A study published in Nature looks at planetary limit for geologic carbon storage.
Dr Robert Sansom, a member of the IET’s Sustainability and Net Zero Policy Centre, said:
“The installation of carbon capture and storage (CCS) can substantially reduce fossil fuel carbon emissions, however, as this latest study shows, it is a powerful tool in the fight against climate change, but it’s not a bottomless solution. We must treat it as a strategic and finite resource, and with this, comes an urgent need to reassess the role of CCS within national and global climate strategies.
“We should prioritise its use for long-term carbon removal, not just as a way to delay the transition away from fossil fuels. Engineers have a vital role to play in making sure storage sites are safe, effective, and used responsibly. We also need to invest in alternative technologies, build public trust, and ensure that countries with fewer resources aren’t left behind.
“We are not going to be able to stop using fossil fuels overnight, so it’s important that the UK has a fossil fuel strategy on how we manage their use going forward and which supports the transition to Net Zero.”
Dr Jen Roberts, Senior Lecturer in Civil and Environmental Engineering at the University of Strathclyde, and Deputy Director of the UK Carbon Capture & Storage Research Centre (UKCCSRC), said:
“There has been a real need for updated and realistic global CO2 storage capacity estimates, so I wholly welcome this new research. Previous global estimates are quite old and outdated now and didn’t consider risk-based spatial constraints that this new work incorporates. As a result, previous work has often framed storage resources as plentiful or unlimited, and this is simply not the case in some geological conditions and contexts. This new research finds more conservative values and thus presents global CO2 storage as a ‘limited intergenerational resource’, which I know many in the CO2 storage community will welcome.
“The pace of global emissions reduction has been too slow, with a range of ramifications including the potential need for carbon removal – both to balance carbon budgets and to prevent temperature rise. This places additional reliance on CO2 geological storage, and this new study explores questions around prioritising CO2 storage.
“It is important to note that global assessments like this may be useful to understand constraints and guide policy, but they have limitations. They are typically very simplified and have big uncertainties. This large-scale, low-resolution analysis takes a highly simplified approach to calculating storage potential, and the estimates of capacity essentially assume the same amount of CO2 can be stored in every cubic metre of sedimentary basin around the world. We still need detailed regional and basin scale analyses which underpin assessments for CO2 geological storage development. The storage calculations from a more granular analysis might be quite different.
“Overall the research brings a nuanced viewpoint on CO2 geological storage; while developing CO2 storage is absolutely necessary for our climate, the constraints are not simple, storage resource is not unlimited, and how the technology scales up is laced with justice implications for generations to come.”
Prof Sam Krevor, Professor of Subsurface Carbon Storage and Royal Academy of Engineering Senior Research Fellow at Imperial College London, said:
“The authors suggest that they have identified that the prudent resource base for CO2 storage globally is far lower than previously estimated because past efforts, largely led by government geological surveys and national laboratories, have not considered important physical and socio-political risks. What the authors fail to acknowledge is that the physical limitations that comprise the vast majority of their identified reductions (ocean depth, sedimentary depth, locations in polar circles) are already incorporated into past assessments, and that when a nearly identical approach was taken to estimate the global storage resource base1, a similar result was obtained, i.e., 2,000 Gt of CO2 storage resource estimated compared with the 10,000+ Gt when compiling detailed regional estimates produced by geological surveys.
“Thus, rather than having identified important considerations that were previously ignored, it is apparent that the authors have implemented a modelling approach that is simply pre-disposed to estimate the resource base for CO2 storage far below estimates arising from established standards developed by government and academic groups over the past 20 years. Whether this systematic bias arises from some fundamental error in the approach can only be assessed once the full dataset can be scrutinised, but it is notable that established methods make use of far more detailed data and analyses of regional geological systems than was used in this work or the previous work1.
“It is a shortcoming of this work that the authors do not validate their modelling approach, or explain major and systematic differences as compared with alternative and established methods. The bias in the estimates would have been revealed immediately by comparison of the authors’ estimates of ‘geological potential’ to any number of detailed regional analyses that have been carried out by government geological surveys, for example in the United Kingdom, Norway, and the United States. Indeed it can be seen in the open peer review documentation that this and many of the issues above were pointed out by the reviewers, but not addressed in the rebuttals. It will be a valuable exercise to understand where the differences arise when using the coarse and imprecise global sedimentary basins and thickness datasets, as is done in this paper, as compared with the established methods that use detailed regional information about local geological systems.
