How much carbon dioxide can the Earth “swallow” from human emissions? This question sounds like asking the Earth’s “stomach capacity.” Geological carbon storage has long been a high-priority option in energy and climate policy discussions. It was once believed that porous rock formations deep within the Earth’s crust could act as a limitless reservoir, continuously absorbing the carbon we emit from fossil fuels. “Escorting” carbon dioxide back underground is like dumping garbage into a never-ending abyss. However, the latest study published in the journal Nature casts a shadow over this optimistic outlook: Earth’s “carbon storehouse” is not only limited in capacity, but could be full in less than two centuries.
Not a Climate Savior
A new study, jointly conducted by a team from the International Institute for Applied Systems Analysis in Austria and Imperial College London, indicates that Earth’s “actual available capacity” for geological carbon storage within its rock formations is approximately 1.46 trillion tons of carbon dioxide. While this figure may seem enormous, at the current rate of global emissions reductions and carbon capture and storage deployment, this space is likely to be exhausted within 180 years. Even more alarming, even if all 1.46 trillion tons of storage were fully utilized, it would only reduce global temperature rise by approximately 0.7°C. Earth is already warming by over 1.2°C above pre-industrial levels, and the international community is striving to limit the temperature rise to 1.5°C. Clearly, carbon burial alone cannot fill the significant gap between emissions and targets.
Rather than adopting overly optimistic assumptions, the research team took a highly pragmatic approach and systematically examined potential storage sites worldwide. They eliminated seismically active zones, ecologically fragile areas, areas beneath densely populated cities, and regions with unstable or explicit policies opposing carbon storage. This latest assessment approach yields conclusions that are more aligned with real-world political, social, and technological constraints, highlighting the non-geological challenges facing the practical implementation of carbon storage.
Energy Shift: The Real Solution
This research further reinforces a key conclusion: geological carbon storage should be considered a supplementary measure, not the primary solution, in climate change response strategies. The real solution lies in a fundamental transformation of the global energy system. Currently, the energy sector contributes nearly three-quarters of global greenhouse gas emissions, with coal, oil, and natural gas being the primary sources. If we fail to significantly reduce our reliance on fossil fuels at the source, even the largest underground storage capacity will ultimately be insufficient.
In its recently released “Roadmap to Net Zero Emissions by 2050,” the International Energy Agency clearly states that to achieve climate goals, the world must triple clean energy investment by 2030 and increase renewable energy generation to over 60%. Large-scale deployment of wind power, solar PV, hydropower, and nuclear power, combined with intelligent grid transformation and cross-regional dispatching, is the core path to replacing traditional coal-fired and gas-fired power generation. At the same time, low-carbon energy carriers such as hydrogen, biomass, and ammonia must play a greater role in the industrial and transportation sectors.
A Transitional Insurance Policy
Although geological carbon storage capacity has a limit, it still has irreplaceable interim value in the energy transition—particularly in addressing emissions from hard-to-abate industrial sectors (such as steel, cement, and chemicals), and as a complement to gas-fired power generation for grid peaking. It can be viewed as a “limited emergency toolbox” rather than a “permanent solution.” During the transitional period, when the energy system has not yet fully decarbonized, the rational deployment of carbon capture, utilization, and storage projects can help smooth the emissions reduction curve and reduce transition costs.
However, as carbon storage resources gradually deplete, their use should be more strategic and prioritized. Policymakers need to establish a scientific storage quota mechanism to ensure that this precious resource is used for the emissions scenarios most needed and difficult to replace, rather than becoming an excuse for continued dependence on fossil fuels.
From Burial to Zero Carbon
The Earth’s carbon storage “appetite” does have limits, reminding us that there is no single “technological shortcut” to the climate crisis. The truly sustainable solution lies in accelerating the construction of a new energy system dominated by renewable energy, promoting electrification and energy efficiency improvements in end-use sectors such as industry, transportation, and buildings, and supplemented by necessary carbon removal technologies. If we continue to place excessive hopes on underground “space” and ignore the urgency of fundamental changes in our energy mix, not only will carbon reservoirs be at risk of becoming overfilled, but humanity will also miss a critical window to achieve climate security. The future belongs not to a civilization that is “skilled at burying carbon,” but to one that is “completely zero carbon.” Time is of the essence for energy transformation.
