"Smetacek is aware of the unanswered questions, and told Nature the Alfred Wegener Institute will not conduct any further fertilization experiments."
That is absolutely fucking ridiculous.
OK, so we know iron fertilisation works. This experiment, earlier experiments, the Oz red oxide dust mentioned above, Saharan similar into the Atlantic.
We also know that it could be greatly improved: some areas of the ocean are known to be solely iron deficient. Others are known to be both iron and silicic acid deficient. The addition of both would produce much more sequestration. Quite apart from anything else, it's the silicic acid which limits diatom growth.
The downsides? Sure, only some of the carbon sinks to the ocean floor to become sedimentary rock in due time. The rest is eaten. So, anyone think that creating vast new fisheries is a serious problem? And the fish poop from them goes to the ocean floor again anyway.
But above all else iron fertilisation is so bloody cheap the cost is, by any reasonable scale, nothing.
We are talking of 50 cents to $2 per tonne CO2 sequestrated. Iron just ain't that expensive and 1 tonne into the water gets 3,000 tonnes CO2 into the plankton (of which only a portion is sequestrated). Hell, you don't even need iron. That "red mud" that went splat all over Hungary a couple of years ago would do. 40% Fe and it also provides the silicic acid needed.
Compare this with plastering Germany with solar cells: $1070 per tonne CO2 not emitted.
No, it ain't a complete solution: there's not enough ocean that is iron deficient to absorb all the emissions. But it sure as hell helps and it's the cheapest sodding thing anyone has ever managed to come up with.
And they're going to stop the experiments?
Seriously, are we being ruled by crazed fucking lunatics? Anyone actually serious about climate change would stick £20-£30 million into this immediately.