UNEP Models Pathway Back to 1.5°C

Keeping global warming from ever exceeding 1.5°C is no longer possible, according to the UN Environment Programme (UNEP). Its lowest-overshoot scenario instead sets out emissions cuts and carbon removal requirements for a roughly 50% chance of bringing warming back to 1.5°C or below by 2100, after reaching 1.7–1.8°C around mid-century.

The scenario appears in UNEP’s Emissions Gap Report 2026, published on 21 October 2026 under the title The Point of Return. In its earlier report, Limiting Overshoot, UNEP describes overshoot as a temperature trajectory: warming passes 1.5°C, peaks and subsequently falls. The term therefore covers that sequence, not just the moment when temperatures cross the threshold.

Against a 2025 baseline, global greenhouse-gas output would have to decline by 18% for 2030, 45% for 2035 and 69% for 2040 under the lowest-overshoot pathway, UNEP estimates. Across the decade from 2025 through 2035, the required reduction averages approximately 5.7% annually.

Countries’ Nationally Determined Contributions, or NDCs, are their climate pledges under the Paris Agreement. UNEP calculates that delivering those commitments in full would reduce emissions by 5–8% for 2030 and 11–15% for 2035, using the same 2025 baseline. The temperature projection associated with full NDC implementation puts warming at approximately 2.6°C during this century.

For a continuation of existing policies, the report projects roughly 2.8°C of warming this century. Its most optimistic scenario based on pledges gives a figure of about 2.1°C, conditional on countries meeting both their NDCs and additional net-zero targets.

UNEP also specifies sector-level requirements for the lowest-overshoot scenario. By 2035, renewable electricity capacity would have to reach at least three times its 2025 level. Over that same period, methane emissions would need a reduction of at least 25%, while coal’s proportion of total energy supply would have to decrease by at least 55%.

Carbon dioxide removal forms another requirement of that pathway: UNEP estimates that approximately 320 gigatonnes would need to be removed and kept in permanent storage during this century. The agency says technological and socioeconomic difficulties make feasibility at that scale uncertain. It also states that carbon removal is not a substitute for cutting emissions.

The Emissions Gap Report series assesses the emissions projected under national policies and pledges against the pathways required for agreed temperature goals.

* This article is based on publicly available information at the time of writing.