A quick thought/question...

I was thinking about "green" vehicle technologies, specifically hydrogen cars of the future. I found this quote...

"When hydrogen cars become the status quo, the U. S. can lessen its dependence upon foreign oil, achieve lower prices at the fuel pumps and cut down on the greenhouse gases that produce global warming."

It got me thinking about the "cut down on the greenhouse gases that produce global warming" part. I do believe it's well known that water vapor is one of the largest greenhouse gases today and it's also common knowledge that hydrogen fueled cars emit water vapor as exhaust.

/sarcasm on
So by exhausting water vapor, will we be warming up the planet even more?
/sarcasm off