UNEP report confirms unavoidable exceedance of Paris Agreement target, with best-case peak of 1.8°C; rapid emissions cuts, methane reductions and carbon removal still offer a route back below the threshold this century.

The world is on course to cross the critical 1.5°C global warming threshold set by the Paris Agreement within the next few years, according to a landmark United Nations Environment Programme report released on Wednesday. 

The findings mark the first explicit acknowledgement at the UN level that keeping long-term warming below this limit is no longer possible under current trajectories, even if countries fully implement their existing climate pledges.

Titled Limiting Overshoot: Navigating exceedance of 1.5°C and pathways towards return, the report stresses that while overshoot is now inevitable, it remains possible to minimise its magnitude and duration, then bring temperatures back below 1.5°C by the end of the century. Under the most optimistic scenario of full implementation of national climate plans plus net-zero targets, peak warming is projected at 1.8°C above pre-industrial levels. Other scenarios point higher, potentially beyond 2°C.

Devastating Impacts Already Emerging

Exceeding 1.5°C will intensify climate risks with every additional fraction of a degree and every year spent above the threshold. Anticipated consequences include more extreme heatwaves, wildfires, floods and storms; accelerated sea-level rise; severe damage to ecosystems such as coral reefs; threats to food security, water supplies and human health; and heightened dangers for Small Island Developing States and low-lying coastal cities.

The report highlights irreversible tipping points whose likelihood rises with the scale and length of overshoot. These include destabilisation of the West Antarctic and Greenland ice sheets, potential collapse or major disruption of the Atlantic Meridional Overturning Circulation, and degradation of the Amazon rainforest. 

According to the report, glaciers could lose more than a quarter of their mass by 2100, contributing 9 to 12.5 cm to sea-level rise and permanently altering water availability in many regions. Recent events, including the August 2026 glacier collapse and flash floods in Nepal and Tibet that killed more than 1,000 people, illustrate the accelerating impacts already underway.

UN Secretary-General António Guterres described recent extreme weather as a clear warning: “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 degrees as small and short as possible. That demands an overshoot of ambition.”

The Overshoot, Peak and Decline Pathway

UNEP identifies an “overshoot, peak and decline” strategy as the best remaining option. This involves immediate and sustained deep cuts in greenhouse gas emissions, including methane, to minimise the peak temperature, followed by long-term net-negative emissions through carefully governed carbon dioxide removal (CDR) technologies and nature-based solutions such as afforestation. Adaptation measures must run in parallel to reduce vulnerability to both expected and abrupt impacts, though limits to adaptation and some irreversible losses are likely, particularly if the peak is not tightly constrained.

Inger Andersen, UNEP Executive Director, was unequivocal: “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. Now is the time we must double down on climate action. We can – and must – get on the right path.”

Persistent Ambition and Implementation Gaps

Nationally determined contributions (NDCs) submitted under the Paris Agreement remain far from sufficient. Full implementation of the latest round of NDCs may produce only a slight decline in emissions from record 2024 levels, leaving a substantial gap relative to pathways consistent with limiting warming well below 2°C, let alone returning to 1.5°C after limited overshoot. An even larger implementation gap exists between pledges and policies currently in force; under existing policies, global emissions are projected to remain broadly stable through 2030 rather than decline sharply.

Related assessments, including UNEP’s Emissions Gap Report 2025, reinforce the picture: projections based on full NDC implementation point to 2.3-2.5°C of warming this century, while current policies lead toward about 2.8°C. Achieving pathways that limit overshoot requires emissions cuts on the order of 35-55 per cent below 2019 levels by 2035, depending on the temperature goal.

Enabling Conditions for Success

The report says that success depends on strong political will, effective multilateralism, inclusive governance, scaled-up finance, and equity – countries with the greatest historical responsibility must move fastest and with the highest ambition. It stresses that mitigation and adaptation are mutually reinforcing and should advance together; interventions delivering both benefits, such as nature-based cooling solutions, deserve priority. 

According to the UNEP report, net-zero is only a milestone toward net-negative emissions. CDR must complement, not replace, rapid emission reductions, and robust governance is essential to manage environmental, equity and scalability risks.

The UNEP report says that even if temperatures eventually return below 1.5°C, irreversible losses and permanently altered conditions are certain. Many communities will face relocation or livelihood changes, raising profound questions of justice, power and political legitimacy that demand new inclusive governance arrangements.

A Narrow Window That Demands Immediate Action

The report frames the current moment as a fork in the road. Years of delayed action have made temporary exceedance unavoidable, yet the shape of the overshoot pathway remains under human control. Faster and deeper cuts starting now can limit the peak closer to 1.8°C, shorten the duration above 1.5°C, reduce damages, lower reliance on uncertain CDR techniques, and improve the prospects of returning below the threshold by 2100.

Leaders from vulnerable nations underscored the stakes. President Surangel Whipps Jr. of Palau called the findings “a further glimpse into a perilous future that has already arrived,” insisting on an urgent and unprecedented increase in political will and investment. Australian Climate Change Minister Chris Bowen, involved in preparations for COP31, pointed to the need to accelerate the shift from fossil fuels to renewables and strengthen cooperation.

As the report says: the science is clear: every fraction of a degree and every year avoided above 1.5°C matters for lives, ecosystems, economies and the feasibility of recovery. The window for limiting overshoot is still open, but it is closing rapidly – immediate, collective and ambitious action is the only route that keeps a safer climate within reach.