This could slow, limit, or even reverse climate change — but it is not a substitute for cutting greenhouse gas emissions.
This is because carbon removal is generally slow-acting and may not be able to be deployed at scales commensurate with society’s current greenhouse emissions.
Carbon removal is sometimes referred to as carbon dioxide removal or CDR, and technologies for implementing carbon removal are sometimes called Negative Emissions Technologies (NETs).
Some prominent ideas for carbon removal include:
- planting massive new forests (afforestation/reforestation)
- using no-till agriculture and other practices to increase the amount of carbon stored in soils (soil carbon sequestration)
- creating charcoal and burying it or plowing it into fields (biochar)
- capturing and sequestering carbon from biofuels and bioenergy plants (bioenergy with CCS or BECCS)
- spreading crushed rocks over land to absorb carbon dioxide from the air or exposing them to carbon dioxide-rich fluids (enhanced mineralization)
- building machines that would suck carbon dioxide directly out of the atmosphere and bury it (direct air capture)
- spreading alkaline materials, such as lime, over the ocean (ocean alkalinization)
- accelerating the transport of carbon to the ocean depths by pumping surface waters downward (artificial downwelling)
These efforts remain critically important, and we need to accelerate them.
Yet the science shows they will not be enough on their own to have a good chance of meeting the goals of the Paris Agreement on climate change.
To prevent the worst impacts of climate change, the world will need to reach net-negative emissions, a point at which we’re actually removing and storing more carbon from the air than we’re putting into the atmosphere.
This will involve deploying techniques that remove carbon from the atmosphere and permanently store it.