Forbes:

. . .But we can take this a step further. We should also be looking at other ideas: say, geoengineering. I agree that some of those ideas (millions of mirrors in space?) are pretty way out there and don’t strike anyone as being particularly cheap. Others though appear to be extraordinarily cheap, quite amazingly so. We should therefore be pursuing them.
Dumping iron into the sea can bury carbon dioxide for centuries, potentially helping reduce the impact of climate change, according to a major new study. The work shows for the first time that much of the algae that blooms when iron filings are added dies and falls into the deep ocean.
It’s been known for a long time that certain parts of the ocean are iron poor, a nutrient needed by various algae. Add the iron (as Saharan winds carrying iron rich dust into the Atlantic often do) and you’ll get algal blooms. What wasn’t certain was whether the carbon in such algal blooms sank to the ocean floor (in the end, to become new sedimentary rocks) or were released back into the water on the death of such algae. This experiment says that some portion does sink and that thus some carbon is sequestrated.
Is this a complete solution to anything? No, not at all: there’s not enough of the ocean which is iron poor for us to fertilise to absorb all emissions. However, it is helpful: which is the first part of the equation. . .

Realistically, is there any geoengineering plan that would get approved for use? We can’t get Russia to agree that Syria is an issue, let alone sign-off on a plan to dump iron into the ocean that would make it colder where the Russians want it warmer.

Until somebody can explain to me how one of these big initiatives would ever pass the U.N. — or whatever body is set up to approve such things — I don’t find any use in discussing them.