The record depends on the index: 2015-16 leads raw ONI at 2.6°C, while 1982-83 leads NOAA's relative index at 2.4°C.
Back to the trend of the day: A huge ocean warm-up has set a heat record weeks before its peak
Poly Rating · from the trend of the day
Strongest El Niño on Record: Top 10 Events and 2026
In September 2026 the daily Niño 3.4 reading passed 2015's record of about 3°C, months before the expected peak, yet on NOAA's warming-adjusted index the 1982-83 event still holds the record.
- No. 1: 1982-83 El Niño
- 9 places
- 10 AIs
01Final list
10 AIs each built their own list of ten independently. Here is one result that is easy to check: every place has a reason, a source, and the list of AIs that included it.
A bright badge means this AI put the entry on its list. A dim badge means it did not.
- 1
1982-83 El Niño
Holds the record on NOAA's relative index at 2.4°C (2.69 monthly), yet sits only fourth on raw ONI at 2.1–2.2. One study puts its income loss at $4.1 trillion.
Included it: Claude, ChatGPT, Gemini, Grok, StepFun, Kimi, DeepSeek, Qwen. Did not include: Meta, Wenxin.In their lists: Claude: 2 · ChatGPT: 2 · Gemini: 3 · Grok: 4 · StepFun: 3 · Kimi: 4 · DeepSeek: 3 · Qwen: 2
What each AI noted 8
- Claudeplace 2
On the relative index this is the record holder (2.4 at CPC, 2.69 monthly), even though it ranks only fourth on raw ONI.
Source ↗ - ChatGPTplace 2
Its +2.4°C relative-index peak matches the strongest historical RONI reading, even though its conventional ONI peak is only +2.1°C.
Source ↗ - Geminiplace 3
Caught global satellites by surprise after the El Chichón eruption obscured sensors, delivering a massive +2.2°C ONI surge that redefined ENSO science.
- Grokplace 4
Highest or near-highest on the relative index (RONI peak 2.52°C) and the event that caught monitors off-guard.
Source ↗ - StepFunplace 3
The 'true strength' champion — strongest relative to the ocean around it, but only third on the raw thermometer.
Source ↗ - Kimiplace 4
Second-tier on the raw thermometer, No. 1 on the warming-adjusted index — and it arrived before forecasters could see it coming.
Source ↗ - DeepSeekplace 3
+2.40°C RONI is the highest observed true-strength peak since 1950.
Source ↗ - Qwenplace 2
Caught scientists completely by surprise before satellites existed; it remains the undisputed king of the Relative Oceanic Niño Index (RONI) at 2.69°C.
Source ↗
8 of 10 - 2
2015-16 El Niño
Holds the raw record at 2.6°C over three months (2.75 monthly), but drops to 2.3 once background ocean warming is removed. Food security of 60–100M people was hit.
Included it: Claude, ChatGPT, Gemini, Grok, StepFun, Kimi, DeepSeek, Qwen. Did not include: Meta, Wenxin.In their lists: Claude: 4 · ChatGPT: 4 · Gemini: 2 · Grok: 2 · StepFun: 4 · Kimi: 2 · DeepSeek: 4 · Qwen: 4
What each AI noted 8
- Claudeplace 4
The raw-temperature record at 2.6 (ONI), 2.75 monthly, but its RONI of 2.3 is lower than 1982-83's.
Source ↗ - ChatGPTplace 4
The historical ONI leader at +2.6°C falls behind 1982–83 on relative strength: +2.3°C versus +2.4°C.
Source ↗ - Geminiplace 2
Recorded the highest raw three-month temperature anomaly in modern history at +2.6°C ONI, triggering the longest global coral bleaching event ever witnessed.
- Grokplace 2
Highest peak ONI on record (~+2.6°C NDJ) before the relative index adjusted the ranking.
Source ↗ - StepFunplace 4
The warmest Pacific of any El Niño on the raw index — and the one whose global cost nobody can agree on.
Source ↗ - Kimiplace 2
The incumbent record-holder: +2.6 to +2.8°C at its winter 2015-16 peak — the number every 2026 forecast is measured against.
Source ↗ - DeepSeekplace 4
+2.6°C ONI is the raw-heat record; 60–100 million people felt it in their food security.
Source ↗ - Qwenplace 4
Holds the official monthly ONI record at 2.8°C, but its real-world impact ranked lower than its thermometer reading due to high global baseline temperatures.
Source ↗
8 of 10 - 3
2026-27 El Niño (forecast)
Estimate: NOAA's forecast median of 2.74°C relative would top every event, but measured three-month values so far are 2.2 raw and 1.7 relative.
