A new scenario framework for CMIP7—the standardized set of emissions pathways used by many climate modelers and referenced in IPCC assessments—concludes that CMIP6’s highest-emissions pathway, SSP5-8.5 (and its earlier counterpart, RCP8.5), has become “implausible” given recent energy-cost trends, climate policy developments and emissions patterns.
The scenario historically known as RCP8.5 has been widely used in research as a high-end benchmark for climate impacts and risk assessments. But the team coordinating scenarios for the next phase of the Coupled Model Intercomparison Project (CMIP7) says the CMIP6 level of very high emissions—represented by SSP5-8.5 and linked in the literature to RCP8.5—no longer meets its plausibility criteria.
In the CMIP7 ScenarioMIP framework published in April 2026 in Geoscientific Model Development, the authors write that CMIP6’s high emissions levels “have become implausible,” citing trends such as falling renewable-energy costs, the emergence of climate policy and recent emissions trends. Instead of carrying forward SSP5-8.5 as the top-end benchmark, the framework lays out a new “High emission scenario” designed to represent emissions “as high as judged to be plausible,” and it is expected to produce forcing levels below SSP5-8.5.
The shift is aimed at updating standardized modeling inputs rather than declaring extreme warming outcomes impossible. The ScenarioMIP paper notes that criticisms have grown over time about the plausibility of the most extreme scenarios, and it frames the CMIP7 scenarios as tools for exploring a range of futures—not as forecasts of what will happen.