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At the heart of the climate crisis lies a harsh physical reality: Once carbon dioxide enters the atmosphere, it can stay there for hundreds or even thousands of years. Although some carbon does cycle in and out of the air via plants, soils, and the ocean, we are emitting far more than these systems can handle, meaning that most of it is just piling up. Burning fossil fuels is like continuously stuffing feathers into a duvet blanketing the Earth.
But there may be ways to begin plucking them out. That’s the promise of carbon removal, a category of technologies and interventions that either pull carbon dioxide from the air and store it securely or enhance the systems that naturally absorb carbon today.
Carbon removal is not, inherently, a license to continue emitting — it is far cheaper and easier to reduce the flow of emissions into the atmosphere than it is to remove them after the fact. Climate action has been so slow, however, that removing carbon has become a pressing consideration.
There are many technical, political, and economic challenges to deploying carbon removal at a meaningful scale. This guide will introduce you to some of those challenges, along with the basics of what carbon removal is, the rationale for trying to do it, and the risks and trade-offs we’ll encounter along the way. Let’s dive in.
Variously called carbon removal, carbon dioxide removal, CDR, and negative emissions technologies, all of these terms refer to efforts to suck carbon from the atmosphere and store it in places where it will not warm the planet, such as oceans, soils, plants, and underground. The science behind carbon removal spans atmospheric studies, oceanography, biology, geology, chemistry, and engineering. The carbon removal “industry” overlaps with oil and gas drilling, farming, forestry, mining, and construction — sometimes several of these sectors at once.
Carbon removal encompasses an astonishingly wide range of activities, but the two best known examples are probably the simple practice of planting a tree and the complex engineering project of building a “direct air capture system.” The latter are typically big machines that use industrial-sized fans to blow air through a material that filters carbon dioxide, and then apply heat to extract the carbon from the filter.
But there are many other methods that fall somewhere in between. “Enhanced rock weathering” involves taking minerals that are known to slowly pull carbon from the air as they break down over millennia and trying to speed up those reactions by grinding them into a fine dust and spreading it on agricultural fields. In “ocean alkalinity enhancement,” minerals are deposited directly into the ocean, catalyzing chemical reactions that may enable surface waters to soak up more carbon from the atmosphere. Companies are also experimenting with ways to take carbon-rich organic waste, like sewage, corn stalks, and forest debris, and bury it permanently underground or transform it into more stable materials like biochar.
IPCC Sixth Assessment Report / Working Group III
If you read the words “carbon capture” literally, then yes, carbon removal involves capturing carbon. It’s common to see news articles use the terms interchangeably. But “carbon capture” is also the name for a technology that addresses a very different problem, with different challenges and implications. For that reason, it’s useful to distinguish carbon removal as its own category.
By definition, carbon removal deals with carbon that was previously emitted into the atmosphere — the feathers piling up in the duvet. Carbon capture, by contrast, has historically referred to systems that collect carbon from the flue of an industrial site, like a power plant, before it can enter the atmosphere.
Some carbon removal methods, such as the aforementioned direct air capture machines, share equipment with carbon capture. Both might use materials called sorbents to separate carbon from flue gas or from the air, and both rely on pipelines and drilling to transport the carbon to underground storage wells. But carbon capture cleans up and extends the relevance of present-day industrial processes and fuels. Carbon removal can be deployed concurrent with or independent of today’s energy systems and addresses the legacy carbon still hanging around.
There are different opinions on this. Some consider “geoengineering” to mean any large-scale intervention to counteract climate change. Others reserve the term for interventions that deal only with the effects of climate change, rather than the root cause. For example, solar radiation management, an idea to release tiny particles into the atmosphere that reflect sunlight back into space, would cool the Earth but not change the concentration of carbon in the atmosphere. If we started to do it at scale and then stopped, global warming would rear right back, unless and until the carbon blanketing the atmosphere was removed.
Any global cooling achieved by carbon removal, by contrast, would likely be more durable. To be clear, scientists don’t propose trying to use carbon removal to bring global average temperatures back down to levels seen during the pre-industrial period. It would already take an almost unimaginably large-scale effort to cool the planet just a half a degree or so with carbon removal — more on that in a bit.
While scientists have been talking about carbon removal for decades, a sense of urgency to develop practicable solutions emerged in the years following the 2015 Paris Climate Agreement. The signatories to that United Nations agreement, which included almost every nation in the world, committed to limit warming to “well below 2 degrees Celsius above pre-industrial levels” and strive for no more than 1.5 degrees of warming.
When scientists with the United Nations’ Intergovernmental Panel on Climate Change reviewed more than a thousand modeled scenarios mapping out how the world could achieve these goals, they found that it would be extraordinarily difficult without some degree of carbon removal. We had emitted so much by that point and made so little progress to change our energy systems that success required either cutting emissions at an unfathomably fast clip, cutting emissions more gradually and rapidly scaling up carbon removal to counteract the residuals, or “overshooting” the temperature targets altogether and using carbon removal to back into them.
If limiting warming to 1.5 degrees was a stretch back then, today it’s become even more implausible. “Recent warming trends and the lack of adequate mitigation measures make it clear that the 1.5°C goal will not be met,” reads a January 2025 report from the independent climate science research group Berkeley Earth. The authors expect the threshold to be crossed in the next five to 10 years. Another independent research group, Climate Action Tracker, estimates that current policies put the world on track to warm 2.7 degrees by the end of the century.
To many, carbon removal may seem Sisyphean. As long as we’re still flooding the atmosphere with carbon, trying to take it out bit by bit sounds futile.