“Ultimately, whether it is 1,200 Gt, 2,000 Gt, or 10,000 Gt, there is far more potential storage resource than is needed for CO2 storage to play a major role in emissions mitigation. Approaching even 1,000 Gt of CO2 stored underground would be a signal achievement in our fight against climate change. Thus even if 200 years from now we are needing to find alternatives to the use of CO2 storage for want of geology, this will be a problem that we can welcome.”
1 Wei, Y. M., Kang, J. N., Liu, L. C., Li, Q., Wang, P. T., Hou, J. J., … & Yu, B. (2021). A proposed global layout of carbon capture and storage in line with a 2 C climate target. Nature Climate Change, 11(2), 112-118
Prof Naomi Vaughan, Professor of Climate Change at the University of East Anglia, said:
“This is a valuable and timely study that quantifies a feasible estimate of geological storage potential. This more conservative estimate of global CO2 storage capacity raises important questions for governments and global society about how this unique resource should be used in the coming decades to reach net zero. Some argue it could be used to extend the life of fossil fuels, or to reduce emissions from the trickier sectors; or it could be prioritised for methods that take existing CO2 out of the atmosphere, allowing us to lower greenhouse gas concentrations more than through emissions reduction alone. We will have to decide.”
Prof Jon Gibbins, Professor of CCS at the University of Sheffield and Director of the UK CCS Research Community network, but commenting in a personal capacity, said:
“This paper seems to state nothing new with respect to the minimum expected amount of global CO2 geological storage capacity. The IPCC Special Report on CCS1 published in 2005 estimated that the lower limit on total global storage capacity is around 1,680 billion tonnes of carbon dioxide vs the estimate of 1,460 billion tonnes of carbon dioxide in this paper, essentially the same number for approximations of this type. The paper cites the seminal and very widely-authored IPCC report as general evidence for the period of global interest in CCS but the authors do not seem to have made this obvious acknowledgement.
“Then, given that the authors’ assumed ‘prudent’ limits are already significantly exceeded by hard evidence from well-established carbon dioxide storage projects, their headline storage capacity number obviously needs to be viewed with some scepticism. And, because these assumed limits have already been demonstrably broken within just the first, relatively few, current injection projects, it is likely that they are not such a big deal. The authors do note that ‘When we apply exclusion layers in the order presented here, we find that that the largest increase in storage would be realized if our assumptions regarding storage and ocean depth were relaxed.’ The authors’ own data suggests that, with more realistic assumed limits, global carbon dioxide storage capacity would be at least doubled.
“The limit on sub-surface injection depth of 2,500 metres used to arrive at the headline value for minimum global CO2 storage capacity is at variance with actual practical evidence from the Aquistore project in Canada, where 620,000 tonnes have been successfully stored at a depth of around 3300 metres2. The Aquistore project, used as a backup ‘overflow’ for the Boundary Dam capture project, is monitored extensively for learning purposes, has been running for ten years and is well-covered in the literature. But the Aquistore evidence does not appear to have been referenced directly in this paper, although the maximum feasible upper depth limit in their sensitivity analyses is reported to be 3,500 metres.
“The paper’s authors also assume a limit of 300 metres of ocean depth for offshore CO2 storage in their headline estimate of global storage potential. Again this is at variance with actual practical experience over about ten years in the Brazilian offshore oil fields, where, just in 2024, over 10 million tonnes of CO2 were reinjected into four different oil fields at a water depth of around 2,000 metres (and a further rock depth of several kilometres) from multiple floating capture units. This paper says ‘drilling for hydrocarbons has been achieved down to water depths of 2,000 metres’ and cites a 2017 reference on Brazilian oil production history but does not appear to include any mention of the extensive subsequent CO2 injection experience described in more up-to-date publications. It then goes on to cite the Deepwater Horizon disaster, involving oil exploration not CO2 injection, as evidence for why CO2 storage in locations with more than 300 metres water depth is unlikely (headline estimate limit) and more than 500 metres (the authors’ maximum contemplated limit) should be considered impossible.
“There is also an error in the Grantham press release: ‘disused mines are the most efficient type of geological storage’ is very definitely not true. You don’t mine for oil and gas and it is reservoirs for these hydrocarbons – some in use, some new, as well as some disused ones – that will be used for CO2 storage, and not old mines. It would be entirely incorrect to suggest that people living in old mining areas need to worry about stored CO2 leakage as a result of this sloppiness.”
