The RCP8.5 (and its close equivalent SSP5-8.5) has effectively been retired from the core framework for the next round of major climate modeling (CMIP7, feeding into IPCC AR7).

This is a meaningful course correction after years of criticism. Roger Pielke Jr. called it “the most significant development in climate research in decades” in his recent Substack post.

Representative Concentration Pathways (RCPs) were developed for CMIP5 (used heavily in IPCC AR5). RCP8.5 assumed a radiative forcing of +8.5 W/m² by 2100 relative to pre-industrial— the highest of the standard set. It implied very high greenhouse gas concentrations, often described (misleadingly) as “business-as-usual” or a no-new-policies baseline.

In practice, it became the most-cited scenario in thousands of impact studies (floods, wildfires, agriculture, health, sea level, etc.) because it produced the strongest “signal” for detecting climate effects amid natural variability—useful for model diagnostics but problematic when treated as the default future.

A new paper by Van Vuuren et al. (2026) for the ScenarioMIP framework (guiding CMIP7) introduces seven updated scenarios and drops RCP8.5/SSP5-8.5 and SSP3-7.0 as core cases.

Reasons cited:

• Falling costs of renewables (solar/wind).
• Expansion of climate policies.
• Actual emission trends and energy outlooks (e.g., IEA current/stated policies scenarios) that diverge sharply from the extreme high-coal pathway.
• The high-end scenarios are now deemed implausible on socioeconomic and technological grounds.

Critics like Pielke, Justin Ritchie, and others had documented for years that RCP8.5 diverged from reality even in the near term: observed/post-2005 emissions, coal trends, and energy projections tracked much lower. It required assumptions (e.g., coal super-abundance ignoring reserves and economics) that were already strained by the 2010s. IPCC AR6 itself noted high-emissions scenarios had “low likelihood” and weren’t typical “no policy” baselines, though legacy use persisted.

For over a decade, RCP8.5 was over-weighted in research, media, and policy communication—often without clear probability labels or caveats that it was an extreme/high-risk pathway, not the expected one. This inflated perceptions of imminent catastrophe and justified aggressive mitigation timelines that downplayed trade-offs (energy reliability, costs, development in poor countries). Self-correction in science is good: dropping implausible baselines improves credibility.

CMIP7 (Coupled Model Intercomparison Project Phase 7) is the next major iteration of the international effort to coordinate Earth System Model (ESM) simulations for understanding past, present, and future climate. Its ScenarioMIP component defines the core future emissions/concentration/land-use pathways that drive these models. The key paper is Van Vuuren et al. (2026) in Geoscientific Model Development, which formalizes a new set of seven scenarios for CMIP7 (feeding into IPCC AR7 and broader research).

Roger Pielke Jr. is a political scientist and policy scholar (University of Colorado Boulder emeritus, now AEI senior fellow) specializing in the intersection of science, policy, disasters, and climate. He accepts the core physics—humans influence the climate via greenhouse gases, and the planet has warmed—but has long criticized how climate science is communicated, how scenarios are used (or misused), the politicization of research, and the overemphasis on aggressive mitigation at the expense of adaptation and innovation.

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RCP8.5 is Officially Dead

The most significant development in climate research in decades

From The Honest Broker

By Roger Pielke Jr.

“[T]he high-emissions RCP8.5 scenario has long been described as a “business-as-usual” pathway with a continued emphasis on energy from fossil fuels with no climate policies in place. This remains 100% accurate . . .“ — from 2021, Chris Field (co-chair of IPCC WG2 AR5) and Marcia McNutt (president of U.S. National Academy of Sciences, Engineering, and Medicine )

The international committee responsible for the official scenarios that feed into climate modeling that are the basis for most projective climate research and the assessments of the Intergovernmental Panel on Climate Change (IPCC) has just published the next generation of climate scenarios.

Big news: The new framework has eliminated the most extreme scenarios that have dominated climate research over much of the past several decades — specifically, RCP8.5, SSP5-8.5, and SSP3-7.0. This is an absolutely huge development in climate science which will have lasting impacts across research and policy.

