Is the hydrogen economy going to make things worse?

I recently learned (from a Finnish science TV program called Prisma) that water vapor is the most significant greenhouse gas in Earth’s atmosphere, being several times more potent than carbon dioxide, which ranks third after water (condensed in clouds). Apparently between 0.5-4.0 per cent of atmosphere consists of water vapor (though I couldn’t find this info in the traditional atmospheric gas breakdown; i.e. nitrogen 78%, oxygen 21%, 0.93% argon, etc…), while only 0.03 per cent is carbon dioxide, which has rapidly risen to enemy number one for various environmentalists.

Alleged global warming is said to increase also the level of water vapor in the atmosphere, primarily by making the oceans warmer and thus increasing evaporation of ocean water into atmosphere. This of course causes further global warming.

However, during the week after the TV show I started thinking about this water vapor issue. Everyone is pretty much waiting for the hydrogen economy of the future, where eventually all the cars run on hydrogen (which is hopefully produced cleanly in where it’s most efficient, as by-product of nuclear reactors). “Burning” hydrogen as a fuel to propel vehicles is clean, much cleaner than today’s combustion engines. Hydrogen fuel cells (HFC) emit only one kind of produce – water vapor. That struck to me, is the hydrogen economy going to help us at all, if too much water vapor in the atmosphere is actually worse than some added carbon dioxide?

That said, I’ve no idea how much water vapor HFCs actually emit and can make no inferences whether the outcome is more or less than this carbon emissions induced global warming that we’re allegedly witnessing right now. I suppose it’s something worth checking though. Gotta admit I went a little WTF when this idea occurred to me. Did you?