1 https://www.ipcc.ch/report/carbon-dioxide-capture-and-storage/
2 https://discoverestevan.com/articles/ptrc-receives-prestigious-award-for-southeast-ccs-project
Brazilian CO2 injection references include:
22 FPSOs in Brazil’s pre-salt enable Petrobras to break C02 reinjection record
https://pure.tudelft.nl/ws/portalfiles/portal/220693591/1-s2.0-S1750583624001750-main.pdf
https://www.energy.gov/sites/default/files/2023-07/6a.%20CCUS%20at%20Petrobras%20-%20CSLF%20meeting%202023%20_%20final%20version%20PDF.pdf
Dr Wei He, a Senior Lecturer in the Department of Engineering at King’s College London, said:
“The headline message is that geologic carbon storage is finite when assessed prudently. This reframes storage potential in terms of usability and risk, which should stimulate further work in both risk assessment and engineering mitigation to refine the global limit or recover the resource via engineering innovations. The equity dimension also matters: linking responsibility for emissions with access to readily usable storage could help accelerate deployment through international collaboration.
“This is a transparent, spatially explicit global assessment that layers multiple risk and feasibility filters on sedimentary basins, then benchmarks results against IPCC scenario demand. The central conclusion—that “easy-to-use” (low-risk) storage is far more limited than raw technical capacity—is well supported by the mapping, sensitivity tests and scenario comparisons. The authors are appropriately cautious about uncertainties and report ranges throughout.
“This research shifts the debate from “How much storage space exists?” to “How much high-quality storage should we carefully plan to use? This study shows that quality screens and socio-environmental constraints cut that figure substantially, consistent with recent feasibility concerns and the difficulty of scaling CCS in practice. Importantly, in my opinion, this does not say “there is no capacity.” It says the readily deployable, low-risk subset is scarce relative to demand in strong-overshoot scenarios—arguing for prioritisation, not abandonment, of CCS for the high-quality storage for climate.
“The practical takeaway is: treat geologic storage as a limited, intergenerational resource reserved for the highest-value uses—hard-to-abate industrial point sources and durable removals (e.g., DAC/BECCS)—rather than offsetting emissions that can be avoided through electrification or renewables.
“CCS is viable and needed, but over-reliance or non-strategic use can be a policy risk. If we lean too heavily on CCS—especially to prolong fossil use—we deplete a scarce resource and still risk breaching the sensible limit this or next century. In short, pursue CCS as part of a portfolio, not as a substitute for rapid mitigation, and use it strategically to maximise the impact of limited high-quality storage.”
Prof Stuart Gilfillan, Professor of Geochemistry at the University of Edinburgh, said:
“Gidden and colleagues offer a useful, science‑based budget for carbon capture and storage (CCS): a “prudent” global limit of about 1,460 billion tonnes of CO2 (over a range 1,290–2,710) within porous sedimentary formations. That is still a very large resource, which is equivalent to several decades of today’s emissions and enough for CCS to play a central role alongside rapid emissions cuts. If devoted to storage of CO2 removed from the atmosphere, it could trim global warming by around 0.4–0.7°C. Rather than downgrading CCS, this work helps target it where it delivers the most climate benefit. It is important to remember that CCS remains the only tool to cut emissions directly from industrial sources.
“The authors calculate this number by mapping where storage makes sense after accounting for earthquake risks, protected and populated areas, and cross‑border issues. This prudence reduces the headline potential, but it also boosts confidence that stored CO2 will remain safely underground, as the climate benefits are preserved if leakage remains below about 0.01% per year. Experience from well‑chosen sites shows this standard is attainable with modern well integrity and monitoring. Hitting 1.5–2°C pathways will still require a major scale‑up from today’s small base, meaning that there is a need to build shared CO2 transport and storage hubs now and there is a need to advance other storage options, such as CO2 mineralization in reactive rocks.
“The policy takeaway is optimistic but disciplined: treat storage as valuable and use it where it matters most, to tackle hard‑to‑abate industrial emissions and high‑durability carbon removals, backed up by strong measurement and long‑term stewardship. As storage opportunities are uneven across countries and some basins cross borders, fair international rules and finance are critical. This paper doesn’t close the door on CCS; it provides the guardrails to deploy it safely, credibly, and to maximum climate effect.”