Included it: Claude, ChatGPT, Gemini, Grok, StepFun, Kimi, DeepSeek, Qwen. Did not include: Meta, Wenxin.In their lists: Claude: 1 · ChatGPT: 1 · Gemini: 4 · Grok: 1 · StepFun: 2 · Kimi: 1 · DeepSeek: 1 · Qwen: 1
What each AI noted 8
- Claudeplace 1
Still mostly a forecast, yet it has already passed 2015 on the daily record (3.11°C against 3.08°C), and Carbon Brief's models average about 4.1°C at the peak.
Source ↗ - ChatGPTplace 1
NOAA's October forecast median reaches +2.74°C on the relative index, above the +2.4°C historical peak, but the latest observed three-month RONI is only +1.7°C.
Source ↗ - Geminiplace 4
Forecast models project extraordinary raw sea surface warmth peaking near +3.1°C (IRI plume) with upper ECMWF ensembles touching +4.0°C, challenging historical heat ceilings.
- Grokplace 1
Daily Niño 3.4 already broke the November 2015 record in September; models project a peak near 4°C.
Source ↗ - StepFunplace 2
It broke the raw heat record two to three months before its peak — no El Niño on record has ever done that.
Source ↗ - Kimiplace 1
Already +3.3°C weekly — past the old record weeks before its December peak, with NOAA giving 69% odds it beats every event since 1950.
Source ↗ - DeepSeekplace 1
Weekly Niño 3.4 has already hit +3.1°C, past 2015’s +3.0°C, while NOAA’s RONI forecast peaks at +2.67°C.
Source ↗ - Qwenplace 1
Forecast to obliterate raw sea-temperature records with an ONI near 4.0°C, but its true RONI strength may only tie the 1982 event because the oceans are already so warm.
Source ↗
8 of 10 - 4
1991-92 El Niño
Widest raw-versus-relative gap: only 1.5 on today's ONI (1.7 on the older version) but 2.1 on the relative index, because Pinatubo had cooled the surrounding tropics.
Included it: Claude, ChatGPT, Gemini, Grok, StepFun, Kimi, DeepSeek, Qwen. Did not include: Meta, Wenxin.In their lists: Claude: 7 · ChatGPT: 5 · Gemini: 8 · Grok: 7 · StepFun: 10 · Kimi: 8 · DeepSeek: 7 · Qwen: 3
What each AI noted 8
- Claudeplace 7
The biggest gap between its two readings: roughly 1.5 on raw ONI but 2.1 to 2.32 on RONI.
Source ↗ - ChatGPTplace 5
An often-overlooked event reaches +2.1°C on RONI but only +1.5°C on ONI, a striking example of how historical rankings change with the metric.
Source ↗ - Geminiplace 8
Reached +1.7°C ONI but had its atmospheric teleconnections masked by the massive aerosol veil injected by Mount Pinatubo's June 1991 volcanic eruption.
- Grokplace 7
Very strong on RONI (peak ~2.32°C) and produced significant droughts in Southern Africa and Australia.
Source ↗ - StepFunplace 10
ONI about 1.6 — 'strong', not 'very strong' — and the clearest proof that the index tier and the impact tier are different lists.
Source ↗ - Kimiplace 8
The El Niño entangled with Mount Pinatubo's ash — climate science spent years separating the volcanic cooling from the ocean warming.
Source ↗ - DeepSeekplace 7
+1.7°C ONI, and southern Africa’s cereal harvest fell by roughly half.
Source ↗ - Qwenplace 3
The first 'modern' super El Niño perfectly tracked by satellites, peaking at +2.4°C ONI and causing massive global coral bleaching and mudslides.
Source ↗
8 of 10 - 5
1972-73 El Niño
2.0 on NOAA's relative index (1.97–2.27 depending on the table), but its impact went further than its heat: Peru's 1973 anchovy catch fell to 1.8M tonnes, almost 85% below 1970.
Included it: Claude, ChatGPT, Gemini, Grok, StepFun, Kimi, DeepSeek, Qwen. Did not include: Meta, Wenxin.In their lists: Claude: 6 · ChatGPT: 6 · Gemini: 6 · Grok: 6 · StepFun: 6 · Kimi: 7 · DeepSeek: 5 · Qwen: 6
What each AI noted 8
- Claudeplace 6
Only 1.8 on raw ONI, but its relative reading is 2.0 to 2.27, which puts it among the top five.
Source ↗ - ChatGPTplace 6
With a +2.0°C relative-index peak, 1972–73 rivals 1965–66 despite looking smaller on a simple ranking of recent sea temperatures.
Source ↗ - Geminiplace 6
Peaked at +2.1°C ONI, triggering the historic crash of the Peruvian anchovy fishery from 12 million metric tons to under 2 million and setting off a global grain and livestock feed crisis.
- Grokplace 6
First widely recognized 'super' event of the modern era, with major impacts on Peruvian fisheries and Indian monsoon.
Source ↗ - StepFunplace 6
Not even in the 'very strong' tier on the index, yet it took about 85% out of the world's biggest single-species fishery.
