1.5°C overshoot explained: UNEP's Emissions Gap Report 2026

Key takeaways

• The UN Environment Programme (UNEP) published Emissions Gap Report 2026: The Point of Return on 21 October 2026. It says the chance of holding warming to 1.5°C with "no or limited" overshoot has been lost.
• In UNEP's "lowest possible" overshoot pathway, warming peaks at about 1.7–1.8°C around mid-century, then has a 50% chance of returning to 1.5°C or below by 2100.
• That pathway needs global greenhouse gas emissions to fall 18% by 2030, 45% by 2035 and 69% by 2040, all relative to 2025. Fully implemented national pledges would deliver only 5–8% by 2030 and 11–15% by 2035.
• Projected warming is higher than in last year's report: 2.8°C under current policies and 2.6°C if every national climate plan is delivered. The 2025 report's figure for full pledge delivery was 2.3–2.5°C.
• To bring temperatures back down, the overshoot pathway also needs about 320 gigatonnes of CO2 to be removed and permanently stored this century. That is roughly eight years of global CO2 emissions at 2024 levels.

What UNEP actually said

UNEP's Emissions Gap Report 2026 says the chance of holding warming to 1.5°C with "no or limited" overshoot has been lost. In its lowest possible 1.5°C overshoot pathway, warming peaks at about 1.7–1.8°C around mid-century, with a 50% chance of returning to 1.5°C or below by 2100. A new study estimates 50,391 heat deaths in European cities in summer 2026, with 32,619 linked to climate change.

That doesn't mean UNEP has dropped 1.5°C as a target. The report changes the question. Avoiding 1.5°C altogether is off the table, so the aim becomes keeping the peak as low and as brief as possible and then bringing temperatures back to 1.5°C by the end of the century. UN News reports that UN Secretary-General António Guterres put it this way: "Overshoot is not surrender." According to the Netherlands Environmental Assessment Agency (PBL), Michel den Elzen, the report's lead author, said 1.5°C with limited overshoot is "no longer possible."

UN News says the report arrives a month before COP31 in Antalya, Türkiye, where the second Global Stocktake of progress under the Paris Agreement begins.

What "overshoot" means scientifically

In climate science, overshoot means global average temperature rises above a chosen threshold, here 1.5°C above pre-industrial levels, for a while and then comes back below it. The Paris goal refers to long-term warming averaged over many years, not to a single hot year. UNEP's 2025 report made the same point when it said the multi-decadal average temperature would exceed 1.5°C, "very likely within the next decade."

Three ideas explain why overshoot is now UNEP's central scenario.

1. Warming follows the total amount of CO2 emitted

Carbon dioxide stays in the atmosphere for a very long time, so warming from CO2 depends mostly on the total amount humans have emitted, not on any one year's emissions. Every year of high emissions adds to that total. PBL's summary of the 2026 report gives a rule of thumb: each five years of CO2 emissions at current levels adds roughly 0.1°C to peak warming. Delay costs warming that is hard to reverse.

2. Net zero stops the rise; it does not reverse it

When CO2 emissions reach net zero, warming from CO2 is expected to level off roughly where it is. Net zero alone doesn't bring the temperature back down. That needs net-negative emissions, meaning more CO2 is removed from the air each year than is released. UNEP's September 2026 report, Limiting Overshoot, calls for long-term net-negative emissions and describes carefully governed carbon dioxide removal (CDR), such as afforestation, as an essential part of that, according to UNEP's UNifeed release.

3. Some damage does not come back down with temperature

A temperature curve can fall again, but some impacts may not reverse. UNRIC reports the 2026 report's warning that each extra fraction of a degree, and each extra year above 1.5°C, raises the risk of irreversible changes to ice sheets, permafrost, ocean circulation and coral systems. That is why UNEP focuses on how high the peak goes and how long it lasts, not just on where temperatures end up in 2100.

How the 2026 numbers compare with the 2025 report

The table below sets out the main figures from UNEP's last two Emissions Gap Reports, as reported on UN and partner-agency pages. The two reports use different baselines for required cuts: 2019 in the 2025 edition and 2025 in the 2026 edition. Those rows can't be compared directly.

Sources: PBL summaries of UNEP Emissions Gap Reports 2025 and 2026; UN News (21 October 2026); UNRIC (21 October 2026).

Two changes stand out. First, the outlook for full pledge delivery got worse, rising from 2.3–2.5°C to 2.6°C. UN News attributes this to the United States' withdrawal from the Paris Agreement and revised estimates of historical emissions, and reports that national plans submitted since the previous report "hardly made a difference." Second, the framing has moved from limiting a possible overshoot to managing a certain one. The 2025 report already said global emissions reached a record 57.7 GtCO2e in 2024, up 2.3% on the year.