Dr Tom Kettlety, Research Fellow in Geological Carbon Storage in the Department of Earth Sciences & Oxford Net Zero, University of Oxford, said:
“The Grantham press release and the associated quotes are fundamentally misleading in their framing of this paper’s findings. ‘Industry’ estimates of accessible storage capacity are already aligned with the capacity estimates this paper finds (in the order of thousands of gigatonnes). Framing this work as a ‘game changer’ and positioning this against an ‘overly optimistic’ industry estimate is exaggeration in my view, and destructive to broader understanding around a small but vital part of stopping climate change.
“No one credible thinks that storage resources are an ‘unlimited solution’, and it’s irresponsible to characterise it this way. The paper’s analysis is reasonable, albeit pessimistic; but this press release appears to be arguing against a position that no credible voice in the CO2 storage industry or policy sphere is taking — these are clear straw man arguments.
“It’s agreed that massive emissions reductions are needed, and that geological storage is necessary in the near-term to cover for sectors that will be very hard to decarbonise. This is necessary to achieve the rapid transition to net zero required to stop climate change. This is also infrastructure that needs to be constructed and scaled up right now, otherwise it won’t be ready in time for when it’s needed.
“These new storage capacity estimates do not change that conclusion. This paper’s results still support — even with their pessimistic assumptions — that there are many decades worth of storage resources that can be used to get to net zero. But these findings will be used to stoke controversy where none should exist.”
Prof Carrie Lear, Professor of Past Climates and Earth System Change at Cardiff University’s School of Earth and Environmental Sciences, said:
“Carbon capture and storage can either decarbonise industrial processes or remove CO₂ from the atmosphere to reverse climate change. We’ve assumed we could do both, storing CO₂ underground where we have extracted fossil fuels. But this study challenges that assumption, showing that if we avoid risks to people and sensitive environments like the Arctic, the safe storage potential drops by a factor of ten.
“If future generations will depend on CCS to maintain net-zero emissions, then we must act now to preserve that option. That means cutting CO₂ emissions rapidly today. We cannot afford to use up this finite resource on short-term industrial fixes when its long-term value lies in restoring a safe climate.
“The study makes cautious assumptions, like limiting offshore CCS to shallow waters. But even if deeper sites become viable, it’s clear we should reduce our reliance on fossil fuels rather than expand industrial activity into fragile deep ocean ecosystems.
“There is no single solution to climate mitigation, it is like a pie made up of many slices. The biggest slice has always been cutting our use of fossil fuels, and that remains true today. Other slices include restoring forests, improving energy efficiency, and using technologies like carbon capture and storage (CCS). But this new study shows that the CCS slice is much smaller than we thought. That means the fossil fuel reduction slice just got bigger and also more urgent. We need to act fast to reduce emissions at the source, because we now have even less room to rely on technological fixes later.”
Prof Myles Allen FRS, Head of Atmospheric, Oceanic and Planetary Physics, University of Oxford, said:
“The paper correctly notes ‘incumbent industry actors must be appropriately incentivized to become net injectors, rather than extractors, of subsurface carbon’. That’s spot on: if you want to dig it up, you need to put it back, and then some. We must make geological CO2 disposal a licensing condition of continued extraction and use of fossil carbon. Only then will we truly discover the scale of this resource.”
Dr Phil Williamson, Honorary Associate Professor at University of East Anglia, said:
“For the past twenty years or so, there has been a plausible escape route from climate catastrophe: we don’t need to stop greenhouse gas emissions just yet, since we will be able to remove CO2 from the atmosphere in future and store it safely underground. Whilst the world seems near-certain to overshoot 1.5C warming, it will be possible to get back to that just-about-liveable level after we have fully experienced the human and economic costs of higher temperatures. Gidden and colleagues question that assumption, by setting limits on the amount of removed CO2 that can be feasibly stored in sedimentary basins. These safe limits are around ten times lower than their initial estimates based on physical storage potential. There may be other storage options, for example in basalt formations or directly in the ocean; however, the former is still highly uncertain, whilst the latter would currently be contrary to international law (as well as having high potential for environmental harm). The new Nature analysis therefore confirms the folly of any policy option other than “stringent near-term gross emission reductions”. It also points out that decisions made in the next few years are likely to have consequences for the human population for at least the next ten generations.”
