The United Nations Environment Programme (UNEP) released its Limiting Overshoot report on 2 September 2026 in Nairobi, warning that global warming is set to cross 1.5°C above pre-industrial levels within the next few years. Even in the most hopeful case where all country promises are kept, temperatures are expected to peak at 1.8°C, while present policies point to around 2.6°C by 2100. The report argues that the goal now must be to keep this breach as low and as short as possible and then bring temperatures back down below 1.5°C.
What Is Climate Overshoot?
Global warming means a rise in the average temperature of the Earth’s surface due to human activity. It happens mainly because of the greenhouse effect. In this process, gases such as carbon dioxide (CO2), methane and nitrous oxide trap heat from the sun in the atmosphere instead of letting it escape to space. Burning coal, oil and gas, cutting forests and expanding farming have raised the level of these greenhouse gases sharply since industrial activity began.
Climate overshoot means the world’s average surface temperature rises above 1.5°C compared to pre-industrial levels for a sustained period, reaches a high point, and then comes back down. Pre-industrial levels refer to the climate before large scale industrialisation, which scientists usually measure using the period 1850 to 1900 when reliable global temperature records began. The report makes it clear that overshoot is a full pathway, not a single hot year.
This distinction is important. In 2024, the annual average temperature crossed 1.5°C above pre-industrial levels for the first time, with an anomaly of about 1.55°C. But the Paris Agreement temperature goal refers to a long term average over 20 years or more, not one calendar year. So 2024 did not by itself mean the Paris goal was lost. The world is treated as being in overshoot only when the average over many decades stays above 1.5°C.
The report describes overshoot as a curve with four stages. First comes exceedance, when temperatures move above 1.5°C. Then comes the peak, the highest point of warming. After that comes decline, when temperatures start falling. Finally comes stabilisation, when temperatures settle at or below 1.5°C again. How high the peak goes and how long the world stays above 1.5°C will decide how much harm people and nature face.
Why the 1.5 Degree Celsius Target Matters
The 1.5°C target comes from the Paris Agreement, a legally binding global treaty on climate change. It was adopted by 195 parties at the 21st UN Climate Change Conference (COP21) in Paris on 12 December 2015 and entered into force on 4 November 2016. The treaty is managed under the United Nations Framework Convention on Climate Change (UNFCCC), the 1992 framework that first brought countries together to act on climate change. Its central aim is to hold the rise in global average temperature to well below 2°C and to try to limit it to 1.5°C above pre-industrial levels.
Countries act on this goal through Nationally Determined Contributions (NDCs). These are national plans in which each country states how much it will cut its greenhouse gas emissions. Countries are expected to submit stronger plans every five years. The idea is that combined national cuts will keep global warming within the Paris limits.
Science shows why half a degree makes a large difference. The Intergovernmental Panel on Climate Change (IPCC), the world’s main body of climate scientists, found in its 2018 Special Report on 1.5°C that risks rise sharply between 1.5°C and 2°C. Heatwaves become hotter and longer. Heavy rainfall and floods become more intense. Droughts last longer. Coral reefs, glaciers and low lying island nations face far greater danger at 2°C than at 1.5°C.
| Warming level | What science indicates |
|---|---|
| Around 1.4°C today | Extreme heat, floods, wildfires and droughts are already more frequent and severe |
| At 1.5°C | Serious impacts on health, farming, water and ecosystems, but still within limits where adaptation can help in many regions |
| At 2°C and above | More than double the share of people exposed to extreme heat compared to 1.5°C, faster glacier loss, deeper food and water stress and higher risk of crossing tipping points |
This is why the report repeats a simple line. Every fraction of a degree avoided means fewer deaths, lower damage, lower costs and a better chance of returning to safety.
Key Findings of the Limiting Overshoot Report
The report is titled Limiting Overshoot: Navigating exceedance of 1.5°C and pathways towards return. It was prepared by the United Nations Environment Programme (UNEP), the leading UN body on the environment. UNEP was founded in 1972 after the Stockholm Conference on the Human Environment and is headquartered in Nairobi, Kenya. It is led by Executive Director Inger Andersen and hosts the UN Environment Assembly, the world’s highest decision making body on the environment with universal membership of all 193 UN Member States.
The report is a spotlight report published on 2 September 2026. It does not repeat the annual tracking of emission gaps. It starts from a new base. Breach of 1.5°C is now treated as highly likely within the next few years, so the focus shifts to how high temperatures will rise, how long they will stay high, and whether they can be brought back down.
Current warming is estimated at about 1.4°C above pre-industrial levels. More than 400 gigatonnes of CO2 have already been added to the atmosphere since the Paris Agreement was adopted. To stay on a path that limits warming to 1.5°C with only a small breach, global greenhouse gas emissions must fall by 55 percent from 2019 levels by 2035. For a 2°C path, the required cut is 35 percent by the same year.
Peak Warming Projections and Current Policies
The report compares what will happen if all promises are kept with what will happen if only present actions continue.
| Scenario | Projected warming | What it means |
|---|---|---|
| Full implementation of all NDCs and net zero pledges (best case) | Peak of around 1.8°C, with a range of 1.7°C to 2.2°C | Even the most hopeful path overshoots 1.5°C, but the peak stays well below 2°C |
| Current policies continued to 2100 | Median of around 2.6°C, with a range of 1.9°C to 3.6°C | Warming keeps rising through the century and the chance of returning to 1.5°C falls sharply |
The gap between 1.8°C and 2.6°C is the space where present choices matter. Lower emissions now mean a lower peak and a shorter stay above 1.5°C. Higher emissions mean a higher peak, longer exposure and greater damage that may not be reversible even if temperatures later fall.
What Happens If the World Stays Above 1.5 Degrees?
