The formal retirement of the long-standing RCP8.5 and SSP5-8.5 emissions scenarios represents a pivotal moment in climate science. As international researchers transition to the more plausible CMIP7 framework, a parallel battle has erupted over the public representation of these updates by major media outlets.
The scientific architecture of global climate modeling is undergoing a major evolution. For over a decade, researchers relied on a high-emissions baseline known as Representative Concentration Pathway 8.5 (RCP8.5) and its successor, Shared Socioeconomic Pathway 5-8.5 (SSP5-8.5), to evaluate extreme climate risks. In April 2026, a milestone framework published in Geoscientific Model Development (Volume 19, Issue 7, pp. 2627–2656) by Detlef van Vuuren and co-authors introduced the seven new emissions pathways for the seventh phase of the Coupled Model Intercomparison Project (CMIP7).
This framework officially retired the old worst-case scenarios, concluding that their extreme assumptions had been rendered implausible by real-world changes. However, as science updates its baseline models, the public communication of these modifications has become a battleground, highlighting the divide between technical accuracy and media reporting.
In his June 10, 2026 "Temperature Check" column for The Guardian, climate correspondent Graham Readfearn critiqued the way News Corp publications represented this change. Commentators had characterized the retirement of the worst-case scenario as a dramatic reduction in projected warming, claiming it proved climate change threat levels were overblown. In reality, the retirement of a highly improbable extreme scenario does not alter the warming projected under current policy paths. The transition to CMIP7 is a refinement to ensure modeling resources are focused on plausible futures, yet the political debate surrounding it demonstrates how easily technical scientific shifts can be misinterpreted in the public sphere.
Climate researchers are updating modeling frameworks to align with global energy policy shifts, replacing outdated extreme projections with plausible pathways.
- CMIP7 Launch: In April 2026, Detlef van Vuuren and colleagues published the new ScenarioMIP-CMIP7 framework, establishing seven emissions pathways for future modeling.
- Scenario Retirement: The extreme high-emissions scenario RCP8.5 (and SSP5-8.5) has been retired from core CMIP7 modeling because its coal-expansion assumptions are now implausible.
- Renewable Impact: Rapid deflation in green technology, including a 90% decline in solar PV costs between 2010 and 2023, helped render the worst-case emissions path obsolete.
- Media Dispute: The Guardian's June 10, 2026 column criticized News Corp's Chris Mitchell for claiming the retirement represented a massive cut to expected global warming.
- Plausible Risks: Retiring the extreme outlier does not reduce expected warming. Current policies still align with the Medium scenario, tracking toward 2.5 degrees to 2.7 degrees Celsius of warming by 2100.
Inside the ScenarioMIP-CMIP7 Framework: The Seven New Pathways
The Coupled Model Intercomparison Project (CMIP) is the global standard for climate modeling, serving as the foundation for the Intergovernmental Panel on Climate Change (IPCC) assessment reports. Under the guidance of the World Climate Research Programme (WCRP) and ScenarioMIP, the framework has transitioned from CMIP6 to CMIP7. This transition represents a shift in how future scenarios are conceptualized. While previous phases utilized a broad matrix of Shared Socioeconomic Pathways (SSPs) paired with forcing levels, CMIP7 streamlines this into seven core emissions pathways designed to capture a range of plausible futures. By focusing resources on these targeted trajectories, researchers can evaluate climate feedbacks with higher precision.
The seven new pathways introduced by Van Vuuren and colleagues are structured to reflect different policy and technological trajectories. These pathways are categorized as High (H), High-to-Low (HL), Medium (M), Medium-to-Low (ML), Low (L), Low-to-Negative (LN), and Very Low (VL). The High (H) scenario represents a plausible upper bound of emissions in a world where global climate policies fail to advance, while the Very Low (VL) scenario models an aggressive decarbonization pathway designed to meet international climate goals. This structure provides modeling groups with a more realistic spectrum of choices than the older CMIP6 set, which contained extreme high-emissions scenarios that diverged from real-world trends.
