UNEP: 1.5°C limit to be breached, but world can still pull temperatures back

The United Nations Environment Programme (UNEP) has said that global warming will exceed the 1.5°C threshold in the coming years, making temporary overshoot unavoidable. In a report released in Nairobi, the agency for the first time outlined a detailed pathway to limit the peak of that overshoot and bring temperatures back below the limit by the end of the century.

The report, titled Limiting Overshoot, warns that breaching the 1.5°C target will cause irreversible damage that adaptation measures cannot fully undo. It states that even if every country meets its current climate pledges and net-zero targets, peak warming would reach 1.8°C. Under existing policies, the world is on track for a rise of about 2.6°C by 2100, with a range of 1.9–3.6°C.

The proposed pathway is described as “by no means an acceptable or preferred pathway; it is simply the best remaining option.” It involves letting temperatures rise above 1.5°C temporarily, holding the peak as low as possible, and then using carbon dioxide removal and sustained emission cuts to bring temperatures back down.

The report builds on the outcome of COP30, held in Belém, Brazil, in 2025. For the first time, a UN climate summit decision acknowledged that a temporary overshoot of 1.5°C was likely, given how rapidly the remaining carbon budget is being consumed. Countries also committed to limiting the size and duration of any overshoot and to closing gaps in adaptation.

The report highlights that time spent above 1.5°C carries compounding risks, including faster sea-level rise, collapse of coral reefs, loss of more than a quarter of global glacier mass by 2100, and up to 14% decline in global food production by 2050 without effective adaptation. It also raises the risk of triggering irreversible tipping points in the West Antarctic and Greenland ice sheets, the Atlantic Meridional Overturning Circulation, and the Amazon rainforest.

One of the report’s key findings is that every five years of continued high emissions adds roughly 0.1°C to peak warming. Reversing that same 0.1°C would require pulling about 220 billion tonnes of carbon dioxide out of the atmosphere, over and above ongoing emission cuts. The report stresses that carbon dioxide removal is necessary in addition to, not instead of, emission cuts, and can only bring temperatures back to 1.5°C if peak warming stays well below 2°C.

UNEP Executive Director Inger Andersen said the report is not a concession. “Let’s be very clear, the 1.5 target is still the goal. But now we need to approach it differently from above,” she said.

The report comes at a time of uncertainty over global climate action. The United States, the world’s largest historical emitter, formally exited the Paris Agreement earlier this year and has announced withdrawal from the UN Framework Convention on Climate Change, the Intergovernmental Panel on Climate Change, and the Green Climate Fund. The report does not directly address these developments but notes the growing difficulty of limiting overshoot as the carbon budget shrinks.

Despite the grim outlook, the report argues that immediate and deep emission cuts remain essential. Even the most optimistic scaling up of such cuts cannot reverse more than a few tenths of a degree this century, it underlines, making early action critical to keeping the overshoot as small and short as possible.