In a nutshell, it works like this: Seed the vast lifeless stretches of ocean with iron and plankton will blossom. They'll capture carbon from the atmosphere and when they die they'll take some of that carbon with them to the ocean depths. It's been compared to tree-planting projects, without the threat of fires which release trapped carbon.
Promoters of the strategy like to cite oceanographer John Martin, who said at the famed Woods Hold Oceanographic Institute: "Give me a half a tanker of iron and I will give you another ice age." Apparently he said it with a mock Dr. Strangelove accent, but no matter. Combine that quote with Kyoto Protocol carbon credits and you've got yourself a business model.
The scientists' letter really only affects the funding of the current research, and that mostly spells bad news for Planktos, a penny stock company that's already on shaky ground, according to its financial reports. Other companies include Climos and Sea Green Ventures, which seems to be based in Florida.
Planktos has been outfitting a research vessel and plans to begin conducting larger scale experiments soon. The other companies and government-backed research centers are also preparing research, but it seems most of results are at least a year away.
The scientists aren't trying to stop the research, just slow one avenue of funding, which is the selling of carbon credits. Sensibly, they simply point out that carbon credits shouldn't be sold until its clear the carbon captured is actually retained."However, the efficiency with which OIF captures carbon from the atmosphere and retains it in the deep ocean, is still uncertain and unintended ecological impacts are not yet fully understood."
It remains a promising technology. This is simply a warning to verifiers to steer clear of Planktos, which has been criticized for loose standards and its rush to sell voluntary carbon offsets, which are targeted at consumers and suffer from flimsy standards.