So what you are basically stating is that water vapour is not a greenhouse gas? Wait! Perhaps water vapour Is a feedback and it can not act as a forcing but rather as a feedback? That makes sense doesn't it? If you increase the amount of water vapour in the atmosphere, due to it's greenhouse gas properties, the warming of the original forcing will be enhanced. If you decrease the amount of water vapour in the atmosphere, due to these same properties, the warming due to water vapour will be decreased. This is the definition of the term 'feedback'. If water vapour did act like the forcing we would have a runaway greenhouse effect. The question of water vapour being a positive or negative feedback is not a question of is it a greenhouse gas or not as you seem to be asking in this question. It is a question of how many clouds will form as a consequence of increased atmospheric water vapour. The question is, "Will atmospheric water vapour increase faster than the atmosphere can hold, thereby increasing cloud cover and providing cooling, or will it be slower than the increase in air parcels due to warming. This is where your 'relative humidity' comes into play. There have been tests of the feedback effect of water vapour before.

Positive water vapour feedback in climate models confirmed by satellite data (1991) - http://www.nature.com/nature/journal/v34...

Watervapor feedback and global warming (2000) - http://www.clidyn.ethz.ch/ese101/Papers/...

Global Cooling After the Eruption of Mount Pinatubo: A Test of Climate Feedback by Water Vapor (2001) - http://envsci.rutgers.edu/~toine379/extr...

Quantifying the water vapour feedback associated with post-Pinatubo global cooling (2004) - http://homepages.see.leeds.ac.uk/~earpmf...

Water-vapor climate feedback inferred from climate fluctuations, 2003–2008 (2008) - http://geotest.tamu.edu/userfiles/229/De...

Edit: If Water vapour has more negative feedbacks than positive ones, and greater amounts, perhaps you could list them as well as the amounts those feedbacks work at?

Umm, what is it you are asking your own graph show the slow rise in water vapor (with some natural variation) 1998 (actually 97/98) was a century high El Nino by all accounts and water vapor peaked in that year as well. What followed 98 was not really a fall but a return to the years just before 98 and there is still a slow rise to be seen, but this is your link and it seems to show three different papers results, from as usual some wordpress source rather than original sources. But even your own link show the absurdity of your own comment.

"why did it rapidly cool down after the El Nino finished"

Gee, could it be the El Nino ended and both water vapor and temperature returned to the pre El Nino state, the second last (red) dot is 2008 another cool year linked to a La Nina, which would support the concept that water vapor is tied to temperature, I really fail to understand why you seem to keep trying to make a fool of yourself with these easily disproved statements, when you seem to simply try to ignore the real answers to them.

I guess that memory of yours which has stated previously you where a retired fisherman and then changed it to retired power station worker fails to also grasp you have previously claimed water vapor has not risen, yet here you post a link that clearly shows it has, have you considered being tested for alzheimer's.

Kano, take a deep breath....

Water vapor stays on average in the atmosphere for 6 days. It does not stay around long enough to sustain the warming, but it does amplify the effects of CO2. [1]

I do understand where you are coming from and at first it took me a while to get it as well. As a fellow fisherman, I suggest you go fishing and think about how this all fits together.

Edit.

The other answerers don't understand what part you are not understanding or think it is so simple you should know this and since you are not getting the answer you are looking for, you get frustrated. Don't get me wrong I am only trying to help here, not pretend that I am smarter then you, as I know full well that I am not.

Water vapor in the atmosphere has a short residence time.



And why not? Amplification works both ways.

James



And all this time I thought it was lack of evidence.

>>but it doesn't show water vapor increases temperature 'positive feedback failed'<<

How did you manage to reach adulthood believing that everything is just one thing that always looks like the same thing - and never changes - and is never affected or altered by any other thing in the whole world?

AGW cultists do not believe in negative feedbacks. It doesn't support the 'cause.'

and increased water vapor is supposed to give increased warming, and warming is supposed to increase water vapor, how come during the 1998 El Nino when temperatures peaked and water vapor also peaked, see here http://tamino.files.wordpress.com/2012/08/humid1.jpg why did it rapidly cool down after the El Nino finished.

I mean that show temperature increases water vapor, but it doesn't show water vapor increases temperature 'positive feedback failed'