Climate scientists reopen a contentious question: What counts as a valid carbon offset?
A new study suggests temporary carbon storage may have a legitimate role in climate mitigation — though not in the way many carbon markets assumed.
For years, climate negotiators and carbon market regulators have treated temporary carbon storage with suspicion.
Trees burn. Soils degrade. Wood products decay. Carbon dioxide removed from the atmosphere for a few decades does not stay out of the atmosphere permanently. That has made temporary carbon removal one of the most disputed questions in climate accounting and net-zero policy.
Now a new study published in Nature on Wednesday is attempting to redraw the argument.
Researchers from the International Institute for Applied Systems Analysis, Peking University, the Chinese Academy of Sciences, the University of Maryland and France’s Laboratoire des Sciences du Climat et de l’Environnement said that temporary carbon storage may play a scientifically legitimate role in climate mitigation — not by compensating for carbon dioxide emissions, but by offsetting short-lived climate pollutants such as methane.
The distinction matters because methane behaves very differently from carbon dioxide in the atmosphere. While CO₂ can persist for centuries, methane breaks down far more quickly. According to the study, temporary carbon storage and methane emissions operate on more comparable timescales, making temporary carbon removal potentially suitable for compensating methane emissions in climate accounting systems.
“Our study set out to answer the following question: if temporary CDR cannot offset CO₂, what can it legitimately offset?” said lead author Yue He of Peking University and guest researcher at IIASA.
The paper enters a politically sensitive area of international climate diplomacy.
Methane has become one of the central fault lines in global climate negotiations, particularly for countries with large agricultural sectors and livestock industries. Governments including New Zealand, Brazil and Ireland face persistent methane emissions that remain difficult to eliminate completely without major economic disruption.
At the same time, scrutiny of carbon offsets has intensified in voluntary carbon markets and climate negotiations. Environmental groups and many scientists have criticized offset systems that treat temporary carbon storage as interchangeable with permanent reductions in fossil-fuel emissions.
The new study reinforces that criticism. The authors explicitly conclude that temporary carbon storage cannot fully compensate for carbon dioxide emissions because CO₂ remains in the atmosphere for centuries to millennia.
Instead, the researchers propose what they describe as a more physically grounded framework: matching temporary carbon removal with short-lived climate pollutants that operate over similar time horizons.
From emissions targets to technical disputes
Using climate metrics already embedded in IPCC and U.N. climate reporting systems, the team calculated compensation ratios for methane emissions under different storage durations. Neutralizing the climate impact of one kilogram of methane, the paper found, would require roughly 498 kilograms of CO₂ stored for 20 years or about 101 kilograms stored for 100 years.
The study also revives debate over whether climate accounting systems should treat short-lived and long-lived greenhouse gases separately.
The authors argue that implementing such a framework would likely require a “two-basket” accounting approach distinguishing between gases like methane and long-lived pollutants such as carbon dioxide.
The proposal touches directly on disputes already unfolding inside climate diplomacy and carbon markets.
Over the past decade, climate negotiations increasingly shifted from broad emissions targets toward more technical disputes over accounting rules, measurement systems and the credibility of net-zero claims. Questions once treated as scientific details now shape the economic and political viability of national climate strategies.
The shift is visible across international carbon governance systems themselves. “The increased heterogeneity in carbon pricing instruments (implemented and under development) has increased government interest in improving policy alignment and interoperability,” the World Bank’s 2026 State and Trends of Carbon Pricing report says.
Direct carbon pricing policies now cover 29% of global greenhouse gas emissions, it adds, and the aim is “to support policy coordination on carbon pricing to reduce negative cross-border spillovers and close gaps on transparency, implementation and ambition.”
Temporary carbon removal sits squarely inside that shift.
“Not all greenhouse gases behave the same way, and not all carbon storage needs to be permanent to be genuinely useful,” said IIASA senior research scholar Thomas Gasser, a coauthor of the paper. “Temporary CDR has real climate value, but only when it is matched to the right type of emissions.”
The findings may appeal particularly to countries struggling with methane-heavy agricultural emissions. But they are also likely to trigger renewed debate over whether differentiated accounting systems create scientifically rigorous flexibility or open new pathways for weak climate claims.
The debate is no longer only about how much carbon countries emit. Increasingly, it is also about the accounting systems governing how emissions are measured, compensated and compared.
Those disputes are moving from academic journals into climate negotiations, carbon markets and national policy frameworks.
“A growing number of governments and non-state actors are pledging to be carbon-free — and obviously that’s good news,” U.N. Secretary-General António Guterres said during the launch of a 2022 U.N. report on net-zero commitments.
“The problem,” he added, “is that the criteria and benchmarks for these net-zero commitments have varying levels of rigor and loopholes wide enough to drive a diesel truck through.”
