Climate modeling groups worldwide have released a new set of emissions scenarios for the seventh phase of the Coupled Model Intercomparison Project, known as CMIP7. These scenarios will serve as a foundation for climate simulations that inform the Intergovernmental Panel on Climate Change’s seventh assessment report. The new scenarios represent a significant departure from their predecessors, which were used in the IPCC’s sixth assessment report.
The most notable change involves how the scenarios are named and structured. Rather than using enigmatic names based on radiative forcing levels, the new CMIP7 scenarios are identified simply by their emissions trajectories, ranging from “low-to-negative” to “high.” Additionally, the scenarios shift away from exploring hypothetical “no-climate-policy” baseline futures. Instead, they examine outcomes where current policies persist, strengthen, or weaken. The updated scenarios also incorporate modified socioeconomic assumptions, with global population projections increased substantially from earlier estimates, predicting approximately 9.9 billion people by 2100.
A significant methodological adjustment involves how the scenarios treat extreme warming outcomes. The high-end emissions projections have been revised downward considerably compared to previous generations, reflecting the recognition that a 21st century dominated by coal use is no longer considered plausible. Conversely, the lowest emissions scenarios have been adjusted upward, with even optimistic pathways now including some unavoidable overshoot of the Paris Agreement’s target to limit warming to 1.5C.
The new scenarios were formally published in April 2026, with underlying emissions data released into the public domain in September. Seven distinct scenarios have been developed to drive model simulations, with initial climate model runs completed in spring 2026 and results expected later this year. The scenarios are based on updated socioeconomic storylines that incorporate new population and economic projections from 2024, with most scenarios using the “middle-of-the-road” assumptions from the original framework.
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