Katryna Niva sailing through Halifax Harbour, investigating the effects of enhancing ocean carbon storage. Credit: Katryna Niva

We replaced the stove with plywood, turning the kitchen of the dive boat into an impromptu research lab. Plugging in wires and connecting tubing, we assembled a scientific instrument within the cramped cabin. Then we cast off into Halifax Harbor, Canada, surveying the turquoise waters for signs of an unusual test: could we use the ocean itself to remove carbon dioxide from the air ?

Carbon dioxide (CO₂) is the most important driver of climate change, but it cannot be seen. Its build-up in the atmosphere is gradual. Its worst consequences take time to emerge. Even if emissions fell sharply tomorrow, the CO₂ already released would continue to warm the planet .

That is why scientists and policymakers are increasingly turning to carbon dioxide removal (CDR): taking CO₂ that has already been released back out of the air.…