UNEP Warns of 1.5°C Overshoot as Climate Risks Rise

Global temperatures are on track to temporarily exceed 1.5°C above preindustrial levels in the coming years, increasing climate risks and impacts, according to a new United Nations Environment Programme report that identifies an overshoot, peak and decline pathway as the best available option to limit the magnitude and duration of the breach.

The report, Limiting Overshoot: Navigating Exceedance of 1.5°C and Pathways Towards Return, published states that exceeding 1.5°C is now widely considered inevitable under current policies and near-term emissions trajectories. Its most favorable scenario projects a temperature peak of around 1.8°C, while other scenarios reach higher levels.

The report argues that the size and duration of the temperature overshoot will determine the severity of impacts and the feasibility and cost of adaptation. Immediate and sustained greenhouse gas emissions cuts, including methane reductions, would be required to limit the peak, followed by long-term net-negative emissions to bring global temperatures back below 1.5°C.

“Ten years ago in Paris, world leaders committed to limiting the temperature rise to 1.5°C, the threshold scientists say is critical to avoid the worst impacts of climate change. The latest report from the United Nations Environment Programme (UNEP) delivers a stark warning: the world is not keeping that promise. We are on the brink of breaking the 1.5-degree limit in the coming years,” António Guterres, United Nations Secretary-General, said in a message on the report.

“We must make this overshoot as small and short as possible, limiting how much temperatures rise and how long they remain above 1.5. This requires, in turn, an ambition surge: accelerating the phase-out of fossil fuels and the renewable energy revolution; drastically reducing methane pollution; and protecting land, forests and oceans.” he noted.

Climate Impacts Increase With Every Fraction of a Degree

UNEP warns that risks will intensify with every additional fraction of a degree above 1.5°C and with every year temperatures remain elevated. Expected impacts include more severe extreme weather events, ecosystem losses and flooding affecting small island developing states and low-lying coastal cities, as well as damage to human health, food security, water supplies, infrastructure and economies.

The probability of crossing irreversible tipping points also increases with the magnitude and duration of higher temperatures. Potential consequences include the destabilization of major ice sheets, degradation of the Amazon rainforest and changes to the Atlantic Meridional Overturning Circulation, or AMOC, a system of ocean currents that plays an important role in regulating climate.

Some impacts could occur abruptly, while others would accumulate over time. UNEP therefore calls for mitigation and adaptation measures to advance together, particularly as higher warming could place limits on the ability of societies and ecosystems to adapt.

“No good outcomes come from remaining above 1.5°C. Around the world, extreme heatwaves are already showing that climate impacts will arrive faster, hit harder and last longer, costing more lives and causing deeper disruption,” said Inger Andersen, Executive Director, UNEP. 

Mexico Must Adapt to a Changing Climate

The projected temperature overshoot has direct implications for Mexico, where climate adaptation will increasingly need to account for conditions that differ from those of previous decades. The UNEP report warns that even if global temperatures eventually return below 1.5°C, some irreversible losses and permanent transformations will occur, requiring communities, governments and economies to adjust to a changed environmental context.

María Zorrilla, Researcher at the University Transdisciplinary Center for Sustainability (CENTRUS), Universidad Iberoamericana, said exceeding 1.5°C should not be interpreted as a failure of climate action, but as a reason to strengthen it. “It has not failed. In fact, it has to be stronger than ever,” Zorrilla said, calling for stronger and more binding international and national commitments to limit the impacts on communities and ecosystems.

“Our planet and our country and our place where we live […] will never be as it was before,” she said, referring to the loss of the relatively stable climate conditions associated with the Holocene.

The response will require mitigation and adaptation to advance together. UNEP identifies rapid emissions reductions, resilience-building and carbon dioxide removal (CDR) as components of the proposed “overshoot, peak and decline” pathway, while stressing that CDR must complement, rather than replace, sustained emissions cuts. Zorrilla similarly pointed to ecosystem restoration, soil and forest management, reforestation, changes in energy systems, reduced energy consumption, adaptation and measures addressing loss and damage.

For Mexico, these measures have implications across sectors, including urban planning and infrastructure, food production, water management, health and local economies. Zorrilla said climate considerations should therefore be incorporated into long-term decisions rather than treated as an isolated environmental issue. Universities, she added, can contribute through research, education and work with communities across disciplines.

She also identified health, food security, water availability and quality, ecosystems and mental health as areas where climate impacts need to be communicated in concrete terms, alongside information on potential responses. “Our idea of the future is a territory that we are disputing right now and that we have to wrest from hopelessness. The future does depend on what we work on today,” Zorrilla said.