Most efforts at combating climate change have focused on reducing carbon emissions or trying to eliminate them, but many climate scientists believe we may have already passed the point of no return. That’s why Noah Deich wants to pull carbon out of the air.

"Not only can we stop making a mess, we can clean it up." Deich is the founder of a nonprofit called the Center for Carbon Removal; its goal is to bring together scientists, political figures and leaders in the energy industries to find the best way to remove CO2 from the atmosphere. "Not only can we stop making a mess, but we can clean it up and hopefully prevent all of the damages scientists expect will happen if we don’t clean it up," he says.

Carbon removal schemes aren’t new, and they aren’t entirely supported by the scientific community, either. Some groups of scientists are working on the problem, and documents like the one published by the UN’s Intergovernmental Panel on Climate Change urge developing this kind of technology in the future. One major barrier is cost. Technology already exists to remove CO2 from smokestacks at a reasonable price, but taking it out of the air raises the price — just how much, though, is disputed.

"It’s not a question of if we can take carbon out of the atmosphere, but I think the question is if all of the technologies that can take carbon out of the atmosphere do it in a cost effective, sustainable and scalable way," Deich says. He believes we can find a cost effective method.

One thing is for sure: the amount of carbon dioxide in the atmosphere is rising One thing is for sure: the amount of carbon dioxide in the atmosphere is rising. Currently, the level of CO2 is just over 400 parts per million — so 400 CO2 molecules for every million gas molecules. It doesn’t sounds like a lot, but scientists say that small changes in the balance can have major impacts. Concentrations of carbon dioxide are projected to almost double to 750 parts per million by 2100, according to research from MIT. Those levels are alarmingly high, since carbon dioxide was at 280 ppm before the industrial revolution picked up in the late 1700s and early 1800s.

The UN's goal for CO2 emissions is currently unrealistic The UN’s goal is to keep CO2 from going over 450ppm in the next century, in the hopes of avoiding the likely catastrophic effects of climate change. That goal currently appears unrealistic, thanks to a lack of investment in the technology and the continued global reliance on fossil fuels, according to many climate scientists. Deals among members of the United Nations could help, but they will have to be swift and unyielding to prevent catastrophic consequences. The largest industrial nations will not just have to promise to try to cut emissions by large numbers, they will have to meet those goals and even try to exceed them.

In terms of technological help, a machine made to pull carbon dioxide out of the air is crucial, says Deich. Recently, just such a machine made headlines: it pulls CO2 out of the air, processes it and combines it with hydrogen to make hydrocarbons so the CO2 can be used as fuel. There are also ideas for storing carbon in soils that can absorb it. "This is really an untapped area for technology innovation," Deich said.

Lackner believes his methods could help stop climate change One method for carbon removal, created by Klaus Lackner, who is the director at the Center for Negative Carbon Emissions, uses sodium carbonate and a resin material to suck up carbon from the air like a plant’s or tree’s leaves do. The resin soaks up the CO2 like a sponge, and the carbon can be removed by adding water in a vacuum sealed container. Then, the CO2 can be pumped underground, in a process called sequestration.

Lackner believes his methods could help stop climate change. He says it’s not likely the atmosphere can handle "800 or 1,000 ppm of CO2, and we will likely get there this century if we don’t do anything about it," Lackner told The Verge. "We will need to balance the system out and find a way to get negative emissions."

Much of the scientific community doesn’t especially care for carbon capture. Many researchers who are working on promoting green energy or planning on capturing the CO2 directly from smoke stacks don’t want a technology that lets people pollute as much as they want so it can be captured later, Lackner says. But plenty of fossil fuels are burned without carbon capture — in planes, ships, and automobiles, for instance — so we will eventually have to capture what’s already in the atmosphere, he says. The real issue is affordability.

The real issue is affordability People like Lackner are hopeful that carbon capture can be made cheap quickly. But that may not be possible. For instance, there’s Sherwood’s plot, a graph that shows how much it will cost to handle a certain volume of material based on how diluted it is. It’s a straight line upward for cost as the material is more diluted. CO2 is 300 times more diluted in air than it is in a smoke stack, according to Lackner. With the cost of taking it out of a smokestack running around $80 to $100 per ton of CO2, it would conceivably be incredibly expensive to take it out of the air. Most estimates for the cost of open air carbon capture range between $200 per ton and $1,000 per ton of CO2.

Lackner wants to find his way around the plot’s skyward trajectory. He agrees with the basic idea behind Sherwood’s plot — that a more dilute substance costs more to capture — but he thinks he can disrupt the linear growth in cost. The way to do that, according to Lackner, is by not forcing the machine to actively seek out carbon dioxide. His device lets CO2 come to it, instead of grabbing everything around in an attempt to find CO2, as its first step of the process— think of it as standing in the wind, rather than sucking in large volumes of air. Designs that allow this type of airflow could get the cost down to $5 or $10 per ton of CO2 captured, Lackner says.

But Lackner’s estimates sharply contrast what some studies of carbon capture devices, which usually estimate capture’s minimum cost as around $200–$400 per ton. Howard Herzog, a senior research engineer at MIT, was one of the researchers who helped conduct a 2011 study that looked at the cost of capturing carbon from outside air. His team based their research on the devices that would capture carbon from smoke stacks, and using Sherwood’s plot, they found an open air machine would likely cost $1,000 per ton of CO2 captured at this point. However, Lackner’s device isn’t the same as the device used to get CO2 from smokestacks, so this estimate may not directly reflect that cost.

There are ways that cost can be driven down, but the overall volume of the air that needs to be handled and how diluted the CO2 is makes it an expensive process, Herzog says. "If you have basically free electricity [for the device], then that changes things, but I just don’t see that happening anytime soon," he says. One of the biggest issues is how much energy a machine needs to capture carbon, so very cheap electricity will be key. Even technologies that are often called free energy, like solar panels, typically cost at least 12 cents per kilowatt hour — and that’s still too expensive. It’s important that the air capture device be running on energy not created by burning much fossil fuels, otherwise you’re just "chasing your tail," Herzog says.