Overview
- The international scenario‑design committee formally retired SSP5‑8.5 in April 2026 and removed it from the set that will underpin the next IPCC assessment.
- SSP5‑8.5 was created in 2011 as a 90th‑percentile worst‑case stress test that assumed extreme inputs such as very high population and a large global coal surge, and scientists warned from 2017 that those assumptions were implausible.
- Despite those warnings, the scenario was widely used in thousands of papers and by institutions including central banks, the World Bank, national adaptation planners, and K–12 curricula, while the U.S. EPA had already stopped using RCP8.5 in regulatory cost‑benefit work in 2022.
- The retirement is changing litigation and evidence fights: climate damage suits that relied on high‑emissions projections face new challenges and filings by defendants such as Chevron allege undisclosed links between lawyers and key attribution studies.
- Scientists and agencies stress that retiring this single extreme pathway does not erase large climate risks because updated scenario ensembles introduced in mid‑May 2026 still show substantial chances of major warming and require updated risk planning.