Title "re: looks like the standard forcing/feedback mistake in your post"
Maybe I'm mistaking which definition of forcing you are using, are you using forcing as the UN uses the term?

It's in the link in my previous post. Wise not to take this bet about the accuracy of your "premise", which sounded like a factual assertion in your post. "

I read the link you provided. It agrees that H2O is major component causing Earth's greenhouse affect- both because more H20 is in the air and as clouds and because "Long-wave (or thermal) radiation is emitted from the surface of the planet and is largely absorbed in the atmosphere. Water vapour is the principle absorber of this radiation (and acknowledged as such by everybody)."

He seems to think that because water is highly dynamic it is less significant as element causing global warming- "Water vapour is a "reactive" GHG with a short atmospheric lifetime of about 1 week."
I not sure how accurate this is. It might be accurate to say the average lifetime of water vapour lasts about a week or maybe 10 days- because a large amount of water vapour could have quite a short lifetime as water vapour. Then he goes on to say, "In contrast, CO2 has a long lifetime (actually calculating a single "lifetime" for it doesn't work; but a given CO2 pulse such as we're supplying now will hang around for.. ohh... a century or more).

I don't think this is accurate.
According to:
http://earthobservatory.nasa.gov/Library/CarbonCycle/carbon_cycle3.html :
"The amounts of carbon that move from the atmosphere through photosynthesis, respiration, and back to the atmosphere are large and produce oscillations in atmospheric carbon dioxide concentrations (see Keeling curve). Over the course of a year, these biological fluxes of carbon are over ten times greater than the amount of carbon introduced to the atmosphere by fossil fuel burning."

So according to his measure of lifetime of a substance..."CO2 pulse... hang around for.. ohh..." a year maybe at most, probably a month.