Dr Injy Johnstone, Oxford University Smith School of Enterprise and the Environment
“This paper provides the most advanced assessment of feasible carbon storage prospects yet – clearly illustrating the critical need to double down on our efforts to cut emissions. The limits to global carbon storage the paper finds mean we must also take carbon removal budgeting seriously so that we can tackle difficult questions head on: such as who should have access to this carbon storage globally and on what terms.”
Prof Kevin Anderson, Professor of Energy and Climate Change at the University of Manchester, said:
“This publication is a welcome intervention, particularly in how it challenges the exaggerated claims and speculative projections associated with carbon capture and storage (CCS). However, its reference to an upper limit of almost 1.5 trillion tonnes of CO₂ storage, while technically feasible, risks legitimising continued “business-as-usual” approaches. Such figures are likely to be used by actors, including much of the integrated assessment modelling (IAM) community, to justify scenarios that rely heavily on CCS and carbon dioxide removal (CDR), while neglecting the possibility of rapid and equitable societal transformation – an omission that significantly distorts the policy pathways they present.
“This is especially concerning given the persistent gap between the promises of CCS and real-world performance. After decades of bold projections, only around 10 million tonnes of CO₂ are captured and permanently stored each year (excluding enhanced oil recovery), representing less than 0.03% of annual global fossil fuel emissions. Rather than serving as a credible mitigation technology, CCS has largely functioned as a rhetorical device to delay robust fossil fuel regulation.
“While there is a legitimate and important role for CCS in cement production, this is typically overshadowed by its broader misuse as a tool to justify continued oil and gas extraction. As such, although the Nature paper makes a valuable contribution, it risks being misread as endorsing the large-scale deployment of CCS and CDR seen in many IAM scenarios – an approach that lacks empirical grounding and continues to undermine serious climate policy and transformative change.”
Dr Ben Caldecott, Director, Oxford Sustainable Finance Group, University of Oxford
“Finite geological storage will need to be stewarded wisely, even more wisely than the paper suggests. The estimates are a very significant overestimate of what geological storage will actually be available as the economics have not been factored in. Only a fraction of that estimated will be accessible at a price society will be willing to pay.”
* ‘A prudent planetary limit for geologic carbon storage’ by Matthew J. Gidden et al. was published in Nature at 4pm UK time on Wednesday 3 September.
DOI: https://doi.org/10.1038/s41586-025-09423-y
Declared interests
Jen Roberts: “I collaborate with Matthew Giddens and Keywan Riahi (two of the authors) through the EU-funded UPTAKE project which is referred to in the acknowledgement statement for this paper.”
Myles Allen: “My group is currently working on a project on Geologically Balanced Fuels for Net Zero Aviation funded by VietJet.”
Injy Johnstone: “No conflicts of interest to declare.”
Ben Caldecott: “No conflicts of interest to declare.”
Phil Williamson: “No conflicts of interest to declare (retired employee of Natural Environment Research Council/UK Research & Innovation).”
Tom Kettlety: “I’ve sat on project scientific advisory boards, provided consulting, and been in research projects with CO2 storage operators, regulators, and associated government departments.”
Naomi Vaughan: “I’ve worked with the lead author on a paper before and published with some of the co-authors. I have no financial or commercial interests in anything.”
Jon Gibbins: “None to declare.”
Stuart Gilfillan: “I have received funding from TotalEnergies in the past, for research related to CO2 origins in the subsurface and reservoir connectivity and Equinor for research related to the subsurface trapping of CO2 in natural CO2 reservoirs. I currently receive funding from the UK Natural Environment Research Council for research related to CO2 mineralisation.”
Wei He: “I recieve industrial funding from Mission Zero Technologies – a company working on direct air capture technology”
Carrie Lear: “I once received some funding from NERC for a PhD studentship that was in collaboration with BG Group. Nothing to do with CCS. We were using BG core material to reconstruct climate in the past.”
Kevin Anderson: “I have no financial interests or formal affiliations with any organisations that support or oppose carbon capture and storage.”
Sam Krevor: “I receive research funding from Shell to carry out research on the geological storage of CO2, although not on the topics that are covered by the paper. I am the Editor-in-chief of the International Journal of Greenhouse Gas Control, the leading scientific journal with a focus on carbon capture and storage, which is published by Elsevier.”