My friend Alex Tabarrok, of the Marginal Revolution blog (probably the single best blog on the web), has posted on one possible geoengineering solution to climate change: iron fertilization of the oceans to promote plankton blooms that would absorb carbon dioxide from the atmosphere. Alex gives credit to Steven Levitt and Stephen Dubner for raising the profile of geoengineering in their new book, Superfreakonomics, even though Tom Schelling and Scott Barrett (among others) have been writing about it for a decade or more. [Apparently, nothing the Nobel laureate Schelling writes reaches public consciousness until it is repeated by, and credited to, the likes of Steven Levitt or Malcolm Gladwell.]
In my view, Alex is a bit too sanguine about the promise of ocean fertilization, which at best could absorb only about 1/7th or so of total anthropogenic carbon emissions (according to this report). Meanwhile, carbon has recently been found to increase ocean acidification, which can massively disrupt marine ecosystems (according to a 2005 study by the Royal Society, here). In other words, ocean fertilization is not a panacea.
Neither, more broadly, is geoengineering. It is one important part of the puzzle of climate stabilization. As Alex notes, it certainly does deserve more attention than it has received to date from policy-makers. But, just as with efforts to reduce carbon emissions, institutional structures must be developed to ensure that (a) specific geoengineering techniques do more good than harm and (b) address potential liability issues.
For climate change, of all issues, there are no panaceas.