The United Nations has warned that the world is on course to exceed the 1.5°C global warming threshold within the next few years, exposing communities and ecosystems to increasingly severe climate risks, but urgent action could still limit the extent of warming and eventually bring global temperatures back below the threshold.
This is according to a new report by the United Nations Environment Programme (UNEP), titled Limiting Overshoot: Navigating Exceedance, which identifies an “overshoot, peak and decline” pathway as the best remaining option for reducing the scale and duration of warming beyond 1.5°C.
The report calls for immediate and sustained cuts in greenhouse gas emissions, including methane, alongside efforts to achieve net-zero emissions. It also highlights the need for carefully governed carbon dioxide removal (CDR) to help reduce atmospheric carbon concentrations and support a long-term return to lower temperatures.
UN Secretary-General António Guterres said the increasing frequency of extreme weather events should serve as a warning of the consequences of continued inaction.
“This summer’s scorching heat, raging wildfires and deadly floods are a warning of what lies ahead. We must make the overshoot above 1.5 degrees as small and short as possible. That demands an overshoot of ambition,” Guterres said.
According to UNEP, the most optimistic pathway would see global temperatures peak at around 1.8°C above pre-industrial levels before beginning to decline. Other pathways could result in significantly higher levels of warming.
The report warns that every additional fraction of a degree above 1.5°C, as well as the length of time temperatures remain elevated, will increase climate-related risks and impacts.
These include more intense heatwaves, floods, wildfires and other extreme weather events, alongside ecosystem degradation and growing threats to food and water security, human health, infrastructure and economies.
Small Island Developing States and low-lying coastal cities are also expected to face heightened risks from sea-level rise and other climate impacts.
UNEP Executive Director Inger Andersen said there would be no favourable outcome from allowing global temperatures to remain above the 1.5°C threshold.
“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,” Andersen said.
She called for stronger climate action through emissions reductions, improved resilience and adaptation, and efforts to ensure that any exceedance of 1.5°C is as limited and brief as possible.
Risks of irreversible climate change
The UNEP report also highlights concerns over climate tipping points, noting that the likelihood of irreversible changes increases as temperatures rise and remain elevated for longer periods.
Potential tipping points include the destabilisation of major ice sheets, degradation of the Amazon rainforest and disruption of the Atlantic Meridional Overturning Circulation, a system of ocean currents that plays an important role in regulating the global climate.
While some impacts could occur suddenly, others could build progressively over time, making early action critical.
UNEP therefore recommends an accelerated transition away from fossil fuels towards renewable energy. Beyond reducing emissions, the transition could deliver additional benefits, including improved air quality and public health, lower energy costs and increased access to electricity.
Adaptation must accompany mitigation
The report stresses that mitigation and adaptation must progress together as countries prepare for a warmer and more uncertain climate.
It recommends prioritising measures that can deliver both mitigation and adaptation benefits, including nature-based cooling solutions.
However, UNEP cautions that adaptation has limits. Higher peak temperatures could make some impacts increasingly difficult or impossible to manage, while adaptation measures could become more expensive as climate risks intensify.
The report calls for adaptation efforts to become more transformational and responsive to emerging and potentially abrupt risks.
Carbon removal critical but not a substitute for emissions cuts
UNEP also emphasises the growing role of carbon dioxide removal in achieving a return to below 1.5°C.
However, the report makes clear that CDR must complement—not replace—deep and sustained reductions in greenhouse gas emissions.
It notes that carbon removal can credibly contribute to a return below 1.5°C only if peak warming remains well below 2°C and remaining emissions are substantially reduced.
Strong governance will therefore be necessary to ensure that carbon removal is deployed responsibly while protecting environmental integrity and addressing issues of equity and scale.
Climate action must be immediate
UNEP said years of delayed climate action mean that even if the world succeeds in returning temperatures below 1.5°C, some irreversible losses and permanently altered conditions will remain.
Some communities could be forced to relocate, while others may have to change their livelihoods as societies adjust to changed environmental conditions.
The report therefore highlights the importance of equity, justice, inclusive governance, climate finance and international cooperation in managing the consequences of climate change.
It argues that countries with the greatest historical responsibility for climate change should move fastest and demonstrate the highest level of ambition.
With COP31 approaching, Australian Minister for Climate Change and Energy and President of Negotiations for COP31, Chris Bowen, said every fraction of a degree matters, particularly for vulnerable Pacific communities.
“Every fraction of a degree of warming above 1.5 leads to increasing and increasingly severe climate impacts, with our Pacific family standing on the frontlines,” Bowen said.
He called for faster renewable energy deployment, reduced dependence on fossil fuels and stronger international climate cooperation.
COP31 President-Designate H.E. Murat Kurum similarly urged countries to translate climate ambition into concrete action, including accelerating electrification, reducing methane emissions, strengthening urban climate resilience and protecting marine and coastal ecosystems.
The UNEP report concludes that an “overshoot, peak and decline” pathway remains possible, but the window for achieving it is narrowing.
How quickly governments cut emissions, strengthen adaptation and deploy responsible carbon removal will ultimately determine how high global temperatures rise, how long they remain elevated and whether the world can eventually return to the 1.5°C goal.
