Both studies were led by researchers from the Exploratory Modeling of Human-natural Systems Research Group of the IIASA Advancing Systems Analysis Program and underline that achieving the Paris Agreement goals will demand durable commitments to large-scale carbon dioxide removal (CDR) extending far beyond current policy timelines.
Stabilizing sea-level rise and permafrost thaw demands long-term carbon removal commitments
The study examines how to halt the growth of delayed climate impacts, such as sea-level rise and permafrost thaw, that continue to intensify even if global temperatures stabilize at 1.5°C. Following the 2025 advisory opinion of the International Court of Justice affirming states' obligations to prevent significant climate harm, the authors assess what would be required to stop these impacts from worsening.
Their conclusion is clear: net-zero emissions alone will not stabilize these long-term damages. To halt sea-level rise and cumulative CO₂ releases from thawing permafrost, global emissions would need to become net-negative and remain so for centuries.
"Delayed impacts are not abstract future risks – they represent significant harm affecting hundreds of millions of people through sea-level rise and infrastructure damage," says Johannes Bednar , lead author of the study. "If we take the Court's opinion seriously, stabilizing these impacts implies a long-term commitment to carbon removal that goes far beyond today's targets."
Coauthor Artem Baklanov adds: "The Paris temperature goals should be understood as milestones rather than endpoints. Stabilization of delayed impacts requires temperatures to eventually decline below 1.5°C, which in turn requires sustained net-negative emissions well beyond 2100."
The authors emphasize that this creates an urgent need for robust legal and institutional architectures to allocate carbon removal responsibilities fairly across countries and generations. Operationalizing principles such as common but differentiated responsibilities, and creating institutions capable of persisting beyond political cycles, will be essential. Yet such long-term governance frameworks remain largely absent from current climate negotiations.
Accounting for climate uncertainty strengthens the case for precautionary action
The second study, published in Nature Communications, addresses how uncertainty in the Earth system should shape optimal climate policy. Widely used integrated assessment modeling approaches seldom account for uncertainty when searching designing optimal climate policies.
Using a unique modeling framework that efficiently integrates physical uncertainty, the researchers derive climate strategies that account for Earth system risks from the outset. The findings show that precautionary approaches require earlier net-zero targets – often about a decade sooner – and significantly higher near-term carbon prices.
Crucially, the results indicate that sustained, potentially century-long net-negative emissions are needed, not to offset temporary overshoot, but to reduce long-term Earth system risks.
"Uncertainty in the climate system calls for precaution, much like uncertainty in income encourages more careful spending," explains Thomas Gasser , lead author of the study. "When we account properly for physical uncertainty, the economically optimal pathway includes planning for sustained net-negative emissions to hedge against adverse outcomes."
A shared message: net zero is only the beginning
Starting from different premises – legal responsibility and technological feasibility in one study, economic welfare optimization under uncertainty in the other – both analyses independently point to the same conclusion: limiting both immediate and delayed climate risks will likely require centuries of net-negative emissions.
The implications for policymakers are profound. Many countries projected to become wealthier after mid-century – while simultaneously facing increasing exposure to sea-level rise and permafrost thaw – have strong incentives to adopt more ambitious Nationally Determined Contributions (NDCs), establish explicit gross carbon dioxide removal targets, and introduce intertemporal instruments such as Carbon Removal Obligations to guarantee the reversal of temperature overshoot.
In summary, climate stabilization will require durable institutions that connect present emissions with future removals across generations.
The study in Nature Communications was funded by the Austrian Science Fund (FWF). The study in Environmental Research Letters was funded by the Oesterreichische Nationalbank (OeNB) and by the Grantham Foundation for the Protection of the Environment.
References
Bednar, J., Baklanov, A., Macinante, J., Hall, J., Gasser, T., Obersteiner, M. (2026) Stabilizing time-lagged climate impacts requires net-negative emissions for centuries. Environmental Research Letters DOI: 10.1088/1748-9326/ae34ca
Gasser, T., Rezai, A., Cheritel, C., Baklanov, A., Obersteiner, M. (2026) Negative emissions to mitigate Earth system risks. Nature Communications DOI: 10.1038/s41467-026-69896-x
