UN: The world is expected to cross the 1.5 degree mark within a few years

A new report by the United Nations Environment Programme states that even in the most optimistic scenario, warming will peak at around 1.8 degrees. Returning to below the threshold set in the Paris Agreement is only possible through immediate and deep cuts in emissions, methane reduction, large-scale carbon removal and large-scale adaptation – and even then some of the damage will be irreversible.

The world is expected to cross the global warming threshold within a few years. 1.5 degrees Celsius above the pre-industrial period, and the remaining goal now is to reduce the deviation as much as possible and then lower the temperature back down. This is the main conclusion of a new report by United Nations Environment Programme, UNEP, published on September 2, 2026, ahead of the climate conference COP31 In Antalya, Turkey.

The report, titled “Limiting the Overshoot: Navigating Beyond 1.5 Degrees and Pathways to Return,” does not present crossing the threshold as a new goal or a surefire outcome. On the contrary: its authors emphasize that there is no harmless level of warming beyond 1.5 degrees, that every tenth of a degree increases the risks, and that even a future decrease in temperature will not undo some of the damage that will be caused along the way.

Even in the optimistic scenario examined in the report—full implementation of national climate plans and additional commitments to reach net-zero emissions—warming is expected to peak at about 1.8 degrees. Under the current policy path, however, the forecast is for warming of about 2.6 degrees by the end of the century, with a wide uncertainty range of 1.9 to 3.6 degrees. Therefore, the question is not just whether the world will exceed the 1.5 degree mark, but how high and prolonged the deviation will be, and what it will take to recover from it.

It is also important to distinguish between a single hot year and crossing the climate threshold. The temperature in a given year can temporarily rise above 1.5 degrees due to a combination of long-term warming and natural fluctuations. The report refers to crossing an average warming level over years, not just a temporary peak.

Every five years of delay adds about a tenth of a degree.

According to the report, every five years that emissions remain high adds about a tenth of a degree to the expected peak warming. More than 400 billion tons of carbon dioxide emitted since 2015 have already raised the lowest level of warming that can still be achieved by about 0.2 degrees.

This has practical implications: Not every deviation above 1.5 degrees is like another. A world that briefly reaches 1.6 degrees and begins to cool is very different from a world that has remained for decades near 2 degrees. The higher the peak of warming and the longer it remains above the threshold, the greater the exposure to extreme heat, the risk of fires, the loss of ice, and the chance of crossing tipping points that are difficult or impossible to reverse.

The report points to, among other things, an accelerating risk to coral reefs, glaciers and ecosystems. In warming scenarios of up to 3 degrees, the world's glaciers could lose more than a quarter of their mass by 2100 and contribute between 9 and 12.5 centimeters to sea level rise. The risks also include irreversible changes to the Greenland and West Antarctic ice sheets, a weakening of the Atlantic Ocean current system and damage to the Amazon rainforest.

The consequences of warming are not limited to nature. Without effective adaptation, global agricultural production could decline by up to 14 percent by 2050. Heat waves, floods, droughts, and rising sea levels threaten health, infrastructure, food security, and entire economies—and are hit particularly hard in countries and communities that have contributed relatively little to the crisis.

Don't give up on the goal, but return to it from above.

The path that the report defines as the best remaining option is “overshoot, peak, and decline”: first limiting the rate of increase and the height of the peak, and then reducing greenhouse gas concentrations to bring the temperature back down. This is not a justification for overshooting or replacing the Paris target, but a strategy for minimizing damage in a situation where the crossing has become very close.

The first stage requires immediate and deep cuts in carbon dioxide emissions, while simultaneously rapidly reducing Methane and other greenhouse gases. Methane has a relatively short life in the atmosphere, so reducing it could affect the rate of warming in the near term. At the same time, it is necessary to stop the expansion of carbon-intensive infrastructure and accelerate the transition from fossil fuels to renewable energy and more efficient systems.

In the second phase, as warming approaches its peak, it will be necessary to reach at least net-zero carbon dioxide and greatly strengthen adaptation. Net-zero means that remaining emissions are balanced by removing an equal amount of carbon from the atmosphere. But according to the report, net-zero is a milestone, not an end point.

