Double Counting of "Greenhouse" Gas Effect

In a paper succinctly called: How much CO2 really contributes to global warming? Spectroscopic studies and modelling of the influence of H2O, CO2 and CH4 on our climate. Hermann Harde of Helmut-Schmidt-Universität Hamburg, Germany presents a summary of their calculation of the notorious “Greenhouse**” warming effect of gases such as CO2 and H20.
The paper calculates the direct affect of CO2 (without feedback mechanism) using a line-by-line calculations of each wavelength of sunlight and using this approach they arrive at a value of direct heating of 0.45C for a doubling of CO2.

The weighted average over all regions as the global climate sensitivity is found to be CS = 0.45°C with an estimated uncertainty of 30%,sensitivity.

This 0.45C compares with the value of  between 1.0 – 1.1C. normally given by the IPCC. It appears the main difference between this and previous estimations is that this model avoids “double counting” radiation absorption of wavelengths which can be absorbed by both CO2 and other gases such as H2O. I.e. if the radiation is already absorbed by H2O it can’t also be absorbed by CO2 or as they put it:

The simulations for the terrestrial and atmospheric warm-up show well attenuating and saturating progressions with increasing CO2-concentration, mainly caused by the strongly saturating absorption of the intensive CO2 bands and the interference with water lines.

The model used is a vast improvement on previous attempts which form the basis of the IPCC prediction of the direct physical impact of CO2 dividing up the atmosphere into 228 layers from the ground up to 86 km and three climate zones and includes polar zone (instead of having only two zones in infamous Myhre-1997 study).

The propagation length of the sun light in these layers, which depends on the angle of incidence to the atmosphere and therefore on the geographic latitude, is included by considering the earth as a truncated icosahedron (bucky ball) consisting of 32 surfaces with well defined angles to the incoming radiation and assigning each of the areas to one of the three climate zones.

The model is also a dynamic model including transport between zones and wonder of wonder, it also includes clouds (which may seem obvious to anyone who has gone out on a cloudless night and felt the frost!)
As  Al Tekhasski said on WUWT:

Sounds very good. I’d like to see their equivalent of “radiative forcing”, although it seems like the article uses more physical approach and evaluates the state of new balance for each increment in CO2, so the illusory “radiative forcing” simply does not enter the picture.

However, in an obvious mistake concern which is bound to draw scorn from those who don’t like the implications of the paper and one which could undermine its credibility, is that the author wrongly compares their result of 0.45C to that of 2-5C of warming estimated by the IPCC, when the 2-5C warming includes a huge positive feedback which the paper’s result does not seem to include.
**Greenhouse. Strictly speaking a greenhouse works in a different way to a “greenhouse gas” because the main effect of a greenhouse is to prevent hot air escaping, whereas a greenhouse gas (which we need to keep the world cosy) works by blocking IR. However, gases which block IR, also emit IR and so their impact is complex and they can also act as cooling gases in some circumstances.

Addendum

I was interested to learn more about this paper and the author, so I’m posting what I found:
Paper is for this Event
European Geosciences Union
General Assembly 2011
Vienna | Austria | 03 – 08 April 2011
Aims & Scope of event
The EGU General Assembly 2011 will bring together geoscientists from all over the world into one meeting covering all disciplines of the Earth, Planetary and Space Sciences. Especially for young scientists the EGU appeals to provide a forum to present their work and discuss their ideas with experts in all fields of geosciences. The EGU is looking forward to cordially welcome you in Vienna!
URL: http://meetings.copernicus.org/egu2011/
This paper comes under:
Poster Programme CL2.6
Earth radiation budget, radiative forcing and climate change
Convener: Martin Wild
Co-Conveners: Rolf Philipona , Paul Stackhouse
URL: http://meetingorganizer.copernicus.org/EGU2011/poster_programme/6420
Dr. Hermann Harde
URL: http://www.hsu-hh.de/laser/index_xf8dd16rfJ6hg6A6.html
Other work:
A New Tool for Computation and Display of Spectra from the HITRAN Database (HITRAN is an acronym for high-resolution transmission molecular absorption database.)
http://www.cfa.harvard.edu/hitran/HITRAN_conf06_presentations/Session5/5.5-Harde.pdf