The world is set to cross the 1.5°C global warming threshold, likely within the next few years, exposing people and ecosystems to increasingly dangerous climate impacts, according to a new UN Environment Programme (UNEP) report. However, it says temperatures can still be brought back below the threshold and the goals of the Paris Agreement achieved.
The report, Limiting Overshoot, identifies an "overshoot, peak and decline" pathway as the best remaining option. Under this approach, temperatures would temporarily exceed 1.5°C, peak and then decline as countries rapidly cut greenhouse gas emissions and eventually remove more carbon dioxide from the atmosphere than they emit.
A Narrower Climate Path
"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," UN Secretary-General António Guterres said.
The pathway requires immediate and sustained reductions in greenhouse gas emissions, including methane, on the road to net-zero emissions. Carbon Dioxide Removal (CDR), which removes carbon from the atmosphere and stores it through afforestation or other means, would also be essential to eventually bring temperatures down.
Every Fraction Matters
Countries would simultaneously need to strengthen adaptation to reduce the vulnerability of societies, communities and economies. UNEP cautions that adaptation has limits and some impacts are likely to be irreversible, particularly if peak temperatures are not kept as low as possible.
"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," UNEP Executive Director Inger Andersen said.
Even Best Case Hits 1.8°C
Under the most optimistic scenario examined in the report, temperatures would peak at 1.8°C above pre-industrial levels, already higher than the Paris Agreement goal of limiting warming to 1.5°C. Most other scenarios foresee higher peaks.
Every additional fraction of a degree and every year spent above 1.5°C would intensify risks. Expected impacts include more severe extreme weather, ecosystem loss and the submersion of Small Island Developing States and low-lying coastal cities. Human health, food security, water supplies, infrastructure and economies would also face severe damage.
Tipping Points Loom
UNEP warns that the likelihood of crossing irreversible climate tipping points increases depending on how high temperatures rise and how long they remain elevated. Potential tipping points include destabilisation of major ice sheets and degradation of the Amazon rainforest.
The report also warns of possible disruption to the Atlantic Meridional Overturning Circulation, a system of ocean currents that plays an important role in regulating the climate. Some climate impacts could emerge abruptly, while others would accumulate over time.
Faster Shift From Fossil Fuels
The report calls for accelerated global action, pointing to the wider benefits of rapidly moving from fossil fuels to renewable energy. Such a transition could improve air quality and public health, lower energy costs and increase access to electricity.
Strong political will, multilateral cooperation, effective policies, inclusive governance and finance will be essential. Equity and justice must underpin climate responses, with countries bearing greater responsibility for climate change expected to act faster and with greater ambition.
Net-Zero Is Not The Finish Line
Mitigation and adaptation must advance together because they reinforce each other. UNEP recommends measures that can achieve both goals, including nature-based cooling, while warning that adaptation must respond to evolving and abruptly emerging risks.
The report says net-zero emissions should be viewed as a milestone towards net-negative emissions rather than the final destination. CDR would be required in addition to sustained cuts in greenhouse gas emissions, not as a substitute for them.
Carbon Removal Has Limits
Carbon removal can credibly help return temperatures below 1.5°C only if peak warming remains well below 2°C and residual emissions are reduced. Strong governance frameworks would also be needed to ensure responsible deployment and address environmental integrity, equity and scale.
Even successfully bringing warming back below 1.5°C would not undo all the damage. Years of insufficient action mean irreversible losses and permanently changed conditions are certain, according to the report.
Communities Face Lasting Change
Some communities could be forced to relocate or change their livelihoods, while societies would have to adjust to changed conditions. This would raise difficult questions involving justice, power and political legitimacy, requiring new and inclusive governance arrangements.
Australian Minister for Climate Change and Energy and COP31 President of Negotiations Chris Bowen said every fraction of warming above 1.5°C would bring increasingly severe impacts, with Pacific communities on the frontlines. He said the energy crisis had reinforced the need to reduce dependence on fossil fuels, accelerate the renewable energy transition and strengthen climate cooperation.
COP31 Faces A Crucial Test
Bowen said COP31 offered an opportunity to turn ambition into action, with Türkiye, Australia and the Pacific seeking a practical, solutions-focused conference.
COP31 President-Designate Murat Kurum said exceeding 1.5°C should not be treated as a new destination but as a situation that must urgently be minimised and reversed. Every year spent in overshoot, he said, increases climate risks and the possibility of irreversible losses.
Action Cannot Wait
Kurum called for faster global electrification, reductions in methane emissions from waste, stronger climate resilience in cities and greater protection for marine and coastal ecosystems. He said today's decisions would determine how high temperatures peak, how long they remain there and how safely the world can return to 1.5°C.
The report's central warning is stark: the world may no longer be deciding simply whether it crosses 1.5°C, but how far beyond that threshold it goes and for how long. UNEP says immediate action is required to keep an "overshoot, peak and decline" pathway, and an eventual return below 1.5°C, within reach.