The redesign also introduces technical improvements, notably a shift toward emissions-driven simulations. Under previous frameworks, climate models were primarily concentration-driven, meaning atmospheric levels of greenhouse gases were prescribed as fixed inputs. In CMIP7, the majority of the seven pathways are designed to be run in emissions-driven mode, allowing the Earth system models to simulate the carbon cycle dynamically. This capability is critical for understanding feedbacks, such as how natural carbon sinks like oceans and forests react to rising emissions. By integrating these feedbacks, CMIP7 aims to provide a more accurate representation of global climate dynamics over the coming century.
The seven new pathways developed for ScenarioMIP-CMIP7 consist of the following categories:
- High (H): A high-end emissions scenario representing slow technology transition and policy failure, projecting approximately 3.5 degrees Celsius of warming by 2100.
- High-to-Low (HL): A scenario exploring a delayed transition, where emissions remain elevated before experiencing a rapid decline mid-century.
- Medium (M): The baseline pathway anchored to current global policy commitments, tracking toward 2.5 degrees to 2.7 degrees Celsius of warming.
- Medium-to-Low (ML): A transitional scenario modeling gradual policy strengthening and acceleration of low-carbon investments.
- Low (L) & Low-to-Negative (LN): Pathways modeling rapid decarbonization, with LN exploring net-negative emissions through carbon removal technologies.
- Very Low (VL): An aggressive, immediate mitigation scenario designed to limit warming to near 1.5 degrees Celsius, though requiring a temporary overshoot.
The Retirement of RCP8.5: Why the Extreme Worst-Case Became Implausible
The retirement of RCP8.5 and its successor SSP5-8.5 is a response to real-world technological and policy progress. Designed over a decade ago, RCP8.5 was intended to represent an extreme, high-emissions pathway characterized by a massive expansion of coal consumption—projecting coal use to increase by up to five times current levels by 2100. It also assumed a complete absence of climate policies and slow technological progress. At the time of its creation, it served as a useful "what-if" scenario for scientists looking to explore high-forcing climate responses. However, as the scenario was adopted in literature, it was frequently misinterpreted as a "business-as-usual" projection, leading to policy assessments based on an unlikely future.
Over the past 15 years, the global energy landscape has changed. The rapid cost deflation of renewable energy has altered the economics of power generation. According to data from the International Renewable Energy Agency (IRENA), the global weighted-average levelized cost of electricity (LCOE) for utility-scale solar photovoltaics (PV) fell by approximately 90% between 2010 and 2023. Onshore wind costs declined by 70%, and offshore wind costs fell by 63% over the same period. In 2023, approximately 81% of new utility-scale renewable capacity was cheaper than the cheapest fossil-fuel alternative, saving the global electricity sector an estimated USD 409 billion in fuel costs. These economic shifts have made a massive return to coal power implausible, rendering the assumptions of RCP8.5 obsolete.
The primary global indicators that led scientists to deem the RCP8.5 emissions pathway implausible include:
- Solar PV Cost Deflation: A 90% decline in levelized generation costs between 2010 and 2023.
- Onshore Wind Cost Reductions: A 70% reduction in electricity generation costs globally.
- Implemented Climate Policies: Introduction of national carbon pricing systems and renewable energy targets.
- Stabilization of Coal Use: Global coal consumption plateauing rather than expanding by 5x as previously assumed.
Furthermore, international policy agreements have established emission constraints that block the extreme pathway. While current national policies are not yet sufficient to limit warming to 1.5 degrees Celsius, they have successfully ruled out the unconstrained emissions growth modeled in RCP8.5. Global coal consumption is currently plateauing rather than growing exponentially, and major economies have implemented carbon pricing, renewable targets, and efficiency mandates. In their April 2026 paper, Detlef van Vuuren and his co-authors acknowledged these shifts, writing:
“Our goal with CMIP7 is to align our model projections with the actual trajectory of global energy policies and renewable deployment. Retiring SSP5-8.5 allows us to allocate modeling resources to the most plausible futures, which still pose severe risks.”
— Detlef van Vuuren, Lead Author and Senior Researcher at PBL, April 2026
The decision to retire RCP8.5 is a recognition that the baseline of global emissions has shifted. While this is positive news for long-term climate projections, scientists emphasize that it does not mean the climate crisis is resolved. The retirement of an extreme scenario simply shifts the focus to the remaining pathways, where significant warming and severe impacts remain possible under current policy trends.
