RCP 8.5, the worst-case climate change scenario predicting a 4.5 degree Celsius increase by 2100, has officially been retired by climate scientists.
In a new paper published in April, over 40 scientists affiliated with the United Nations Intergovernmental Panel on Climate Change (UNIPCC) called for the retirement of RCP8.5, calling it “implausible” due to the lower costs of renewables, climate policy, and declining emissions trends.
President Trump celebrated the development, writing on social media: “GOOD RIDDANCE … the United Nations TOP Climate Committee just admitted that its own projections (RCP8.5) were WRONG! WRONG! WRONG!”
First devised in 2011, RCP 8.5 is one of four hypothetical representative concentration pathways (RCPs) for near- and long-term climate modeling. Here’s how the EPA explains the four RCPs:
RCP 2.6 – This scenario is characterized as having very low greenhouse gas concentration levels. It is a “peak-and-decline” scenario and assumes that GHGs are reduced substantially over time. This is the most benign climate scenario of the four.
RCP 4.5 – This scenario assumes a stabilization will occur shortly after 2100, and assumes less emissions than RCP 6.0, which is also a stabilization scenario.
RCP 6.0 – This is a stabilization scenario in which the increase in GHG emissions stabilizes shortly after 2100 through the application of a range of technologies and strategies for reducing GHG emissions.
RCP 8.5 – This scenario is characterized by increasing GHG emissions over time, and factors in the highest GHG concentration levels of all the scenarios by 2100.
Roger Pielke Jr., writing in the Washington Post, said climate scenarios like the soon-to-be-retired RCP8.5 are “faulty inputs”—arguing that the new high-end scenario should be a “thought experiment” and “not a forecast.”
This repudiation of climate alarmism is consistent with the declining support for net-zero emissions goals here and abroad. Northeastern governors are watering down climate goals and expressing support for natural gas pipelines, citing energy affordability concerns.
Americans might support climate policies, but it’s not a top issue going into the 2026 midterm elections. Moreover, Americans are unwilling to pay an additional $1/month for climate policies, with only 38% expressing support. Last year, Pew Research Center found that 54% of Americans believe some environmental deregulation won’t come at the expense of maintaining clean air and water quality in the U.S.
For decades, Americans were told that the world is ending due to catastrophic climate change. Yet none of those predictions have panned out. Having peaked in 2005, carbon emissions are at historic lows in the U.S—declining 17.4% between 2005 and 2023 due to the shale revolution. More new species are annually discovered. And the Earth, overall, is more green today, even as more energy is produced and resources are consumed.
Scientists must be held accountable for pushing faulty climate modeling practices. Retiring RCP 8.5 is a good first step.