UN says world will pass 1.5C warming limit and must climb back from overshoot

UN says the 1.5C limit will be passed

The United Nations Environment Programme (UNEP) has formally acknowledged that the world will exceed the 1.5C warming threshold at the heart of the 2015 Paris climate accord, dropping its previous position that the target was still within reach. According to PBS NewsHour, which reported on a first-of-its-kind assessment issued Wednesday, the planet will cross the line within the next few years.

Scientists estimate the world is already about 1.4C above mid-19th-century temperatures, measured as a 20-year average rather than from any single year. UN Secretary-General António Guterres said humanity is racing past the limit that was meant to prevent climate catastrophe.

The 1.5C figure became the accepted goal after the Paris accord, when the UN asked its climate science arm to compare warming limits and researchers concluded that harms to people and ecosystems become dramatic at 2C in ways they do not at 1.5C.

From prevention to overshoot

Instead of prevention, the report proposes managing an "overshoot": let temperatures pass 1.5C, keep the peak as low as possible, and then bring the planet back below the threshold, ideally before 2100. UNEP Executive Director Inger Andersen said the 1.5C goal still stands, but it now has to be approached from above rather than from below.

The report's projections span a wide range. Under the most optimistic scenario, warming peaks around 1.8C at mid-century if countries deliver ambitious climate goals; on current government policies, temperatures reach about 2.6C by 2100. Joeri Rogelj, a report co-author at Imperial College London, said every five years of delay in cutting emissions adds at least a tenth of a degree to the eventual peak. Fellow co-author Richard Betts of the University of Exeter said the world will likely sit above 1.5C for many decades, and that while a warmer world must now be lived with, a great deal can still be done to limit how warm it gets.

Scientists outside the process broadly accepted the reframing. Andrew Weaver of the University of Victoria, who was not part of the study, said 1.5C is not a cliff where everything is lost, because every tenth of a degree avoided still means less damage.

Coping with a warmer interim world

The report describes decades of what it calls coping and containment. During overshoot, more people are expected to die or fall ill from extreme weather, food production is projected to fall, water shortages will worsen, economies will suffer, and species such as coral face extinction. Andersen argued that adaptation efforts must expand, particularly to protect the poor, because some impacts can no longer be avoided.

The assessment also warns of tipping points with irreversible, cascading effects, including the loss of the West Antarctic and Greenland ice sheets, the loss of the Amazon rainforest, and the shutdown of the Atlantic circulation system that helps keep Europe warm. Some locations, it concludes, could become effectively uninsurable or even uninhabitable. Betts pointed to the recent deadly flooding in Nepal, which involved a dislodging Himalayan glacier, as the kind of event expected to become more frequent, and a reason to limit peak warming.

The way back depends on carbon removal

Returning below 1.5C, the report says, requires ending fossil fuel use and pulling carbon dioxide back out of the atmosphere. Planting trees, the traditional approach, could shave off at most about a tenth of a degree, so newer removal methods will be needed, though outside scientists cited by PBS NewsHour described those as unreliable and costly. Stanford's Rob Jackson, who was not part of the report, said the world failed to slow emissions in time and that overshoot now demands both halting and reversing them, calling it the best hope but not a likely outcome. Bill Hare of Climate Analytics said UNEP describes the predicament well but is far weaker on showing a way out of it.

Why it matters

This is the moment the world's central environmental body stopped treating 1.5C as a guardrail that could still be held and started treating it as a line the planet will cross and then work back from. That reframing carries through to planning: adaptation budgets, insurance and infrastructure decisions now have to assume decades of above-threshold conditions and heightened tipping-point risk, while emissions cuts and carbon removal determine how high the peak gets and how long the overshoot lasts. The report's own numbers make the stakes concrete, with nearly a full degree separating its best case from today's policies by 2100, and its core argument that every fraction of a degree still counts applies as much to engineering and deployment choices in the coming years as to diplomacy.