Source ↗ - Kimiplace 7
The event that collapsed Peru's anchovy fishery and sent feed and food price shockwaves around the world.
Source ↗ - DeepSeekplace 5
+2.1°C ONI, the first event in NOAA’s record to trigger a global food-crisis response.
Source ↗ - Qwenplace 6
Peaked around +2.0°C ONI, but its real-world impact was catastrophic, collapsing the Peruvian anchovy fishery and triggering a 1970s global food price crisis.
Source ↗
8 of 10 - 6
1965-66 El Niño
Tied at 2.0 on the relative index with 1972-73 although its raw ONI is only 1.8. A forgotten event that moves up once warming is removed.
Included it: Claude, ChatGPT, Gemini, Grok, Kimi, Qwen. Did not include: Meta, StepFun, DeepSeek, Wenxin.In their lists: Claude: 8 · ChatGPT: 7 · Gemini: 9 · Grok: 8 · Kimi: 9 · Qwen: 9
What each AI noted 6
- Claudeplace 8
Equal fifth on CPC RONI (2.0), with a raw ONI of 1.8 in late 1965.
Source ↗ - ChatGPTplace 7
Its +2.0°C relative peak is stronger than many better-known modern events, demonstrating why a warming-background adjustment matters.
Source ↗ - Geminiplace 9
Peaked at +1.6°C ONI, producing one of the most severe Indian monsoon failures on record and pushing millions across the subcontinent into emergency grain reliance.
- Grokplace 8
Strong event with documented impacts, ranking among the larger mid-20th-century cases.
Source ↗ - Kimiplace 9
The forgotten +2.0 RONI event — tied fifth-strongest on the warming-adjusted index, almost never in the headlines.
Source ↗ - Qwenplace 9
Peaked near +1.5°C ONI but disrupted early global weather patterns enough to spur the first coordinated international meteorological monitoring efforts.
Source ↗
6 of 10 - 7
1957-58 El Niño
Raw ONI is 1.7, but one relative table puts it at 2.02. NOAA's own relative peak was not extracted, so this place is less certain.
Included it: Claude, ChatGPT, Gemini, Grok, Kimi, DeepSeek, Qwen. Did not include: Meta, StepFun, Wenxin.In their lists: Claude: 9 · ChatGPT: 8 · Gemini: 7 · Grok: 9 · Kimi: 10 · DeepSeek: 10 · Qwen: 7
What each AI noted 7
- Claudeplace 9
ONI of 1.7 but RONI of 2.02, the oldest event above 2.0 in the GGWeather table.
Source ↗ - ChatGPTplace 8
The first major event of the modern instrumental record reached +1.7°C on today's revised ONI, illustrating that extreme ENSO episodes predate recent global ocean warming.
Source ↗ - Geminiplace 7
The foundational El Niño of the modern observation era, peaking at +1.8°C ONI during the International Geophysical Year and establishing the physical basis of tropical teleconnections.
- Grokplace 9
Early instrumental-era event that helped establish the pattern of global teleconnections.
Source ↗ - Kimiplace 10
The strongest event of the pre-satellite age — measured by sparse ship and buoy data, and still classed 'strong' in NOAA's tables.
Source ↗ - DeepSeekplace 10
+1.7°C ONI, the first strong event in NOAA’s continuous 1950-onward table.
Source ↗ - Qwenplace 7
The first event heavily studied by modern oceanographers during the International Geophysical Year, peaking near +1.8°C ONI.
Source ↗
7 of 10 - 8
1986-88 El Niño
A long, flat event: both indices peak at 1.5°C, and raw ONI held there for months in 1987 rather than spiking.
Included it: Claude, ChatGPT, StepFun, DeepSeek, Qwen. Did not include: Meta, Gemini, Grok, Kimi, Wenxin.In their lists: Claude: 10 · ChatGPT: 10 · StepFun: 7 · DeepSeek: 8 · Qwen: 10
What each AI noted 5
- Claudeplace 10
A long, flat event: ONI held at 1.5 for months in 1987 (JAS and ASO) without a sharp peak.
Source ↗ - ChatGPTplace 10
Its peak indices are both +1.5°C, but its long development across 1986–88 makes it noteworthy beyond a single peak number.
Source ↗ - StepFunplace 7
One of only six events NOAA calls 'exceptionally wet' for the US Southeast — strong on land, modest on the index.
Source ↗ - DeepSeekplace 8
+1.7°C ONI, enough to help set up the 1988 North American drought.
Source ↗ - Qwenplace 10
Often forgotten because it followed a giant event, but its long duration sustained impacts on Southern African agriculture for nearly three years.
Source ↗
5 of 10 - 9
2023-24 El Niño
Very strong on raw ONI (2.0) but only 1.4 on the relative index, the clearest case of warming inflating the raw figure. It still brought Zambia's worst recorded drought.