The September "Limiting Overshoot" report

The Emissions Gap Report builds on a separate UNEP assessment, Limiting Overshoot, released in Nairobi on 2 September 2026. According to UNEP's UNifeed material, that report says warming is set to cross 1.5°C, likely within the next few years. It names an "overshoot, peak, and decline" pathway as the best remaining option to keep the size and length of the overshoot as small as possible and to return below 1.5°C as soon as possible.

The September report also says adaptation will be necessary but will probably hit limits, with irreversible impacts, especially if the peak is not kept low. Keeping the peak down, it argues, reduces risk, makes adaptation cheaper and easier, and improves the odds of bringing temperatures back down. At the launch, UNEP Executive Director Inger Andersen said: "There are no good outcomes if we remain above 1.5°C." She added that "1.5 absolutely remains the goal." Guterres said the overshoot should be made "as small and short as possible."

What it would take to bring temperatures back down

The 2026 report sets out what its lowest-overshoot pathway requires. Taken together, the measures show how big the task is.

Steep, early emission cuts

Relative to 2025, emissions would have to fall 18% by 2030, 45% by 2035 and 69% by 2040. According to UNRIC, Guterres described the required pace as "close to 6 per cent every single year until 2035." Full implementation of existing pledges would cut emissions by only 11–15% by 2035. That shortfall is the "gap" the report is named after.

A rapid move away from fossil fuels

UN News and UNRIC report the following reductions relative to 2025 in the pathway:

Sources: UN News and UNRIC, 21 October 2026.

UNRIC adds that renewable energy capacity would need to triple by 2035 compared with 2025. The report also points to the first Global Stocktake's goals of tripling renewables and doubling the rate of energy-efficiency improvement by 2030, cutting non-CO2 gases such as methane, and halting and reversing deforestation. It finds progress on most of them insufficient.

Large-scale carbon removal

Even with deep cuts, getting back below 1.5°C means taking CO2 out of the atmosphere. PBL's summary puts the requirement at about 320 gigatonnes of CO2 removed and permanently stored this century. Methods listed by UNRIC include reforestation and technologies that capture, mineralise and store CO2 underground. UNEP's September report says removals must come in addition to emission cuts, not instead of them.

Signs of progress

The report isn't entirely bleak. UNRIC quotes Andersen as saying that global renewable electricity capacity has grown three times faster than expected when the Paris Agreement was signed, and that solar PV build-out has grown seven times faster. UNRIC also reports that coal and oil supply has grown more slowly than projected and that several G20 members have sustained emission reductions. PBL says that if these trends continue, with additional policies, renewable capacity could triple by 2030.

The cost of overshoot is already visible in the oceans. In its first global assessment of coral reefs under the Red List of Ecosystems, the IUCN rates 96% of reef ecosystems Critically Endangered and identifies projected marine heatwaves as the main driver, as explained in our report on the coral reef collapse risk.

What it means

For readers following climate policy, the main change is in the wording UNEP uses. Until recently, UN reports described 1.5°C as a narrowing window. The 2026 report says that window, in its no-overshoot form, has closed. The working goal is now a temporary peak of around 1.7–1.8°C followed by a decline, and even that depends on cuts far deeper than any government has pledged plus carbon removal at a scale that doesn't yet exist.

This has three practical consequences. Negotiations at COP31 and in the second Global Stocktake will probably focus on how high and how long the overshoot will be, not on whether there will be one. Carbon removal moves from a side topic to a central requirement, which raises questions about permanence, governance and who pays. And adaptation gets more urgent, because UNEP itself expects some impacts above 1.5°C to be beyond adaptation's limits.

Much is still uncertain. The return to 1.5°C by 2100 in UNEP's best case has only a 50% chance, and it assumes cuts begin immediately and continue for decades. The sources reviewed for this article don't say how quickly temperatures would actually fall after the peak, or how much of the needed carbon removal could realistically be built. Those details are expected to be debated as governments respond ahead of COP31.

Related coverage

• NASA-led model doubles Thwaites Glacier sea-level projection
• UK approves Shell's long-delayed Jackdaw North Sea gas field
• Natural gas futures slide nearly 5% on mild US weather outlook
• How Astronomers Measured the Big Bang's Helium to 0.5% Precision

Sources

• UN News: Global warming will breach 1.5°C (21 October 2026)
• UNRIC: Climate: The 1.5°C goal of the Paris Agreement is no longer viable (21 October 2026)
• UNEP: Emissions Gap Report 2026: The Point of Return (report page)
• PBL Netherlands Environmental Assessment Agency: UNEP Emissions Gap Report 2026
• PBL Netherlands Environmental Assessment Agency: UNEP Emissions Gap Report 2025
• UNifeed (UNEP): Limiting Overshoot report (2 September 2026)
• UNifeed: UN / UNEP Limiting Overshoot report press conference (2 September 2026)