The world’s top climate science body may be too optimistic on how much carbon emissions humans can trap and store underground to fight rising temperatures, a new report suggests.
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Potential limitations to how fast the nascent venture of carbon storage can scale have been overlooked by the United Nations’ Intergovernmental Panel on Climate Change (IPCC), the study published in the Nature journal said.
The finding means the world may need to move faster on limiting fossil fuel use and reducing carbon emissions to keep climate change under control, than what the most authoritative climate science group has indicated.
The IPCC’s latest climate mitigation report published in 2022 had presented projections of up to 30 gigatonnes of carbon dioxide (CO2) injected underground yearly by 2050, with the most likely figure being somewhere over 6 gigatonnes.
Researchers from the UK’s Imperial College London now believe the upper limit is just 16 gigatonnes, and the more plausible range being 5 to 6 gigatonnes.
Trapping carbon emissions deep underground is seen as essential in keeping global temperature rise to within 1.5 or 2 degrees Celsius from preindustrial times – two safety thresholds policymakers commonly refer to.
Prior to storage, greenhouse gases are usually collected at point sources such as the vent pipes of oil fields, or smokestacks of power plants. Entrepreneurs are also trying to pull carbon dioxide out of the atmosphere in a process known as direct air capture.
Scientists believe avoiding carbon emissions should take priority as much as possible, but doing just that is no longer sufficient in arresting climate change.
The IPCC had referred to a series of computer models to generate its report on future carbon storage volume. The Imperial researchers said some of these models do not account for limits on how much greenhouse gas can be feasibly pumped underground every year, nor the cost increases in ramping up projects. If real-world historical data is used, projections could fall further, they added.
Much could also depend on the national carbon storage deployment plans of large countries. Of the 16 gigatonnes peak identified by the researchers in their own projections, at least 10 gigatonnes would have to be stored in the United States every year by 2050.
But the US itself has indicated a storage rate of just 1 gigatonne yearly by then in its long-term climate strategy. Both IPCC and Imperial researchers believe the US has a greater storage potential than stated, but if its policy holds true, global aggregate storage falls to just around 6 gigatonnes at its maximum.
In another scenario that limited China’s carbon storage rate to the rate at which it has been extracting oil – a process relying on similar geological techniques – total storage falls by another gigatonne.
Overestimations are also particularly pronounced in Indonesia and South Korea, the latest study stated.
It also noted that the real-world deployment of carbon capture and storage technologies has been falling short of near-term projections, with about 70 per cent of 149 projects supposed to be operational by 2020 not implemented due to cost, technology and profitability issues.
Even if all the projects materialised, the total capture capacity would have only been 130 megatonnes. Global CO2 emissions last year reached a record 35.8 gigatonnes – a figure 275 times higher.
“The discrepancy between real-world development and projected trajectories highlights limitations to CO2 storage scale-up that are not captured by existing integrated assessment models,” the study said.
The fossil fuel industry and many countries dependent on oil production are banking on the scale-up of carbon capture and storage to continue its operations as global warming worsens. Critics believe they are chasing a pipe dream.
Direct air capture, meanwhile, has not been proven to be cost-effective despite interest and funding from the world’s largest companies including tech giant Microsoft and fashion retailer H&M. Each tonne of CO2 pulled from the air currently costs US$600-1,000.
An IPCC spokesperson said the organisation does not comment on individual studies in response to Eco-Business queries. The scientific body does not run its own computer models, and instead assesses existing literature and provides conclusions drawing from these studies.
The IPCC had indicated “high confidence” that carbon capture and storage “is an option to reduce emissions from large-scale fossil-based energy and industry sources, provided geological storage is available”. It also said it had high confidence that “net zero CO2 industrial-sector emissions are possible but challenging”.
