drilled reef cores rather than beach boulders, reproduce the roughly 40 percent figure.
- Whether the stratification pathway gets a direct observational test, given that the attribution currently rests on exclusion.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence68
- Adoption
- Not scored
- Hype gap+22
- Incentives58
- Confidence74
Perspective Coverage
6 publishers- Builder
- Builder 47%
- Operator
- Operator 41%
- Investor
- Investor 12%
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Cole and colleagues sampled cores from 13 corals, including living colonies and boulders of ancient coral, from the Galápagos Islands.
- [2]
Corals grow 1 to 2 centimetres per year by secreting layers of calcium carbonate whose chemistry records the seawater temperature in which they grew.
- [3]
During an El Niño, waters around the Galápagos generally run one to two degrees C above normal; in a strong El Niño year they can reach more than two degrees C above normal, and the event described in the article is predicted to hit three degrees above normal.
- [4]
The group sampled the cores a millimetre at a time and measured the strontium-to-calcium ratio, supplemented by oxygen isotope ratios.
- [5]
Because El Niño extremes occur every few years, the researchers focused on core samples that spanned at least 20 years.
- [6]
Corals substitute strontium for calcium in their skeletons more when waters are cooler, and the ratio of two oxygen isotopes in the coral also changes with water temperature.
- [7]
Forecasters have become almost certain that the 2026 to 2027 El Niño will be an all-time record event.
- [8]
Cole: "There are forecasts that we might get as hot as 1.7 or 1.8 degrees Celsius above preindustrial temperatures, which is quite a bit higher than the current record."
- [9]
The study, first-authored by Julia Cole of the University of Michigan and titled "Recent strengthening of eastern Pacific ENSO is unprecedented in the last millennium paleorecord", was published in Science on Aug. 27.
- [10]
Cole: "Our data, for the first time, allow us to go back into the pre-industrial period and say with some confidence that what's happening in the last 40 or 50 years is really unusual."
- [11]
Climate models have given mixed signals about whether El Niño events could become stronger with climate change.
- [12]
The researchers used climate models simulating the last 1,000 years with histories of volcanic eruptions and solar variability; the models found no large shifts in El Niño that suggested natural processes could create such large changes.
- [13]
Kim Cobb, director of Brown University's Institute at Brown for Environment and Society, who was not involved with the study, calls the new evidence "a critical piece of the puzzle" in understanding how rising global temperatures are altering the cycle.
- [14]
How climate change is causing El Niño to strengthen is not yet clear; some models suggest ocean stratification, in which a warmer and rainier surface layer becomes less dense, more isolated from deeper cooler water, and more responsive when winds shift during an El Niño.
- [15]
Cole and her team spent years searching for boulders of fossilized coral washed up on Galápagos beaches to take samples spanning at least a couple of decades, providing "windows" into points in the past, as Cole puts it.
- [16]
El Niño events occur every two to seven years as part of the Pacific Ocean's El Niño-Southern Oscillation cycle.
- [17]
Earth's last El Niño ran from June 2023 to April 2024, delivering an injection of heat that made 2024 the hottest year on record.
- [18]
During El Niño, storm tracks over the US shift southward, bringing more rain to the desert Southwest and less to the Northwest, and similar shifts worldwide lead to droughts and flooding that bring disease, crop failure and wildfires.
- [19]
Cole: "We kept adding records thinking, well, this is going to get more complicated, but it really didn't. This is such a clear story."
- [20]
Cole: "No country has the resources to be fully protected from these impacts. This is one more reason we need to move away from fossil fuels, the root cause of the problem."
- [21]
Physical evidence from fossilized corals in the western and central Pacific had bolstered the argument that climate change is strengthening El Niño; the new study used corals from the Galápagos Islands in the eastern tropical Pacific.
- [22]
Study co-author Julia Cole says of the Galápagos: "It lies in the heart of where El Niño has some of its strongest impacts."
- [23]
Sampling at 1 mm intervals through skeleton that accumulates 10 to 20 mm per year yields roughly 10 to 20 samples per year of growth.
- [24]
Thirteen cores each spanning at least 20 years amounts to at least 260 coral-years of record, which is 26 percent of a 1,000-year interval if no two cores overlap in time.
- [25]
The study found El Niño events have become nearly 40% stronger in the last 40 years than they were in the preindustrial era.
- [26]
El Niño events in the last four decades were stronger than any in the 1,000 years before about 1850, when humans began affecting the climate with greenhouse gases.
- [27]
The coral record showed strong El Niños occurring in the last 40 to 50 years, whereas El Niños before that period showed "a pretty consistent pattern of lower intensity El Niños".
Sources
6 independent publishers whose own reporting we read for this story.
- discovermagazine.comAncient Corals Reveal Today's El Niños Are the Strongest in 1,000 Years
1 article · August 27, 2026
- livescience.com'This is such a clear story': Climate change is supercharging El Niño to unprecedented strengths, study finds
1 article · August 27, 2026
- nature.comWhy are El Ninos getting stronger? 1000-year-coral record points to climate change
1 article · August 26, 2026
- newscientist.comGalapagos corals suggest climate change drives stronger El Niños
1 article · August 27, 2026
- phys.orgEl Niños have been more intense over the last 40 years than in the previous 1,000 years, coral records reveal
3 articles · August 30, 2026
- scientificamerican.comClimate change is supercharging El Niños, coral records show
1 article · August 27, 2026
Topics and entities
Topics
- Climate change attribution
- El Nino-Southern Oscillation
- Coral Proxy Records
- Extreme weather and drought risk
- Paleoclimatology
Entities
- Galápagos Islands
- Michael McPhaden
- University of Michigan
- Science
- Julien Emile-Geay
- Brown University
- NOAA