Global temperature rise is on course to exceed 1.5°C above pre-industrial levels within the next few years, pushing climate risks and impacts to increasingly dangerous heights, a first-of-its-kind report from the United Nations Environment Programme (UNEP) has warned.

Despite the bleak outlook – compounded by a summer of heatwaves, drought, flash floods, and global average sea surface temperature increases – it remains possible to bring rising temperatures back down to safer levels and achieve the goals of the Paris Agreement.

The new report, Limiting Overshoot sets out an “overshoot, peak, and decline” pathway as the best remaining option to minimise the magnitude and duration of the coming breach, and the return to 1.5°C warming as soon 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°C as small and short as possible. That demands an overshoot of ambition,” said UN Secretary-General, Antonio Guterres.

The pathway laid out in the report would work to minimise peak temperature rise through immediate and sustained cuts to greenhouse gas emissions, including methane, on the road to net-zero, and would bring temperatures back down through long-term net-negative emissions. It adds that carefully governed Carbon Dioxide Removal (CDR) – the process of removing carbon from the air and storing it – would be an essential part of the mix.

Alongside this, it calls for adaptation measures to reduce vulnerability to current expected and unexpected climate impacts. The report is clear, however, that there will likely be limits to adaptation and irreversible impacts, particularly if peak temperatures aren’t minimised.

Following this pathway nevertheless would still reduce risk, ease the cost and difficulty of adapting, and improve the odds of bringing temperatures back down.

“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,” said Inger Andersen, Executive Director of UNEP.

“Now is the time we must double down on climate action. We can – and must – get on the right path. By cutting greenhouse gas emissions, strengthening resilience and adaptation, and ensuring exceedance of 1.5°C is as small and short as possible.”

Even in the most optimistic scenario modelled, temperature rise is projected to peak at 1.8°C above pre-industrial levels – already above the Paris Agreement’s 1.5°C goal. Most other scenarios predict higher peaks still. 

Above 1.5°C, risks intensify with every extra fraction of a degree and every additional year spent there. The report anticipates intensified extreme weather, ecosystem loss, and the submersion of Small Island Developing States and low-lying coastal cities, alongside severe damage to human health, food security, water supplies, nature, cities, infrastructure, and economies.

The likelihood of crossing irreversible tipping points rises with both the magnitude and the duration of higher temperatures. These include the destabilisation of major ice sheets, degradation of the Amazon rainforest, and disruption of the Atlantic Meridional Overturning Circulation (AMOC) – the system of currents that moves warm surface water north and cold deep water south, and plays a key role in regulating the global climate. 

Given that a rapid shift from fossil fuels to renewable energy would also improve air quality and public health as well as lower energy costs and expand access to electricity, the report calls for accelerated, collective, global action to move onto an overshoot, peak, and decline pathway.

The report also argues that net zero is a milestone on the way to net-negative and to achieve this, CDR will be a critical element to sustained emissions cuts. It can only credibly contribute to a return below 1.5°C if peak warming stays well below 2°C and all residual emissions are reduced. Strong governance of CDR will therefore be essential to manage its implications for environmental integrity, equity, and scale.

Irreversible losses and permanently changed conditions are now certain. Many communities may be forced to relocate or change livelihoods while societies more broadly will face the challenge of adjusting, the report states. 

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