Deconstructing the Media War: The News Corp Mischaracterization
The retirement of RCP8.5 has triggered a debate in the media, exposing the gap between scientific consensus and public reporting. Following the announcement of the CMIP7 scenario updates, several News Corp publications, including Australia's Sky News and The Australian, published commentary on the change. A prominent example was authored by Chris Mitchell, who served as the editor-in-chief of The Australian from 2002 to 2015. Mitchell characterized the retirement of RCP8.5 as an admission that climate science had been exaggerated, claiming the update "dramatically cuts the forecast warming of the planet by the end of this century."
In his June 10, 2026 "Temperature Check" column, The Guardian's Graham Readfearn challenged this interpretation, describing it as a gross mischaracterisation of the science. Readfearn pointed out that retiring a high-end scenario does not change the warming projected under the most likely pathways. The previous worst-case scenario was an extreme outlier, not a forecast. By removing this outlier, the scientific community is focusing its modeling efforts on the pathways that align with current policy trends. Expected warming has not been reduced; rather, the scientific community has updated its models to exclude a pathway that was already considered highly unlikely by experts. Readfearn noted:
“When is rare good news on climate science actually bad? When News Corp misrepresents it... The retirement of a highly implausible extreme scenario does not mean that the warming we actually expect is lower. It means we are focusing our scientific efforts on the pathways that represent our current reality.”
— Graham Readfearn, Climate Correspondent, The Guardian, June 2026
The media dispute highlights a persistent challenge in communicating climate risk. Technical updates to scientific models are often framed as political concessions. When scientists retire an extreme scenario to improve model accuracy, commentators can misinterpret the adjustment as evidence that climate change is less of a threat. This framing downplays the risks associated with the medium and low-emissions pathways, which still project significant warming and severe ecological consequences.
CMIP6 vs. CMIP7: A Comparative Analysis of Scenario Pathways
To understand the significance of the CMIP7 update, it is useful to compare it with the previous CMIP6 framework. The older CMIP6 set utilized five primary Shared Socioeconomic Pathways (SSPs) representing different global development paths, ranging from sustainable development (SSP1) to fossil-fueled development (SSP5). In contrast, the CMIP7 set streamlines this structure into seven pathways that reflect modern policy trends and energy economics. The table below compares these two generations of scenarios, showing how the high-end, medium, and low pathways have evolved:
| Scenario Cohort / Phase | Projected Warming by 2100 | Primary Energy Source Assumptions | Policy & Real-World Feasibility |
|---|---|---|---|
| CMIP6 SSP5-8.5 (Retired Worst-Case) | 4.4°C – 5.0°C ≈ Parity | 5x Coal Expansion / Zero Green Tech ▼ Behind | Deemed Highly Implausible ▼ Behind |
| CMIP7 High (H - New High End) | ~3.5°C ▲ Leading | High Emissions / Slow Policy Progress ≈ Parity | Plausible as High-End Risk ▲ Leading |
| CMIP7 Medium (M - Current Policy) | 2.5°C – 2.7°C ▲ Leading | Gradual Transition / Stable Policies ▲ Leading | Most Likely Baseline Path ▲ Leading |
| CMIP7 Low (L - Paris Aligned) | 1.8°C – 2.0°C ▲ Leading | Rapid Transition / Net-Zero Targets ▲ Leading | Requires Accelerated Action ≈ Parity |
The comparison shows how the high-end scenario has changed. While SSP5-8.5 projected warming of up to 5.0 degrees Celsius, the new CMIP7 High (H) scenario projects around 3.5 degrees Celsius. This reduction reflects the impact of renewable energy deployment and global climate policies. However, the Medium (M) scenario—which aligns with current policy trajectories—remains largely consistent across both generations, projecting 2.5 degrees to 2.7 degrees Celsius of warming. This consistency shows that while the extreme worst-case has been retired, expected warming under current policy trends has not changed.
The CMIP7 Low (L) scenario aligns with the Paris Agreement targets, projecting warming of 1.8 degrees to 2.0 degrees Celsius. This pathway assumes that countries meet their net-zero targets, requiring an acceleration of decarbonization efforts. By structuring CMIP7 around these updated pathways, researchers can provide policymakers with a more realistic framework for evaluating the costs and benefits of different climate actions, avoiding the distractions of highly implausible scenarios.
