Overview
- A UN scientific assessment and integrated‑assessment modelers have concluded that RCP8.5, a very high no‑policy emissions pathway originally used as a 90th‑percentile ‘worst‑case’ example, is unlikely to be realized and should no longer serve as a default baseline.
- Modelers say rapid falls in renewable costs and revised assumptions in energy and socioeconomic models produced a narrower high‑end projection near roughly 3.5°C by century’s end instead of the higher warming linked to RCP8.5.
- Experts warn that retiring RCP8.5 changes how researchers and communicators frame climate risk but does not remove major threats because medium and high scenarios still imply multi‑degree warming if emissions remain positive.
- Practical consequences include the need to reassess thousands of studies, regulations, and infrastructure plans that used RCP8.5 as a benchmark, with policymakers and planners likely to update risk baselines and adaptation choices.
- Coverage of the change has split—some outlets framed the move as a rollback of ‘doomsday’ claims while scientists urged clearer context—and the next steps will focus on clearer scenario use, updated modeling, and policy action to cut emissions or scale carbon removal.