The future is not what it used to be.

Today’s post commends the researchers who have brought climate scenarios more in line with current understandings, but also raises some significant continuing issues with the scenarios.

Let’s get started . . .

The new scenarios come from the Coupled Model Intercomparison Project (CMIP) — a project of the World Climate Research Programme (WCRP), co-sponsored by the World Meteorological Organization, the International Science Council, and UNESCO’s Intergovernmental Oceanographic Commission.

Under CMIP, now in its seventh iteration, sits another little-known committee with responsibility for developing the scenarios necessary for earth system models to project future climate.1 That committee — called ScenarioMIP — just published the new scenario framework that will underpin the IPCC’s Seventh Assessment Report (AR7) and much of the research that it will draw upon.

In a paper released earlier this month, Van Vuuren et al. (VVetal26) introduce a new set of seven scenarios. The authors write of the obsolete high end emissions scenarios (emphasis added):

“For the 21st century, this range will be smaller than assessed before: on the high-end of the range, the CMIP6 high emission levels (quantified by SSP5-8.5) have become implausible, based on trends in the costs of renewables, the emergence of climate policy and recent emission trends.”

Read that again — The high end scenarios are Implausible.2

I disagree that the implausibility of the high-end scenarios resulted from the falling costs of renewables or the emergence of climate policy, but that is a debate for another day.

What matters today is that the group with official responsibility for developing climate scenarios for the IPCC and broader research community has now admitted that the scenarios that have dominated climate research, assessment, and policy during the past two cycles of the IPCC assessment process are implausible: They describe impossible futures.

Tens of thousands of research papers have been — and continue to be — published using these scenarios, a similar number of media headlines have amplified their findings, and governments and international organization have built these implausible scenarios into policy and regulation.

We now know that all of this is built on a foundation of sand.

What changed

The new CMIP7 ScenarioMIP framework offers seven scenarios spanning a range from “VERY LOW” through “HIGH.” The current naming convention drops the radiative-forcing target labels of the SSP era — there is no “8.5” scenario, and no “7.0” scenario, but as I’ll show below, each scenario has a radiative forcing level in 2100.

I ran the available new scenarios (HIGH, MEDIUM, LOW, and VERY LOW) through the FaIR calibrated and constrained ensemble that Sanderson and Smith (2025) used to characterize the CMIP7 set (FaIR v. 2.2.0 as described in their README file). I then ran each of the five tier-1 SSPs through the same emulator with identical parameters to ensure that the results are apples-to-apples. The full methodology, data, and code is in the appendix to this post.

The headline results follow.

CO₂ emissions: fossil fuels and industry, 2000–2100

The chart above shows fossil-fuel and industry CO₂ emissions for four CMIP7 scenarios alongside the five tier-1 SSPs and the two main reference scenarios from the 2025 IEA World Energy Outlook.

Note the massive gap between the new HIGH and SSP5-8.5. The new HIGH reaches 71 Gt CO₂/yr in 2100 — far below SSP5-8.5 at 128 Gt in 2100. Nothing in the CMIP7 set comes close to SSP5-8.5. The new HIGH also sits below SSP3-7.0 by about 9% in terms of cumulative emissions to 2100. Note also the gap between MEDIUM (solid yellow) and SSP2-4.5 (dashed yellow), which I’ll return to below.

Both of the most recent IEA near term scenarios — which run to 2050 — fall below MEDIUM and SSP2-4.5.

The table below compares the CMIP7 scenarios to their closest AR6 analogues, showing that the overall range has constricted. The higher scenarios have come down and the lower scenarios have come up — except VERY LOW, which moved down.

2100 effective radiative forcing and end-of-century temperature

The table below lists AR6 and CMIP7 scenarios from highest to lowest 2100 radiative forcing. The middle column shows the average global temperature change from an 1850-1900 baseline, under the climate emulator used by CMIP7. The right column shows the average temperature change for the SSPs as projected by the IPCC AR6.

Read the full story here.