Attempting to filter enough carbon dioxide out of the atmosphere to make a significant impact on climate change would require hundreds of billions of dollars in government spending, according to a new report.

The suite of technologies emerging to attempt that task all fall under an umbrella called carbon dioxide removal, or CDR. It’s still risky and astronomically expensive. But there’s been growing chatter about it, particularly as the US continues producing record amounts of oil and gas.

According to the new report by research firm Rhodium Group, the US needs to spend roughly $100 billion a year on CDR in order to scale up to a level that would help the country meet its climate goals. A majority of that needs to come in the form of supportive policies like tax credits and procurement programs.

For comparison, the Inflation Reduction Act passed in 2021 includes $369 billion for clean energy incentives — the nation’s largest climate investment to date. So $100 billion of government spending annually, as the report recommends, is a lot to spend on novel technologies that have yet to prove themselves at scale and potentially still not enough to make this strategy effective. It’s a big gamble, with the livability of our planet as we know it on the line.

Solving climate change is a numbers game, and the goal — as defined by the United Nations Intergovernmental Panel on Climate Change — is to reach net-zero carbon dioxide emissions by roughly 2050. That’s what’s needed to stop global average temperatures from rising 1.5 degrees Celsius higher than they were before the Industrial Revolution.

Crossing that threshold means that climate-related disasters like extreme heat, sea level rise, and biodiversity loss become significantly worse, perhaps surpassing humans’ ability to adapt to these changes in the most vulnerable parts of the world. That 1.5-degree target was set in the Paris agreement nearly a decade ago in 2015 — but greenhouse gas emissions are still climbing.

The US is already dumping a good chunk of cash into capturing CO2, even though the only way to stop climate change and meet goals set under the Paris agreement is to stop depending on fossil fuels. The 2021 Bipartisan Infrastructure Law includes $3.5 billion to build new carbon removal hubs across the US. Big companies including Microsoft and Amazon are also paying startups to capture some of their pollution. And the fossil fuel industry has embraced the technology, even using it to market supposedly more sustainable oil. Apparently, that still isn’t enough.

The US will need the capacity to draw down a gigaton of CO2 by 2050 to meet net-zero goals, the report says. It’s an enormous amount of carbon dioxide to capture, equivalent to roughly 20 percent of the nation’s carbon footprint. The country’s capacity to take carbon dioxide out of the atmosphere is tiny in comparison now — in the low single-digit megatons so far.

The report points to three different tactics for taking carbon dioxide out of the atmosphere: natural methods that rely on plants, soil, and the ocean to absorb CO2; building machines that capture carbon dioxide; and hybrid technologies that employ both natural and engineered processes. All three strategies pose their own challenges.

Tree planting has been the most popular nature-based tactic so far — to little success. A growing body of research and investigations has found that offsetting emissions with forestry projects has largely failed. The trees often don’t survive long enough to make a meaningful dent in atmospheric CO2, for example, and then there’s double counting when more than one group claims the carbon credits.

Machines that suck carbon dioxide out of the air or seawater are supposed to be better at keeping track of the amount of CO2 they trap. But the enormous amount of energy they use makes these devices inefficient and exorbitantly expensive. It costs upward of $600 to filter a ton of CO2 out of the air. Multiply that by a gigaton (a billion metric tons) and you get to hundreds of billions of dollars of spending.

With that in mind, spending $100 billion on CDR is likely a minimum of what these technologies could cost, according to Joseph Romm, senior research fellow at the Penn Center for Science, Sustainability, and the Media.

“I think there is a misleading level of certainty in this report,” Romm says. “It is premature to be scaling up any of these [technologies]. These need a lot more study.” There are so many limitations to the most studied CDR techniques — including tree planting and machines that capture CO2 — that Romm says the money would be better spent researching other ways to reduce greenhouse gas emissions.

“The two most urgent things that we have to do now, are stopping deforestation and stopping putting more CO2 into the air,” he says. Once that’s happening, then it could be worth it to stretch resources toward carbon dioxide removal that tackles our historic emissions. But why put a Band-Aid on the problem if we aren’t stopping the bleeding?