Included it: Claude, ChatGPT, Gemini, Grok, StepFun, Kimi, DeepSeek, Qwen. Did not include: Meta, Wenxin.In their lists: Claude: 5 · ChatGPT: 9 · Gemini: 5 · Grok: 5 · StepFun: 5 · Kimi: 5 · DeepSeek: 6 · Qwen: 5
What each AI noted 8
- Claudeplace 5
Its ONI peak of 2.0 is tied with the strongest events on the raw scale, but I found no published RONI peak for it.
Source ↗ - ChatGPTplace 9
Its +2.0°C ONI becomes just +1.4°C RONI, making it the clearest recent example of why unusually warm ocean water need not mean an equally exceptional ENSO contrast.
Source ↗ - Geminiplace 5
Peaked at +2.0°C ONI atop an unprecedented global marine heatwave, causing widespread drought declarations across Southern Africa despite a lower relative anomaly.
- Grokplace 5
Reached very strong tier (~+2.0°C ONI) against a warmer baseline, contributing to record global heat and bleaching.
Source ↗ - StepFunplace 5
A 'moderate' El Niño on the index that still displaced about 2.5 million people in the Horn of Africa.
Source ↗ - Kimiplace 5
Only about +2.0°C — yet it emptied the Panama Canal and forced four Southern African nations to declare drought disasters.
Source ↗ - DeepSeekplace 6
+2.0°C raw ONI but only +1.42°C RONI — the widest raw-vs-true gap in the top five.
Source ↗ - Qwenplace 5
Only reached a peak ONI of 2.0°C, but pushed global air temperatures to unprecedented highs because the background ocean heat was already elevated.
Source ↗
8 of 10
02Worth knowing
What the AIs noticed while building the list.
NOAA made the relative index official in February 2026. On it, 2023-24 drops from 2.0 to 1.4: the same ocean gets a different verdict.
Forecast peaks are not one number. NOAA's relative median is 2.74°C, while ECMWF's near 4°C uses a raw 1981-2010 baseline, so the two cannot share one column.
Heat rank and damage rank differ: for 1997-98 alone, income-loss estimates range from $2.1 trillion to $5.7 trillion.
No seasonal forecast of this size has ever been verified, because an El Niño this strong has never happened.
03Questions people ask
What does the strongest El Niño on record actually mean for humans?
Higher odds of drought, floods and heat, not certain outcomes. WFP expects about 49 million more people in acute hunger by end-2027, and the 1997-98 event was linked to about 23,000 deaths.
Source ↗What does the strongest El Niño on record actually mean?
It depends on the index. Raw ONI puts 2015-16 first at 2.6°C; NOAA's relative index, which removes background ocean warming, puts 1982-83 first at 2.4°C.
Source ↗What year and season is the strongest El Niño on record?
November 2015–January 2016 on raw ONI (2.6°C), and October 1982–February 1983 on the relative index (2.4°C). The 2026-27 event is forecast to peak around November–December 2026.
Source ↗What was the strongest El Niño on record, and why do the numbers differ?
Among completed events, 2015-16 on raw heat, but its peak is quoted as 2.6°C (three-month), 2.75°C (monthly) or 2.8°C. The averaging window and baseline move the record by about 0.2°C.
Source ↗04How we counted
In plain words, no formulas.
1The question
Top 10 Strongest El Niño Events: Where 2026 Stands on Raw Heat, True Strength and Real-World Impact
2Why this topic
The reader learns why the same El Niño can count as a record or not, depending on the baseline and the index, and why the hottest event is not always the most damaging one.
3Where it applies
Global, events since 1950 plus the 2026-27 forecast
4What we looked at
- Peak Oceanic Niño Index (Niño 3.4 three-month anomaly), all events on the same baseline
- Peak Relative Oceanic Niño Index, which removes background tropical ocean warming
- Whether the figure is observed or still a forecast, and how well forecasts tracked observations at this stage of the event
- Gap between the sea-temperature rank and the rank by real-world impact (rainfall shifts, drought, economic loss)
- NOAA Climate Prediction Center – ONI (ERSSTv6) — Raw three-month Niño 3.4 sea temperature anomaly since 1950
- NOAA Climate Prediction Center – Relative ONI (RONI) — Niño 3.4 anomaly with background tropical ocean warming removed; NOAA's official index since February 2026
- NOAA CPC RONI outlook — Forecast distribution of the relative index for 2026-27: October–December median 2.74°C
- NOAA CPC ENSO Diagnostic Discussion — Chance of a historic event (RONI of +2.5°C or more): 69% in August, 83% in October
5Who ranked
10 AIs, each building its own list of ten independently and naming a source for every place: Claude, ChatGPT, Meta, Gemini, Grok, StepFun, Kimi, DeepSeek, Wenxin, Qwen.