The report warns that there are no good outcomes if the world remains above 1.5°C. Risks grow with every extra tenth of a degree and with every extra year spent in overshoot. Extreme heat is already showing how fast impacts strike and how long they last. Homes are flooded, harvests are lost and communities are hit again before they fully recover from the last disaster.
Above 1.5°C, heavy rainfall, floods, droughts, wildfires and coastal erosion become more severe. Glaciers melt faster, which threatens rivers that feed farming and hydropower. Pressure on food and water grows. Coral reefs, forests and polar systems face losses that cannot be fully repaired. Small island nations and low lying coastal areas face the harshest threat from sea level rise and storms.
Some changes may appear suddenly, while others will build up slowly. The report stresses that some losses will be irreversible even if temperatures later decline. Species that vanish, glaciers that disappear and sea level rise that floods land cannot be undone simply by cooling the planet later. The longer the overshoot lasts, the higher the chance of crossing tipping points, thresholds after which parts of the climate system shift into a new and unstable state on their own.
Adaptation also has limits. Adaptation means steps that reduce harm from climate change, such as heat action plans, flood defences, drought resistant crops and stronger water systems. These steps can save lives and protect incomes. But if peak warming is high, adaptation becomes harder, more costly and less effective. In the most exposed regions, there will be places where adaptation can no longer prevent severe harm.
How the World Can Limit Peak Warming and Return Below 1.5 Degrees
The report proposes one best remaining option. It calls it the overshoot, peak and decline pathway. The aim is to make the breach as small and as short as possible and then return to below 1.5°C as soon as possible. This path does not weaken the 1.5°C goal. It treats overshoot as a reason for faster action, not for delay.
The first part of the path is to cut emissions at once and without break. This includes carbon dioxide and methane. Methane is a short lived climate pollutant that traps far more heat than carbon dioxide over a short period. Cutting methane quickly can slow warming in the near term. Reaching global net zero carbon dioxide emissions is also vital. Net zero means the amount of carbon dioxide added to the air equals the amount removed, so warming stops rising. Only after net zero can the world move toward net negative emissions, where removals exceed additions over a long period and temperatures begin to fall.
The second part is to remove carbon already in the air in a careful and responsible way. Carbon Dioxide Removal (CDR) means human actions that take carbon dioxide out of the atmosphere and store it safely for a long time in plants, soils, rocks, oceans or products. CDR cannot replace deep emission cuts. It must work along with them. The report states that a return below 1.5°C is credible only if peak warming stays well below 2°C and all remaining emissions are reduced as far as possible.
| Type of removal | Examples | Current status |
|---|---|---|
| Conventional CDR | Planting new forests, managing existing forests better, restoring wetlands, storing more carbon in farm soils | Provides about 2 gigatonnes of CO2 removal per year today, almost all current removal |
| Novel CDR | Bioenergy with carbon capture and storage, direct air capture with storage, enhanced rock weathering, biochar | Provides only a tiny share today, about 0.002 gigatonnes per year, but growing fast |
The limits of removal are strict. The report notes that it would take more than 100 years of tree planting and forest care at the present scale, with zero leftover emissions, to lower warming by just 0.1°C. Removal also competes for land, water and energy and can harm food systems if done poorly. Current country plans for removal fall far short of what 1.5°C paths need, which is around 7 to 9 gigatonnes per year by 2050. Strong rules, clear monitoring and action that protects land, food and water are therefore essential.
The third part is to adapt while cutting emissions. Mitigation means reducing greenhouse gas emissions. Adaptation means preparing for the warming that can no longer be avoided. The report states that the two must advance together and at scale. Early adaptation pays. Clean energy, resilient food and water systems and stronger public services can protect people and support growth at the same time. But this needs political will, inclusive policies and large flows of public and private finance, especially to developing nations that face the worst impacts with the fewest resources.
Climate Overshoot vs Earth Overshoot Day
The term overshoot causes confusion because it is used in two different ways. Climate overshoot is about temperature. It describes the UNEP pathway where global average temperature rises above 1.5°C, peaks and then declines. Earth Overshoot Day is about resource use. It marks the date in a year when human demand for nature exceeds what the Earth can renew in that year.
| Feature | Climate overshoot | Earth Overshoot Day |
|---|---|---|
| What it measures | Global surface temperature compared to pre-industrial levels | Human use of land, forests, fish and carbon absorption compared to nature’s capacity |
| Who tracks it | UNEP, IPCC and the World Meteorological Organization (WMO) through climate science | The Global Footprint Network through ecological footprint accounts |
| Key figure in 2026 debate | Peak of 1.8°C in best case, 2.6°C under current policies | Falls in late July or early August in recent years, showing humanity uses about 1.7 Earths worth of resources |
The two ideas point to the same root cause. Burning fossil fuels, clearing forests and overusing resources raise both carbon levels and ecological pressure. But only climate overshoot tells whether the Paris temperature goal can still be met from above through lower peaks, shorter duration and net negative emissions.
Key Takeaways
- The Limiting Overshoot report was released by UNEP on 2 September 2026 in Nairobi.
- Global warming is likely to breach 1.5°C above pre-industrial levels within the next few years on a multidecadal average basis.
- The best case peak is around 1.8°C, while current policies point to around 2.6°C by 2100 with a range of 1.9°C to 3.6°C.
- The Paris Agreement adopted on 12 December 2015 aims to hold warming well below 2°C and pursue efforts to limit it to 1.5°C.
- UNEP was founded in 1972 after the Stockholm Conference and is headquartered in Nairobi, Kenya.
- Returning below 1.5°C needs immediate emission cuts including methane, plus sustained net negative CO2 emissions through governed Carbon Dioxide Removal.