Technical Advancements in CMIP7: Emissions-Driven Models and the 2500 AD Horizon
CMIP7 introduces several technical updates designed to improve the accuracy and policy relevance of climate projections. The primary advancement is the transition to emissions-driven simulations as the default mode for most of the seven pathways. Under previous CMIP generations, models were concentration-driven, meaning atmospheric greenhouse gas concentrations were prescribed as fixed inputs. While this approach simplified computations, it did not account for how natural carbon sinks—such as oceans and terrestrial vegetation—respond to climate change. In emissions-driven mode, models simulate these carbon cycle dynamics directly, calculating atmospheric concentrations based on emissions inputs and carbon sink feedback loops.
This capability is critical for understanding the risk of carbon feedback loops, where warming causes natural systems to release greenhouse gases, accelerating climate change. For example, warming can cause soils to release carbon or reduce the capacity of oceans to absorb carbon dioxide. By simulating these dynamics, CMIP7 models can provide a more accurate representation of how the Earth system responds to different emissions pathways, helping researchers identify potential tipping points. The primary technical enhancements integrated into the CMIP7 modeling suite include:
- Emissions-Driven Mode: Allowing models to calculate carbon cycle feedbacks dynamically rather than using fixed atmospheric concentrations.
- Long-Term Extensions to 2500 AD: Extending projections for select pathways to study slow-acting climate feedbacks, such as ice sheet melting and deep ocean warming.
- Systematic Uncertainty Quantification: Implementing standardized metrics to evaluate and compare uncertainty across different model simulations.
Another update in CMIP7 is the inclusion of long-term extensions reaching up to the year 2500 AD for select pathways. While most policy discussions focus on the year 2100, many climate impacts—such as sea-level rise and ice sheet melting—occur over longer timescales. By extending projections to 2500, CMIP7 allows researchers to study these long-term feedbacks and evaluate the irreversibility of climate changes. This long-term perspective is critical for understanding the full impact of current emissions on future generations and developing long-term adaptation strategies.
The Overshoot Reality: The new CMIP7 Very Low (VL) scenario indicates that limiting global warming to 1.5 degrees Celsius is no longer achievable without a temporary overshoot. This means that even under aggressive decarbonization pathways, global temperatures are projected to exceed the 1.5 degrees Celsius threshold before declining later in the century, highlighting the need to develop carbon dioxide removal (CDR) technologies.
Conclusion: Bridging the Gap Between Science and Public Communication
The transition from CMIP6 to CMIP7 represents a scientific refinement of global climate modeling. By retiring the implausible RCP8.5/SSP5-8.5 scenario and focusing on a streamlined set of seven pathways, the climate science community is improving model accuracy and alignment with real-world trends. This update is a positive step that allows researchers to focus resources on the most likely futures. However, the media coverage surrounding this change reveals a persistent challenge in public communication. The framing of this technical adjustment as a reduction in expected warming shows how easily technical scientific updates can be misinterpreted in public debate.
As global temperatures continue to rise, clear communication of climate risk is essential. The retirement of the worst-case scenario does not change the warming projected under current policy trajectories, which remains a severe threat. The lessons of June 2026 suggest that future climate policy will depend on how effectively we communicate scientific complexity to the public, ensuring that technical updates are understood as refinements rather than political concessions. Bridging this communication gap is critical for maintaining public support for climate action and building a resilient global infrastructure.
Sources and References
- Geoscientific Model Development - The Scenario Model Intercomparison Project for CMIP7: gmd.copernicus.org
- The Guardian - When is rare good news on climate science actually bad? When News Corp misrepresents it: theguardian.com
- International Renewable Energy Agency (IRENA) - Renewable Power Generation Costs in 2023: irena.org
- World Climate Research Programme (WCRP) - CMIP7 Experimental Design and ScenarioMIP Guidelines: wcrp-climate.org
- Intergovernmental Panel on Climate Change (IPCC) - Scenario Integration and Seventh Assessment Planning: ipcc.ch
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