Factcheck: Trump’s false claims about the IPCC and ‘RCP8.5’ climate scenario – Image for illustrative purposes only (Image credits: Unsplash)
US President Donald Trump recently took to social media to dismiss a long-used emissions pathway known as RCP8.5, calling it “wrong, wrong, wrong” and claiming the United Nations’ top climate body had quietly abandoned it. The statement, posted on his Truth Social platform in mid-May, quickly spread through outlets aligned with his views. Yet the remarks rest on several inaccuracies about how climate scenarios are created and who controls them. The timing coincides with the release of fresh projections that adjust the range of plausible futures without eliminating the risks of substantial warming.
What Trump Claimed and How It Spread
Trump described RCP8.5 as a scenario the Intergovernmental Panel on Climate Change had now rejected. He paired the dismissal with his usual nickname for Democrats and suggested the change represented a major reversal. The post appeared on the evening of 16 May and was soon echoed by several conservative publications.
Some reports repeated the idea that the IPCC itself had developed or retired the pathway. Others added further details that went beyond the original statement, such as claims of a sudden swap to seven new alternatives. Coverage also referenced an earlier executive order from May 2025 that listed RCP8.5 among examples of misleading scientific inputs used by federal agencies. Project 2025, a policy document from 2023, had already urged the removal of such scenarios from regulatory work.
The Purpose and History of RCP8.5
Emissions scenarios serve as tools for exploring possible futures rather than forecasts of what will occur. RCP8.5 was one of four representative concentration pathways published in 2011 to cover a wide range of outcomes drawn from existing research. Its label refers to the level of radiative forcing, measured in watts per square metre, that would result by 2100 under very high emissions and no new climate policies.
At the time of its creation, the pathway sat near the upper end of baseline scenarios in the literature. It assumed continued rapid growth in coal use and population without mitigation efforts. Later work replaced the RCPs with shared socioeconomic pathways, or SSPs, which added narratives about economic and technological development. The highest of these, SSP5-8.5, produced similar temperature outcomes to the original RCP8.5.
Why the Pathway Remains Controversial
Scientists have long noted that RCP8.5 was always intended as a low-probability, high-risk case for studying extreme outcomes. Some studies nevertheless treated it as a business-as-usual trajectory, which drew criticism for overstating its likelihood. Actual emissions since the early 2010s have tracked closer to a medium pathway, RCP4.5, as renewable costs fell and some policy measures took hold.
Critics highlighted the scenario’s assumption of a five-fold rise in global coal consumption by 2100, an expansion viewed as unrealistic given current trends. Others pointed out that even high-emissions cases can still illuminate risks from climate feedbacks that might amplify warming beyond initial estimates. The pathway therefore retained value for risk assessment even as its central plausibility declined.
New Scenarios and the IPCC’s Limited Role
Researchers working through the Scenario Model Intercomparison Project have now produced seven updated pathways for the next round of climate modelling. These replace the earlier set and reflect both technological progress and the fact that very high or very low emissions futures have become less consistent with recent data. The highest new pathway points to roughly 3.2 °C of warming by 2100, with a range of 2.5 °C to 4.3 °C.
The process is coordinated by the Coupled Model Intercomparison Project under the World Climate Research Programme, not by the IPCC. Modelling centres run common experiments using the same inputs so results can be compared directly. The IPCC later synthesises the published literature that emerges from these runs, but it does not design or retire the scenarios themselves. One author of the new paper noted that the narrowed range rules out both the previous high end and the possibility of limiting warming to 1.5 °C without significant overshoot in the coming decades.
The world is now on a trajectory to 2.5-3C of warming. As a result, we don’t have any scenario anymore that can reach 1.5C with limited overshoot.
These adjustments carry both encouraging and sobering implications. Progress on renewables and policy has made the most extreme pathway less relevant, yet the remaining high scenario still carries severe impacts. The latest work therefore underscores the need for continued action even as the outer bounds of possible futures have tightened.
