The world is likely to surpass the critical 1.5°C global warming threshold within the next few years, increasing the risks of extreme weather, ecosystem loss and irreversible climate impacts, according to a new report by the United Nations Environment Programme (UNEP).
The report, titled Limiting Overshoot, says the best remaining option is to follow an “overshoot, peak and decline” pathway—allowing temperatures to temporarily exceed 1.5°C before bringing them down below the threshold as quickly as possible.
According to UNEP, even the most optimistic scenario would see global temperatures peak at around 1.8°C above pre-industrial levels, while several other projections indicate warming could exceed 2°C.
The report warns that climate-related risks will intensify with every additional fraction of a degree above 1.5°C. These include more severe heatwaves, floods, wildfires and storms, as well as growing threats to food and water security, human health, infrastructure and economies.
Low-lying coastal areas and Small Island Developing States are expected to face particularly severe consequences, including the possible loss or submergence of inhabited areas.
UNEP also highlighted the increasing risk of climate tipping points, including the destabilisation of major ice sheets, degradation of the Amazon rainforest and disruption of the Atlantic Meridional Overturning Circulation, a major ocean-current system that helps regulate the global climate.
UN Secretary-General António Guterres said recent extreme weather events should be treated as a warning of what lies ahead and called for the overshoot above 1.5°C to be kept “as small and short as possible.”
The report recommends immediate and sustained reductions in greenhouse-gas emissions, including methane, alongside a rapid transition away from fossil fuels. It also identifies carefully governed carbon dioxide removal as an important tool for eventually reducing atmospheric carbon and bringing global temperatures down.
However, UNEP stressed that carbon removal cannot replace emissions cuts. Net-zero emissions should be viewed as a milestone toward net-negative emissions, while carbon dioxide removal should be used alongside—not instead of—deep reductions in greenhouse-gas emissions.
Adaptation must also progress alongside mitigation, the report said. Governments and communities need to strengthen resilience against both expected and unexpected climate impacts. Nature-based measures that can simultaneously support climate mitigation and adaptation should receive greater attention.
Inger Andersen, Executive Director of UNEP, urged governments to accelerate climate action, warning that climate impacts are already becoming more severe.
The report further emphasises the importance of political commitment, effective policies, international cooperation, climate finance and inclusive governance. It calls for greater responsibility from countries that have contributed most to historical greenhouse-gas emissions.
Even if global temperatures eventually return below 1.5°C, UNEP cautions that some losses will be irreversible. Communities could be forced to relocate, livelihoods may change and governments may face difficult questions involving climate justice, political legitimacy and equitable distribution of resources.
UNEP therefore describes the “overshoot, peak and decline” approach as a new frontier in climate action but stresses that it must begin immediately rather than being left for future generations.