It is wonderful to learn that “fertilizing” the oceans with iron filings could not only produce algae that can be turned into biofuels, but that the greening of the oceans could also help absorb carbon dioxide in the atmosphere (“Sea Green,” September 22, 2007). However, the only viable way of dealing with alternative energy sources is to consider their best mix, as well as their place among the “traditional” energy sources. None of the many ideas on offer today, no matter how wonderful, will work by themselves. As your article shows, the area of the entire North Sea would probably be needed to yield enough algae to replace the fossil fuels used today in transport alone. The remaining question is whether or not the international market is likely to produce the best mix of energy sources that would satisfy energy needs of the entire planet. I rather doubt it. If anything, that market would need to be regulated on the basis of a thorough understanding of the best mix of energy sources, which is likely to shift over time as new technologies come on line. Perhaps the best administrative framework for regulation of the energy market can be provided by the United Nations. Climate change may give it the teeth the organization well deserves.