The Warmest Years: Global Temperature Outlook for 2027

Key figures (as of October 2026)

Where the record stands

The consolidated January assessment now combines eight major datasets. Six are built from measurements at weather stations, on ships and from buoys. Two are reanalyses, which blend past observations, including satellite data, with models. Because their methods differ slightly, the datasets give slightly different values and sometimes different rankings.

In the consolidated record, 2024 is the warmest year, at about 1.55°C above the 1850-1900 average with an uncertainty of ±0.13°C. It was probably the first calendar year above 1.5°C. The year 2025, which began and ended under La Niña's cooling influence, came in at 1.44°C. Two datasets ranked it second warmest and six ranked it third. Across all eight datasets, 2023 to 2025 are the three warmest years, averaging 1.48°C, and the eleven years from 2015 to 2025 are the eleven warmest.

2026: a rapid shift to El Niño

El Niño conditions developed in May and early June 2026 and strengthened at one of the fastest rates on record, with the key Pacific index averaging about 1.5°C above normal over May to July and 2.0°C in July. In September the east-central Pacific sea surface was 2.1°C above normal, with readings above 4°C in parts of the eastern equatorial Pacific. Forecasters expect a strong-to-very-strong El Niño through January to March 2027, with a better than 83% chance. They give a 54% to 83% chance, depending on the season, that it will exceed every event measured since 1950.

Global temperatures have followed. January to September 2026 was the second-warmest such period on record, after 2024. August and September were the first two consecutive months above 1.5°C since late 2025, and September was 1.63°C above the pre-industrial average. Sea surface temperatures set records for any month in August and again in September. Whether 2026 itself ends as the warmest year depends on the dataset. One major dataset now gives it about a 96% chance of a record, while another rates second place as the most likely outcome.

Why 2027 matters most

Global temperatures react to the tropical Pacific with a delay of about three months. An El Niño that peaks around November or December 2026 should therefore have its greatest warming effect on 2027. The same pattern appeared in 1997-98, 2015-16 and 2023-24. In each case the year the event formed was warm, and the following year set a clear record.

Published outlooks agree:

• Central projection: one widely used projection puts 2027 at about 1.71°C above pre-industrial, with a 90% range of 1.49 to 1.93°C. That gives a 92% chance of a new record and a 94% chance of exceeding 1.5°C.
• National forecasting service: the long-range forecasters of a major national weather service say 2027 is "very likely" to replace 2024 as the warmest year.
• Updated analysis (August): an August update of the same projection put the chance of a 2027 record at about 95%.
• Five-year outlook (May 2026): the international outlook for 2026 to 2030, issued before El Niño fully developed, gave an 86% chance that at least one year in the period beats 2024. It also expected El Niño conditions to be favoured especially in 2027 and 2028, and said a single year above 2°C is exceptionally unlikely (less than 1%).

The main reasons 2027 might fall short are an early peak and fast decay of El Niño, or a large volcanic eruption that cools the planet for a year or two.

Scenarios: 2027's rank in the consolidated global temperature record

Resolution rule: 2027's rank among all years since 1850 in the consolidated, multi-dataset annual global temperature assessment issued by the international meteorological body. The resolving release is its confirmation of the 2027 global temperature as first published, expected about mid-January 2028; the 2025 figures were confirmed on 14 January 2026. The rank stated for the consolidated record decides the band. Some releases give only a range or a split across datasets, such as "one of the three warmest". In that case the median rank of the datasets listed in the release decides. If the median falls between two ranks, the cooler (lower) rank applies. A tie means the release describes the years as tied or joint, or gives them the same consolidated figure at its published rounding (two decimal places); a year tied for warmest falls in band 1. A tie at second falls in band 2, a tie at third falls in band 3, and a tie at fourth or lower falls in band 4. Later revisions do not count. If no such assessment covering 2027 is published by 30 June 2028, the forecast is withdrawn. The four bands are mutually exclusive and cover every outcome. Probabilities are the Centre's analytical estimates.

What to watch

1. El Niño's peak and decay: monthly Pacific readings through early 2027, and whether the peak comes before or after December.
2. Final 2026 figures: the 2026 global temperature confirmed in January 2027, which sets the bar for 2027.
3. Forecasts for 2027: annual global temperature forecasts for 2027, usually published in December.
4. Monthly records: whether early 2027 months set records, as typically happens after a strong El Niño.
5. Volcanic activity: any large eruption that injects material into the stratosphere.

Figures as of October 2026. Probabilities are analytical estimates by the Ghaf Centre for Studies & Research.