El Nino's daily Pacific anomaly reached 3.08 C in September, months before its expected peak
Science News reports the El Nino region's daily sea surface anomaly hit 3.08 C on September 21, past the 3.02 C mark set in November 2015. NOAA's preferred index still ranks the 1997-98 event stronger, leaving two analogues in play for the coming seasons.
The Scientist · Science desk
What happened
- The daily sea surface temperature anomaly in the central and eastern equatorial Pacific reached 3.08 degrees Celsius above the 1991-2020 average on September 21, the highest in the record.
- NOAA has not declared the event the strongest on record, because it scores El Nino strength from a rolling three-month average rather than from a single daily reading.
- Nathaniel Johnson of NOAA's Geophysical Fluid Dynamics Laboratory said the event will probably strengthen further and reach its peak within the next few months.
- Drought is already killing crops and animals in Central America, and in Indonesia the drought blamed on El Nino has fueled wildfires across the archipelago.
- Johnson said the pattern has already suppressed the Atlantic hurricane season and enhanced the Pacific one, with droughts appearing in Central America.
Why it matters
- What doesn't add up contradiction Any plan keyed to the phrase "record broken" depends on which dashboard you read: the published figures for the same week differ by half the margin over 2015.
- What it limits constraint Scaling the remote seasonal impacts up from the absolute record risks over-forecasting them, since the index NOAA says better captures global influence still puts 1997-98 ahead.
- Who's exposed exposure Shippers face rationed Panama Canal transits into a second season: the locks run on reservoir water, 5% of global trade moves through them, and traffic was cut before the peak arrived.
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Zeke Hausfather, a climatologist at Berkeley Earth, calls the same week a tie. He put the Nino 3.4 anomaly at 3.07 degrees Celsius, level with 2015-16 [6]. Scientific American reported 3.05 C, the figure the climate specialist Jeff Berardelli posted, and called it the highest since 2015 [8]. The three published values span 0.03 C, half the 0.06 C margin between the new high and November 2015's 3.02 C [25]. They come from different boxes of ocean, different days and different baselines. The September 21 reading was above both the 1991-2020 and the 1982-2010 average [15]. Hausfather's figures, published on the Climate Brink dashboard, score the Nino 3.4 box against a 30-year average using NOAA's satellite-and-buoy record [27].
NOAA has also changed what it scores. The Relative Oceanic Nino Index measures warming in Nino 3.4 against warming across the whole tropical belt, so that general ocean heating does not inflate the number [7]. On that index the 1997-98 event still leads [5]. The Climate Prediction Center's latest seasonal forecast suggests that record falls soon [13], and AFP reported the same expectation [7]. Scientific American noted that on a background-adjusted measure this El Nino is not at an all-time high but is hotter than it has ever been for late September [12].
So there are two analogues, and which one applies depends on the impact. For anything keyed to absolute warmth, nothing in the record matches this [1]. The 3.08 C does not tell you how hard the remote signals will land, because those are what the relative index was built to represent: NOAA says it better captures the pattern's ability to sway weather globally [5]. Those signals arrive later. Johnson said El Nino typically brings rainier conditions to the southern United States in late fall and drier than normal weather to the Pacific Northwest. It also brings warmer than average conditions across the northern United States and Canada, along with drought over northern South America and the Amazon and a weakening Indian monsoon [18].
Daniel Swain, a climate scientist at the University of California Agriculture and Natural Resources, said this will probably turn out to be the strongest El Nino event of our lives so far [22]. Kim Wood of the University of Arizona said sea surface temperatures have been "unparalleled" for this time of year "for a while" [9]. Hausfather, in an email to AFP, said September "is very likely to have the highest monthly anomalies on record, barring something quite unexpected in the coming week" [26].
The largest figure in the coverage comes from a model. Researchers at the Climate Impact Lab at the University of Chicago estimate the released ocean heat could add about 1.2 C to global land temperatures over the coming months and cause more than 450,000 additional heat-related deaths by February 2027 [29]. Science News reports that estimate without the method or the baseline behind it. On why this event is so strong, Johnson said attribution is "really an unanswered question" [14]; Nathan Lenssen of the National Center for Atmospheric Research said the debate is unsettled but that a warmer planet has more energy in its oceans for El Nino to release [16]. A recent study of coral skeletons found a "striking amplification" of El Ninos over the past 40 years compared with the preindustrial period [21].
What to watch
- Whether NOAA's three-month Relative Oceanic Nino Index passes the 1997-98 value in a Climate Prediction Center update, which would leave one analogue instead of two.
- Whether Hausfather's September monthly anomaly lands as the highest on record once the month closes.
- How many transit slots the Panama Canal authority offers as the peak approaches.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence70
- Adoption
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- Hype gap+20
- Incentives
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- Confidence68
Perspective Coverage
3 publishers- Builder
- Builder 18%
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Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
On September 21, the daily sea surface temperature in the central and eastern equatorial Pacific Ocean reached 3.08 degrees Celsius warmer than the 1991 to 2020 average, more extreme than any other El Nino ever recorded.
- [2]
Prior to September, the most extreme anomaly on record was 3.02 degrees Celsius, set by an El Nino in November 2015.
- [3]
El Nino emerged in June, and since then the daily average sea surface temperature has climbed extraordinarily high in the heart of the Pacific region where El Nino develops.
- [4]
NOAA has yet to declare this event the strongest on record; it uses a rolling three-month-average anomaly, rather than the daily anomaly, in calculations of an El Nino's strength.
