Planktos plans to fertilize the oceans with iron to stimulate growth of phytoplankton, microscopic marine plants that soak up carbon dioxide. Their ship plans to dissolve tons of iron over a 10,000-square-km patch.
https://www.youtube.com/v/Qe1fOxQSUKs
For more details, see:
Planktos.com
The Independent
NY Times