2026 Warmest Year on Record Forecast Hits 96% as Oceans Set a New High

The 2026 warmest year on record forecast moved again on Thursday 22 October. Berkeley Earth, in its September 2026 update, now calculates roughly a 96% chance that 2026 will narrowly exceed 2024 as the warmest year on record, up from about 93% in its August update. The only plausible alternative in its modelling is a second-place finish, at about 4%.

Hold that number next to a different one. Bloomberg, via Moneyweb, reports that the US National Oceanic and Atmospheric Administration (NOAA) forecasts 2026 is still unlikely to supplant 2024, though it will come a close second. Two reputable outlooks, two different answers — and the gap between them is the story, not a mistake to be averaged away.

September 2026 second warmest September, by a whisker

Berkeley Earth puts September 2026 as nominally the second warmest September since records began in 1850, at 1.65 ± 0.11 °C above the 1850–1900 average, about 0.06 °C behind September 2023. Its anomaly was nominally the third largest of any month on record, behind only September 2023 and August 2026. The run of months above 1.5 °C that began in July continued.

The warmth was not evenly spread, which rarely makes the headline. Roughly 11.5% of Earth’s surface had its warmest September on record, and 53 countries set national September records, including Spain, Portugal, Andorra and Italy. Spain recorded 45.7 °C at El Granado in Andalusia on 3 September, equalling its national September record, and its weather agency issued red heat alerts in September for the first time since such warnings began in 2007, Berkeley Earth reports. France, meanwhile, had its second warmest September in a record reaching back into the eighteenth century, and its third driest September since 1958.

Record ocean temperatures September 2026: the number that stands out

Land did not lead this month. The oceans did. Berkeley Earth measured average ocean temperatures at 1.368 ± 0.068 °C above the 1850–1900 average — a clear September record, set by a margin of about 0.14 °C over September 2023, and nominally the warmest ocean month of any kind in its record. Thinc’s summary of the release singles out the same figure as the update’s most striking point.

That matters for a plain reason. Ocean heat is stored, not fleeting. A record-warm ocean in September keeps feeding warmth into the air above it for months, which is why a single month’s ocean figure can move a full-year forecast.

What the 2026 warmest year on record forecast rests on

One event sits underneath all of it. El Niño has reached record strength on the conventional Niño 3.4 index, Berkeley Earth reports: the September monthly index was about 2.9 °C, beating the 2.75 °C reached in 2015 and in 1877, and daily values had climbed to 3.4 °C by early October. Its peak is still expected later this year — October model runs pointed to a peak more likely in December than November — and because the global temperature response lags the Pacific peak by several months, much of the warming carries into 2027.

Berkeley Earth is careful about how the superlative should be read. On raw Pacific temperatures, the event has already eclipsed any past El Niño; adjusted for the background warming of the oceans, its trajectory looks more like other very strong events — a very strong El Niño boosted in absolute terms by a warmer ocean, with impacts that could still reach an intensity not seen before. Berkeley Earth research scientist Zeke Hausfather, quoted by Bloomberg, went further on the evidence researchers have debated: “It may well be possible that this could be the strongest El Niño event in a thousand years.”

The speed of the revision deserves its own line. Berkeley Earth gave 2026 only a 12% chance of a record at the start of the year, and the odds had fallen further by May; the August update lifted them to about 93%, and September’s data added the rest. The EU’s Copernicus Climate Change Service, with data through September, shows 2026 as the second hottest year to date, Bloomberg reports — a present-tense ranking that does not by itself settle where the year finishes.

Analysis: Berkeley Earth and NOAA are not contradicting each other so much as answering with different datasets, baselines and appetites for calling a narrow finish early. Berkeley Earth’s own margin is explicit — “narrowly exceed” — and its forecast is contingent on this El Niño developing in typical fashion. What is not in dispute anywhere in this reporting is the direction: record ocean heat, a record-strength El Niño still building, and a late-year surge strong enough to drag a year that started unremarkably to the edge of the record books.

Information verified through 24 October 2026.

Sources

1. “September 2026 Temperature Update” — Berkeley Earth, released 22 October 2026 — https://berkeleyearth.org/september-2026-temperature-update/
2. “Odds of 2026 becoming the hottest year surge higher with El Niño” — Eric Roston, Bloomberg, via Moneyweb, 24 October 2026 — https://www.moneyweb.co.za/news-fast-news/odds-of-2026-becoming-the-hottest-year-surge-higher-with-el-nino/
3. “August 2026 Temperature Update” — Berkeley Earth, September 2026 — https://berkeleyearth.org/august-2026-temperature-update/
4. “Oceans Hit Record High as El Niño Emerges as Strongest Ever” — This Is Not Cool (Thinc), 22 October 2026 — https://thinc.blog/2026/10/22/oceans-hit-record-high-as-el-nino-emerges-as-strongest-ever/