November 17, 2023

Global temperature record

ERA5 records its first global day more than 2°C above the pre-industrial average

Nobody knew on the day. The 2°C threshold was crossed on 17 November and only spotted four days later, when the near-real-time data caught up.

One day at 2.07°C

The ERA5 reanalysis calculated global mean surface-air temperature on 17 November 2023 as 2.07°C above the estimated 1850–1900 average — the first day above 2°C in a record that begins in 1940.

Measured against the modern 1991–2020 reference instead, the same day was 1.17°C warm. The displayed anomaly depends heavily on which baseline you pick.

The following day came in at 2.06°C in provisional data, making it a two-day episode rather than a single outlier.

Found four days late

No announcement was made on 17 November. The milestone was identified afterwards from the near-real-time ERA5T stream and publicly reported by Copernicus on 21 November.

ERA5 is a reanalysis that combines observations with a weather model, not a single global thermometer reading, and the ERA5T stream undergoes later quality control.

The figure is a global daily average; it does not mean every location on Earth was 2.07°C above its own pre-industrial temperature.

Not a Paris Agreement breach

Carlo Buontempo, director of the Copernicus Climate Change Service, emphasised that two daily exceedances did not themselves constitute a breach of the Paris Agreement, whose temperature goals concern long-term warming.

The annual figure for 2023 also depends on the dataset: ERA5 gave 1.48°C above 1850–1900, while WMO's consolidation of six datasets gave 1.45°C ± 0.12°C.

WMO confirmed 2023 as the warmest year in the 174-year instrumental record.

Sources

Researched 24 Aug 2026 5 sources not yet audited

How this was checked

Researched from the web into a fact sheet and rewritten from that sheet. This article has not yet had an independent model audit. How the pipeline works →

What the sources leave uncertain

ERA5 is a reanalysis combining observations with a weather model, not a single global thermometer reading.
The result was initially issued through the near-real-time ERA5T stream, which undergoes later quality control.
“First on record” is specifically supported by ERA5, whose daily record begins in 1940; the anomaly is measured against an estimated 1850–1900 baseline.
Daily variability is not the same quantity as long-term human-caused global warming averaged over years or decades.