More than that, articles like https://www.scientificamerican.com/article/fertilizing-ocean... indicate that the sequestration efficacy varies widely based on a variety of parameters that we do not yet know enough to control. In particular the type of diatom that blooms matters. A lot. And it isn't obvious how to get the one that you want.
Furthermore there is a question of what happens when deep ocean currents turn over the ocean. Does that CO2 come back out? We don't know. And that is the difference between solving the problem versus kicking it down the road for a few centuries.
But still environmentalists have moved to get all research into the topic shut down. Which I think is shortsighted at best. We have a big enough problem and few enough plausible options that I don't believe we should shut this one down.
Furthermore there is a question of what happens when deep ocean currents turn over the ocean. Does that CO2 come back out? We don't know. And that is the difference between solving the problem versus kicking it down the road for a few centuries.
But still environmentalists have moved to get all research into the topic shut down. Which I think is shortsighted at best. We have a big enough problem and few enough plausible options that I don't believe we should shut this one down.