AI Insight
A new United Nations Environment Programme report confirms that Earth will exceed the 1.5°C warming limit set by the Paris Agreement, marking the first time UNEP has declared this threshold impossible rather than unlikely to maintain. The report proposes an "overshoot, peak and decline" pathway requiring near-total elimination of greenhouse gas emissions by mid-century combined with massive deployment of carbon dioxide removal technologies, both natural (reforestation, ecosystem restoration) and technological (carbon capture and storage). To eventually return to 1.5°C, warming must not exceed 1.8°C, beyond which cooling becomes increasingly difficult.
Why it matters
This represents a fundamental shift in climate policy from prevention to mitigation and reversal, requiring unprecedented scaling of carbon removal technologies that currently exist in only 12 successful projects worldwide. The pathway demands rates of deployment exceeding even solar power's rapid expansion, with uncertain feasibility given potential storage capacity limits and competing land use needs.
Understand the Science
body {background-color: #D2D1D5;}
Research & Developments is a blog for brief updates that provide context for the flurry of news that impacts science and scientists today.
Humanity is certain to exceed the warming limit set by the Paris Agreement, a legally binding treaty meant to cap the world’s carbon emissions, according to a new report from the United Nations Environment Programme (UNEP).
Now, to reduce severe threats to human health, food security, water supplies, and more, societies will need to reach net-negative greenhouse gas emissions by not only cutting those emissions, but expanding carbon dioxide removal projects, a pathway called “overshoot, peak and decline.”
The 1.5°C (2.7°F) goal “must now be approached from above.”
Following such a pathway would require virtually eliminating greenhouse gas emissions by mid-century and rapidly deploying carbon dioxide removal technologies, including conventional tactics such as planting trees and restoring ecosystems, and new ones, such as carbon capture and storage.
“This is by no means an acceptable or preferred pathway,” the report stated. “It is simply the best remaining option.”
The 1.5°C (2.7°F) goal “must now be approached from above,” Inger Andersen, the executive director of UNEP, wrote in the report’s foreword. The report is the first time that UNEP has referred to staying beneath the 1.5°C (2.7°F) warming limit as impossible rather than unlikely.
The news that Earth will likely breach this limit was expected by climate scientists: In February 2025, a pair of studies published in Nature Climate Change determined that Earth had likely already entered the 20-year period in which global temperatures would exceed 1.5°C (2.7°F).
In order to bring global temperatures back to the 1.5°C (2.7°F) mark, Earth’s warming must not exceed 1.8°C (3.2°F), the new report states. Beyond that mark, cooling Earth back to the 1.5°C (2.7°F) level this century “becomes increasingly challenging.”
Reaching the amount of carbon dioxide removal required for the “overshoot, peak and decline” pathway would be an enormous task for the world’s governments and economies. Technologies that remove carbon from the air and store it underground are still limited in scale, and so far, just 12 projects have been successful. Just to limit warming to 1.5°C (2.7°F), even without overshooting that limit, the world would need to deploy carbon dioxide removal technologies at rates faster than those seen for solar power, which is far from the current reality.
Scientists aren’t sure Earth’s subsurface could even store the amount of carbon necessary to keep Earth at net-zero emissions. “Just maintaining net-zero CO₂ emissions could exhaust current estimated storage capacity in sedimentary basins by 2200,” the report stated.
Related
• Read the Report: “Limiting Overshoot—Navigating Exceedance of 1.5°C and Pathways Towards Return”
• Climate Goals Missed, U.N. Says World Must Now Remove Carbon at Scale
• Carbon Brief: Q&A: The Current State of ‘Carbon Dioxide Removal’ Around the World
• UNEP: Overshoot Explained: 5 Things to Understand About a World Beyond 1.5°C
Glen Peters, a senior researcher at the CICERO Center for International Climate Research in Norway who was not involved in the UNEP report, told The New York Times that various obstacles are in the way of large-scale carbon removal projects. Large amounts of land would need to be reforested for conventional carbon removal, for instance, which could spark conflicts with agriculture. Wildfires, as well as climate change itself, could prevent or damage plant growth.
Still, a rapid upscaling of carbon dioxide removal, paired with strong governance frameworks to ensure ethical deployment, is critical, according to UNEP. Without such action, the breaching of dangerous tipping points in Earth systems, such as irreversible changes to ice sheets or the slowing of the Atlantic Meridional Overturning Circulation (AMOC), will become more likely, paired with growing human and ecological suffering.
“We need stronger political will,” Andersen wrote. “Decisions taken now and in the next few years will determine whether viable options remain to reverse warming towards 1.5°C.”
—Grace van Deelen (@gvd.bsky.social), Staff Writer
These updates are made possible through information from the scientific community. Do you have a story about science or scientists? Send us a tip at eos@agu.org.
Text © 2026. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
Source: The World Will Overshoot 1.5°C and Must Now Remove Carbon, United Nations Says