Ann: Hazer Achieves First Hydrogen and Graphite at CDP, page-176

So, just elaborating on my previous one-liner. The amount of water in the atmosphere is regulated by the water-carrying capacity of the atmosphere irrespective of the rate of "emissions" of water. Any emissions of water from combustion (of hydrogen, hydrocarbons or anything else) is completely dwarfed by evaporation from the oceans. Burning hydrogen will not make one dot of different to the amount of water vapor in the atmosphere. The article linked by hatmopit is a good read about the water-carrying capacity of the atmosphere, but water emissions from combustion are irrelevant to the effects it discusses.