I am just finishing reading the new book "Censoring Science" by Mark Bowen about Jim Hansen, NASA climatologist and its primary global warming scientist at the Goddard Institute for Space Studies. There are several comments made therein about problems with a hydrogen economy based on fuel cells, specifically the damaging effect of inevitably leaked hydrogen on our critical ozone layer in our stratosphere. ("Tromp et al., Potential Environmental Impact of a Hydrogen Economy on the Stratosphere", Science, vol. 300, pp.1740-1742. 2003).`By the way, Dr. Hansen has so far been successful in fighting off Swift-Boat type attacks from his own NASA administrator, Sean O'Keefe, a political appointee and good friend of VP Dick Cheney.`As an author of multiple publications in Science, I recommend thorough and serious study to interested readers.