UN report urges immediate action on overshoot as world set to cross 1.5°C

The report, Limiting Overshoot, identifies an ‘overshoot, peak, and decline’ pathway as the best remaining option to limit warming, reduce harm to vulnerable communities, and return to below 1.5°C as soon as possible.

This pathway would minimize peak temperature rise through immediate and sustained cuts to greenhouse gas emissions, including methane, on the road to net-zero, and bring down temperatures through long-term net-negative emissions. Carefully governed Carbon Dioxide Removal (CDR) – the process of removing carbon from the air and storing it durably – needs to be part of the mix, in addition to, rather than instead of, sustained emissions reductions.

Adaptation will also be essential, although there are limits to how far communities and ecosystems can adapt as warming increases.

“Insufficient emission cuts mean we are set to exceed 1.5°C. This summer's extremes at not even 1.5°C show what's at stake. We need to win the race to net zero carbon emissions, massively upscale adaptation, address the loss and damage caused, and build up capacity for long-term warming reversal. Dealing with an overshoot world demands everything, everywhere, all at once,” says IIASA Integrated Climate Impacts Research Group Leader, Carl Schleussner, who was a lead author of Chapter 1 of the report and a member of the Scientific Advisory Board.

Apart from Schleussner, the following IIASA authors contributed to the report: Reinhard Mechler, lead author, Chapter 2 and member of the Scientific Advisory Board; Shonali Pachauri, contributing author, Chapter 3; Gaurav Ganti, contributing author, Chapter 3; and Marina Andrijevic, contributing author, Chapter 4.

Devastating impacts

The most optimistic scenarios still available to us would see temperature rise peak at 1.8°C above pre-industrial levels, while most other scenarios predict peaks above 2°C.

Above 1.5°C, risks and impacts will intensify with every fraction of a degree, including extreme weather, ecosystem loss, submersion of Small Island Developing States and low-lying coastal cities, and damage to health, food and water security, infrastructure, and economies.

The likelihood of crossing irreversible tipping points increases with the magnitude and duration of higher temperatures. These include the destabilization of major ice sheets, degradation of the Amazon rainforest, and disruption of the Atlantic Meridional Overturning Circulation – the system of currents that plays a key role in regulating the climate. Some impacts may emerge abruptly, while others will accumulate over time.

Conditions for success

Strong political will and multilateralism, effective policies, inclusive governance and finance are key, underpinned by equity and justice. Countries with greater responsibility for climate change should act with the greatest ambition, while mitigation and adaptation must advance together.

The report emphasizes that net-zero is a milestone towards net-negative emissions, with CDR needed in addition to, not instead of, sustained emissions reductions. CDR can only contribute credibly to a return below 1.5°C if peak warming remains well below 2°C and residual emissions are reduced. Strong governance frameworks will be critical to ensure responsible deployment and manage implications for environmental integrity, equity and scale.

IIASA is a global leader on Overshoot Science

In 2025, IIASA hosted the first-ever Overshoot Conference. The implications of temporarily exceeding 1.5°C – and the choices needed to limit peak warming, adapt to unavoidable impacts, and bring temperatures back down – will also be at the center of the Overshoot Conference 2026, which will be co-hosted by IIASA and Tsinghua University in Beijing, China, in November 2026. The conference will again bring together leading researchers, policymakers, innovators, and communicators to advance the global dialogue on overshoot pathways and responses. The deadline for the submission of scientific contributions to the conference closes on 6 September. 

Together with its partners, IIASA has also produced a podcast series exploring the challenges, trade-offs, and opportunities involved in tackling overshoot from multiple perspectives. Across nine episodes, leading experts share insights from their fields, offering a preview of the key themes that will shape discussions at the conference.

Visit the official conference website for more information on the 2026 Overshoot Conference.

Read the full report.