Will Copernicus report October 2026 as the warmest October on record?
deadline 2026-11-20
confidence medium
tier 1 evidence
18%PolySignal estimate
Resolution criterion
Yes if the Copernicus Climate Change Service (C3S) monthly climate bulletin for October 2026 states that October 2026 was the warmest October in the ERA5 record for global surface air temperature. Second-warmest or lower, or no bulletin published by 20 November 2026, resolves No.
Verified starting state
Copernicus (bulletin of 9–12 October 2026): September 2026 was the second-warmest September in the ERA5 record, 1.63°C above the 1850–1900 average and 0.11°C cooler than September 2023. The September Niño-3.4 sea-surface temperature reached an all-time monthly high of 29.70°C, El Niño is expected to intensify further, and months above 1.5°C are expected to continue into 2027. The monthly bulletin usually appears in the first days of the following month.
What pushes it up
- Recent months have set temperature records (August 2026 record, September 2026 second‑warmest) indicating a strong warming trend [tier 1]
- The Copernicus bulletin notes months above 1.5 °C are expected to continue into 2027, suggesting October could be unusually warm [tier 1]
What pushes it down
- No actual October temperature data or bulletin has been released yet, so the claim is still speculative
- The only October‑related information comes from trend statements, not concrete measurements; tier‑4 articles provide no additional evidence [tier 4]
What would move this number most
The actual October 2026 temperature anomaly relative to the ERA5 record
How this number is built
| Deadline | 2026-11-20 |
| Base rate | 5% |
| Best evidence | tier 1 · 2 article(s) used |
| Independent runs | 15 · 20 (spread 5 pts) |
| Confidence | medium |
| Evidence cap | not triggered |
| Last revised | 2026-10-14 14:44 |
| Model | openai/gpt-oss-120b (Groq) |
Sources consulted