After listening to some interesting talks yesterday about various methods of producing hydrogen as a means to reduce our dependence on fuels that release CO2 into the atmosphere, I was a bit shaken to come across the following article on BBC news – Water builds the heat in Europe.
I guess I knew that water vapor was considered to be a greenhouse gas – here is a nice summary page from the US National Oceanic and Atmospheric Administration (NOAA) about Greenhouse Gases.
Apparently the nature of water vapor as a greenhouse gas in general is well understood, but there is less understanding and modeling about the historical variations of the water cycle that one might think.
Anyway, here is my concern – If water vapor is a greenhouse gas, will reducing carbon emissions have the desired effect if that reduction is accomplished by replacing CO2 emissions with H2O emissions? The reason I am worried is that is exactly what you do when you use hydrogen instead of carbon (coal) or hydrocarbons (petroleum). We have been continually reminded that combustion or electolytic combination of hydrogen with oxygen produces energy and “pure water” as the waste products.
However, most of the processes that are being considered produce that water at temperatures well above the boiling point – in other words, using vast quantities of hydrogen as an energy source will have some kind of impact on the quantity of water vapor in the atmosphere. I have no idea what kinds of feedback mechanisms should be considered, but it sure seems logical that the overall trend would be an increase in water vapor over time as more and more H2O is released in the form of steam.
Any ideas and comments would be most welcome.