We're a Step Closer to Geoengineering the Oceans

The National Academy of Sciences released a major report chronicling six techniques to turn the oceans into carbon dioxide vacuums.

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A wave crashes off Teahupoo, Tahiti, a popular surf break. The water is a rich turquoise blue and spray shoots off the top of the wave..
The perfect place to hang 10 and store some carbon.
Photo: Brian Bielmann/AFP (Getty Images)

The U.S. government has moved one step closer to turning science fiction into reality. On Wednesday, the federally funded National Academy of Sciences released a new report laying out six avenues to alter the oceans in an attempt to suck more carbon dioxide out of the sky and store it for centuries to come.

The ideas explored in the 300-page, peer-reviewed report include using electrical currents on seawater and dumping iron in the ocean to encourage massive plankton blooms. All six are far from ready for primetime, but the report is essentially a roadmap for a research program and legal framework for the techniques.

The blanket term for these methods—and others that use land and machinery alike—is carbon dioxide removal, also known as a form of geoengineering. We have very little capacity to do that right now, and the companies that are doing it charge much more than the target outlined in the report and in other research ($100 per ton of carbon stashed away). The NAS has previously laid out a roadmap for land-based techniques, but the new report looks at the world’s largest carbon sink. It comes at a time when the urgency of climate change is growing, yet world leaders have largely failed to take the necessary steps to end fossil fuel use.


Oceans already suck up a quarter of humanity’s carbon emissions. But they, along with other biological carbon sinks, will need to do more than that in the future to keep global warming below the 1.5-degree-Celsius (2.7-degree-Fahrenheit) threshold outlined in international agreements. The most commonly studied form of ocean geoengineering is iron fertilization, which would encourage plankton blooms to suck up carbon. Other techniques will also likely sound familiar, including seaweed cultivation and ecosystem restoration.

But the other three are more fantastical. Among them are inducing artificial upwelling and downwelling, so that the ocean water on the surface takes up more carbon, then siphons it down to the deep sea. Another approach is putting lime or other alkaline agents in the ocean. That would reduce ocean acidification, itself the result of a reaction when seawater comes in contact with carbon dioxide, and allow oceans to take up more carbon pollution. The third is electrochemical carbon removal, pumping seawater through machinery that would draw carbon dioxide out of it and then safely store it away.


All techniques have multiple hurdles to overcome, ranging from feasibility to regulatory. Dumping tons of iron in the ocean, for example, could have unintended consequences on marine life and fisheries, while zapping carbon dioxide out of ocean water would require large amounts of energy. These are all bleeding-edge areas of research with major outstanding questions. Among them is how permanent these approaches are. To be successful, sequestered carbon will likely need to end up in the deep sea. If it stays in the first 3,280 feet (1,000 meters) of the ocean, it will likely be put back in the atmosphere at some point, negating the benefits of sucking it up in the first place. These and other high-stakes research questions would form the backbone of any carbon dioxide removal study program.

Some environmental laws at the national and international level cover geoengineering the seas. The report notes the Paris Agreement gives implicit support to carbon dioxide removal with several mentions of carbon sinks. But other treaties, such as the Convention on Biological Diversity, have put a “de facto moratorium” on geoengineering the seas.


“None of these regulations, treaties, or laws were written with CDR in mind,” Scott Doney, an ocean researcher at the University of Virginia who led the report, said at a launch event for the report.Moving forward, we’ll need to do a deeper dive” on research and regulations in tandem, he added.

Those hurdles, along with ones of equity and respecting tribal treaty rights, and risks all matter. But they don’t outweigh the need to explore how to suck carbon dioxide from the sky. Other analyses like those done by the Intergovernmental Panel on Climate Change have estimated that the world will collectively need to remove about 10 gigatons of carbon dioxide from the atmosphere per year by midcentury to not overshoot the 1.5-degree-Celsius range of heating. To that end, the report puts together both a foundational plan and a full-blown research program. To get research off the ground, the report calls for $125 million in investments over the next decade, with the biggest chunk at $50 million going to public outreach and engagement. A rigorous research program would cost an estimated $2.4 billion, or 0.3% of the just-passed annual Pentagon budget.


The need for a democratic and inclusive program has never been more vital. The field of carbon dioxide removal has increasingly become a focal point of billionaire climate philanthropy and venture capital. The reasons are twofold. One is the aforementioned not-cooking-the-planet thing. But it’s also a chance to make some people fabulously rich, if the private sector has its way. Removing about 10 gigatons of carbon dioxide from the atmosphere annually by midcentury means this could be a $1 trillion per year industry.

The report calls for private investment to play a role in studying the six avenues of sequestration, though Doney noted the need for a “robust” framework set by lawmakers. That means governments will need to set an agenda, engage citizens, and create regulations to ensure we don’t end up with a bunch of rogue for-profit companies driving the bus. We’ve seen what that can look like.


Update, 12/8/21, 11:36 a.m.: This post has been updated with comments from the report launch.