The United Nations Environment Programme (UNEP) has warned that global temperatures are likely to cross the critical 1.5°C warming threshold within the next few years, exposing the world to intensifying climate risks.
In a new report titled “Limiting Overshoot”, UNEP said the world could still return to below 1.5°C, but only if countries rapidly cut greenhouse gas emissions, strengthen adaptation and achieve net-negative emissions.
The report, released on Wednesday, said an “overshoot, peak and decline” pathway was the best option for limiting both the extent and duration of temperatures exceeding the Paris Agreement threshold.
Under this pathway, global warming would first exceed 1.5°C, peak and subsequently decline as emissions fall to net zero and then become net negative through sustained carbon dioxide removal.
According to the study, the most optimistic scenario would see warming peak at about 1.8°C above pre-industrial levels, while most other scenarios project higher peaks.
The report noted that every additional fraction of a degree and every year spent above 1.5°C would increase climate risks, including extreme weather, ecosystem loss and severe damage to human health, food security, water supplies, infrastructure and economies.
It warned that higher and prolonged warming would also increase the likelihood of triggering irreversible tipping points, including the destabilisation of major ice sheets, degradation of the Amazon rainforest and disruption of the Atlantic Meridional Overturning Circulation.
The report said adaptation would remain essential because some climate impacts were already unavoidable. However, it warned that societies would face limits in how effectively they could adapt, particularly if peak warming was not minimised.
It called for mitigation and adaptation efforts to advance together, prioritising interventions that can achieve both, including nature-based cooling.
The report also identified carefully governed carbon dioxide removal (CDR), including afforestation and other methods of removing carbon from the atmosphere, as essential to eventually bringing temperatures below 1.5°C.
It stressed, however, that CDR must supplement, not replace, deep and sustained reductions in greenhouse gas emissions.
The study identified strong political commitment, international cooperation, effective policies, inclusive governance, climate finance and equity as critical conditions for success.
Countries with greater responsibility for climate change, it said, should act fastest and with the greatest ambition.
It cautioned that even if global temperatures eventually return below 1.5°C, years of warming would leave irreversible losses and permanently altered conditions, potentially forcing communities to relocate or change their livelihoods.
The report therefore urged immediate action, warning that further delays could make a safe return to the Paris Agreement temperature goal increasingly difficult.
Reacting to the report, UN Secretary-General António Guterres said the world must ensure that any overshoot above 1.5°C is as small and short-lived as possible.
“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.
UNEP Executive Director Inger Andersen said climate impacts were already accelerating as temperatures rose.
“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 urged governments to intensify emissions cuts, strengthen resilience and adaptation, and minimise the duration of warming above the threshold.
Australian Climate Change and Energy Minister Chris Bowen, President of Negotiations for COP31, said every fraction of warming mattered, particularly for Pacific communities on the frontline of climate change.
He said COP31 should translate ambition into practical action by accelerating renewable energy deployment, reducing dependence on fossil fuels and strengthening international climate cooperation.
Murat Kurum, COP31 President-Designate, said exceeding 1.5°C should not become a new climate destination.
“The Overshoot Report makes clear that exceeding 1.5°C should not be seen as a new destination, but as a pathway we must urgently work to minimise and reverse,” Kurum said.
