One of the most insanely awesome strategies for combating global warming is oceanic iron seeding. The basic idea is you take a whole bunch of whatever element is limiting plankton growth on the high seas (in most places iron; sometimes nitrogen or phosphorus) and dump it in the ocean. The result is a plankton bloom, which removes carbon dioxide from the atmosphere and in theory could lead to lower temperatures. While the concept has been around for a while--in 1985 climatologist John Martin famously remarked, "Give me a half-tanker of iron and I'll give you the next ice age"--it's never been taken all that seriously.
But, as The New York Times reports, with the growing popularity of carbon offsets, there's suddenly money to be made if this can actually work. Planktos, a company involved in the carbon-offset market, has deployed a research vessel off the coast of Florida to do an iron-seeding test run. There are a number of obstacles to the widespread commercialization of the practice. For one thing, no one's really sure what fraction of the carbon dioxide taken up by plankton blooms actually ends up being buried on the seafloor, as opposed to being cycled back to the atmosphere through respiration (which would defeat the whole purpose of the scheme). It's been estimated that iron seeding could cost upwards of $100 per ton of carbon dioxide sequestered, which is not at all commercially viable (though Planktos probably wouldn't be undertaking this research unless the company had some reason to believe it can be done for less than that). And most scientists are none too fond of geoengineering schemes in general. What's disturbing, though, is that there's effectively no law governing the practice:
If a company wants to seed the ocean, there is little that scientists--or governments--can do to stop them. Few enforceable treaties exist in international waters, and if a company wanted to avoid them, it would be easy to do so.
If this turns out to work, what's to stop Osama bin Laden from taking a few shiploads of nails and wreaking havoc on the world?? (Roland Emmerich, take note!)