Limited safe carbon storage could lower warming by less than 1 degree

Limited safe carbon storage could lower warming by less than 1 degree
by Robert Schreiber
Berlin, Germany (SPX) Sep 07, 2025

A new study led by the International Institute for Applied Systems Analysis (IIASA) has mapped safe underground storage areas for carbon dioxide and found that their practical use would only reduce global warming by about 0.7C. This figure is nearly ten times lower than earlier industry-based projections of 6C, which included storage in high-risk locations where carbon injection could trigger earthquakes or contaminate water supplies.

The research, published in Nature, estimates a global safe storage limit of around 1,460 billion tons of CO2, much lower than previous 14,000 gigatonne estimates that overlooked risks to human health and ecosystems. The findings underscore that geological storage should be treated as a scarce, finite resource.

"Carbon storage should be treated as an exhaustible, intergenerational resource, requiring responsible management," said lead author Matthew Gidden of IIASA and the University of Maryland. "Hard choices must be made about which countries, which sectors, and even which generations are able to utilize it."

The team examined sedimentary basins worldwide, ruling out sites too shallow, too deep, or located offshore where costs and risks are prohibitive. Once safety criteria were applied, potential storage capacity dropped sharply. If all safe capacity were used solely for CO2 removal, without additional emissions, global temperatures could fall by no more than 0.7C.

This contrasts with earlier projections of up to 6C reversal, which ignored safety concerns. The authors caution that cooling Earth is not a simple reversal of the warming process, and the climate system may not return to previous conditions even if temperatures decline.

"Geological storage space needs to be thought of as a scarce resource that should be managed responsibly," said coauthor Joeri Rogelj of IIASA and the Grantham Institute. He stressed that it should not be wasted on offsetting avoidable CO2 emissions from fossil fuel power or outdated engines.

Countries such as the US, Russia, China, Brazil, and Australia hold the largest safe storage capacity, especially in disused mines. Saudi Arabia, the Democratic Republic of the Congo, and Kazakhstan were rated among the lowest risk. In contrast, India, Norway, Canada, and EU nations saw significant declines in viable storage once risks were factored in. About 70% of viable capacity is onshore, with the rest offshore.

The study raises equity concerns, as nations with the greatest historical emissions also hold the most storage capacity. "This is not just a technical issue. It is about justice across generations and across nations," said coauthor Siddharth Joshi of IIASA. "Decisions today will determine whether storage is used wisely or wasted."

The authors warn that many climate scenarios guiding policy would exceed the prudent storage limit before 2100, underscoring the need for international coordination. Even using all safe capacity, warming could not be pulled back below 2C if emissions continue rising.

"Carbon storage is often portrayed as a way out of the climate crisis. Our findings make clear that it is a limited tool," Gidden said. "Used strategically alongside deep emissions cuts, it can help meet climate goals. Used carelessly, it will close off options for future generations."

Research Report:A prudent planetary limit for geologic carbon storage