At last month’s climate conference in Glasgow, U.N. Secretary General António Guterres declared that the global goal of limiting warming to 1.5 degrees Celsius was still alive, but “on life support.”

Carbon dioxide removal (CDR)—the process of drawing carbon dioxide out of the atmosphere and storing it on land or in the oceans—could be part of the medicine needed to bring it back to life. But, like all experimental treatments, its use presents a range of challenges. Overcoming them will require a coordinated effort by a wide range of stakeholders, from research scientists and investors to policymakers and lawyers to environmental and community groups.

There is no question that limiting global warming to 1.5 degrees Celsius will require massive reductions in fossil fuel use and associated greenhouse gas emissions. But even that might not be enough. In a report published earlier this year, the Intergovernmental Panel on Climate concluded that, to achieve the 1.5 degree target, CDR will likely need to be deployed at a large scale “well before 2050.”

Variety of Techniques

Scientists have proposed a variety of CDR techniques that could, at least in theory, be deployed on land or in the oceans. Commonly discussed land-based approaches include afforestation and reforestation, bioenergy with carbon capture and storage, and direct air capture.

While all of these approaches hold promise, they also have major limitations, including large land and/or energy requirements. This has sparked interest in ocean-based approaches, like seaweed cultivation, ocean fertilization and alkalinization, and artificial upwelling.

So far, no CDR techniques have been deployed at a large scale, and many require significantly more research before that can happen. A new report from the National Academies of Sciences identifies over $1 billion worth of “priority research” that will be needed over the next 10 years to better assess the feasibility and impacts of key ocean CDR techniques. That includes $125