Claim: "The IPCC says extreme climate scenarios are no longer plausible, by retiring the RCP8.5 scenario"
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No. The IPCC doesn’t create or retire scenarios, as it has said itself. RCP8.5 was never a forecast: it was a deliberately extreme, no-climate-policy scenario from 2011. Scientists have now dropped it because cheaper renewables and climate policy have made that future implausible, which is real progress.
But under current policies the world is still heading for around 2.8°C (UN, October 2026), with a real chance of going well beyond 3°C. The UN has called warming at this level catastrophic. It would bring far worse heat, flooding and crop failures than we already see today. More from Carbon Brief.
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Who makes the scenarios? Not the IPCC. Climate scenarios are designed by the international research community through the Coupled Model Intercomparison Project (CMIP), part of the UN’s World Climate Research Programme. The IPCC assesses these alongside many other scenarios but does not develop them or decide when they are retired.
What was RCP8.5? It was the highest of four “Representative Concentration Pathways” published in 2011. It assumed no climate policy and a huge expansion of coal, and was designed to explore high-end risks, not to predict the future. The numbers (2.6, 4.5, 6.0, 8.5) describe the extra energy trapped by greenhouse gases, not degrees of warming. The RCPs were themselves replaced in 2017 by the “Shared Socioeconomic Pathways” used in the IPCC’s last major assessment.
What has changed? In April 2026, scientists published seven new scenarios for the next round of climate modelling. They conclude that the very highest emissions pathways are now implausible because of falling renewable costs, climate policy and recent emissions trends. But the same work also concludes that the most optimistic pathways have gone: limiting warming to 1.5°C without a significant overshoot is no longer possible. Even the new “high” scenario reaches around 3.3°C by 2100, with a range of 2.5–4.4°C (Carbon Brief).
Where are we heading? UNEP’s Emissions Gap Report 2026 (21 October 2026) finds a 66 per cent chance of keeping warming below 2.8°C by 2100 under current policies, with temperatures still rising after that. It also finds a 1 in 10 chance of exceeding 3.4°C this century, with the range reaching 4.5°C. The current-policies trajectory has bent from around 4°C before the Paris Agreement to 2.8°C today. That is real progress, but 2.8°C is not a ceiling, and the UN has described warming at this level as catastrophic.
