UNEP accepts the world will overshoot 1.5°C and sets out what a return would take
UNEP’s Limiting Overshoot report, published 2 September 2026, puts best-case peak warming at 1.8C and says a return to 1.5C needs far more carbon removal.
Photo by Alfo Medeiros on Pexels
The United Nations Environment Programme published a report on 2 September 2026 that treats climate overshoot as a settled outcome rather than a risk. “Limiting Overshoot: Navigating exceedance of 1.5°C and pathways towards return” is a 139-page spotlight report issued from Nairobi, and it states that even the most optimistic scenario of current government pledges puts expected peak temperature rise at 1.8°C. Under current policies the report gives a median of around 2.6°C by 2100, with a range of 1.9°C to 3.6°C.
This is a change of framing rather than of science. UNEP’s annual Emissions Gap Report has tracked the shortfall between pledges and pathways since 2010. The new report starts from the assumption that 1.5°C will be exceeded and asks what governs how high the peak goes, how long it lasts, and whether temperatures can come back down.
What the report means by climate overshoot
The definition matters, because a single hot year is not overshoot. The report’s glossary states that “The world is considered in overshoot when the multidecadal average global surface air temperature increase exceeds a specified warming level (e.g. 1.5°C), not when the global temperature in a single year exceeds that warming level.” It splits the episode into four stages: exceedance, a plateauing stage at peak warming, a decline stage, and a stabilization stage once temperatures return to or below 1.5°C.
On timing, the report is not fully consistent with itself. Its executive summary and foreword say the threshold will likely be crossed “within the next few years”, while chapter one states that central estimates indicate global warming will cross 1.5°C “within the next decade”. The report gives current warming as approximately 1.4°C. The Associated Press added that this measure is based on a 20-year average, a framing the report does not attach to that figure.
The peak is what the report says to fight for
The headline numbers are about peak warming rather than end-of-century warming. Even under a scenario assuming full implementation of all national climate plans plus additional net-zero targets, central estimates peak at around 1.8°C, with a range of 1.7°C to 2.2°C. A footnote adds that this case still encompasses 1.5°C, but only with a low probability of about 20 per cent.
| Pathway in the UNEP report | Warming | Range or probability |
|---|---|---|
| Current warming today | About 1.4°C | Stated without a range |
| Current policies, median at 2100 | Around 2.6°C | 1.9°C to 3.6°C |
| All NDCs plus long-term net-zero targets, at peak | Around 1.8°C | 1.7°C to 2.2°C |
| Most ambitious pathways, using observed emissions to 2025 | Peak of 1.6°C to 1.8°C | At 50 per cent probability |
| Stringent mitigation starting around 2025 | Peak exceeds 1.5°C by about 0.2°C | Best estimate |
| Each additional five years of sustained high emissions | Adds about 0.1°C to peak warming | Stated as an approximation |
Source: UNEP, “Limiting Overshoot”, chapter 1, 2 September 2026.
More than 400 gigatonnes of CO2 have been emitted cumulatively since the Paris Agreement, according to the report. For pathways that limit warming to 1.5°C with limited exceedance, it cites the Emissions Gap Report 2025 requirement that global greenhouse gas emissions fall 55 per cent from 2019 levels by 2035, assuming action began in 2020. António Guterres, UN Secretary-General, stated that “We must make the overshoot above 1.5 degrees as small and short as possible. That demands an overshoot of ambition.”
Carbon removal has to grow several times over
Coming back down requires removing more carbon than is emitted, and the report is blunt about the gap between what exists and what the pathways assume. Total carbon dioxide removal stands at around 2.2 gigatonnes of CO2 a year today, almost all of it conventional land-based removal through afforestation, ecosystem restoration and forest management. Even pathways with the least overshoot require that to rise to 2.7 to 4.1 gigatonnes a year by 2035 and 6.5 to 13.3 gigatonnes a year by 2050.
Novel methods are further behind. The report states that direct air capture with storage, bioenergy with carbon capture and storage, biochar and enhanced rock weathering together account for less than 0.1 per cent of conventional removal today. It projects them expanding to 0.9 to 6.4 gigatonnes a year by mid-century and 4.7 to 17.8 gigatonnes a year by 2100. Direct air capture with storage costs approximately 100 to 600 US dollars per tonne of CO2. Winss has covered where two of those methods stand commercially in Mafix raising $5.4m for enhanced rock weathering and in carbon removal through enhanced rock weathering and biochar application.
