The UN 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.
UNEP, in a new report titled “Limiting Overshoot”, 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.
In a report released on Wednesday, UNEP said an “overshoot, peak and decline” pathway is the best option to limit both the extent and duration of temperatures exceeding the Paris Agreement threshold.
Under this pathway, the report said 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 risks.
The risks, the study showed, included 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 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.
It warned that there would be limits to how effectively societies could adapt, particularly if peak warming was not minimised.
It called for mitigation and adaptation 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, however, stressed 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, the report 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 livelihoods.
The report therefore urged immediate action, warning that delaying further could make a safe return to the Paris Agreement temperature goal increasingly difficult.
In his reaction, 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.
On her part, 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.