UNEP Releases Report on Limiting Global Temperature Overshoot
On 2 September, the United Nations Environment Programme (UNEP) released Limiting Overshoot: Responding to a World Exceeding 1.5°C and Exploring Pathways for Temperature Decline. The report states that, given insufficient progress in reducing global greenhouse gas emissions, the multi-year average global temperature is expected to exceed 1.5°C above pre-industrial levels within the next few years. Against this backdrop, the focus of international climate action will increasingly need to shift from solely avoiding an exceedance of 1.5°C to limiting the magnitude and duration of temperature overshoot and enabling global temperatures to decline thereafter.
Global Temperature Goals Face Growing Challenges as Climate Risks Intensify
The report notes that 2024 was the first individual calendar year in which the global average temperature exceeded 1.5°C above pre-industrial levels. Even under an optimistic scenario in which global emissions are halved over the next decade and net-zero emissions are achieved around mid-century, peak warming could still reach approximately 1.8°C.
Under countries’ current emissions-reduction pledges, global warming is projected to reach 2.3–2.5°C by the end of the century. If current policies continue, warming could reach approximately 2.8°C. Even in the most optimistic scenario assessed, global temperatures are projected to peak at around 1.8°C above pre-industrial levels, exceeding the 1.5°C temperature goal set out in the Paris Agreement. Most other scenarios result in still higher levels of peak warming.
Once warming exceeds 1.5°C, climate impacts and the risk of crossing critical tipping points are expected to increase with every additional 0.1°C of warming. Potential consequences include more severe extreme weather events, ecosystem loss, and increasing inundation risks for small island developing States and low-lying coastal cities. Human health, food security, water supplies, natural systems, cities, infrastructure and economies are also expected to face increasingly severe impacts.
The report warns that both the likelihood and severity of irreversible changes increase as the magnitude and duration of warming grow. Potential tipping points include destabilization of major ice sheets, degradation of the Amazon rainforest and disruption of the Atlantic Meridional Overturning Circulation (AMOC). The AMOC transports warm surface waters northward and cold deep waters southward and plays a critical role in regulating the global climate system. Some climate impacts could occur abruptly, while others may accumulate progressively over time.
An “Overshoot, Peak and Decline” Pathway Emerges as a Practical Option
The report identifies an “overshoot, peak and decline” pathway as the most feasible approach currently available for limiting both the magnitude and duration of temperature overshoot and bringing global temperatures back below 1.5°C as early as possible.
Minimizing peak warming under this pathway requires immediate and sustained reductions in greenhouse gas emissions, including methane, throughout the transition towards net-zero emissions. In the longer term, achieving sustained net-negative emissions would be necessary to drive global temperatures downward.
Carbon dioxide removal (CDR), implemented under robust and precautionary governance frameworks, would therefore form an integral part of the overall strategy. This could involve removing CO₂ from the atmosphere and storing it through afforestation and other durable carbon-removal and storage approaches.
Mitigation, Adaptation and Equitable Governance Must Advance in Parallel
Pursuing an overshoot, peak and decline pathway will also require stronger adaptation measures to reduce the vulnerability of societies, communities and economies to the current, anticipated and potentially unforeseen impacts of climate change.
Although adaptation has limits and some impacts may become irreversible—particularly if peak warming is not kept as low as possible—the report emphasizes that limiting the magnitude and duration of overshoot can reduce climate-related risks and impacts, lower the difficulty and cost of adaptation, and improve the prospects of eventually bringing global temperatures back below 1.5°C.
The report further stresses that an overshoot, peak and decline pathway is likely to become a defining climate challenge for the next generation. This, however, must not be interpreted as justification for postponing action or transferring responsibility to future generations. Keeping such a pathway feasible requires immediate and sustained action today.
Source：
[1]https://www.iea.org/reports/global-hydrogen-review-2026
[2]https://mp.weixin.qq.com/s/9CuBsBO8nYD6HfVfcsVshg