One of the most controversial geoengineering schemes that has been proposed to slow the course of global warming, ocean fertilization, received mixed reviews from a new study. The idea involves dumping iron into the ocean to nourish plankton and spur enormous blooms, which would then die off and fall to the sea floor, bringing the carbon dioxide they'd absorbed with them. Now, researchers studying natural plankton blooms near Antarctica have new evidence to fuel the debate over the efficacy of the process, and whether or not it can get our planet out of hot water.