MOST scientists sceptical of the theory of anthropogenic global warming (AGW) accepted that carbon dioxide is a greenhouse gas; they simply don’t believe it is very potent relative to other natural forces. But there are a group of physicists, most notably several of the authors of the book ‘Slaying the Sky Dragon: Death of the Greenhouse Gas Theory’ who even argue against the greenhouse effect theory.
For some weeks, every Friday, I have been publishing an essay from one of these scientists a Mexican Nasif S. Nahle – though Nahle is not an author of ‘Slaying the Sky Dragon’. When I first started publishing Dr Nahle I received emails from various sceptics suggesting that in promoting his work I was doing a disservice to the sceptic’s cause; that I should not be challenging the basic accepted physics of back radiation.
The essence of greenhouse theory is that thermal radiation from the earth’s surface is absorbed by atmospheric greenhouse gases, and is re-radiated including back towards the earth’s surface. As a result of this back radiation the temperature of the earth is higher than it would be if direct heating by solar radiation were the only warming mechanism.
Dr Nahle argues that there is no warming from back radiation and one reason is because heat cannot flow from a cooler area (the atmosphere) to a warmer area (the earth surface).
I have enjoyed posting essays from Dr Nahle as he argues from first principles, and with examples, and he engages with his critics in the comment threads. In short, he provides food for thought.
And given the importance of back radiation to greenhouse gas theory, I have been surprised that there has not been a more definitive rebuttal of his core argument in the comment threads. Indeed it is irrelevant to argue that he is wrong because his work is not published in the peer-reviewed literature, or that it does not accord with what is written in mainstream textbooks or that it is too specific.
I am keen to publish more essays on this important topic, particularly from the more mainstream perspective that is in defence of back radiation as a core part of anthropogenic global warming theory.
This morning I noted the following comment from Bob Ashworth with reference to Dr Nahle’s work:
“I am an old chemical engineer who has worked in coal conversion and combustion my whole life. Nasif is correct.
The IPCC adopted the work completed by Kiehl and Trenberth  of the National Center for Atmospheric Research, Boulder Colorado to show how radiative forcing from greenhouse gases causes the earth to warm. Here is a statement from that paper:
The long wave radiative forcing of the climate system for both clear [125 W/m2 (watts/square meter)] and cloudy (155 W/m2) conditions are discussed. We find that for the clear sky case the contribution due to water vapor to the total long wave radiative forcing is 75 W/m2, while for carbon dioxide it is 32 W/m2.
Really, when the average water vapour concentration in the lower troposphere is around 2.5 volume % (or 25,000 ppmv) and carbon dioxide concentration is less than 400 ppmv? The CO2 concentration is only 1.6% of the water vapour concentration. In the Hottel and Egbert correlation the only difference between water vapour and carbon dioxide regarding the radiation effect is their partial pressures. Partial pressures of gases are proportional to their volumetric concentrations. Based on this and using the water vapour effect as a basis at 75 W/m2 then the CO2 effect would be 1.2 W/m2, not the 32 W/m2 stated.
The Kiehl and Trenberth work also violates both the first (can’t get more energy out than you put in) and second (heat transfer is only from a hotter to cooler body, never vice versa) laws of thermodynamics.
 Kiehl, J. T. and Trenberth, K. E., 1997, Earth’s Annual Global Mean Energy Budget, Bull. Amer. Meteor. Soc., 78, 197-208. http://www.cgd.ucar.edu/cas/abstracts/files/kevin1997_1.html
Posts from Dr Nahle are here: http://jennifermarohasy.com/blog/author/nasif-s-nahle/