For years scientists used a worst-case scenario — RCP8.5, later called SSP5-8.5 — as a benchmark for what could happen if fossil fuel use continued unchecked: more than 4 °C of global warming by 2100 with catastrophic heat waves, rising seas, crop failures and mass displacement. A scientific assessment published in April concludes that this doomsday pathway is now less probable. It was never a prediction but a low-probability, high-impact scenario meant to stress-test planning.
Researchers say the change reflects deep shifts in energy trends since the late 2000s, when coal, oil and gas dominated projections. Rapid growth in renewables and policy measures adopted by many governments have pushed emissions trajectories away from the most extreme pathway. Lead authors and other climate scientists describe this as fundamentally good news, while warning it should not breed complacency.
At the same time, scientists have dropped their most optimistic scenario. Emissions have not fallen fast enough, and the world is still on track to temporarily exceed 1.5 °C above pre-industrial levels. Current projections suggest warming could reach roughly 3 °C by 2100 if reductions do not accelerate — a level that would greatly intensify impacts already being felt: more deadly heat waves, larger floods and storms, worse droughts and wildfires, widespread crop failures, loss of coastal lands to sea-level rise affecting hundreds of millions of people, and broad harm to food security, economies and public health.
The revised assessment has been seized on by climate skeptics and some politicians to claim scientists were mistaken. Critics argue the change undermines the case for strong climate policy. Climate experts call those reactions a diversionary tactic, stressing that the revision actually reflects successful shifts in technology and policy, not a vindication of inaction.
Beyond the technical debate, the political stakes remain high. National leaders and parties have used the new findings to either argue for rolling back climate measures or to double down on action. Scientists emphasize the distinction between lower probability of the worst-case path and the ongoing, serious risk of several degrees of warming if emissions continue to rise.
In parallel with the scientific update, the United Nations General Assembly approved a nonbinding resolution endorsing an advisory opinion from the International Court of Justice. The ICJ opinion and the UN text underline that states may violate international law if they fail to protect people from dangerous climate impacts. The resolution, led by the Pacific island nation Vanuatu and supported by many countries, calls for stronger climate obligations, references phasing out subsidies for fossil fuel exploration and production, and suggests those responsible could face liability for damages.
The measure was opposed by some nations, including the United States, Russia, Iran and Saudi Arabia. Nonetheless, proponents hope the resolution strengthens the legal and moral case for governments to accelerate emissions cuts and to provide support for countries already suffering severe effects.
The bottom line from scientists and policymakers: the most extreme warming scenario is now less likely thanks to faster-than-expected renewable deployment and policy shifts, but significant warming remains probable unless emissions fall much more rapidly. The revised picture reduces the likelihood of an extreme outlier, but it does not remove the urgent need for deep, immediate action to limit warming and protect vulnerable people and ecosystems.