Carl Brehmer: Fact trumps theory with the greenhouse effect: A case study

I plucked this comment off the Hockey Schtick, as it ties in well with a recent post which generated a lot of comment. That post was looking at back radiation over dry areas. This one looks at the role of water vapour – claimed to be a ‘positive feedback’ by co2 driven global warming theorists.

One version of the “greenhouse effect/water vapor feedback” hypothesis that involves the mid to upper levels of the troposphere and water vapor feedback recognizes that humidity causes a slower lapse rate, which raises the altitude at which the air temperature drops to -18C—the affective radiating temperature of the atmosphere. Some people call this altitude the “top of the atmosphere” (TOA).
This version of the “greenhouse effect” hypothesis then applies the standard lapse rate of 6.8C/km to both the older lower altitude and the newer higher altitude to calculate the projected ground level temperature at the bottom of these two respective atmospheric columns.

To better visualize this version of the “greenhouse effect” hypothesis lets use some actual weather balloon soundings from above Las Vegas (specific humidity = 1.04 g/kg) on a particular day and compare it to weather balloon soundings over Little Rock (specific humidity of 13.83 g/kg) that particular day. These soundings are from http://weather.uwyo.edu/upperair/sounding.html and they were both recorded at 11:00 AM, June 1, 2011.

As expected, because of Little Rock’s extra humidity the TOA over Little Rock (6961m) was higher than the TOA over Las Vegas (6806). When I applied the standard lapse rate of 6.8 °C/km to the TOA altitudes in both locations to calculate the “expected” temperature at 750m (the altitude in Las Vegas) I came up with the following numbers:

Las Vegas = 23.3 °C @ 757m
Little Rock = 23.9 °C @ 743m

Had I stopped right here I could have asserted that the extra humidity in Little Rock is estimated to create a +0.6°C positive feedback. But I didn’t stop there. I looked at the actual temperatures at around 750m (the altitude of Las Vegas) and this is what I saw:

Las Vegas = 30.4 °C @ 757m
Little Rock = 24.4 °C @ 743m

As you can see, the extra humidity in the atmospheric column over Little Rock actually created a -6 °C negative feedback! So, even though the TOA above Little Rock was higher in altitude the ground level temperature was lower by 6 °C.

Can anyone guess why the “greenhouse effect” hypothesis predicted a positive water vapor feedback when in reality the humidity in Little Rock created a strong negative feedback?

That’s right! When I applied the standard lapse rate of 6.8 °C/1,000m to the TOA of the dry column of air over Las Vegas it greatly underestimated the ground temperature under that dry atmospheric column. This made the estimated temperature under the moist atmospheric column in Little Rock appear higher than the ground level temperature under the arid atmospheric column in Las Vegas, which is a complete reverse of realtiy.

Again, these figures . . .

Las Vegas = 30.4 °C @ 757m
Little Rock = 24.4 °C @ 743m

. . . are actual temperatures taken on the same day that shows the actual affect of the extra humidity in Little Rock on ground level temperatures, which was a -6 °C negative feedback. This echoes the observations made in the video. If you are curious the actual lapse rate to the TOA over Little Rock was 6.9 °C/km while the actual lapse rate to the TOA over Las Vegas was 8 °C/km.

One final thought, the “greenhouse effect” hypothesis is based upon Joseph Fourier’s calculations that asserts that the surface of the earth is too warm by about 33°C and that water vapor itself (depending upon the author) creates about 20°C of warming. Regardless of how sophisticated the hypothesis, how massive the computer models, how voluminous the peer-reviewed literature, if water vapor can (and has) been demonstrated to be associated with ground level cooling instead of warming then something is askew with that hypothesis.

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