The worst-case climate scenario is no longer on the table—and that's not because scientists gave up, but because human action is working. Last week, when the Intergovernmental Panel on Climate Change released seven new climate scenarios to guide the next round of global warming projections, something momentous happened: the high-emissions scenario known as RCP8.5 and its successor SSP5-8.5 were removed from the range of plausible futures. These scenarios, which envisioned nations making no effort to cut emissions and actively expanding fossil fuel use, predicted carbon dioxide levels would nearly triple to 1,135 parts per million by 2100, warming the planet by 4.5°C above pre-industrial levels. That nightmare is no longer considered a realistic path forward.
The decision signals something profound: the expansion of renewable energy, electric vehicles, and battery technology has measurably slowed the growth of global emissions. This doesn't mean the crisis is solved. Emissions remain at record highs and warming is accelerating. But it does mean that our collective effort to transition away from fossil fuels has made a tangible difference in what the future will actually look like.
Climate scenarios are the scientific community's way of acknowledging that our future isn't fixed. Scientists don't predict which outcome will occur; instead, they map out a range of plausible pathways based on what's happened so far and what might happen in politics and technology over coming decades. They model these scenarios using different climate models to ensure comprehensive data at global, regional, and local scales. Because the future depends on human choices, all scenarios in the range are treated as equally plausible—which is precisely why their removal of the worst case carries such weight.
The new scenarios still paint a sobering picture. The worst-case pathway now envisions warming of around 3.5°C by 2100, which would still be "very, very bad." And the most optimistic scenario is less hopeful than we might have hoped: it foresees warming peaking at about 1.9°C, compared to the 1.5°C target that seemed possible in earlier projections. We have, in other words, closed off the best possible future even as we've averted the worst one.
The removal of RCP8.5 didn't go unnoticed by climate skeptics, who seized on the decision as evidence that climate models are unreliable or that climate change itself was overstated. These claims misread the science entirely. The scenario was removed not because scientists were wrong, but because the world has begun—however unevenly—to act. Solar panels, wind turbines, electric vehicles, and battery storage have changed the trajectory we're on.
Our current path sits somewhere in the middle of the new range: below the high-emissions scenario, but well above what we'd need to achieve the most optimistic outcome. We've definitely now passed the point where we can limit warming to 1.5°C permanently. But there's still a narrow window to temporarily overshoot that threshold while working to draw carbon dioxide back out of the atmosphere and return to it.
This is neither cause for complacency nor for despair. The removal of the worst-case scenario proves that action—real, tangible, technology-driven action—changes what's possible. The job is far from done. But for the first time in decades of climate science, the evidence suggests we're beginning to win.