iron fertilization
I am a bit slow off the mark with this posting from Nature's Climate Feedback blog, but last month they put up a little news about iron fertilization of oceans as a geoengineering technique for removal of atmospheric CO2.
Have a read, but in a nutshell: that Indo-German experiment is going forward in the Southern Ocean and recent studies of naturally occurring blooms are not cause to celebrate, as actual sequestration into deep water is not very high.
As with this story, humanity needs to keep the cork in the champagne bottle for at least a little while longer...