Will NASA GISS report a global surface temperature anomaly of at least +1.40 °C (vs. 1951–1980) for November 2026?
deadline 2026-12-20
confidence medium
tier 1 evidence
58%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 2026-12-20, shows a value >= +1.40 °C for November 2026 (row 2026, column Nov). The value read at that moment is final; later revisions do not change the outcome. If the value is not yet published on 2026-12-20, the check is repeated until 2026-12-30, after which the question is voided. Also voided if NASA changes the dataset version or the 1951–1980 baseline. Reference at creation: +1.38 °C (September 2026). Data: GISTEMP Team, GISS Surface Temperature Analysis (GISTEMP), version 4, NASA Goddard Institute for Space Studies.
Verified starting state
Computed base rate: 46% of two-month changes in the NASA GISTEMP monthly anomaly since 1990 reached the change implied by this threshold (threshold 1.4 °C rounded up to 0.05 °C; reference 1.38 °C in 2026-09). Overlapping windows: small effective sample.
What pushes it up
- September 2026 is already at a high baseline of +1.38 °C, requiring only a small +0.02 °C increase by November 2026 [1].
- Global climate warming trends and recent autumn temperature patterns frequently yield monthly GISTEMP anomalies above +1.40 °C [1].
What pushes it down
- Short-term internal climate variability and fluctuations in ocean surface temperatures could lower the anomaly below +1.40 °C [1].
- Early Copernicus ERA5 indicators for October show a moderate anomaly (+0.79 °C vs 1991–2020), indicating no immediate sharp spike in global heat [1].
What would move this number most
Natural short-term global temperature variability and tropical ocean conditions between September and November 2026.
How this number is built
| Deadline | 2026-12-20 |
| Base rate | 46% |
| Best evidence | tier 1 · 1 article(s) used |
| Independent runs | 48 · 58 · 62 (spread 14 pts) |
| Confidence | medium |
| Evidence cap | not triggered |
| Last revised | 2026-10-11 13:31 |
| Model | gemini-3.5-flash |
Sources consulted
Probability history
2026-10-11 13:31 58% 0 article(s) on file · gemini-3.5-flash
- What pushes it up. September 2026 is already at a high baseline of +1.38 °C, requiring only a small +0.02 °C increase by November 2026 [1].
- What pushes it up. Global climate warming trends and recent autumn temperature patterns frequently yield monthly GISTEMP anomalies above +1.40 °C [1].
- What pushes it down. Short-term internal climate variability and fluctuations in ocean surface temperatures could lower the anomaly below +1.40 °C [1].
- What pushes it down. Early Copernicus ERA5 indicators for October show a moderate anomaly (+0.79 °C vs 1991–2020), indicating no immediate sharp spike in global heat [1].
- What would move this number most. Natural short-term global temperature variability and tropical ocean conditions between September and November 2026.
2026-10-11 09:13 42% 0 article(s) on file · gemini-3.7-flash
- What pushes it up. August 2026 started at +1.40 °C, meaning only a modest rise of +0.05 °C across two months is needed to hit the +1.45 °C threshold [tier 1].
- What pushes it up. Early Copernicus ERA5 data for the first 9 days of October 2026 shows a strong anomaly of +0.79 °C vs 1991–2020, pointing toward elevated global warmth [tier 1].
- What pushes it down. Historically, only 38% of two-month increments sustain a +0.05 °C increase, indicating month-to-month cooling or stagnation is frequent [tier 1].
- What pushes it down. Nine days of ERA5 reanalysis provide only a partial month signal with substantial intra-month volatility and known differences from GISTEMP processing [tier 1].
- What would move this number most. Whether global temperatures remain elevated through the remainder of October 2026 or cool down as month-to-month noise reverts.
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.