Climat · Français

Will the NSIDC Sea Ice Index report an average Northern Hemisphere sea ice extent of at least 9.20 million km² for November 2026?

deadline 2026-12-10 confidence medium tier 1 evidence
20%Asturna estimate

Resolution criterion

Resolves YES if the NSIDC Sea Ice Index v4 monthly file for the Northern Hemisphere (https://noaadata.apps.nsidc.org/NOAA/G02135/north/monthly/data/N_11_extent_v4.0.csv), read for the first time on or after 2026-12-10, shows an extent >= 9.20 million km² for November 2026 (region N). The value read at that moment is final; later revisions do not change the outcome. If the row is not yet published on 2026-12-10, the check is repeated until 2026-12-20, after which the question is voided. Also voided if NSIDC changes the dataset version or the definition of the monthly file. Reference at creation: average daily extent of the first five days of the month = 8.17 million km² (latest daily value 8.31 on 2026-11-05; daily values are an estimation aid only and never decide). Data: NSIDC Sea Ice Index, Version 4 (NOAA@NSIDC, dataset G02135), National Snow and Ice Data Center.

Verified starting state

Computed base rate: 24% of past years (1988 onward, 38 years) saw the NSIDC monthly mean exceed the average of the first five days of the month by at least the margin implied by this threshold (threshold 9.20 million km2, first-five-day mean 8.17). One value per year: small sample. Data: NSIDC Sea Ice Index, Version 4 (NOAA@NSIDC, G02135).

What pushes it up

What pushes it down

What would move this number most

The intensity of Arctic cooling and wind patterns over the final two weeks of November, which determine the speed of ice expansion into the Bering and Barents Seas.

How this number is built

Deadline2026-12-10
Base rate24%
Best evidencetier 1 · 2 article(s) used
Independent runs20 · 20 (spread 0 pts)
Confidencemedium
Evidence capnot triggered
Last revised2026-11-14 09:26
Modelgemini-3-flash-preview

Sources consulted

Arctic Sea Ice Ties for 10th-Lowest Summer Minimum as Antarctic Ice Likely Peaks at Third-Lowesttier 3 · Nature World News · 2026-09-25NSIDC Sea Ice Index v4 - official data series that settles this questiontier 1 · NSIDC Sea Ice Index v4 · 2026-11-14

Probability history

2026-11-14 09:26 20% 11 article(s) on file · gemini-3-flash-preview
  • What pushes it up. Daily ice extent is growing at a steady rate of approximately 0.077 million km² per day as of mid-November [tier 1].
  • What pushes it up. Historical data shows that end-of-November daily extents above 10.5 million km² are possible, which would be necessary to reach the target [tier 1].
  • What pushes it down. The 2026 Arctic summer minimum tied for the 10th-lowest on record, suggesting a year with lower-than-average ice availability [tier 3].
  • What pushes it down. The required average for the remaining 18 days of November (9.69 million km²) is significantly higher than the current daily extent of 8.85 million km² [tier 1].
  • What pushes it down. The required increase from the start of the month (1.03 million km²) is higher than the 75th percentile of historical increases (+1.02 million km²) [tier 1].
  • What would move this number most. The intensity of Arctic cooling and wind patterns over the final two weeks of November, which determine the speed of ice expansion into the Bering and Barents Seas.
2026-11-13 12:04 41% 11 article(s) on file · gemini-3.6-flash
  • What pushes it up. Refreeze momentum is strong in early November 2026, with the daily Arctic sea ice extent reaching 8.84 million km² on November 11 [1].
  • What pushes it down. Achieving a monthly average of 9.20 million km² requires the remaining 19 days of November to average ~9.65 million km², demanding sustained high ice growth [1].
  • What pushes it down. Long-term climate trends continue to suppress overall Arctic ice expansion compared to earlier decades [2].
  • What would move this number most. Whether the daily refreeze rate maintains its fast pace through late November across freezing sectors like Hudson Bay and the Bering Sea.
2026-11-12 09:19 22% 10 article(s) on file · gemini-3-flash-preview
  • What pushes it up. Daily sea ice extent has shown steady growth in the first 10 days of November, rising from an average of 8.17 million km² in the first five days to a daily value of 8.71 million km² by November 10 [tier 1].
  • What pushes it up. The growth rate between November 5 and November 10 (approximately 0.08 million km²/day) shows slight acceleration compared to the very beginning of the month [tier 1].
  • What pushes it down. The 2026 Arctic summer minimum tied for the 10th-lowest on record, which typically correlates with warmer ocean temperatures and slower autumn freeze-up [tier 3].
  • What pushes it down. To reach the 9.20 million km² monthly average, the remaining 20 days of November must average approximately 9.61 million km², which is significantly higher than the current daily extent of 8.71 million km² [tier 1].
  • What pushes it down. The required increase of 1.03 million km² over the first-five-day average is slightly above the 75th percentile (+1.02) of historical November growth margins [tier 1].
  • What would move this number most. The primary uncertainty is the atmospheric pressure patterns (such as the Arctic Oscillation) over the final two weeks of November, which can either accelerate ice spread through cooling or retard it through storm activity and warm air advection.
2026-11-11 09:28 27% 10 article(s) on file · gemini-3-flash-preview
  • What pushes it up. Daily sea ice extent has shown steady growth, increasing from an average of 8.17 million km² in the first five days to 8.66 million km² by November 9 [tier 1].
  • What pushes it up. The current growth rate of approximately 0.087 million km² per day is slightly above the pace needed to reach the 9.20 million km² monthly average [tier 1].
  • What pushes it down. The 2026 summer minimum was the 10th lowest on record, indicating a low starting point for the freeze-up season and generally warmer Arctic conditions [tier 3].
  • What pushes it down. The required growth to reach the 9.20 million km² threshold (1.03 million km²) is higher than the historical 75th percentile of November growth (+1.02 million km²) [tier 1].
  • What would move this number most. The rate of ice formation in the second half of November, which is highly dependent on Arctic weather patterns and wind conditions that can either accelerate or stall ice expansion.
2026-11-10 15:03 30% 8 article(s) on file · gemini-3.8-flash
  • What pushes it up. By 2026-11-08, daily Arctic extent rose quickly to 8.58 million km², lifting the 8-day average to 8.30 million km² and showing healthy early-November ice expansion [tier 1].
  • What pushes it up. Arctic sea ice tied for 10th-lowest summer minimum in 2026, which, while low historically, avoided record-low summer baselines that severely retard autumn refreeze [tier 3].
  • What pushes it down. A monthly gain of 1.03 million km² over the 8.17 million km² starting level exceeds the historical 75th percentile gain (+1.02 million km²), requiring sustained above-average freeze rates throughout the rest of November [tier 1].
  • What pushes it down. Long-term warming trends and frequent late-autumn storm activity in marginal seas frequently impede refreezing during mid-to-late November, limiting the likelihood of a high-percentile monthly gain [tier 1].
  • What would move this number most. The rate of freeze-up in the Chukchi, Barents, and Bering Seas over the final two weeks of November.
2026-11-07 07:50 17% 8 article(s) on file · openai/gpt-oss-120b (Groq)
  • What pushes it down. Recent analysis notes a record‑low summer minimum and continuing decline in Arctic sea ice, suggesting November extents will stay below the 9.20 Mkm² mark [tier 3]
  • What would move this number most. The actual November 2026 sea‑ice extent, which depends on weather patterns and oceanic conditions in the weeks leading up to the month’s end