METRIQOm®The global climate challenge has entered a more dangerous phase. According to the United Nations Environment Programme’s landmark report, Limiting Overshoot: Navigating Exceedance of 1.5°C and Pathways Towards Return, exceeding 1.5°C above pre-industrial levels is now widely assessed as unavoidable under current policies and plausible near-term emission pathways. The central estimate of human-induced warming is expected to cross this threshold within the next few years.
This does not mean that the 1.5°C objective has been abandoned. The strategic priority has shifted from preventing any exceedance to minimizing how high temperatures rise, how long they remain above 1.5°C and how quickly they can subsequently decline.
Understanding the 1.5°C Threshold
The Paris Agreement commits countries to hold global warming well below 2°C and pursue efforts to limit it to 1.5°C. This long-term temperature goal is assessed over decades rather than by using the temperature of one isolated year.
The World Meteorological Organization confirmed that 2024 was the first calendar year to exceed 1.5°C above the 1850–1900 average. A single year above 1.5°C did not, by itself, constitute a formal breach of the Paris temperature goal, but it was a strong warning that the long-term threshold was approaching rapidly.
The UNEP assessment now concludes that the central estimate of human-induced warming will cross 1.5°C within the next few years. It also indicates that the world has probably entered the 20-year period whose average warming will reach this level.
The Remaining Carbon Budget Is Nearly Exhausted
To retain a 50% chance of limiting warming to 1.5°C, the world can emit only approximately 130 billion tonnes of CO₂ from 2026 onward. Fossil fuels and industrial activity produced approximately 40 billion tonnes of CO₂ in 2024 alone. If emissions remain at roughly that level, the remaining carbon budget would be exhausted in about three years.
This calculation does not mean that climate action becomes pointless when the budget is exhausted. It means that every additional year of high emissions increases peak warming, expands future carbon-removal requirements and raises the probability of irreversible damage. UNEP estimates that approximately five additional years of sustained high emissions could add around 0.1°C to peak warming.
Where Current Pathways Are Leading
The UNEP report presents a significant gap between existing policies and the most ambitious available scenario:
- Under current policies, median global warming is projected to reach approximately 2.6°C by 2100, with an assessed range of 1.9°C to 3.6°C.
- If countries fully implement all Nationally Determined Contributions and their long-term net-zero targets, the most optimistic UNEP scenario projects warming to peak at approximately 1.8°C, with an assessed range of 1.7°C to 2.2°C.
Even the best-case scenario therefore involves an overshoot. However, the difference between a peak of 1.8°C and a pathway above 2°C is critical for human health, food and water security, infrastructure, ecosystems, economic stability and the ability of vulnerable communities to adapt.
The New Strategy: Overshoot, Peak and Decline
UNEP identifies an “overshoot, peak and decline” pathway as the most viable remaining strategy. This is not permission to delay decarbonization or rely excessively on future carbon removal. It requires immediate emission reductions, stronger adaptation and carefully governed carbon dioxide removal working together.
| Phase | Core objective | Priority actions |
|---|---|---|
| Overshoot | Keep the exceedance as low and short as possible | Deliver immediate and sustained reductions in CO₂, methane and other greenhouse gases; accelerate the transition from fossil fuels; protect natural carbon stocks; and strengthen adaptation. |
| Peak | Stop temperatures from continuing to rise | Reach global net-zero CO₂ emissions, deeply reduce other greenhouse gases and use credible carbon dioxide removal to balance genuinely residual emissions. |
| Decline | Gradually reduce temperatures toward or below 1.5°C | Maintain net-negative CO₂ emissions, further reduce residual methane and other emissions, and continue long-term adaptation and resilience measures. |
Carbon dioxide removal will be necessary, but it cannot replace emission reduction. The UNEP assessment stresses that removal can contribute credibly to returning below 1.5°C only if peak warming remains well below 2°C and residual emissions are reduced as far as practicable. Reversing warming will also be slow: approximately 220 billion tonnes of net-negative CO₂ emissions may be required to reduce global temperature by around 0.1°C.
What This Means for Governments and Businesses
Every additional fraction of a degree increases climate risks. According to UNEP, higher temperatures and longer periods of overshoot increase the probability of severe weather, ecosystem loss, food and water insecurity, infrastructure disruption and irreversible tipping points involving ice sheets, forests and ocean circulation.
For businesses, climate strategy can no longer be limited to distant net-zero commitments or annual carbon reporting. Organizations must connect climate risk with asset design, capital expenditure, insurance, procurement, energy transition, water security, supply-chain resilience, emergency planning and business continuity. Adaptation and mitigation must be managed as integrated operational controls.
The 1.5°C threshold is not a cliff beyond which action becomes irrelevant. Every fraction of warming avoided protects lives, assets, ecosystems and economic value. The leadership question is therefore no longer simply, “Can we prevent an overshoot?” It is: What are we doing now to limit the peak, strengthen resilience and accelerate the decline?
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