The global annual mean surface temperature anomaly falls below zero relative to 1951-1980 baselines before 203

Question

Six frontier AI models put this at 1% by 3 Nov 2031. Full reasoning from every model.

WillHappen.ai · Accepted Answer

1% — the median of 6 frontier models, resolving by 2031-11-03.

Answer

Gemini (Google): 1% — Only an unprecedented catastrophic aerosol injection from a supervolcano or nuclear war could drop anomalies below zero by 2030. Recent annual anomalies sit above +1.0C relative to 1951-1980, requiring an unprecedented >1.0C multi-year global plunge. The last year below the 1951-1980 baseline was 1976; even severe Pinatubo-scale eruptions cool globally by only ~0.5C. A massive VEI 7+ eruption or nuclear winter event is the only mechanism that could overcome greenhouse forcing this decade.

Answer

Claude (Anthropic): 1% — Would require reversing decades of warming trend in under 5 years, which is not physically plausible. GISTEMP anomaly relative to 1951-1980 is already around +1.0 to +1.2°C and rising, not near zero. No known climate mechanism (volcanic, solar, ENSO) could produce a multi-decade-scale cooling of this magnitude within 5 years. Base rate for such a reversal is essentially zero given consistent multi-decade warming trend across all major datasets.

Answer

GPT (OpenAI): 1% — Absent an extreme, sustained global cooling shock, the 1951–1980 annual mean baseline is far below today’s climate. NASA and HadCRUT would need a full calendar year below their 1951–1980 average by 2030, not merely a cool month or region. Recent annual anomalies are roughly +1°C or more above that baseline; even major La Niña years have remained positive. Only a huge volcanic aerosol event, nuclear-scale disruption, or rapid forcing reversal could move the odds materially.

Answer

Grok (xAI): 1% — A 1.2°C+ drop in 3 years needs a Pinatubo-scale or larger forcing that current ENSO/volcano odds do not supply. NASA/HadCRUT 2023–24 sit +1.17 to +1.3 °C vs 1951–80; 2025–29 must all stay below 0. No analog since 1880 shows a 1 °C cooling in <5 yr without a VEI-6+ eruption plus La Niña; none is forecast. Only a 1991-Pinatubo-plus event in 2027–28 would move the needle; that base rate is ~1 %.

Answer

DeepSeek (DeepSeek): 1% — This requires a ~1.3C drop in global temperature within a few years, which no known mechanism can deliver. The last time any year ran below the 1951-1980 baseline was 1976; every year since has been warmer, with 2024 near +1.3C. Even a record La Niña plus a major volcanic eruption would likely only shave a few tenths of a degree, not the ~1.3C needed. Only a civilization-scale aerosol injection or a Tambora-scale eruption plus extreme internal variability could flip the sign, and neither is credibly forecast by 2030.

Answer

Qwen (Alibaba): 1% — Current anomaly is ~+1.2°C above the 1951-1980 baseline; no known natural mechanism can produce a >1.2°C drop in a single year. Pinatubo (1991), the largest modern eruption, caused only ~0.4-0.5°C temporary cooling—roughly a third of what's needed. Ocean thermal inertia means even a Tambora-scale event would not push annual means below the 1951-1980 baseline within one year. Only a nuclear-winter-scale or large-asteroid scenario could plausibly do this; annual probability of such events is well under 0.1%.

The global annual mean surface temperature anomaly falls below zero relative to 1951-1980 baselines before 2030.

What each one said

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