Ah, trapping it would work, I was just thinking that in arid large cities like, oh, say, denver, having a couple hundred thousand cars emitting water vapor every day could make a difference. However, unless you get the hydrogen from water, wouldn't the water emitted eventually cause a noticeable change? I know that around here, we would be glad for the extra water, but I doubt that goes for everyone everywhere.
Are the people working on fuel cell tech thinking of using water, or something else? I know you can dissolve aluminum in some solution or another to get hydrogen, but water would be more plentiful, and some of it is in less demand than aluminum.
Khar, unless my elementary school education has betrayed me, we breathe out co2, don't we? So of course having all our industries and vehicles emit co2 won't cause any noticeable difference, we have been breathing out co2 for millions of years (or 6000, depending on who you ask), and no problems so far. Oh wait...
Hmm... Using fusion power to split water, if they found a way to set aside the tritium and deuterium from the rest of the hydrogen, which shouldn't be difficult, they figured out how to separate U-235 from 238, use the deut and trit to power the fusion plants, it obviously wouldn't go anywhere near maintaining itself, but the drain would be somewhat slower at least. Of course, that wouldn't work for another 50 years or so, less if the Japanese ITER facility gets running soon. More if it ends up being a dead end, but lets not be so negative.