Geoengineering is a special category of technology requiring careful, independent investigation before sinking big bucks on them, or, heaven forbid, risking the planet with one of them. As such, geoengineering approaches often receive scrutiny from some very savvy scientists, who not only want to do good science, but have self-preservation as a driver, as well.
Thus we see one of our premier ocean research institutes, Woods Hole, convening a conference in 2007 on iron fertilization of the oceans. They have a nice, 6-part write-up on this conference, here. One interesting tidbit concerns the person (the late John Martin) credited with the idea, who apparently recalled later that he had said, in a “Dr. Strangelove accent” at an informal seminar:
“Give me half a tanker of iron, and I’ll give you an ice age”
In other words, Martin was being facetious. The Woods Hole conference covered the relative ineffectiveness of the method (not much carbon gets sequestered, and most experiments done to that date were completely unsuccessful); and numerous ecological concerns, including depletion of nutrients (thus suppressing phytoplankton growth down-current), undesirable food chain effects, and growth of toxic algae. The latter issue has recently been confirmed, as I discussed here.
Good scientists being good diplomats, by and large, the 2007 Woods Hole conference did give a nod to further research as being one way to help better consider the pluses and minuses of the approach. Further research is a research institute’s bread and butter, after all. But the conclusions are clear: this method is about as useful as a flood in a fizzies factory, as the old saying goes.