- [5]
NOAA has shifted to a new method for measuring El Nino strength, the Relative Oceanic Nino Index, which better represents the phenomenon's ability to sway weather globally; by that measurement the current El Nino has yet to surpass the strength of the 1997-98 event.
- [6]
Zeke Hausfather, a climatologist at Berkeley Earth, said the sea surface temperature anomaly in the tropical Pacific stands at 3.07 degrees Celsius, tying the 2015-16 El Nino.
- [7]
NOAA has shifted to the Relative Oceanic Nino Index, which gauges warming in the Nino 3.4 region against warming across the whole tropical belt to better account for climate change heating oceans in general; on that metric the numbers run lower and the current El Nino is still below the record, though expected to eventually break it.
- [8]
Sea surface temperatures in the region are 3.05 degrees Celsius warmer than usual, the highest anomaly seen since 2015, when temperatures were 3.02 degrees Celsius above normal, climate specialist Jeff Berardelli noted in a social media post.
- [9]
Kim Wood, an associate professor of hydrology and atmospheric sciences at the University of Arizona, said in a social media post that sea surface temperatures have been "unparalleled" for this time of year "for a while."
- [10]
"It has been a remarkable event," said Nathaniel Johnson, a climate scientist at NOAA's Geophysical Fluid Dynamics Laboratory in Princeton, N.J.
- [11]
Johnson said the El Nino will probably grow stronger: "We're probably going to reach our peak within the next few months."
- [12]
Using a measurement that accounts for background warming ocean temperatures as a result of climate change, this year's El Nino has not yet hit an all-time high, but it is hotter than it has ever been for late September.
- [13]
The latest seasonal forecast from NOAA's Climate Prediction Center suggests the 1997-98 record on the relative index is on track to be broken soon.
- [14]
Asked how much of the El Nino's strength was fueled by human-caused climate change, Johnson said: "It's really an unanswered question," adding that there is not yet a scientific consensus on how climate change is affecting El Nino.
- [15]
On September 21 the 3.08 degree Celsius reading was above both the 1991 to 2020 average and the 1982 to 2010 average.
- [16]
Nathan Lenssen, a climate scientist at the National Center for Atmospheric Research in Boulder, Colo., said it is a matter of debate how much can be directly attributed to climate change, but that due to the warming of the planet there is more energy in the oceans now, and El Ninos are when the ocean releases some of that heat into the atmosphere.
- [17]
Johnson said the season has already seen a suppressed Atlantic hurricane season, an enhanced Pacific hurricane season and droughts in Central America.
- [18]
Johnson said that as late fall arrives, El Nino tends to bring rainier conditions over the southern United States, drier than normal conditions over the Pacific Northwest and warmer than average conditions over the northern United States and Canada, and that droughts tend to occur over northern South America and the Amazon alongside a weakening of the Indian monsoon.
- [19]
The Panama Canal carries 5% of global trade and cannot function without the reservoir water it uses to power its locks; authorities have had to slash traffic through the canal.
- [20]
This El Nino is already hitting Central America hard, where animals and crops are dying from drought, and in Indonesia it is blamed for drought that has fueled wildfires.
- [21]
A recent study based on coral skeletons found there had been "striking amplification" of El Ninos in the past 40 years compared with the preindustrial period.
- [22]
"This is probably going to be the superlative El Nino event of our lives so far," said Daniel Swain, a climate scientist at the University of California Agriculture and Natural Resources.
- [23]
El Nino events typically raise global temperatures, putting this year and 2027 at risk of being among the hottest years ever recorded.
- [24]
The September 21 daily anomaly exceeds the previous record daily anomaly by 0.06 degrees Celsius.
- [25]
The three published values for the current anomaly (3.08, 3.07 and 3.05 degrees Celsius) span 0.03 degrees Celsius, half the 0.06 degree margin by which the new high exceeds the November 2015 record.
- [26]
Hausfather said in an email: "This month (September) is very likely to have the highest monthly anomalies on record, barring something quite unexpected in the coming week."
- [27]
Hausfather's figures, published on the Climate Brink dashboard, draw on NOAA's satellite-and-buoy sea surface record and are based on how much daily sea surface temperatures in the Nino 3.4 region are above a 30-year average.
- [28]
El Nino sets in when trade winds blowing east to west temporarily ease, allowing warm water that normally piles up in the western Pacific to slide back east and rise to the surface.
- [29]
Researchers from the Climate Impact Lab at the University of Chicago report that the oceanic heat released could contribute to an increase in global land temperatures of about 1.2 degrees Celsius over the coming months, leading to over 450,000 additional heat-related deaths by February 2027.
Sources
3 independent publishers whose own reporting we read for this story.
- phys.orgEl Niño weather pattern enters record territory: Scientist
1 article · September 22, 2026
- sciencenews.orgThis year’s El Niño just broke a record months before it’s expected to peak
1 article · September 24, 2026
- scientificamerican.comThis year’s El Niño just broke another sobering record
1 article · September 22, 2026
Topics and entities
Entities
- Zeke Hausfather
- Nathaniel Johnson
- NOAA Geophysical Fluid Dynamics Laboratory
- AFP
- Daniel Swain
- NSF National Center for Atmospheric Research
- Oceanic Niño Index
- NOAA
- NOAA Climate Prediction Center
- Climate Impact Lab
- Relative Oceanic Nino Index