Via The Age:

New research from Sydney University appears to have scotched ambitious plans to fertilise the ocean and spawn huge plankton blooms. … [they’ found large-scale iron fertilisation would be a waste of time and money in almost all conditions.

”It blows iron fertilisation out of the water,” said Daniel Harrison, whose paper on the subject is published in the International Journal of Global Warming. ”It is possible to do iron fertilisation efficiently but the perfect conditions you would need are so rare that it would be a very limited contribution to the problem.” … But Mr Harrison’s work shows fertilising a square kilometre of the Southern Ocean would only store about 10 kilograms of carbon dioxide – about as much as a car would emit from burning four litres of petrol

No DOI yet. See here for the abstract.

On average, a single fertilisation is found to result in a net sequestration of 0.01 t C km-2 sequestered for 100 years or more at a cost of US$457 per tonne CO2. Iron fertilisation experiments show high variability in the amount of biomass created and the fraction exported to depth, the range of uncertainty provides a risk of more carbon released to the atmosphere than sequestered for 100 years, or alternatively, reduced cost if optimistic parameters are assumed. Previous estimates of cost fail to recognise the economic challenge of distributing low concentrations of iron over large areas of the ocean surface and the subsequent loss processes that result in only a small net storage of carbon per km2 fertilised. The cost could be lowered by the use of more energy efficient means to distribute the small amounts of iron required over large regions of remote ocean surface, by improving the performance of the iron fertiliser, or potentially by conducting fertilisation activities only under ideal oceanographic conditions.

There’s an “International Journal of Global Warming”? What a terrible name for an academic journal! “Global warming” is a quantity; climate change is the complex phenomenon of which that quantity is a part. Just because the public can’t get it straight is no reason for academics to indulge in it.