SSP5- 8.5 is still referenced in older studies and some risk assessments, but it is no longer treated as a plausible “business- as- usual” pathway and is being phased out of the core scenario set for the next IPCC assessment cycle.
Current status (as of 2026)
- In the IPCC AR6 (2021- 2023) and CMIP6 modeling, SSP5- 8.5 was the highest-emissions scenario (very high fossil-fuel development, ~8.5 W/m² radiative forcing by 2100). It produced the upper end of the temperature ranges often quoted (including the ~10- 12 °C Arctic warming figures).
- By 2026, the ScenarioMIP group (responsible for scenarios used in CMIP and IPCC reports) has formally judged the high- end emissions levels of SSP5- 8.5 (and its predecessor RCP8.5) implausible. Reasons cited include:
- Rapid declines in renewable energy costs
- Emergence of climate policies
- Observed emission trends that are lower than the extreme pathways assumed in SSP5- 8.5
A key 2026 paper (van Vuuren et al.) and the new CMIP7 scenario framework drop or heavily de-emphasize SSP5- 8.5 and SSP3- 7.0 as central cases. The new “high” scenario is substantially lower in cumulative emissions.
How it is still used
- Many published papers, impact studies, and some national climate assessments still cite results from SSP5- 8.5 because the CMIP6 model archive is the most complete available.
- It continues to serve as a stress- test and low- probability upper- bound case for exploring high- end physical risks (e.g., extreme sea- level rise, ice- sheet response).
- It is not considered a realistic projection of where current policies or even “no new policy” trajectories are heading. Current- policy estimates typically align closer to SSP2- 4.5 (roughly 2.5- 3 °C global warming by 2100).
Bottom line
SSP5- 8.5 remains in the scientific literature and is still occasionally used for sensitivity analysis, but the climate research community and the scenario developers preparing for IPCC AR7 no longer regard it as a credible central or likely high- end pathway. Newer scenario sets have a lower and narrower high-end range.
The current high- end projection (as of the 2026 CMIP7 / ScenarioMIP framework) is substantially lower than the old SSP5- 8.5.
CMIP7 “High” (H) scenario
This is now the highest emissions pathway retained for the next generation of climate modeling (CMIP7) that will feed into IPCC AR7:
- Median global warming in 2100: ~3.3 °C above pre- industrial (1850–1900)
- Likely range (approx. 5- 95%): 2.6- 4.4 °C
- Cumulative CO₂ emissions (2024- 2100): ~3,820 GtCO₂ (roughly half of the old SSP5-8.5)
- Annual CO₂ emissions in 2100: ~55 GtCO₂/yr (versus ~126 Gt in SSP5- 8.5)
It assumes a rollback or failure of current climate policies combined with development trends that still produce high (but no longer extreme) fossil- fuel use. It is explicitly described as an exploratory and high- end case rather than a “business- as- usual” or most- likely pathway.
Context and comparison
| Scenario | Median warming 2100 | Notes |
|---|---|---|
| Old SSP5-8.5 (CMIP6) | ~4.4- 4.8 °C | Now considered implausible |
| CMIP7 High (H) | ~3.3 °C | Current official high-end |
| CMIP7 Medium (current policies) | ~2.9 °C | Closest to today’s trajectory |
| Current policy estimates (independent) | ~2.6- 2.8 °C | Real- world tracking |
Important caveats:
- Climate- system uncertainties (especially climate sensitivity and carbon- cycle feedback) mean warming under the High scenario could still exceed 4 °C by 2100 in the upper part of the range.
- Temperatures continue rising after 2100 under the High pathway.
- Full Earth- system model runs of these new scenarios are still underway; the numbers above are primarily from simple climate model emulators (e.g., FaIR) constrained to AR6 assessments.
In short, the official high- end has been revised downward significantly, but it still implies substantial further warming and associated impacts if emissions remain high.
CMIP7 Scenario Methodology (ScenarioMIP- CMIP7)
The new scenario framework for the Coupled Model Intercomparison Project Phase 7 (CMIP7) is detailed in van Vuuren et al. (2026), published in Geoscientific Model Development (doi: 10.5194/gmd-19-2627- 2026). It was developed by the Scenario Model Intercomparison Project (ScenarioMIP) team through multiple rounds of community consultation.
1. Overall Design Goals
- Provide a limited, policy- relevant set of scenarios that span high- end climate risks, current- policy trajectories, and Paris- aligned low- emissions pathways.
- Improve realism relative to CMIP6 by incorporating recent emission trends, renewable energy cost declines, and existing climate policies.
- Support both physical climate science and impacts, adaptation, mitigation research.
- Enable long- term studies (extensions to 2300- 2500) of irreversibility, sea-level rise commitment, and carbon-cycle dynamics.
2. Key Methodological Innovations
- Emissions- driven (preferred) rather than concentration- driven
Most experiments are intended to be run by prescribing greenhouse- gas emissions directly to Earth System Models (ESMs). This allows interactive carbon- cycle feedback (land and ocean uptake, permafrost, etc.) to evolve, better capturing Earth- system uncertainty. (Concentration- driven runs remain an option for models that cannot run emission- driven.) - Updated socioeconomic foundations
Scenarios are built on revised Shared Socioeconomic Pathways (SSPs) and generated by multiple Integrated Assessment Models (IAMs): AIM, COFFEE, GCAM, IMAGE, MESSAGE-GLOBIOM-GAINS, REMIND-MAgPIE, and WITCH. - Harmonization to recent observations
Pathways are harmonized to observed emissions through ~2023. A common historical emissions dataset is compiled for all relevant species and IAM regions, then sectorally harmonized and spatially gridded for ESM input. - Seven marker scenarios (selected from ~90 candidates)
- Long- term extensions
Stylized extensions beyond 2100 (to 2500) using rule- based methods (e.g., FLEX) to study multi- century responses.
3. Workflow Steps
- Community design process and peer review (multiple iterations, 11 reviewers for the final paper).
- Generation of candidate pathways by IAMs using updated SSPs.
- Selection of 7 marker scenarios spanning the desired emissions/climate range.
- Harmonization of historical + future emissions (all climatically relevant species).
- Production of gridded emissions and land-use data.
- Emulation with simple climate models (e.g., FaIR) for preliminary temperature outcomes.
- Delivery of forcing datasets to ESM groups for full climate projections.
- Use in downstream MIPs (ISIMIP, AerChemMIP, CDRMIP, etc.) and IPCC AR7.
4. Why the High End Was Lowered
The previous high- end (SSP5- 8.5) was judged implausible due to:
- Observed emission trajectories tracking closer to middle- of-the- road pathways.
- Faster- than- expected declines in renewable costs.
- Existing climate policies already in place.
The new High scenario still explores substantial warming (median ~3.3 °C by 2100, range up to ~4.4 °C) but with roughly half the cumulative CO₂ of SSP5-8.5.
Primary Reference
van Vuuren, D. P., O’Neill, B. C., Tebaldi, C., et al. (2026). The Scenario Model Intercomparison Project for CMIP7 (ScenarioMIP- CMIP7). Geosci. Model Dev., 19, 2627–2656.
https://doi.org/10.5194/gmd-19-2627-2026
Official explainer: https://wcrp-cmip.org/explainer-scenarios-for-cmip7/
This framework prioritizes policy relevance, Earth- system realism (via emission- driven runs), and a narrower but still wide range of futures compared with CMIP6.
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