Depending on variables such as vegetation health, the amount of carbon they remove can vary widely. “One of the main risks of some of these biology-based proposals is the assumption that you can easily equate X number of trees with X million tons of carbon without actually looking at what kind of trees they are and where they are” Replanting,” Cox said. The amount of carbon captured may end up being negligible. “You have a lot of trees, which is fantastic. You don’t necessarily get climate benefits. “
Another technology, known as bioenergy with carbon capture and storage, or BECCS, also relies on a single crop, usually a fast-growing grass. In this case, vegetation is burned to generate energy, and the resulting emissions are sequestered underground. But it also has its own set of dubious side effects — it requires large swathes of crops and copious amounts of water to lower carbon levels in the atmosphere: A paper published last month found that, in the U.S. alone, at scale by 2100, BECCS will put 130 million Americans under water stress.
But there is even a risk in restoring forests to their former glory as the global climate goes wild, as that glory becomes increasingly dangerous. Supercharged wildfires are now destroying forests, rather than gently resetting ecosystems to make way for new growth. If you spend a lot of time and money rehabilitating one of the forests to sequester the carbon, and then it burns, all the carbon goes back into the atmosphere.Or, if a particular country’s political system changes and ReplyAfforestation to ofAfforestation, you will have the same problem. Check out what happened to Amazon.
“I would argue that many of the proposals for land clearance could be risky,” Cox said. “Because you have a very, very high risk that the carbon removal doesn’t happen in the first place, or it does, but it reverses after 10 years.”
Terrible “moral hazard”
Researchers have developed a way to simulate natural carbon sequestration using a technique called direct air capture (DAC). These machines suck in air, pass it through membranes to remove carbon dioxide, and then pump it into the ground, locking it in permanently. The tide may be turning to DACs in the US. Last month, the Biden administration committed $3.5 billion to support direct air capture. (That was five years after a California congressman introduced a bill to fund geoengineering research, but it never got anywhere.)
But this also faces two big problems. The first is that DACs exist nowhere near the scale needed to reduce excess carbon in the atmosphere. A plant that came online last year in Iceland captured the equivalent emissions of just 870 cars.A 2021 study calculated that 1% to 2% of global GDP would need to be invested to capture 2.3 gigatonnes of carbon dioxide2 By 2050, this is a fraction of current annual emissions (about 40 gigatons). “There’s a risk that we won’t be able to scale and deploy fast enough,” says Benjamin Sovacool, who studies geoengineering risks at Aarhus University in Denmark. “It looks like we have to deploy these at a different pace than any energy transition we’ve had before because the scale is so massive.”
The second problem is one of “moral hazard”, the tendency to rely on the DAC as a crutch instead of doing what is necessary: slashing greenhouse gas emissions. If a country’s leaders expect to be able to eliminate emissions through DAC, they don’t have to worry about reducing those emissions in the first place. It’s like waiting for a miracle antiviral drug — except the required dose doesn’t exist yet.
The extreme and desperate nature of geoengineering could backfire—rather than encouraging complacency or reliance on last-minute technological fixes, it could alarm the public enough that they will start treating climate change as an emergency. But, Sovacool said, “Politicians may be more susceptible to moral hazard because they only think about the present. They are happy to push as many future generations as possible.”