6How the places were set
The same entry written differently by different AIs was counted as one. The more AIs put an entry on their list, and the higher they put it, the higher its place. "AI agreement" shows how many of the AIs had it on their own list. Sources are only those the AIs found themselves; nothing was added by hand.
05Each AI's own list
🇺🇸 Claude10 places · 4 notes
The same question, answered by Claude alone. The final list above combines all the AIs.
- 1El Niño 2026-27 (forecast)
Still mostly a forecast, yet it has already passed 2015 on the daily record (3.11°C against 3.08°C), and Carbon Brief's models average about 4.1°C at the peak.
Source ↗ - 2El Niño 1982-83
On the relative index this is the record holder (2.4 at CPC, 2.69 monthly), even though it ranks only fourth on raw ONI.
Source ↗ - 3El Niño 1997-98
The costliest event in one estimate ($5.7 trillion), yet another model gives only $2.1 trillion for the same event.
Source ↗ - 4El Niño 2015-16
The raw-temperature record at 2.6 (ONI), 2.75 monthly, but its RONI of 2.3 is lower than 1982-83's.
Source ↗ - 5El Niño 2023-24
Its ONI peak of 2.0 is tied with the strongest events on the raw scale, but I found no published RONI peak for it.
Source ↗ - 6El Niño 1972-73
Only 1.8 on raw ONI, but its relative reading is 2.0 to 2.27, which puts it among the top five.
Source ↗ - 7El Niño 1991-92
The biggest gap between its two readings: roughly 1.5 on raw ONI but 2.1 to 2.32 on RONI.
Source ↗ - 8El Niño 1965-66
Equal fifth on CPC RONI (2.0), with a raw ONI of 1.8 in late 1965.
Source ↗ - 9El Niño 1957-58
ONI of 1.7 but RONI of 2.02, the oldest event above 2.0 in the GGWeather table.
Source ↗ - 10El Niño 1987-88
A long, flat event: ONI held at 1.5 for months in 1987 (JAS and ASO) without a sharp peak.
Source ↗
What Claude noticed
The strongest El Niño on record depends on the index. By raw Niño 3.4, 2015-16 holds the record (2.75°C monthly), with the reconstructed 1877-78 event at 2.73°C. By relative index, 1982-83 holds it (2.69°C).
Forecasts say 2026 beats both records. Carbon Brief reports that every one of 674 model runs exceeds 2015-16, by about 1.3°C on average. Its RONI-adjusted median peak is 3.1°C and 77% of runs still beat the relative record.
The temperature record is hard to translate into impact. Two economic studies disagree on 1997-98 ($5.7 trillion against $2.1 trillion), and the biggest rise in global temperature usually comes months after the Pacific peak, so most 2026-27 impact is expected in 2027.
Forecasts have been running low. Zeke Hausfather said observations kept overshooting earlier projections, but August came in about 0.3°C below Carbon Brief's forecast.
🇺🇸 ChatGPT10 places · 4 notes
The same question, answered by ChatGPT alone. The final list above combines all the AIs.
- 12026–27 El Niño (forecast, provisional)
NOAA's October forecast median reaches +2.74°C on the relative index, above the +2.4°C historical peak, but the latest observed three-month RONI is only +1.7°C.
Source ↗ - 21982–83 El Niño
Its +2.4°C relative-index peak matches the strongest historical RONI reading, even though its conventional ONI peak is only +2.1°C.
Source ↗ - 31997–98 El Niño
One of the classic super El Niños: +2.4°C conventional ONI and +2.3°C relative RONI, with an exceptionally strong tropical Pacific signal.
Source ↗ - 42015–16 El Niño
The historical ONI leader at +2.6°C falls behind 1982–83 on relative strength: +2.3°C versus +2.4°C.
Source ↗ - 51991–92 El Niño
An often-overlooked event reaches +2.1°C on RONI but only +1.5°C on ONI, a striking example of how historical rankings change with the metric.
Source ↗ - 61972–73 El Niño
With a +2.0°C relative-index peak, 1972–73 rivals 1965–66 despite looking smaller on a simple ranking of recent sea temperatures.
Source ↗ - 71965–66 El Niño
Its +2.0°C relative peak is stronger than many better-known modern events, demonstrating why a warming-background adjustment matters.
Source ↗ - 81957–58 El Niño
The first major event of the modern instrumental record reached +1.7°C on today's revised ONI, illustrating that extreme ENSO episodes predate recent global ocean warming.
Source ↗ - 92023–24 El Niño
Its +2.0°C ONI becomes just +1.4°C RONI, making it the clearest recent example of why unusually warm ocean water need not mean an equally exceptional ENSO contrast.
Source ↗ - 101986–88 El Niño
Its peak indices are both +1.5°C, but its long development across 1986–88 makes it noteworthy beyond a single peak number.
