[zeestephen]

Re: The byproduct of burning hydrogen is harmless water vapor...

Whoops.

Water vapor is the most powerful green house gas in our atmosphere.

[Farmerbob]

[...water vapor...]

And the oceans are already rising!

[Telepathic Intruder]

"Water vapor is the most powerful green house gas in our atmosphere"

That said, it is also easily scrubbed from the atmosphere. It happens every time it rains. And when the temperature lowers a bit, it turns into clouds which reflect sunlight back into space. But then greenhouse gasses is not something that keeps be awake at night anyway.