resolved · Unscored / disputed
Scenario B projected continued global warming under reduced but continuing trace-gas growth.
Source-backed summary; not presented as a verbatim quotation.
James Hansen and colleagues
NASA climate scientists · United States
The world at the time.
Hansen’s team published three trace-gas scenarios rather than a single unconditional future. Scenario B became the commonly evaluated middle pathway.
What happened.
Scenario B produced about 50% more warming than observed over 1988–2017. IPCC’s retrospective attributes much of the difference to higher assumed forcing.
Predicted vs actual.
| Metric | Predicted | Actual | Variance / caveat |
|---|---|---|---|
| Scenario B warming versus observation, 1988–2017 | About 1.5 times observed warming | Observed reference = 1.0 | About 50% excess before forcing adjustment |
The counter-signal.
The original paper identified uncertain climate sensitivity, ocean heat uptake and omitted forcings. These qualifications were part of the forecast, not explanations invented after the outcome.
Verdict.
Reasoning: sound · Outcome: partial
Raw scenario warming overshot; forcing-adjusted model performance was substantially better.
Cause of death / explanatory lens.
No cause of death assigned
The lesson.
How much of a forecast error comes from its causal model and how much from its assumed future inputs?
Sources.
- Global climate changes as forecast by GISSprimary · 1988-08-20 · scenario definition and contemporary limitations
- Global climate changes, journal publicationprimary · 1988-08-20 · publication date
- AR6 WGI chapter 1primary · 2021 · 1988–2017 comparison
Related predictions.
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