Marine geoengineering projects aimed at increasing carbon dioxide storage in the ocean are on the rise. Recent years have seen more than 50 field tests of different technologies, and hundreds of thousands of carbon credits have been issued to fund the research. But the idea of experimenting with the ocean is highly controversial, especially as the technologies have not been proven at scale. As part The World’s ongoing series The Big Fix, Host Carolyn Beeler speaks with Susanna Lidström, a researcher at the KTH Royal Institute of Technology in Stockholm, Sweden, about the tension between the swell of interest in marine geoengineering and the lack of scientific consensus about its role as a climate solution.