Source ↗
What ChatGPT noticed
The record depends on the thermometer: 2015–16 leads the observed historical ONI table at +2.6°C, while 1982–83 reaches the highest observed RONI peak at +2.4°C.
NOAA's October 2026 forecast median of +2.74°C RONI exceeds the observed historical +2.4°C peak by 0.34°C, but that difference is still forecast rather than measured.
NOAA formally adopted the relative index for ENSO monitoring in February 2026, making the definition of strongest more consequential than ever for comparing historical events.
ECMWF warns that the relative index removes much of the tropical warming background but cannot remove the physical effects of global warming on evaporation, atmospheric moisture or extreme weather.
🇺🇸 Gemini10 places
The same question, answered by Gemini alone. The final list above combines all the AIs.
- 11997–1998 El Niño
Holds the record for true thermodynamic contrast, peaking at +2.4°C raw ONI and a historic +2.3°C Relative ONI against a cooler late-90s baseline.
- 22015–2016 El Niño
Recorded the highest raw three-month temperature anomaly in modern history at +2.6°C ONI, triggering the longest global coral bleaching event ever witnessed.
- 31982–1983 El Niño
Caught global satellites by surprise after the El Chichón eruption obscured sensors, delivering a massive +2.2°C ONI surge that redefined ENSO science.
- 42026–2027 El Niño (Forecast / Developing)
Forecast models project extraordinary raw sea surface warmth peaking near +3.1°C (IRI plume) with upper ECMWF ensembles touching +4.0°C, challenging historical heat ceilings.
- 52023–2024 El Niño
Peaked at +2.0°C ONI atop an unprecedented global marine heatwave, causing widespread drought declarations across Southern Africa despite a lower relative anomaly.
- 61972–1973 El Niño
Peaked at +2.1°C ONI, triggering the historic crash of the Peruvian anchovy fishery from 12 million metric tons to under 2 million and setting off a global grain and livestock feed crisis.
- 71957–1958 El Niño
The foundational El Niño of the modern observation era, peaking at +1.8°C ONI during the International Geophysical Year and establishing the physical basis of tropical teleconnections.
- 81991–1992 El Niño
Reached +1.7°C ONI but had its atmospheric teleconnections masked by the massive aerosol veil injected by Mount Pinatubo's June 1991 volcanic eruption.
- 91965–1966 El Niño
Peaked at +1.6°C ONI, producing one of the most severe Indian monsoon failures on record and pushing millions across the subcontinent into emergency grain reliance.
- 102009–2010 El Niño
A premier Central Pacific (Modoki) event peaking at +1.6°C ONI, showing how warming concentrated along the international dateline shifts global storm tracks differently than eastern-basin super events.
🇺🇸 Grok10 places · 4 notes
The same question, answered by Grok alone. The final list above combines all the AIs.
- 12026-27 El Niño (forecast/developing)
Daily Niño 3.4 already broke the November 2015 record in September; models project a peak near 4°C.
Source ↗ - 22015-16 El Niño
Highest peak ONI on record (~+2.6°C NDJ) before the relative index adjusted the ranking.
Source ↗ - 31997-98 El Niño
Benchmark very strong event (~+2.4°C ONI) that redefined impacts before 2015-16 edged it on raw heat.
Source ↗ - 41982-83 El Niño
Highest or near-highest on the relative index (RONI peak 2.52°C) and the event that caught monitors off-guard.
Source ↗ - 52023-24 El Niño
Reached very strong tier (~+2.0°C ONI) against a warmer baseline, contributing to record global heat and bleaching.
Source ↗ - 61972-73 El Niño
First widely recognized 'super' event of the modern era, with major impacts on Peruvian fisheries and Indian monsoon.
Source ↗ - 71991-92 El Niño
Very strong on RONI (peak ~2.32°C) and produced significant droughts in Southern Africa and Australia.
Source ↗ - 81965-66 El Niño
Strong event with documented impacts, ranking among the larger mid-20th-century cases.
Source ↗ - 91957-58 El Niño
Early instrumental-era event that helped establish the pattern of global teleconnections.
Source ↗ - 102009-10 El Niño
Moderate-to-strong event with clear drought signals in Southeast Asia and Australia.
Source ↗
What Grok noticed
Daily and weekly Niño 3.4 values in September-October 2026 already exceeded the prior record from November 2015, weeks before the typical peak.
On the relative index (RONI, NOAA official since Feb 2026), 1982-83 often ranks ahead of 2015-16; raw ONI still places 2015-16 highest observed.
Forecasts give an 83% chance the October-December 2026 RONI reaches ≥ +2.5°C, which would exceed every event since 1950; multi-model peaks approach 4°C conventional.
Proxy records (corals, tree rings) suggest the largest modern events are near the top of the past millennium; if models verify, 2026-27 has a high chance of ranking among the strongest in 1,000 years on raw indices.
