A new UN report says crossing the Paris climate threshold now looks unavoidable, but how far temperatures rise, how long they stay there and whether they can eventually be brought back down are still shaped by the choices we make now
For almost a decade, keeping global warming below 1.5C has been one of the defining goals of global climate action. Now, for the first time, the UN Environment Programme (UNEP) has concluded that the world is likely to breach that threshold within the next few years, while also making clear that crossing it does not mean temperatures have to remain there or that further efforts to limit warming become futile.
Published on Wednesday, UNEP’s Limiting Overshoot report describes what it calls an “overshoot, peak and decline” pathway, in which temperatures rise beyond 1.5C before peaking as greenhouse gas emissions fall towards net zero, then begin to decline if humanity succeeds in removing more carbon dioxide from the atmosphere than it releases.
Under the most ambitious scenario examined by UNEP, warming would peak at around 1.8C by the middle of the century. By contrast, policies currently in place would put the world on course for around 2.6C of warming by 2100, according to the report, which underlines why every fraction of a degree avoided continues to reduce the scale of harm.
Climate scientists have long warned that 1.5C is not a line separating a safe world from one in which further action becomes pointless. Risks increase as temperatures rise, so a world that reaches 1.6C is less dangerous than one that reaches 1.7C, while spending a shorter period above 1.5C would also reduce the damage compared with remaining there for decades.
“The 1.5 limit is not ‘some magical climate cliff’ where it’s just game over,” Andrew Weaver, a climate scientists at the University of Victoria, Canada, who was not involved with the report, told the Associated Press. “Every tenth of a degree we avoid still means less damage.”
Although 2024 was the first individual year in which average global temperatures exceeded 1.5C above pre-industrial levels, the Paris agreement threshold is assessed over a longer period rather than a single unusually hot year. Sustained warming is now estimated at around 1.4C, meaning the world has not yet formally crossed the threshold, although UNEP now believes doing so is likely within the next few years.
The report argues that the response should be to keep any overshoot as low and as short as possible, rather than treating the breach as evidence that the original goal should simply be abandoned. “Decisions, science and, most importantly, mindsets need to shift to seeing 1.5C as a goal we’ll be approaching from above rather than below,” said Mirey Atallah, chief of UNEP’s adaptation and resilience branch and coordinator of the report.
Returning temperatures below 1.5C would still require deep and sustained reductions in fossil fuel emissions followed by a period of net-negative emissions, with carbon dioxide removed and stored through forests and other natural approaches alongside technologies that have yet to operate at anything like the scale envisaged.
UNEP also stresses that carbon removal cannot substitute for cutting emissions, while some damage caused during an overshoot could prove irreversible. Higher temperatures increase the risks to ice sheets, the Amazon rainforest and the Atlantic circulation system, as well as intensifying heatwaves, flooding, food insecurity and ecosystem loss. Even if temperatures later fall, rising seas, lost species and other changes cannot simply be reversed.
What the report changes is not the seriousness of crossing 1.5C, but the way that threshold can be understood once it happens. The eventual peak, the length of time the world spends above 1.5C and whether temperatures can ultimately be brought down again will still depend heavily on the speed and scale of emissions cuts made in the years ahead.
As report co-author Richard Betts, a climate scientists at the University of Exeter, England, put it: “It’s a reality check. We have to live with this warmer world. But there’s still a lot we can do to limit warming.”
Main image: Pascual Fernandez Gomez
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Facts Only
* The UN Environment Programme (UNEP) published the Limiting Overshoot report on Wednesday.
* The report concludes the world is likely to breach the 1.5C warming threshold within the next few years.
* Current policies put the world on course for approximately 2.6C of warming by 2100.
* The most ambitious scenario examined by UNEP projects warming peaking at around 1.8C by mid-century.
* Sustained global warming is currently estimated at approximately 1.4C.
* 2024 was the first individual year where average global temperatures exceeded 1.5C above pre-industrial levels.
* Returning temperatures below 1.5C requires reductions in fossil fuel emissions followed by net-negative emissions.
* Carbon dioxide removal methods mentioned include forests, natural approaches, and undeveloped technologies.
* Risks associated with higher temperatures include impacts on ice sheets, the Amazon rainforest, and the Atlantic circulation system.
* Andrew Weaver is a climate scientist at the University of Victoria, Canada.
* Richard Betts is a climate scientist at the University of Exeter, England.
* Mirey Atallah is the chief of UNEP’s adaptation and resilience branch.
Executive Summary
Global warming is likely to exceed the 1.5C threshold established by the Paris Agreement within a few years. While a single year of breach occurred in 2024, sustained warming currently sits at 1.4C. The objective has shifted from preventing a breach to managing an "overshoot, peak, and decline" pathway. In this model, temperatures rise beyond 1.5C, peak as emissions hit net zero, and eventually decline through the removal of carbon dioxide from the atmosphere.
The severity of the outcome depends on current choices. Ambitious action could limit the peak to 1.8C by mid-century, whereas current policies trend toward 2.6C by 2100. While every fraction of a degree avoided reduces harm, some damage—such as species loss and sea-level rise—may be irreversible even if temperatures later drop. Success in returning to 1.5C requires deep fossil fuel cuts combined with large-scale carbon removal technologies that are not yet operational at the necessary scale.
Full Take
The strongest version of this narrative is a pragmatic pivot: acknowledging a likely failure to meet a specific numeric goal (1.5C) to prevent a total collapse of climate ambition. By redefining the threshold as a "goal we'll be approaching from above," the framework seeks to avoid the "climate cliff" psychology—where crossing a line is perceived as "game over"—and instead emphasizes that every tenth of a degree remains significant.
This shift reflects a transition from a preventative paradigm to a mitigation-and-recovery paradigm. It introduces a heavy reliance on "net-negative emissions" and carbon removal technologies that currently lack the necessary scale. This creates a precarious dependency on future technical breakthroughs to justify current "overshoot" trajectories.
The underlying assumption is that human agency can precisely calibrate the "peak" and "decline" of global temperatures. However, the mention of irreversible tipping points (Amazon rainforest, Atlantic circulation) suggests a tension between the optimistic "overshoot" model and the reality of non-linear biological and geological systems.
Patterns detected: none
Root Cause: This narrative is driven by the need to maintain institutional momentum and public willpower in the face of a missed target. It echoes historical patterns of "goalpost shifting" used in complex systemic management to prevent defeatism.
Implications: This approach preserves hope and action but risks creating a moral hazard by framing the 1.5C breach as manageable. The costs of this "overshoot" will be borne disproportionately by ecosystems and populations unable to adapt to temporary but intense spikes in temperature.
Bridge Questions: What specific evidence suggests that carbon removal technologies can be scaled rapidly enough to effect a decline? At what point does an "overshoot" trigger a feedback loop that makes a "decline" physically impossible?
Counterstrike Scan: A bad actor pushing this narrative would use the "unavoidable" breach of 1.5C to argue that since the goal is already lost, aggressive emissions cuts are futile. The actual content avoids this by explicitly stating that every fraction of a degree still matters. The content is clean.