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UNEP: World set to cross 1.5°C global warming, but can still limit, adapt to and return from higher temperatures
- Report puts best-case scenario peak temperature rise at 1.8°C; others suggest over 2°C
- Above 1.5°C, climate impacts and risks of tipping points intensify with every fraction of a degree
- ‘Overshoot, peak and decline’ pathway best remaining option to help vulnerable nations and communities cope and return to below 1.5°C
Nairobi, 2 September 2026 – Global temperature rise is set to cross 1.5°C, likely within the next few years, pushing climate risks and impacts to increasingly dangerous heights, but it is still possible to bring temperatures down and achieve global goals in the Paris Agreement, according to a new UN Environment Programme (UNEP) report.
The report, Limiting Overshoot, identifies an ‘overshoot, peak, and decline’ pathway as the best remaining option to minimize the magnitude and duration of this overshoot and try to return to below 1.5°C as soon as possible.
"Ten years ago in Paris, leaders pledged to limit temperature rise to 1.5 degrees Celsius, the threshold scientists say is critical to avoiding the worst climate devastation. The latest report from the UN Environment Programme delivers a stark warning: The world is failing to keep that promise. We are set to breach the 1.5-degree limit within the next few years," UN Secretary-General Antőnio Guterres said in a message on the report.
"We must make the overshoot as small and short as possible – limiting how high temperatures rise and how long they remain above 1.5. That demands an overshoot of ambition: Accelerating the phaseout of fossil fuels and the renewables revolution; Slashing methane pollution; And protecting land, forest and oceans.”
This pathway would minimize peak temperature rise through immediate and sustained cuts to greenhouse gas emissions, including methane, on the road to net-zero, and bring down temperatures through long-term net-negative emissions, with carefully governed Carbon Dioxide Removal (CDR) – the process of removing carbon from the air and storing it through afforestation or other means – an essential part of the mix.
At the same time, following the pathway would involve adaptation actions that reduce vulnerability to the current, expected and unexpected impacts of climate change on societies, communities and economies – although there will likely be limits to adaptation and irreversible impacts, especially if peak temperatures are not minimized.
The report stresses such a pathway would reduce risks and impacts, make adaptation less difficult and expensive, and increase the chances of lowering temperatures.
“There are no good outcomes if we remain above 1.5°C. Across the globe, extreme heatwaves are already proving that climate impacts will strike faster, hit harder, and last longer - costing more lives and causing deeper disruption,” said Inger Andersen, Executive Director of UNEP. “Now is the time we must double down on climate action. We can – and must – get on the right path. By cutting greenhouse gas emissions, strengthening resilience and adaptation, and ensuring exceedance of 1.5°C is as small and short as possible.”
Devastating impacts
The most optimistic scenario will see temperature rise peak at 1.8°C above pre-industrial levels, above the goal of limiting warming to 1.5°C set by the Paris Agreement. Most other scenarios predict higher peaks.
Above 1.5°C, risks and impacts will intensify with every extra fraction of a degree and every year. Anticipated impacts include intensified extreme weather, ecosystem loss, and submersion of Small Island Developing States and low-lying coastal cities. Severe damage to human health, food security, water supplies, nature, cities, infrastructure, and economies is expected.
The report warns that the likelihood of crossing irreversible tipping points increases with the magnitude and duration of higher temperatures. These include the destabilization of major ice sheets, degradation of the Amazon rainforest and disruption of the Atlantic Meridional Overturning Circulation (the system of currents that moves warm surface water north and cold deep water south, playing a key role in regulating the climate). Some impacts may emerge abruptly, while others will accumulate over time.
Considering the scale of the risks and the co-benefits of climate interventions such as a rapid transition away from fossil fuels to renewable energy – improving air quality and public health, lowering energy costs and increasing access to electricity – the report urges accelerated, collective and global action to get on an overshoot, peak and decline pathway. How quickly and strongly this action happens will define the shape and trajectory of the pathway.