Two constraints in the report limit how far removal can be stretched. It would take over 100 years of afforestation and forest management at the current scale, with zero residual CO2 emissions, to bring warming back by 0.1°C. And even optimistic scaling of removal “is unlikely to deliver a temperature reversal beyond a few tenths of a degree this century”. The report sets a threshold on the peak itself: beyond around 1.8°C, decline to 1.5°C during the 21st century becomes increasingly challenging.
What the overshoot period does
The report names four tipping elements: the West Antarctic Ice Sheet, the Greenland Ice Sheet, the Atlantic Meridional Overturning Circulation, and the climate-biosphere system of the Amazon rainforest. It deliberately attaches no specific temperature thresholds to them, stating instead that evidence increasingly indicates that sustained warming above 1.5°C raises the risk of triggering one or more. On the AMOC it notes that limiting peak warming to less than 2°C may limit the overall weakening considerably, and that model projections show recovery on the timescale of centuries.
| Impact quantified in the report | Figure |
|---|---|
| Glacier mass lost by 2100, for warming up to about 3°C | More than a quarter |
| Sea level rise from that glacier loss | 9 to 12.5 cm |
| Decline in global food production by 2050 without effective adaptation | Up to 14 per cent |
| Multi-sector risk exposure, 1.5°C to 2°C | Projected to double |
| Multi-sector risk exposure, 2°C to 3°C | Projected to double again |
| Small island developing states, disaster-related GDP losses since 1970 | USD 153 billion against average GDP of USD 13.7 billion |
| Share of 33 assessed small island states above the 40 per cent debt-to-GDP sustainability threshold | 70 per cent |
Source: UNEP, “Limiting Overshoot”, chapters 3 and 4, 2 September 2026, citing WMO 2020 and GCA 2025 for the small island figures.
The finance picture in the report is narrow but concrete. The Fund for Responding to Loss and Damage held pledges of the order of 800 million US dollars as of late 2025, against developing-country needs that Tavoni et al. (2024) place at around 395 billion US dollars for 2025, with an indicative range of 128 billion to 937 billion. Inger Andersen, Executive Director of UNEP, stated that “There are no good outcomes if we remain above 1.5°C”, and added that “Now is the time we must double down on climate action.”
Where the near-term numbers sit
One set of figures widely attached to this report belongs to a different one. The scenario limiting overshoot to about 0.3°C with a 66 per cent chance, requiring 2030 emissions to fall 26 per cent and 2035 emissions 46 per cent against 2019 levels, comes from the Emissions Gap Report 2025, published on 4 November 2025. Those numbers do not appear in “Limiting Overshoot”, which instead cites the 55 per cent by 2035 figure for limited-exceedance pathways. National-level tracking of that gap is the subject of Agora’s finding that Germany is set to miss its 2026 climate target, and the underlying literature is being catalogued in Carbon Brief’s Project Cosmos climate research database.
The report was assembled by a core team of ten, a scientific advisory board of 24 members and about 45 named reviewers, all contributing in their individual capacities. Chapter one was led by Joeri Rogelj of Imperial College London and Carl-Friedrich Schleussner of the International Institute for Applied Systems Analysis. Part of the research was supported by United Kingdom aid through the Climate Adaptation and Resilience research programme. The report carries the DOI 10.59117/20.500.11822/49857 and ISBN 978-92-807-4301-2.
About UNEP
The United Nations Environment Programme was created after the 1972 United Nations Conference on the Human Environment in Stockholm, held from 5 to 16 June that year. Kenya offered it a home, making Nairobi the first United Nations headquarters in the global south. Its governing body is the UN Environment Assembly, and its stated role is to provide leadership and encourage partnership in caring for the environment.
Its flagship publications are the annual Emissions Gap Report, produced since 2010 with the UNEP Copenhagen Climate Centre and partners and launched each year ahead of the UN climate conference, the Adaptation Gap Report, and the Global Environment Outlook. Inger Andersen has been Executive Director since 2019, a post she holds alongside the rank of Under-Secretary-General of the United Nations. “Limiting Overshoot” is a standalone spotlight report rather than part of the Emissions Gap series, and it draws on the 2025 edition of that series for its warming projections and required emission cuts.
Sources: United Nations Environment Programme; United Nations Environment Programme; United Nations Environment Programme; United Nations Environment Programme; Inside Climate News; Associated Press; United Nations Environment Programme
Featured image: photo by Alfo Medeiros on Pexels (free Pexels license).
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I specialize in sustainability education, curriculum co-creation, and early-stage project strategy. At WINSS, I craft articles on sustainability, transformative AI, and related topics. When I’m not writing, you’ll find me chasing the perfect sushi roll, exploring cities around the globe, or unwinding with my dog Puffy — the world’s most loyal sidekick.