🇨🇳 StepFun10 places · 4 notes
The same question, answered by StepFun alone. The final list above combines all the AIs.
- 1El Niño 1997-98
The only super El Niño that finishes top-two on the thermometer and first on the damage bill.
Source ↗ - 2El Niño 2026-27 (forecast)
It broke the raw heat record two to three months before its peak — no El Niño on record has ever done that.
Source ↗ - 3El Niño 1982-83
The 'true strength' champion — strongest relative to the ocean around it, but only third on the raw thermometer.
Source ↗ - 4El Niño 2015-16
The warmest Pacific of any El Niño on the raw index — and the one whose global cost nobody can agree on.
Source ↗ - 5El Niño 2023-24
A 'moderate' El Niño on the index that still displaced about 2.5 million people in the Horn of Africa.
Source ↗ - 6El Niño 1972-73
Not even in the 'very strong' tier on the index, yet it took about 85% out of the world's biggest single-species fishery.
Source ↗ - 7El Niño 1986-87
One of only six events NOAA calls 'exceptionally wet' for the US Southeast — strong on land, modest on the index.
Source ↗ - 8El Niño 2009-10
A strong El Niño that never made the global hunger headlines — the baseline for how little the index alone explains.
Source ↗ - 9El Niño 1963-64
The oldest of NOAA's six 'exceptionally wet' Southeast events — from before the satellite era even started.
Source ↗ - 10El Niño 1991-92
ONI about 1.6 — 'strong', not 'very strong' — and the clearest proof that the index tier and the impact tier are different lists.
Source ↗
What StepFun noticed
The 2026 event is growing faster than any prior El Niño on an ONI basis — it has already outpaced 1997-98, the previous gold standard for explosive onsets, and it did so while the background ocean was at record warmth. That combination is why the raw and relative rankings can disagree so sharply.
NOAA quietly changed the official answer in February 2026: the Relative ONI, which strips out background tropical ocean warming, replaced ONI for monitoring and prediction. On that measure the 2023-24 event was about 0.6°C weaker than the old index said — the same ocean, a different verdict.
The deadliest El Niño on record is not in the satellite era at all. The 1877-78 event is described as the strongest on record and is linked to a global famine that killed more than 50 million people — a reminder that 'strongest on record' and 'worst for humans' are measured on different scales entirely.
Forecasters disagree by more than a degree on where 2026 peaks: ECMWF's SEAS5 points near 4°C for November-December, the IRI multi-model plume near 3.1°C, and Carbon Brief's relative-measure median at 3.1°C against a prior record of 2.69°C. Three different answers to the same question, all published this season.
🇨🇳 Kimi10 places · 4 notes
The same question, answered by Kimi alone. The final list above combines all the AIs.
- 12026-27 El Niño (forecast)
Already +3.3°C weekly — past the old record weeks before its December peak, with NOAA giving 69% odds it beats every event since 1950.
Source ↗ - 22015-16 El Niño
The incumbent record-holder: +2.6 to +2.8°C at its winter 2015-16 peak — the number every 2026 forecast is measured against.
Source ↗ - 31997-98 El Niño
The benchmark for two decades — and it peaked almost a full degree below what 2026 is forecast to reach.
Source ↗ - 41982-83 El Niño
Second-tier on the raw thermometer, No. 1 on the warming-adjusted index — and it arrived before forecasters could see it coming.
Source ↗ - 52023-24 El Niño
Only about +2.0°C — yet it emptied the Panama Canal and forced four Southern African nations to declare drought disasters.
Source ↗ - 61877-78 El Niño
A 19th-century statistical dead heat with 2015-16 — measured by ship logs, remembered for drought and famine around the world.
Source ↗ - 71972-73 El Niño
The event that collapsed Peru's anchovy fishery and sent feed and food price shockwaves around the world.
Source ↗ - 81991-92 El Niño
The El Niño entangled with Mount Pinatubo's ash — climate science spent years separating the volcanic cooling from the ocean warming.
Source ↗ - 91965-66 El Niño
The forgotten +2.0 RONI event — tied fifth-strongest on the warming-adjusted index, almost never in the headlines.
Source ↗ - 101957-58 El Niño
The strongest event of the pre-satellite age — measured by sparse ship and buoy data, and still classed 'strong' in NOAA's tables.
Source ↗
What Kimi noticed
The index reshuffles history: remove background tropical warming and the all-time record belongs to 1982-83 (+2.69°C RONI), not 2015-16 — and 2023-24 drops from 'very strong' to merely 'strong'.
2026 is developing faster than 1997-98, the previous gold standard for explosive onsets — and unlike 2015 it started the year in near-La Niña conditions.
The deadliest benchmark peaked a full degree cooler than the 2026 forecast: 1997-98 reached 2.37°C and was still linked to an estimated 23,000 deaths — raw heat rank and human impact rank are different lists.
