UNEP Releases Report on Limiting Temperature Overshoot
On September 2, the United Nations Environment Programme (UNEP) released *Limiting Overshoot: Responding to Warming Above 1.5°C and Exploring Pathways Back Down*, stating for the first time that, owing to insufficient progress in global greenhouse gas (GHG) emission reductions, the global multi-year average warming level will exceed 1.5°C within the coming years. The focus of international climate governance therefore needs to shift from "avoiding overshoot" to "limiting the magnitude and duration of overshoot and bringing temperatures back down." Key points of the report are as follows.
Global temperature control situation is more severe; climate risks may be released at an accelerating pace
The report notes that in 2024, the global annual average temperature exceeded 1.5°C above pre-industrial levels for the first time in a single year. Even if global emissions are halved over the next decade and net-zero emissions are achieved by mid-century, peak warming could still reach around 1.8°C under the most optimistic scenario. Based on current national emission reduction pledges, global warming is projected to reach 2.3–2.5°C by the end of the century; if current policies are maintained, warming could reach 2.8°C. Under the most optimistic scenario, global warming would peak at 1.8°C above pre-industrial levels—higher than the Paris Agreement's goal of limiting warming to within 1.5°C. Most other scenarios project even higher peak warming. Once warming exceeds 1.5°C, the risks of climate impacts and the crossing of tipping points increase with each additional 0.1°C of warming. Projected impacts include intensifying extreme weather, loss of ecosystems, and the risk of inundation for small island developing states and low-lying coastal cities; human health, food security, water supply, nature, cities, infrastructure and economies are also expected to be severely affected. The report warns that as warming grows in magnitude and duration, the likelihood of crossing irreversible tipping points rises. These tipping points include destabilisation of major ice sheets, degradation of the Amazon rainforest, and disruption of the Atlantic Meridional Overturning Circulation (AMOC), which transports warm surface water northward and cold deep water southward, playing a critical role in climate regulation. Some impacts may occur suddenly, while others may accumulate gradually over time.
The "overshoot–peak–decline" pathway becomes a realistic option
The report states that the "overshoot, peak and decline" pathway is currently the best feasible option for limiting the magnitude and duration of temperature overshoot and for bringing warming back down to below 1.5°C as early as possible. To potentially lower peak warming, this pathway requires immediate and sustained cuts in greenhouse gas emissions—including methane—on the road to net zero, and driving temperatures down through long-term net-negative emissions. At the same time, carbon dioxide removal (CDR) undertaken under a prudent governance framework, with sequestration through reforestation or other means, will also be an indispensable component of this comprehensive approach.
Mitigation, adaptation and equitable governance need to be strengthened in parallel
At the same time, following this pathway also requires adaptation actions to reduce the vulnerability of societies, communities and economies to the current, projected and unexpected impacts of climate change. Although adaptation capacity has its limits and irreversible impacts may occur—especially if peak warming is not limited as much as possible—the report emphasises that this pathway can reduce related risks and impacts, lower the difficulty and cost of adaptation, and increase the likelihood of bringing temperatures back down. The report stresses that the "overshoot, peak and decline" pathway will be a major climate issue facing the next generation, but this must not be an excuse to shelve the problem and leave it for future generations to solve. To ensure this pathway remains viable, action must be taken immediately.
Source：https://mp.weixin.qq.com/s/vGUHpX0FhOCZMR3MvK0efg