{"id":2072,"slug":"ipcc-likelihood-ladder","title":"IPCC likelihood ladder — the calibrated tier convention in high-stakes science communication","kind":"reference","scope":"business","status":"current","audiences":["kevin","candid-team"],"topics":["tier-design-principles"],"reference_body":"**Claim:** The IPCC uses a fixed, defined ladder of likelihood terms. Per AR6 and the Mastrandrea et al. (2010) Guidance Note:\n\n- **virtually certain:** 99-100% probability\n- **very likely:** 90-100%\n- **likely:** 66-100%\n- **about as likely as not:** 33-66%\n- **unlikely:** 0-33%\n- **very unlikely:** 0-10%\n- **exceptionally unlikely:** 0-1%\n\nDesigned precisely to communicate graded confidence without false precision.\n\n**Source:** IPCC AR6; Mastrandrea et al. 2010. Verified.\n\n**Why this matters for Candid:** The widget's 4 difficulty tiers are this pattern applied to a different domain. Each tier label should map to a defined input range and a stable interpretation — like the IPCC ladder, not loose marketing-speak.","rationale_body":null,"metadata":null,"links":{"outgoing":[],"incoming":[{"slug":"research-brief-smb-widget-presenting-tiers-june-2026","title":"Research brief: SMB widget presentation layer — tiered results without overclaiming (June 2026)","kind":"reference","scope":"business","link_type":"relates-to"},{"slug":"rule-four-tiers-with-visual-scale-and-drivers","title":"Rule — 4 tiers max, plain labels, visual scale, drivers shown","kind":"rule","scope":"business","link_type":"depends-on"},{"slug":"budescu-2009-2014-ipcc-verbal-mistinterpret","title":"Budescu et al. 2009/2014 — IPCC verbal terms interpreted REGRESSIVELY; numeric pairing fixes","kind":"reference","scope":"business","link_type":"relates-to"}]},"created_at":"2026-06-23T19:16:03.409Z","updated_at":"2026-06-23T19:16:03.409Z"}