The balance of evidence suggests specific humidity is increasing. The one paper that shows it has decreased is discussed in the Skeptical Science article.

Global analysis:

http://geotest.tamu.edu/userfiles/216/De...

http://journals.ametsoc.org/doi/pdf/10.1...

http://www.metoffice.gov.uk/hadobs/hadth...

Regional analysis:

http://journals.ametsoc.org/doi/abs/10.1...

Also discussed here:

http://www.skepticalscience.com/humidity...

Dissenting view:

http://www.eike-klima-energie.eu/uploads...

I would say that nobody knows, that's despite the papers that gcnp58 references and the "expert" opinion of Joe Bastardi that Jeff Engr gives. I know some of the people on those papers and they are quite good, still I don't think the data warrant taking the results very seriously. (And Jeff Engr, if you're going to cite a source, pick someone other than Joe Bastardi if you want to be taken seriously. You might as well be citing Bozo the Clown or Mr. Wizard).

People have worked very hard to look for trends using the radiosonde data. Unfortunately radiosonde data on dewpoint/humidity can be quite inaccurate. It's actually fairly difficult to measure humidity accurately, and the hygristors that have been used have had numerous problems. In fact, the U.S. is in the process of replacing all of the Sippican hygristors with ones from Vaisala, I believe. It's not the first time they've been changed, either.

I believe that accurate assessment of water vapor in the atmosphere will have to wait until GPS has been around long enough to get long term trends from the zenith delays. Everybody believes the GPS values of precipitable water (integrated water vapor), but they've only been around for about 20 years at the longest. I've got my own data set that I could look at, but it's only 8 years long. I could extend that to 10 years fairly easily, but what would be the point? The saturation vapor pressure goes about 6% for every Kelvin of warming, That's right around the error level for the measurement, I guess we can improve SNR by combining data from many stations, but there is no guarantee they were even using the same hygristors.

I'd really wait for a couple more decades of GPS measurements before believing any trends.

Pinatubo and El-Chichon warmed the Stratosphere by several degrees for a few years on both incidences, which increased the amount of water vapor that the stratosphere could hold. The dwell time of water vapor in the stratosphere is considerably longer than the troposphere, so it will take many years for the stratosphere to return to Pre Pinatubo conditions.

As far as your statement about stratospheric cooling there has been no recent change in stratospheric temperatures. And then, the stratosphere only cooled in response to the aftermath of two significant volcanic events.

ftp://ftp.ssmi.com/msu/graphics/tls/plot...

Data I have seen on the trpoics water vapor is decreasing. Evidence, Dry bulb temperatures dropped a little and at the same time Wet bulb temperatures have dropped. This means both relative humidity and TOTAL water content in the air has dropped significantly.

Source - Joe Bastardi

No reason or mechanisms were given. Only raw data. Science and our understanding of the psychrometric charts tell us the rest.

Hi Darwinist Here you go http://science.dodlive.mil/2012/09/09/wh... Is this why Obama stopped the shuttle program? 350 tons of water vapor released in the stratosphere from every launch http://en.wikipedia.org/wiki/List_of_spa... and what about high flying aircraft

We need an unbiased source, which will display graphs which refect global trends, rather than one cherrypicked location, to determine if water vapor is increasing. And indeed it is.

http://www.esrl.noaa.gov/gmd/about/ozone...

Doubt it! temperatures would have to be getting warmer. At least a measurable amount.

Why do you think a 0.2C change would create that much more moisture that is measurable?

Equilibrium? How far out of wack can temperatures be? There would have to be some substantial warming for that to happen.

As the planet continues due to AGW water vapor increases, So does the CO2 coming from the oceans

Because of the global warming.

Its decreasing look at the graph.

http://c3headlines.typepad.com/.a/6a0105...

http://www.c3headlines.com/2013/01/atmos...

I understand that stratospheric water vapor is decreasing; presumably as a result of stratospheric cooling, but what about the troposphere? In a warming atmosphere I would expect H2O to be increasing, also that overall levels would be increasing as around 90% of the atmospheric mass is in the troposphere.

I don't know for certain though, so what is the trend in water vapor in different layers of the atmosphere? And what is the overall trend?

Finally, what is the significance of a change in water vapor at different levels?

Some have claimed here that water vapor is not increasing. Though I think that unlikely, I would like to get my facts straight.

Thanks in anticipation.