For global temperatures to drop noticeably, net negative emissions would be necessary: removing more carbon dioxide from the air than is emitted. Even reaching net zero for all greenhouse gases would, according to the analysis, lead to a very slow decline of about 0.3 degrees per century. A real return to below 1.5 degrees would therefore require a sustained effort beyond net zero.

Carbon sequestration is no substitute for reducing emissions

The report examines natural and technological methods for removing carbon dioxide: afforestation, ecosystem restoration and forest management, along with direct air capture, bioenergy with carbon capture and storage, and other methods. But its authors warn against relying on future carbon removal as an excuse to postpone reducing emissions now.

To reduce the temperature by just a tenth of a degree, it would be necessary to remove about 220 billion tons of carbon dioxide from the atmosphere in addition to emissions. By comparison, even if residual carbon emissions were to be reduced to zero, at the current rate of afforestation and forest management, it would take more than a century to achieve such cooling. Even optimistic scenarios for expanding carbon removal are not expected to change more than a few tenths of a degree during this century.

Returning to below 1.5 degrees within the century remains physically possible only if peak warming remains significantly below 2 degrees, residual emissions are rapidly reduced, and carbon removal capacity is responsibly expanded. Beyond a peak of about 1.8 degrees, returning within the century becomes increasingly difficult.

Even a drop in temperature doesn't set the world back.

Average temperatures may fall after a period of negative emissions, but the climate system is not a button that can be turned back. Sea levels will continue to rise for a long time due to warming oceans and melting ice. Extinct species will not return, ecosystems may be permanently altered, and communities forced to evacuate from coasts or areas that have become difficult to live in may not be able to return.

The report therefore places adaptation alongside emissions reductions, not after them. Countries will need to prepare health systems for heat waves, protect coastlines and infrastructure, adapt agriculture and water management, and establish disaster warning and financing mechanisms. As warming increases, adaptation becomes more expensive and in some places reaches physical and social limits.

Alongside the scientific and technological challenge is the question of justice. Countries that have emitted more throughout history and that have greater economic and technological capacity have, according to the report, a responsibility to act more quickly and assist with financing, technology transfer, and adaptation in vulnerable countries. Without such cooperation, even a climate plan that is possible on paper is likely to fail politically and socially.

Three steps, one task

UNEP divides the response into three overlapping phases. The immediate phase requires sharp emissions reductions and expanded adaptation. During the peak period of warming, decarbonization must be completed, reaching at least net zero and preserving human and natural systems. The decline phase requires net negative emissions over time and continued adaptation to the ongoing damage.

The report does not offer a single, definitive forecast, nor a definitive policy plan. It presents the limits of what is possible and the cost of delay. The message heading into COP31 is that the imminent crossing of the 1.5 degree threshold is no reason to give up, but it also does not allow for business as usual. The road back will be slow, expensive and incomplete; every ton not emitted and every tenth of a degree avoided will still determine the extent of the damage for generations.

Questions and Answers

Has the world already passed the 1.5 degree mark?

In some years, global temperatures could already be more than 1.5 degrees above the pre-industrial average. But the Paris target refers to long-term warming, not a single year. According to the UNEP report, a sustained crossing of this level is expected within a few years.

Does crossing the threshold mean that the Paris target is meaningless?

No. The difference between a small, short-term deviation and prolonged warming approaching 2 degrees is very large. The 1.5 degree target continues to serve as a benchmark for reducing risk, even if it becomes necessary to return to it after a temporary deviation.

Why is net zero not enough to lower the temperature?

Net-zero roughly stabilizes the amount of carbon dioxide in the atmosphere and therefore stops most of the additional warming, but does not remove the excess carbon that has already accumulated. For significant cooling, net negative emissions are required over time.

Can planting trees bring the world back below 1.5 degrees?

Restoring forests and ecosystems is essential, but its scope is limited and it is not a substitute for stopping emissions. According to the report, even a reduction of one-tenth of a degree requires the net removal of about 220 billion tons of carbon dioxide, far beyond the current rate of removal.

What is the most important thing that can be done right now?

Rapidly and deeply reduce emissions of carbon dioxide, methane, and other greenhouse gases, while investing in adaptation. The lower and shorter the warming peak, the less damage will be done and the greater the possibility of returning temperatures to below 1.5 degrees.