For decades, underground carbon storage has been championed as a near-limitless solution to curb greenhouse gas emissions and address global warming. However, a groundbreaking study led by researchers at the International Institute for Applied Systems Analysis (IIASA) challenges this widely held notion by presenting for the first time a comprehensive map of safe, practical geological storage sites worldwide. The findings, published in Nature, demonstrate that the realistic and responsible capacity for geological carbon sequestration is nearly ten times smaller than previously estimated by industry reports. This revision has profound implications for climate strategies that rely heavily on carbon capture and storage (CCS) technologies as a primary mitigation tool.
The study meticulously evaluated sedimentary basins—vast rock formations composed of accumulated sand, mud, and organic materials that typically serve as reservoirs for fossil fuels and potential CO₂ storage. Instead of relying on broad technical potential estimates, the team rigorously incorporated critical safety criteria that have historically been overlooked. They considered factors such as the likelihood of CO₂ leakage, the risk of inducing seismic activity, groundwater contamination hazards, and proximity to human populations and biodiversity-rich protected areas. Additionally, the geological depth and economic feasibility of storage sites played a pivotal role in refining capacity estimates, effectively ruling out reservoirs that were too shallow, too deep, or within challenging offshore environments.
The cumulative outcome of these stringent evaluations is a sobering forecast: only around 1,460 gigatonnes of CO₂ can be stored underground globally under safe and environmentally responsible conditions. This figure starkly contrasts with previous estimates nearing 14,000 gigatonnes promoted by industry sources, which failed to account for the limitations and risks inherent in real-world geological contexts. Consequently, this study signals that geological carbon storage must be treated not as an inexhaustible fix but as a finite planetary resource with stringent management demands.
In terms of climate impact, the researchers projected the maximum potential for warming reversal solely through carbon dioxide removal (CDR) into these safe geological reservoirs. They estimate a best-case scenario of approximately 0.7 degrees Celsius reduction in global temperatures if all accessible storage sites are utilized exclusively for CO₂ removal and anthropogenic emissions are otherwise eliminated. This is in stark contrast to optimistic earlier studies suggesting possible reductions between 5 to 6 degrees Celsius, which were grounded in estimates that disregarded significant safety trade-offs.
This recalibration of carbon storage potential underscores a critical divergence between theoretical technical possibilities and pragmatic environmental and social constraints. The authors caution that such storage is not a panacea for the climate crisis and cannot substitute for aggressive emissions reduction policies. Moreover, they highlight that the climate system’s response to carbon removal may not mirror the sequence in which emissions exert warming effects, posing uncertainties around the extent and timing of temperature declines achieved through CDR technologies.
The study’s coauthor Joeri Rogelj emphasized that this research should catalyze a paradigm shift in how carbon storage is perceived and integrated into climate action frameworks. “Geological storage cannot simply be relied upon as an unlimited fallback to steady fossil fuel usage,” he explains. Instead, he advocates for a strategic deployment of storage resources that prioritize halting and reversing warming trends rather than offsetting ongoing emissions from fossil fuel combustion and legacy infrastructure.
A striking regional analysis within the paper reveals geographic disparities in safe storage capacity. Fossil fuel-producing nations, including the United States, Russia, China, Brazil, and Australia, possess the largest amounts of viable storage, often associated with depleted mines and reservoirs. Conversely, countries like Saudi Arabia, Kazakhstan, and the Democratic Republic of Congo exhibit low environmental risk profiles that favor safe carbon storage. However, countries such as India, Norway, Canada, and many in the European Union experience significant reductions in storage potential once safety parameters are enforced, complicating their reliance on CCS as a mitigation strategy.
Despite the technological maturity of carbon capture and storage—spanning nearly three decades—the study notes that large-scale deployment remains limited, hindered by the labor-intensive and localized nature of site characterization. Each potential storage site requires detailed geological analysis to assess permeability, cap rock integrity, and subsurface pressure dynamics, among other factors that influence the ability to securely trap carbon. This exhaustive process has contributed to overoptimistic assumptions in prior research, which often included sites harboring significant risks to human health and environmental safety.
Beyond technical parameters, the study highlights elemental issues of justice and responsibility. Countries with the largest historical emissions frequently also hold the most significant safe storage resources, placing a moral imperative on these nations to lead in the judicious use of geological carbon storage. The research underscores the intergenerational obligation to manage this exhaustible resource wisely to preserve options for future climate mitigation and adaptation.
International collaboration emerges as a vital theme as well. Given that many integrated assessment and climate policy scenarios assessed by the Intergovernmental Panel on Climate Change (IPCC) appear poised to surpass these planetary limits well before the century’s end, strategic planning and transparent governance mechanisms become indispensable. Policymakers will need to navigate complex trade-offs between continued fossil fuel reliance and the finite opportunity to use geological storage as a component of broader carbon management portfolios.
Matthew Gidden, lead author and senior researcher at IIASA and the University of Maryland’s Center for Global Sustainability, stresses that carbon storage, while important, must be contextualized within broader climate strategies. “Our findings make clear that using all of the safe geological storage capacity would not suffice to keep global warming below critical thresholds on their own,” he observes. “Countries serious about the Paris Agreement must integrate rapid emissions reduction alongside strategic carbon removal efforts to ensure a viable climate future.”
The study closes with a firm call for accountability, transparency, and long-term vision in the deployment of geological carbon storage. Recognizing the technology as a finite and valuable climate asset, rather than an infinite sink, reshapes how climate systems modeling, policy planning, and industry investment should proceed in the years ahead. The authors have also launched an interactive platform to empower stakeholders—researchers, policymakers, and the public alike—to explore their data visually and grasp region-specific potentials and risks.
By injecting a necessary dose of realism into the discourse surrounding CCS, this research marks a pivotal moment. Carbon storage remains a key instrument within the climate toolbox but demands a recalibrated approach that embraces safety, equity, and sustainability as its guiding principles. Without such stewardship, scientific optimism risks becoming strategic folly.
Subject of Research: Geological carbon storage capacity and safety assessments in the context of climate mitigation.
Article Title: A prudent planetary limit for geologic carbon storage
News Publication Date: 3 September 2025
Web References:
- IIASA Website: www.iiasa.ac.at
- DOI: 10.1038/s41586-025-09423-y
References:
Gidden, M.J., Joshi, S., Armitage, J.J., et al. (2025). A prudent planetary limit for geologic carbon storage. Nature. DOI: 10.1038/s41586-025-09423-y
Keywords:
Carbon capture, Carbon sequestration, Geological storage capacity, Climate change mitigation, Carbon dioxide removal, Environmental risk assessment, Fossil fuel emissions, Sustainable development, Climate equity, Sedimentary basins, Climate policy, Intergenerational justice
