January 8, 2026 — A few months ago, the oceanographer Adam Subhas and his colleagues turned the sea red. At first it looked as if the scientists had dumped a few barrels of beet juice into the Gulf of Maine. A narrow band of crimson water lingered in the wake of one of their chartered vessels, briefly tinging violet here or magenta there when tumbled by wind and waves. As the ship began to make a circle, the maroon trail elongated and expanded, soon filling a much larger part of the sea. Onlookers on a passing vessel might have mistaken the scene for the aftermath of a shark attack.
It was, in fact, something even more unusual — and, to some people, no less alarming. The scientists were deliberately pumping about 16,200 gallons of sodium hydroxide, more commonly known as lye, into the ocean, along with a red dye that made the solution easier to track. It was the final phase of a study on a promising yet controversial climate intervention, one that could simultaneously mitigate both global warming and another, equally terrifying consequence of carbon emissions: the rapid acidification of the world’s oceans.
Since the advent of the industrial age, the oceans have absorbed about one-third of humanity’s heat-trapping carbon emissions. Were it not for that immense buffer, the planet would be substantially warmer and more tempestuous than it is today. As carbon dioxide from the atmosphere dissolves into the ocean, however, it reacts with seawater to form carbonic acid, which disrupts the ocean’s chemical balance and reduces its capacity to absorb more carbon. Prolonged acidification will severely threaten marine ecosystems and fisheries on which more than one billion people depend.
To counteract these effects, scientists have proposed a type of geoengineering known as ocean alkalinity enhancement, which essentially involves concocting antacids for the sea. Modifying the planet’s chemistry in this way allows more carbon to flow from the atmosphere to the ocean, where it can be stored for thousands of years. Experts emphasize that such mediation would be entirely ineffectual without first slashing greenhouse-gas emissions. Yet they also agree that emissions reductions alone are no longer sufficient to prevent the planet from warming two degrees Celsius above the preindustrial base line, at which point extreme weather, sea-ice decline, species loss and crop failures would be anywhere from two to 10 times as bad as they are now and at which tens of millions more people would be subjected to severe heat, flooding and water scarcity. Given that the oceans cover more than 70 percent of the planet’s surface and are fundamental to climate regulation, it seems inevitable that they will be part of these supplemental efforts.