Worst Climate Futures Less Likely, Best Ones Slipping Away

A major update to the world’s climate scenarios has delivered a nuanced verdict on humanity’s warming future: the most catastrophic outcomes are now far less likely, but the best possible future is quietly slipping out of reach. The new findings, published by an international team of scientists, reflect both the success of the renewable energy revolution and the sobering reality that current efforts remain insufficient to meet the world’s most ambitious climate goals.

A Narrowing Window

The new set of seven plausible carbon pollution scenarios, published on April 7 in the journal Geoscientific Model Development, represents the first major update to the climate modeling framework since the scenarios used in the last IPCC assessment cycle. Known as ScenarioMIP-CMIP7, the framework is designed to guide climate research and policy through the coming decades.

At the heart of the update is what scientists describe as a “narrowing of the futures.” The old worst-case scenario, known as RCP8.5, which projected 4.5°C (8.1°F) of warming by 2100, has been abandoned as implausible. The new high-end scenario projects about 3.5°C (6.3°F) of warming — a full degree Celsius less than its predecessor.

“There is kind of a narrowing of the futures. It cannot be as bad as we thought, but it cannot be as good as we hoped,” said Detlef Van Vuuren, lead author of the study and a climate scientist at Utrecht University and the Netherlands Environmental Assessment Agency, as reported by AP News.

Why the Worst Case Was Ruled Out

The primary reason the most extreme warming scenario is no longer considered plausible is the dramatic cost reduction in renewable energy. Solar and wind power costs have fallen by nearly 90% over the past 10 to 15 years, making the coal-intensive future assumed by RCP8.5 economically unrealistic.

Keywan Riahi, who led the 2011 study that introduced the RCP8.5 scenario and now directs the Energy, Climate and Environment Program at the International Institute for Applied Systems Analysis, told the AP that the scenario “was never a likely case.” It was designed, he explained, as “a plausible higher bound of what possible emissions could look like” — not a prediction of where the world was heading.

Global carbon emissions, while still rising, have flattened significantly compared to earlier projections. University of Michigan environment dean Jonathan Overpeck noted that “we are making progress in slowing climate change with a well-established affordable range of solutions — especially, solar, wind, battery storage, and electrified transportation.”

The Best Case: Overshooting 1.5°C

While the worst case has improved, the best case has worsened. The updated low-end scenario now projects warming that will overshoot the Paris Agreement’s 1.5°C (2.7°F) target, peaking at about 1.7°C (3.1°F) for potentially 70 years before possibly returning below 1.5°C later in the century — but only if carbon dioxide removal technologies can be deployed at massive scale.

The world is currently about 1.3°C (2.3°F) above pre-industrial times, warming at a pace of roughly 0.1°C (0.18°F) every five years. The “middle” scenario, which scientists say reflects the trajectory the world is currently on, projects about 3°C (5.4°F) of warming by 2100.

“This is just physics,” said Bill Hare, CEO of Climate Analytics. “We’re losing the ability to limit warming even by two degrees without strong action and people need to be aware of that and be aware that it’s a political failure. It’s not an act of God or anything. It is just because politicians in many places are not acting fast enough.”

Climate Feedbacks: The Wild Card

The new scenarios only model emissions that humans can control. Natural climate feedbacks — such as carbon release from thawing permafrost, Amazon rainforest dieback, and changes to ocean currents and cloud reflectivity — could add another 0.5°C of warming beyond what emissions alone cause, warned Johan Rockström, director of the Potsdam Institute for Climate Impact Research.

“We enter danger both from extreme events (such as floods, heat waves and droughts) but also from risks of crossing tipping points” such as loss of coral and glaciers, Rockström told the AP.

Political Fallout

The scenario update has already become a political flashpoint. President Donald Trump posted on Truth Social that the United Nations had admitted its projections were “WRONG! WRONG! WRONG!” — a claim that scientists and fact-checkers have pushed back against.

Van Vuuren responded directly to the president’s characterization: “The risks of climate change have not disappeared. The good news is that we did not follow the most dramatic emission pathway. However, we are still heading towards a future with significant climate impacts; a future we should avoid.”

Cornell University climate scientist Natalie Mahowald emphasized the human stakes, noting that “the people who will suffer the most are on the small island developing states. Some of them will go underwater.”

What Comes Next

Earth system model simulations based on the new scenarios are planned to begin in spring 2026, with results expected to provide a clearer picture of the temperature ranges ahead. The findings will feed into the 2028 global stocktake, where nations assess collective progress toward the Paris Agreement goals.

The central message from scientists is clear: humanity has averted the absolute worst by embracing clean energy, but the window to secure the best possible future is closing faster than expected — and the consequences of missing it will be measured in degrees of warming, rising seas, and lives affected across the planet.