No forecast this extreme has ever been verified: seasonal models have demonstrated skill for ordinary events, but no ensemble has ever predicted — and then confirmed — a 3.6°C El Niño, because one has never happened.
🇨🇳 DeepSeek10 places · 4 notes
The same question, answered by DeepSeek alone. The final list above combines all the AIs.
- 12026-27 El Niño (forecast)
Weekly Niño 3.4 has already hit +3.1°C, past 2015’s +3.0°C, while NOAA’s RONI forecast peaks at +2.67°C.
Source ↗ - 21997-98 El Niño
+2.28°C RONI, second only to 1982-83 — and the event that put modern El Niño damage on the map.
Source ↗ - 31982-83 El Niño
+2.40°C RONI is the highest observed true-strength peak since 1950.
Source ↗ - 42015-16 El Niño
+2.6°C ONI is the raw-heat record; 60–100 million people felt it in their food security.
Source ↗ - 51972-73 El Niño
+2.1°C ONI, the first event in NOAA’s record to trigger a global food-crisis response.
Source ↗ - 62023-24 El Niño
+2.0°C raw ONI but only +1.42°C RONI — the widest raw-vs-true gap in the top five.
Source ↗ - 71991-92 El Niño
+1.7°C ONI, and southern Africa’s cereal harvest fell by roughly half.
Source ↗ - 81987-88 El Niño
+1.7°C ONI, enough to help set up the 1988 North American drought.
Source ↗ - 92009-10 El Niño
+1.6°C ONI — strong, west-based, and far less globally disruptive than its rank suggests.
Source ↗ - 101957-58 El Niño
+1.7°C ONI, the first strong event in NOAA’s continuous 1950-onward table.
Source ↗
What DeepSeek noticed
The weekly Niño 3.4 reading hit +3.1°C in late September 2026, beating 2015-16’s +3.0°C weekly peak nearly two months before the usual peak — but the three-month RONI was still only about +1.4°C through August.
On true strength, 1982-83 still holds the record: its +2.40°C RONI is above 1997-98’s +2.28°C and 2015-16’s +2.25°C. Raw ONI gives 2015-16 the crown instead.
2023-24 looked top-five on the old raw index (+2.0°C ONI) but only moderate on RONI (+1.42°C), and its expected Northern Hemisphere winter teleconnections largely failed.
Forecast peaks are not one number: ECMWF shows about +4°C, the IRI multi-model median is +3.45°C on the traditional index, and NOAA’s official RONI median is +2.67°C. They are not directly interchangeable.
🇨🇳 Qwen10 places · 2 notes
The same question, answered by Qwen alone. The final list above combines all the AIs.
- 12026-27 El Niño
Forecast to obliterate raw sea-temperature records with an ONI near 4.0°C, but its true RONI strength may only tie the 1982 event because the oceans are already so warm.
Source ↗ - 21982-83 El Niño
Caught scientists completely by surprise before satellites existed; it remains the undisputed king of the Relative Oceanic Niño Index (RONI) at 2.69°C.
Source ↗ - 31997-98 El Niño
The first 'modern' super El Niño perfectly tracked by satellites, peaking at +2.4°C ONI and causing massive global coral bleaching and mudslides.
Source ↗ - 42015-16 El Niño
Holds the official monthly ONI record at 2.8°C, but its real-world impact ranked lower than its thermometer reading due to high global baseline temperatures.
Source ↗ - 52023-24 El Niño
Only reached a peak ONI of 2.0°C, but pushed global air temperatures to unprecedented highs because the background ocean heat was already elevated.
Source ↗ - 61972-73 El Niño
Peaked around +2.0°C ONI, but its real-world impact was catastrophic, collapsing the Peruvian anchovy fishery and triggering a 1970s global food price crisis.
Source ↗ - 71957-58 El Niño
The first event heavily studied by modern oceanographers during the International Geophysical Year, peaking near +1.8°C ONI.
Source ↗ - 81991-95 Prolonged El Niño
Not the highest single-month peak (~1.6°C), but its multi-year persistence made it one of the most economically disruptive events of the 1990s.
Source ↗ - 91965-66 El Niño
Peaked near +1.5°C ONI but disrupted early global weather patterns enough to spur the first coordinated international meteorological monitoring efforts.
Source ↗ - 101986-87 El Niño
Often forgotten because it followed a giant event, but its long duration sustained impacts on Southern African agriculture for nearly three years.
Source ↗
What Qwen noticed
The background warming penalty: Because the oceans are generally warmer now, an El Niño must be significantly hotter in absolute terms just to achieve the same 'relative' strength as events in the 1980s.
The surprise factor of 1982: The 1982-83 event occurred before the TOGA-TAO buoy array was built, meaning scientists literally didn't see it coming until global weather patterns had already shifted.