But our relatively slow progress cleaning up our energy systems only strengthens the case to develop carbon removal. Just think of all the carbon that’s continuing to accumulate! If we reach a point in the future where energy is cleaner and emissions are significantly lower, carbon removal offers a chance to siphon out some of it and start to reverse the dangerous effects of climate change. If we don’t start building that capacity today, future generations will not have that option.
Scientists also make the case that carbon removal will be essential to halting climate change, never mind reversing it. That’s because there are some human activities that are so difficult or expensive to decarbonize — think commercial aviation, shipping, agriculture — that it may be easier, more economical, or even more environmentally friendly to remove the greenhouse gases they emit after the fact. Stopping the planet from warming does not necessarily require eliminating all emissions. The more likely path is to achieve “net zero,” a point where any remaining emissions are counterbalanced by an equal amount of carbon removal, including from human activities as well as natural carbon sinks.
It would certainly be easier, less expensive, and less resource-intensive to cut emissions today than it will be to remove them in the future. Some scientists have even argued we may be better off assuming carbon removal will not work at scale, as that might motivate more rapid emissions reductions. But the IPCC concluded pretty definitively in 2022 that carbon removal will be required if we want to stabilize global temperatures below 2 degrees this century.
The Paris Agreement temperature targets are not thresholds after which the world falls apart. But every tenth of a degree of warming will strain the Earth’s systems and test human survival more than the last. Abandoning carbon removal means accepting whatever dangerous and devastating effects we fail to avoid.
The latest edition of the “State of CDR” report, put together by a group of leading carbon removal researchers, found that all of the Paris Agreement-consistent scenarios modeled in the scientific literature require removing between 4 billion and 6 billion metric tons of carbon per year by 2035, and between 6 billion and 10 billion metric tons by 2050. For context, they estimate that the world currently removes about 2 billion metric tons of carbon per year over and above what the Earth would naturally absorb without human interference, 99% of which comes from planting trees and managing forests.
These estimates, however, are steeped in uncertainty, as the models make assumptions about the cost and speed of decarbonization and society’s willingness to make behavioral changes such as eating less meat and flying less. We could work toward other futures with less reliance on carbon removal. We could also passively drift toward one that calls for far more.
In short, the amount of carbon removal that may be desirable in the future depends largely on how quickly we reduce emissions and how successful we are in solving the hardest-to-decarbonize parts of the economy. It also depends on what kinds of trade-offs society is willing to make. Large-scale carbon removal would likely be resource-intensive, requiring a lot of land, energy, or both, and could impinge on other sustainability goals.
Afforestation and reforestation are responsible for most carbon removal that happens today, and planting more trees is essential to tackling climate change. But it would be a mistake to bank our carbon removal strategy on that approach alone. For one, depending on how much carbon removal is needed, there may not be enough land that can or should be forested without encroaching on food production or other uses. Large-scale tree planting efforts also often produce monoculture plantations, which are an inexpensive way to maximize carbon sequestration but can harm biodiversity.
The other argument for developing alternative solutions has to do with time. As I explained earlier, carbon dioxide emissions can stay in the atmosphere for millennia. Most tree species do not live longer than 1,000 years, and some are known to survive only for a few decades. The carbon stored in trees is vulnerable to fires, pests, disease, drought, and the simple fact of mortality. Climate change is already increasing these risks.
If we use carbon removal to neutralize residual fossil fuel emissions — which, again, could help us halt warming faster than we otherwise would be able to — the carbon will need to stay out of the atmosphere for as long as the emissions stay in. When we rely on trees to offset CO2 emissions, the climate scientist Zeke Hausfather wrote in a 2022 New York Times op-ed, we “risk merely hitting the climate ‘snooze’ button, kicking the can to future generations who will have to deal with those emissions.”
Every form of carbon removal has trade-offs. Direct air capture uses lots of energy; enhanced rock weathering relies on dirty mining processes and its effectiveness is difficult to measure. It’s still too early to know the extent to which these can be minimized, or to say what the ideal mix of solutions looks like.
There are hundreds of companies and research labs around the world working on various methods to remove carbon from the atmosphere, and the number of real-world projects is growing every year. But the field’s progress is limited by funding. There’s no natural market for carbon removal — it’s essentially a public service. Most of the money going into the field has come from tech companies like Microsoft and Stripe, which have voluntarily paid for carbon removals that haven’t happened yet to help startups access capital to deploy demonstration projects.
Experts across the industry say that in order for carbon removal to scale, governments will need to play a much bigger role. For one, they’ll likely need to pony up for research and development. The U.S. government has been spending about $1 billion per year to support carbon removal research, but according to one estimate, we’ll need to scale that to $100 billion per year by 2050 in order to make the technology set a viable solution. Many argue that compliance markets, in which governments require companies to lower their emissions and permit the purchase of carbon removal to meet targets, will be key to creating sustained demand. (These are not to be confused with carbon offsets, which have also been part of these markets, but have been more focused on projects that avoid emissions.) That’s already starting to happen abroad — this summer, the U.K. decided to incorporate removals into its emissions cap and trade program in 2029, and the E.U. proposed doing the same.
The few programs we do have in the U.S., on the other hand, are currently at risk. Congress appropriated $3.5 billion to the Department of Energy in 2021 to develop several direct air capture “hubs,” but Secretary of Energy Chris Wright may try to cancel the program. The agency also had a pilot program in which it planned to pre-pay for carbon removal, similar to what the tech companies have done, but it’s unclear whether that will move forward. But there’s more action in other countries.
Another central preoccupation in the field today is the development of robust standards that ensure we can accurately measure and report how much carbon is removed by each method. While this is relatively straightforward for a direct air capture system, which is a closed system, it’s much harder for enhanced rock weathering, for example, where there are a lot of outside variables that could affect the fate of the carbon.
