Will NASA GISS report a global surface temperature anomaly of at least +1.45 °C (vs. 1951–1980) for October 2026?
deadline 2026-11-20
confidence medium
tier 1 evidence
25%PolySignal estimate
Resolution criterion
Resolves YES if the NASA GISS file GISTEMP v4 land-ocean monthly means (https://data.giss.nasa.gov/gistemp/tabledata_v4/GLB.Ts+dSST.csv), read for the first time on or after 2026-11-20, shows a value >= +1.45 °C for October 2026 (row 2026, column Oct). The value read at that moment is final; later revisions do not change the outcome. If the value is not yet published on 2026-11-20, the check is repeated until 2026-11-30, after which the question is voided. Also voided if NASA changes the dataset version or the 1951–1980 baseline. Reference at creation: +1.40 °C (August 2026). Data: GISTEMP Team, GISS Surface Temperature Analysis (GISTEMP), version 4, NASA Goddard Institute for Space Studies.
Verified starting state
Computed base rate: 38% of two-month changes in the NASA GISTEMP monthly anomaly since 1990 reached the change implied by this threshold (threshold 1.45 °C rounded up to 0.05 °C; reference 1.4 °C in 2026-08). Overlapping windows: small effective sample.
What pushes it up
- The base rate of 38% represents a significant historical probability of reaching the threshold [1].
- September 2026 ERA5 anomaly maps to a warm +1.39 °C in GISTEMP, keeping the baseline relatively high [1].
What pushes it down
- Early October 2026 ERA5 data (first 6 days) shows a lower anomaly of +0.73 °C, which is a drop from September's +0.82 °C [1].
- A projected October GISTEMP anomaly based on early ERA5 data points to roughly +1.30 °C, well below the +1.45 °C threshold [1].
What would move this number most
The temperature trend over the remaining 25 days of October 2026, which could deviate significantly from the first 6 days.
How this number is built
| Deadline | 2026-11-20 |
| Base rate | 38% |
| Best evidence | tier 1 · 1 article(s) used |
| Independent runs | 22 · 28 (spread 6 pts) |
| Confidence | medium |
| Evidence cap | not triggered |
| Last revised | 2026-10-08 20:59 |
| Model | gemini-3.5-flash |
Sources consulted
Probability history
2026-10-08 20:59 25% 0 article(s) on file · gemini-3.5-flash
- What pushes it up. The base rate of 38% represents a significant historical probability of reaching the threshold [1].
- What pushes it up. September 2026 ERA5 anomaly maps to a warm +1.39 °C in GISTEMP, keeping the baseline relatively high [1].
- What pushes it down. Early October 2026 ERA5 data (first 6 days) shows a lower anomaly of +0.73 °C, which is a drop from September's +0.82 °C [1].
- What pushes it down. A projected October GISTEMP anomaly based on early ERA5 data points to roughly +1.30 °C, well below the +1.45 °C threshold [1].
- What would move this number most. The temperature trend over the remaining 25 days of October 2026, which could deviate significantly from the first 6 days.
2026-10-08 19:45 30% 0 article(s) on file · gemini-3-flash-preview
- What pushes it up. Long-term anthropogenic warming trend increases the frequency of monthly anomalies exceeding +1.40 °C [1]
- What pushes it up. The August 2026 anomaly of +1.40 °C provides a high starting point for the two-month window [1]
- What pushes it down. The September 2026 ERA5 proxy of +0.82 °C suggests a GISTEMP equivalent of approximately 1.39 °C, which is below the target [1]
- What pushes it down. Preliminary ERA5 data for the first 6 days of October (+0.73 °C) indicates a cooling trend relative to September, mapping to roughly 1.30 °C in GISTEMP [1]
- What would move this number most. The high volatility of monthly temperature anomalies and the fact that only 6 days of October data are currently available.