UN report maps steep emissions cuts needed to return to 1.5°C

A United Nations Environment Programme report finds that global greenhouse gas emissions would need to fall 18% below 2025 levels by 2030, 45% below by 2035 and 69% below by 2040 to put the world on a pathway that could return global warming to 1.5°C or lower by the end of the century. The UNEP Emissions Gap Report 2026 examines a “lowest possible” overshoot scenario in which warming peaks at about 1.7–1.8°C around the middle of the century and has an approximately 50% chance of falling back to 1.5°C or below by 2100. Researchers from the International Institute for Applied Systems Analysis contributed to the report, including its central scenario analysis, energy pathways and assessments of climate policies.

The required emissions trajectory is far steeper than the reductions expected from national climate pledges. Full implementation of nationally determined contributions, or NDCs, would lower emissions by only 5–8% from 2025 levels by 2030 and by 11–15% by 2035, according to the report. The IIASA-led Scenario Compass Initiative supplied the scenario data used in the analysis. These figures are policy-pathway estimates rather than observed reductions: they describe what would be required under the lowest-possible-overshoot pathway and how far current commitments fall short. The report also warns that the earlier starting point has deteriorated because of changes in participation in the Paris Agreement and revised estimates of historical emissions.

Current policies point toward particularly high warming, while stronger delivery of existing NDCs produces only a limited improvement. If current policies continue, warming could reach 2.8°C this century and continue increasing after 2100, compared with 2.6°C if all NDCs are delivered and comparable efforts continue. Even the achievement of additional net-zero targets would limit projected warming to 2.1°C. These results are worse than the projections in the previous year’s report, and the report’s authors state that new NDCs have made a negligible difference to that deterioration. They also calculate that every five years of carbon dioxide emissions at current levels adds approximately 0.1°C to peak warming.

The report’s lowest-possible-overshoot pathway is not simply a continuation of present trends. It requires rapid cuts across the economy, sustained implementation of climate policies and major changes in electricity production. By 2035, electricity generated by solar and wind would need to be at least three times its current level, while carbon dioxide emissions from energy systems would need to decline by at least 35%. Globally, coal-fired electricity generation would have to be effectively phased out by 2040, and solar and wind generation would need to grow at least five-and-a-half-fold. The scenario also calls for a transition away from fossil fuels in energy systems, reductions in non-carbon-dioxide greenhouse gas emissions, and measures to halt and reverse deforestation and forest degradation.

Some elements of the first Global Stocktake under the Paris Agreement are already showing progress. Countries agreed to triple renewable energy capacity, double the annual rate of energy-efficiency improvement by 2030, transition away from fossil fuels in energy systems, reduce non-CO2 emissions, and halt and reverse deforestation and forest degradation. Since the Paris Agreement was adopted, global renewable electricity capacity has expanded three times faster than anticipated. Yet the report finds insufficient progress in other areas. Sophie Boehm of the World Resources Institute said that renewables are already a game-changing element of climate action and the only area found to be on track for 2030, but their growth alone cannot close the emissions gap.

Fossil-fuel use remains a central obstacle. According to Louise Jeffery of the New Climate Institute, coal and oil consumption grew much more slowly over the past decade than expected in 2015, while gas use broadly followed the trajectory previously projected. Jeffery said this progress still requires a U-turn across all fossil fuels, with the most rapid change needed in electricity supply. The contrast illustrates why additions of renewable capacity are not by themselves sufficient: generation must also displace fossil-fuel sources at a pace capable of producing the deep emissions reductions required by the report’s pathway. Setu Pelz of IIASA said meeting the minimum effort levels for minimizing 1.5°C overshoot will require cooperation that reflects differences in responsibility and capability.

The report also finds growing evidence that climate policies can reduce emissions in developed and developing countries and can produce structural changes rather than merely short-term adjustments. Its review draws on more than 220 evaluations covering different sectors and national contexts. Evaluated electricity-sector policies were associated with average emissions reductions of 9%, while economic instruments such as carbon taxes and cap-and-trade schemes produced reductions of 5–13% over the periods examined. These outcomes are averages from a varied policy literature, not uniform effects, and the report cautions that successful interventions remain concentrated in particular countries, sectors and time periods. Their wider value depends on replication, extension and sustained implementation.

Even the lowest-possible-overshoot pathway would require removing and permanently storing roughly 320 gigatonnes of carbon dioxide over the century, an amount equivalent to about eight years of global CO2 emissions in 2024. The report describes the feasibility of this requirement as uncertain because of socioeconomic and technological challenges. Carbon dioxide removal therefore cannot substitute for near-term emissions cuts; the scenario depends on both sharply reducing emissions and deploying large-scale removal and permanent storage later in the century. Keywan Riahi of IIASA said the policy challenge is to scale up proven emissions reductions through fast, deep and sustained action while limiting reliance on large-scale carbon dioxide removal.

IIASA researchers involved in the report characterized the remaining window as narrow but not closed. Shonali Pachauri, who coauthored Chapter 1, said every additional fraction of a degree and every additional year above 1.5°C increases climate risks and narrows the options for a safe future. Joeri Rogelj, who served as a lead author for Chapter 4, emphasized the gap between the emissions reductions needed and those implied by current policies and national commitments. The report’s central conclusion is that the Paris Agreement goals remain reachable, but only with fast, deep and sustained emissions reductions and greater delivery of the first Global Stocktake commitments. The modeled return to 1.5°C remains uncertain, and the report’s low-overshoot pathway is designed to minimize the peak and duration of warming rather than guarantee a specific temperature in 2100.

Subject of Research: UN scenario analysis of emissions cuts, technology transitions and policy measures needed to limit and reverse global warming above 1.5°C.

Article Title: New UN report lays out emissions cuts needed for return to 1.5°C

Article References: New UN report lays out emissions cuts needed for return to 1.5°C. Original publication (Bibliographic details unavailable.)

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Keywords: 1.5°C warming, greenhouse gas emissions, UNEP Emissions Gap Report, climate policy, nationally determined contributions, renewable electricity, fossil fuels, carbon dioxide removal, Scenario Compass Initiative, global warming, report, lays