UNEP Limiting Overshoot Report: 1.5°C warming overshoot is now ‘unavoidable’

Key facts

• The UNEP report titled "Limiting Overshoot" says crossing the 1.5°C threshold is unavoidable, with global temperatures expected to peak at about 1.8°C above pre-industrial levels even under an optimistic scenario.
• The 1.5°C target was a key outcome of the Paris Agreement, signed in 2015 by 193 countries and the European Union.
• Under Article 2 of the Paris Agreement, nations must commit to keep global average temperatures well below 2°C above pre-industrial levels, and ideally capped at 1.5°C.
• The 1.5°C limit was never considered a completely safe level of warming, but staying closer to it reduces the severity of risks to people and ecosystems.
• The report notes that climate impacts intensify as warming rises, with growing risks of irreversible changes such as Amazon dieback, permafrost thaw and ice-sheet collapse.
• UNEP acknowledges that even in an optimistic scenario where governments fully implement current climate plans and net-zero pledges, warming is expected to peak at about 1.8°C.
• UNEP says the world will exceed the 1.5°C limit, but that does not mean abandoning the target; countries will have to approach 1.5°C from above rather than below.
• Overshooting 1.5°C will still cause harmful, long-lasting damage, even if temperatures are eventually brought back down.
• Some changes may be difficult or even impossible to reverse, including risks involving the Greenland and West Antarctic ice sheets, the Amazon rainforest, and the Atlantic Meridional Overturning Circulation.
• UNEP says carbon dioxide removal will be necessary, but even optimistic deployment is unlikely to reverse more than a few tenths of a degree of warming this century.
• At current rates, afforestation and forest management alone would take more than 100 years to reduce warming by just 0.1°C.
• Returning below 1.5°C would not undo all damage; sea-level rise, extinctions and ecosystem shifts may continue even as temperatures decline.
• A smaller, shorter overshoot would mean less damage and improve chances of bringing warming back below 1.5°C.
• Cutting methane and other short-lived climate pollutants can help slow warming relatively quickly.
• The report lays out a three-step response: slash emissions and protect vulnerable people and ecosystems immediately; reach at least net zero at peak warming; then sustain net-negative CO₂ emissions to bring temperatures down.
• The consequences of overshoot will not be shared equally; countries that have contributed least to global warming are often among the most exposed.
• At COP30 in Belém, Brazil, countries agreed on the need to sharply scale up adaptation finance for developing countries.
• UNEP estimated adaptation needs for developing countries could exceed $310 billion a year by 2035, around 12 times current international public finance flows.