Conditions for success
Strong political will and multilateralism, effective policies, inclusive governance, and finance are all important enabling conditions for action – and equity and justice must underpin all responses. Countries with greater responsibility for climate change should act the fastest with the greatest ambition.
The report also finds that mitigation and adaptation, which are mutually reinforcing, must advance together, while being responsive to emerging risks. Interventions that achieve both mitigation and adaptation goals – such as nature-based cooling – should be prioritized. Adaptation set up now forms the foundation for efforts to come, but it must become transformational and responsive to evolving non-linear and abruptly arising risks – including those that will harm mitigation efforts.
The report emphasizes that net-zero is a milestone towards net-negative, with CDR needed in addition to, not instead of, sustained reductions in greenhouse gas emissions. However, CDR can only contribute credibly to a return below 1.5°C if peak warming remains well below 2°C and all residual emissions are reduced. Strong governance frameworks for CDR will be critical to allow responsible deployment and manage implications for environmental integrity, equity, scale.
Responding to a changed future
Years of inaction mean that even if a return to below 1.5°C is secured, irreversible losses and permanently changed conditions are certain. Many communities may be forced to relocate or change livelihoods, while societies will face the challenge of re-adjustment. This raises issues of justice, power, and political legitimacy, which will require new, inclusive governance arrangements to resolve difficult issues.
This report is a reminder that an overshoot, peak and decline pathway is a next generation climate frontier, but one which cannot be left unattended to for the next generation to tackle. Immediate action is required for such a pathway to remain possible.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Martina Linnenluecke is the Director of the Centre for Climate Risk and Resilience at UTS Business School and is a Professor of Environmental Finance
"The prospect of a 1.5 degrees overshoot substantially changes the climate risks for businesses, investors and governments. Overshoot is not a simple temporary departure from a temperature target, but a lasting shift that will mean operating under higher physical risks and much greater uncertainty, potentially for decades. This will place substantial pressures on infrastructure and supply chains.
For business, adaptation will become a strategic and financial issue and will no longer be a peripheral sustainability concern. Research undertaken by the Centre for Climate Risk and Resilience examines how critical infrastructure systems that many businesses rely on can be strengthened in light of the anticipated changes. Our findings show that significant adaptation investments and collaborative action will be required.
Businesses will have to consider if the assets and investment decisions that were designed around historical climate conditions are still fit for purpose. Mitigation will remain a high priority to avoid future warming. Investment increasingly needs to be anticipatory, flexible and capable of being revised as conditions change. The decisions we take now will materially shape both the severity of future climate risks and our capacity to manage them."
Andy Reisinger is an Honorary Associate Professor at Australian National University, and lead author of the report's chapter on mitigation
"This is the first report by a United Nations agency that says unambiguously that we will cross 1.5°C in the next few years, given insufficient actions to reduce greenhouse gas emissions.
"It’s a wake-up call to governments and industry to confront this reality, but not a reason to give up on 1.5°C as a long-term goal. The failure to reduce emissions has increasingly dangerous and disruptive consequences around the world, in the form of significant heat-related deaths, flooding, disruption to food production and economies, ice loss in mountain and polar regions, and repeated mass bleaching of coral reefs. These losses and damages will escalate further and often land hardest on the shoulders of those least responsible for those mounting risks.
"Adapting to climate change clearly must become a greater focus, but there are limits to how much adaptation can prevent. At the same time as dealing with increasing climate-related disasters, the world therefore needs to accelerate efforts to reduce emissions of all greenhouse gases and reach at least net-zero CO2 emissions globally by mid-century.
"We know how to and can still do this. This would halt global warming as close to 1.5°C as is still possible and keep at least some of the risks manageable. More importantly, the report emphasizes that the long-term goal remains to return to 1.5°C, as indeed governments reaffirmed only last year. Bringing global warming back down will be challenging and complex but is possible, provided that governments and industry begin to think and act beyond current net-zero targets.
