[LMB] CO2 - Re: Butter Bugs! Well, almost.... OT:

Greg Hennessy greg.hennessy at cox.net
Fri Jun 27 04:53:06 BST 2008


> Consistent with what I said:
> http://pubs.acs.org/subscribe/journals/ci/31/special/may01_viewpoint.html

Quoting from your link:
"The results show that the average absorption coefficient obtained for the 
atmosphere closely corresponds to that for the 5.6–7.6-µm water radiation band, 
when water is in the concentration range 60–80% RH—on target for atmospheric 
conditions. The absorption coefficient is 1–2 orders of magnitude higher than 
the coefficient values for the CO2 bands at a concentration of 400 ppm. This 
would seem to eliminate CO2 and thus provide closure to that argument.
This overall position can be summarized by saying that water accounts, on 
average, for >95% of the radiative absorption. And, because of the variation in 
the absorption due to water variation, anything future increases in CO2 might 
do, water will already have done."

There is no doubt that it is a true statement that considered over all visible 
wavelengths (including UV and near to mid IR) that water has higher absorption 
than CO2. I haven't done any calculation, but I will even concede that the 
quoted number of water absorbing 95% of the radiative flux is correct.

That still does not equal a conclusion that water provides 95 percent of the 
greenhouse effect. The actual calculation requires a full radiative transfer 
solution and is highly nonlinear. A graph of the absorption spectra
of water and CO2 has already been posted in this thread.



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