The UNEP Emissions Gap Report 2026 provides a clear answer: limiting global warming to 1.5°C with little or no overshoot is no longer feasible. Even under the most ambitious remaining scenario, global temperatures will peak at 1.7–1.8°C and could return to 1.5°C by 2100. In September, the Earth was 1.63°C warmer than pre-industrial levels, according to Copernicus, and the 1.5°C threshold established by the Paris Agreement now looks less like a target and more like a threshold we are already crossing. The question is no longer whether we will exceed it, but by how much and for how long. Copernicus expects months with temperatures above 1.5°C to continue into 2027.
The WMO’s May 2026 update estimates a 91% probability that at least one year between 2026 and 2030 will exceed 1.5°C, and a 75% probability that the five-year average will exceed this threshold. A single exceptionally warm year does not mean that the Paris Agreement’s target has been definitively missed, as the target refers to long-term warming, typically measured over a 20-year period. However, such years are becoming increasingly frequent.
How Far Are We from the Target, and What Needs to Be Done?
To keep the overshoot as low as possible, global emissions would need to fall by 18% by 2030 and 45% by 2035, compared with 2025 levels. Current national climate commitments, even if fully implemented, would deliver reductions of only 5–8% and 11–15%, respectively.
Under current policies, the world is heading towards 2.8°C of warming by 2100. Global emissions reached approximately 58.4 billion tonnes of CO₂ equivalent in 2025, remaining almost unchanged from 2024. Every fraction of a degree matters: the difference between 1.7°C and 2.8°C puts communities and economic stability on fundamentally different trajectories.
There are, however, reasons for optimism. The expansion of renewable energy has far exceeded previous forecasts, and more than 200 policy evaluations demonstrate that well-designed climate policies can deliver genuine emissions reductions.
Why the Duration of Warming Above 1.5°C Matters
What matters is not only how high temperatures rise, but also how long they remain elevated. A 2024 study published in Nature found that every 100 years spent above 1.5°C adds approximately 40 centimetres to sea-level rise by 2300. This increase comes on top of the approximately 80 centimetres already expected, even if warming stabilises at 1.5°C. The risk of crossing critical, potentially irreversible thresholds (tipping points) remains significant unless warming falls back below 1°C.
Zero Carbon Analytics further notes that oceans respond slowly, meaning marine ecosystems could remain less hospitable for centuries. It distinguishes between impacts that may be reversible and those that may not:
- Potentially reversible: Exposure to dangerous levels of heat.
- Potentially permanent or long-lasting: Biodiversity loss, sea-level rise, the crossing of critical tipping points, and deaths from extreme heat that have already occurred.
The duration of the overshoot depends on how quickly emissions are reduced and whether we can subsequently remove carbon dioxide from the atmosphere. Time is running out: researchers at the University of Leeds estimate the remaining carbon budget for 1.5°C at approximately 130 billion tonnes, equivalent to just over three years of current emissions.
The authors of the Nature study warn that several hundred gigatonnes of carbon removal capacity may be required, and that this capacity would need to be developed early. Meanwhile, UNEP’s most ambitious scenario assumes the removal of approximately 320 billion tonnes of CO₂ from the atmosphere by 2100. Given the considerable uncertainty surrounding whether carbon removal can be deployed at such a scale, reducing emissions today remains essential.
What This Means for Your Business
- Focus on duration, not just peak warming. Test scenarios with the same maximum temperature but different periods spent above 1.5°C. Zero Carbon Analytics also recommends considering a peak warming limit of around 1.8°C.
- Distinguish reversible impacts from permanent ones. Sea-level rise, biodiversity loss, and critical tipping points require a different response from heat exposure, which may decline in the future.
- Do not rely on future carbon removal. Many scenarios assume that large quantities of carbon dioxide will be removed from the atmosphere in the future. Consider what it would mean for your company if this process were delayed or never materialised.
- Prioritise adaptation as well. As overshooting becomes increasingly likely, investments in adaptation and resilience become more important for both businesses and financial institutions.
Would you like to understand what exceeding the 1.5°C threshold could mean for your business? VERALLIS can help you incorporate overshoot scenarios into your climate risk assessments.
Sources
UNEP: Emissions Gap Report 2026 (The Point of Return)
Carbon Brief: UNEP, Opportunity Has “Been Lost” to Meet 1.5C Warming Limit Without “Overshoot”
UNRIC: UNEP Emissions Gap Report 2026, 1.5°C Overshoot Inevitable
Copernicus: Second-Warmest September, Global Temperatures Stay Above 1.5°C
WMO: New Report Suggests More Global Temperature Records Ahead
Nature (2024): Overshoot and Committed Sea-Level Rise (Schleussner et al.)
Carbon Brief: How to Minimise the Risks from Overshooting the 1.5°C Limit
Zero Carbon Analytics: Beyond 1.5°C, What the Science Says About Overshoot
University of Leeds: Three Years Left of Remaining Carbon Budget for 1.5°C