"As the report says, this is by no means an acceptable or preferred path to take, but is by now simply the best remaining option."
Scientia Professor Andy Pitman is Director of the ARC Centre of Excellence for Climate Extremes at The University of New South Wales
"This is a welcome report by the UNEP that states what has been widely known within the climate science community; limiting warming to less than 1.5 degrees was always very optimistic and is no longer possible. The statement that the most optimistic scenario is now 1.8 degrees is reasonable, but very optimistic. Avoiding severe impacts from global warming should be the goal of every government and raising ambitions to rapidly reduce emissions is urgent. Very few countries have this ambition and consequently the Paris Agreement’s ceiling of limiting warming to well below 2 degrees is unlikely to be achieved."
Dr Tom Mortlock is Head of Climate Analytics Asia-Pacific at Aon, and Adjunct Fellow in the Climate Change Research Centre at UNSW
"The UNEP report highlights the near inevitability of the world surpassing the 1.5-degree threshold set in Paris a decade ago. Because of the loose definition of what the 1.5-degree target actually is, we won’t know we’ve surpassed it until it has occurred. However, given the Earth has already warmed by 1.4 degrees since the pre-industrial era, and we are going into one of the biggest El Niño events on record, there is a high likelihood that 2027 will be the warmest year on record.
It’s worth remembering that 1.5 degrees is not an arbitrary line in the sand. It is linked to crucial Earth system tipping points, such as mass coral bleaching and ice sheet instabilities, from which there is no natural reversal within human timeframes. Surpassing 1.5 degrees will introduce more non-linear and step-change factors into already increasing and complex physical climate risks.
The report underscores the need for overshoot and reversal, but to do this, we need to significantly scale up and evolve carbon dioxide removal technologies. This will require the crowding in of private and public capital in a way we have not been able to achieve to date.
In the meantime, resilience is key. There needs to be a refocus of disaster spending on risk reduction rather than post-event clean-up.
In Australia, we have one of the highest natural catastrophe losses per capita in the world, and this has been increasing decade on decade since the 1970s. The main cause has been exposure growth in increasingly hazardous areas, underscoring the importance of resilience by design for Australia's future in a 1.5-degree-plus world."
Peter Newman is the Professor of Sustainability at Curtin University
"This report prescribes why the future will include many more cataclysmic climate-induced disasters like Nepal. We are now leaving what is known as the ‘safe operating space’ where cities and agriculture were able to develop over the last 10,000 years.
We are rapidly adopting renewable energy, and it is all working well, so we need to accelerate its adoption. This requires a similarly rapid decline in fossil fuels. There are no roles for fossil fuels in the transition now. The next phase of climate action requires our complete commitment to removing all fossil fuels.
The role of science and technology has been to show us how to do this transition, and we now have the answers being demonstrated with strong economic benefits and opportunities.
Australia needs to take their leadership role in COP 31, and our best demonstrations of the transition, onto the world stage and provide global leadership in this critical period in history."
Malte Meinshausen is a Professor of Climate Science at the University of Melbourne and Climate Science Director at Climate Resource, Melbourne, Australia
"Thanks to the global energy transition towards renewables, we managed to avoid the world's worst-case scenarios in recent years. At the same time, the mitigation actions were not decisive enough: we also lost our best-case scenario. That best-case scenario was to overshoot 1.5C only slightly, up to 1.6C. The new reality is that decisive action can now avoid peak warming at best to 1.7C or 1.8C, before bringing it down to 1.5C again.
Compared with our options five years ago, the new paths are more costly, come with more floods, fires and droughts and the need to draw, at some point, carbon emissions out of the atmosphere that we are currently emitting. Acting now is still the cheaper option than not acting now, as we can still achieve 1.5C in the longer term.
Having exceeded the speed limit means we have to step on the brakes, not to abolish the speed limit. The speed limit is 1.5C - and we are now definitely on the course of temporarily at least overshooting it."
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