- The storage available for safe carbon storage could be far lower than current estimates, according to a new study.
- Carbon capture and storage (CCS) has been touted as a viable method for drawing billions of tons of CO2 out of the air, typically securing it in rock formations deep underground.
- However, this new analysis suggests that many locations suitable for carbon storage may also pose risks, such as water contamination or earthquakes.
- That finding led the study authors to conclude that the “prudent” available storage is much less than has been estimated.
A new analysis suggests that the “prudent” storage available for carbon dioxide to head off further global warming is more limited than other recent estimates.
Accounting for the risks associated with carbon capture and storage (CCS), the study found that stashing carbon underground in suitable locations would likely reduce warming by only about 0.7° Celsius (1.3° Fahrenheit). That figure is far below other estimated potential reductions of 5-6°C (9-11°F), potentially making CCS less promising than believed.
The most common form of CCS involves injecting CO2 into underground rock formations, which in theory would lock it away and out of the atmosphere for millennia. Past research suggests there’s space on Earth to store 8,000-55,000 gigatons of CO2, leading some to conclude that the potential for CCS is virtually boundless. However, more recent studies have shown the constraints of this technique.
This latest research, published Sept. 3 in the journal Nature, finds that many of the potential areas for CCS on Earth may be too risky to use. The paper argues that CCS needs to be used judiciously to deal with CO2 emissions, reserving it for carbon-intensive energy applications that aren’t easy to replace with renewable alternatives, such as agriculture, said Matthew Gidden, the study’s lead author and a senior researcher in the International Institute for Applied Systems Analysis in Austria. Meanwhile, society could save that precious carbon storage space by greening global transportation.
“We know that geologically storing carbon is likely to be a very important tool in the toolbox in order to achieve net-zero and net-negative CO2 emissions,” said Gidden, also an associate research scholar at the University of Maryland in the U.S. But effective use of CCS, given its availability, requires treating it as a limited resource, according to the researchers.
“There are trade-offs, not only today in terms of what we’re planning to do, but also in the future,” he told Mongabay. “So what options are we leaving future generations?”
Gidden and his co-authors note that CCS is a critical part of countries’ climate commitments, in line with the goal of the Paris Agreement to restrict average global warming to 2°C (3.6°F) above pre-industrial levels. However, CCS has been slow to ramp up, with widely differing hypotheses about how much carbon we can actually store.
So the team set out to find out the “prudent” limits on CCS. They mapped out areas for geologic storage globally, finding room for a total of 11,800 gigatons of CO2. They then excluded certain regions because of the risk of contaminating water sources, setting off earthquakes, or CO2 leakage. They also left out sites within 25 kilometers (16 miles) of populated areas. They concluded that these risks drastically reduced the amount of available storage to around 1,460 Gt of CO2.
“[T]he research correctly frames geological storage as a finite intergenerational resource requiring strategic management,” Jarad Daniels, CEO of Australia-based nonprofit Global CCS Institute (GCCSI), wrote in an email to Mongabay. “This supports prioritising CCS for essential applications — industrial point sources that cannot be electrified and durable carbon removal technologies.”
Daniels also said the research “confirms that geological storage remains more than sufficient for CCS to play a crucial role in limiting global warming.” Still, he said he believes their methods rested on “overly restrictive assumptions about risk and technical parameters of CCS projects.” For one thing, Daniels said, a 25-km buffer for human settlements is “conservative,” and he pointed to examples of CCS currently in progress, such as Carbfix in Iceland, that sit closer to population centers. Elsewhere, others, like the Northern Lights project in Norway, inject CO2 to depths greater than those used by Gidden and his colleagues.
“Existing projects demonstrate through rigorous permitting and risk assessments that high safety standards can be met in practice,” Daniels added.
Gidden said the uncertainty around viable and safe CCS makes it critical to provide realistic numbers that policymakers can use in plans to address climate change, especially over time. Scientists still aren’t sure that removing CO2 from the atmosphere will lower the global temperature by the same amount that it rises when CO2 is emitted, for example.
To Daniels and the GCCSI, the findings point to the need for boosting CCS capability as quickly as possible.
“Immediate action is imperative,” he said. “This study reinforces that every year of delay makes climate goals more difficult and expensive to achieve.”
CCS is critical for mitigating climate change, Gidden said. But, he added, current projections indicate that the global temperature could rise to 3°C (5.4°F) above the pre-industrial average by 2100. That means the potential for CCS that he and his colleagues mapped out wouldn’t be enough to bring temperatures back within the Paris Agreement’s 2°C threshold.
Instead, halting and reversing climate change will require reducing carbon emissions as soon as possible and investing in other solutions, the authors write. Gidden pointed out that forests and other terrestrial ecosystems currently draw 2 Gt of CO2 from the atmosphere — more than any other method.
“That is a number that we can sustainably expand,” he said. “We can do more reforestation, we can do more conservation. We can take care of and conserve our natural biomes.”
And that strategy comes with “co-benefits,” he added, such as the protection of other ecosystem services and biodiversity.
“We really need to be using all available tools in our toolbox,” Gidden said, “and that leads with conservation of natural carbon sinks.”
Banner image: In August 2025, CO2 was stored for the first time in Norway-based Equinor’s Northern Lights reservoir outside the city of Bergen. Image courtesy of Torstein Lund Eik/©Equinor.
John Cannon is a staff features writer with Mongabay. Find him on Bluesky and LinkedIn.
Citations:
Gidden, M. J., Joshi, S., Armitage, J. J., Christ, A.-B., Boettcher, M., Brutschin, E., … Schleussner, C.-F. (2025). A prudent planetary limit for geologic carbon storage. Nature, 645(8079), 124-132. doi:10.1038/s41586-025-09423-y
Kearns, J., Teletzke, G., Palmer, J., Thomann, H., Kheshgi, H., Chen, Y.-H. H., … Herzog, H. (2017). Developing a consistent database for regional geologic CO2 storage capacity worldwide. Energy Procedia, 114, 4697-4709. doi:10.1016/j.egypro.2017.03.1603
Zhang, Y., Jackson, C., & Krevor, S. (2024). The feasibility of reaching gigatonne scale CO2 storage by mid-century. Nature Communications, 15(1), 6913. doi:10.1038/s41467-024-51226-8
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