HAYS, KANSAS — In April 2026, leading scientists for the United Nations Intergovernmental Panel on Climate Change (IPCC) announced that the RCP 8.5 climate scenario is no longer a reasonable prediction due to the growth of renewable energy and climate policies. RCP 8.5 was one of four Representative Concentration Pathways used to model greenhouse gas emissions and their effect on global warming.
RCP 8.5, published in 2011, assumed humans would continue burning fossil fuels with abandon through the 21st century, leading to nearly 5 degrees Celsius of warming above preindustrial levels. It projected a fivefold increase in coal use by 2100. Under RCP 8.5, Florida’s coastline would be submerged, sub-Saharan Africa would produce more than 85 million climate migrants by 2050, and half of the world’s plant and animal species would go extinct.
Climate scientist Zeke Hausfather stated, "After [RCP 8.5] was created, through a game of telephone, people started calling it the ‘business as usual’ scenario." He added, "It’s useful to have worst-case scenarios. The problem for a while is that people were conflating the worst case with the most likely outcome."
Former Department of Energy Under Secretary for Science Steven Koonin described RCP 8.5 as a stress test akin to "an engineer simulating 250 army tanks on a bridge." He said some activists, journalists, and scientists used RCP 8.5 to scare the public into reducing emissions and that some "destroyed the reputations of scientists who dared to say, ‘Wait a minute.’"
Chris Field, a climate scientist at Stanford University, refuted claims that the scientific community deliberately misled the public by promoting RCP 8.5. "We wanted to understand a wide range. It’s important to recognize that no one in the climate community, certainly not the climate modelers or economists, know what the future trajectory of emissions will be," he said.
Under current emission trends, the planet is projected to follow RCP 4.5, a middle scenario expected to result in up to 3 degrees Celsius of warming. Hausfather stated, "[RCP 4.5] is still a very bad outcome." The RCP 4.5 scenario assumes continued reductions in coal use and a flattening then decline in fossil fuel consumption. At 2 degrees of warming, studies suggest coral reefs could collapse and as many as 1 in 4 plant and animal species in the Amazon and Galápagos could face local extinction.
Climate scientists say the retirement of RCP 8.5 is not a reason to reduce clean-energy efforts. Some coal proponents, including former President Donald Trump, celebrated the shift as evidence that climate concerns are overblown.