[cogitator]

Without water vapor feedback, the CO2 driven global warming scenario is below the noise level of temperature changes.

Correct, but this study confirms that there is a positive water vapor feedback, and indicates that it can also be quantified. That's a major advance.

I found a really interesting figure, which it would be nice to reproduce but I can't. It's in this Powerpoint presentation:

noaasis.noaa.gov/2003/bates.ppt

Find the "Water Vapor Feedback" slide.

It confirms exactly what you say (not that I was disputing you!). Direct CO2 greenhouse heating provides 0.17 C (the slide notes that this is model dependent). Tropospheric heating by CO2 provides 0.33 C (total of 0.5 C). Water vapor feedback, and this was based on the constant relative humidity assumption now in question, was 1.7 C, for a total of 2.2 C.

It will be very interesting to find out how much weaker the researchers (or others) think that this research indicates the water feedback mechanism is, as discussed with JasonC above.

[JasonC]

That's interesting. If you have a reference for the troposheric warming term, I'd like to look at it. Understand my primary interest here is tracking power, keeping a power budget. To do that I must distinguish between modeled quantities and correlations on the one hand, and experimentally verified physical observations that measure watts per square meter on the other.

Do you know of a paper that explains, "we actually measure and see so and so many watts per square meter, in excess of direct CO2 forcing, from tropospheric heating"? (Also, don't satellite and balloon measurements show precious little high altitude temperature change, as opposed to surface measurements, to begin with?)

[ancient_geezer]

It will be very interesting to find out how much weaker the researchers (or others) think that this research indicates the water feedback mechanism is

A graphic of the data as compared to constant relative humidity, the author's climate model, and measurment. (Google provides again :O)

http://earthobservatory.nasa.gov/Study/WaterVapor/water_vapor4.html

 

 

Constant relative humidity is what the UN/IPCC global warming models assume It would appear that measurement falls as much as an order of magnitude(factor of 10) below that level.

[ancient_geezer]

A hyperlink to the primary paper describing author's model, as well as the HALOE & MLS measurements in section 5 Observations of UT water vapor on page 10 of the PDF.

http://www.atmos.umd.edu/~dessler/publications.html

Minschwaner, K., and A.E. Dessler, Water vapor feedback in the tropical upper troposphere: Model results and observations, J. Climate, in press, 2004. [PDF:] Preprint

The particular chart shown in reply #22 above can be found on page 25 of the Preprint PDF along with a much more detailed description of what is displayed in that graph.