San Francisco Chronicle: For more than a dozen years, researchers have been fertilizing small patches of the world’s oceans with iron to see if they could make the floating plants called phytoplankton flourish into massive blooms that would absorb carbon dioxide, the worst planet-warming greenhouse gas in the atmosphere. The idea was that the absorbed carbon would sink to the ocean bottom and remain there essentially forever. Many experts have hailed the idea as one surefire solution to the problem of global …