I’ve just encountered a new global warming site called Global warming solved (archived). The site appears to be run by a family who also owns a journal called The Open Peer-Reviewed Journal, the first 8 papers in which are all authored by them. You can find the journal quite easily if you wish, but these papers include a review of millenial temperature reconstructions, a review of temperature homogenisation, and a major correction to the physics of the greenhouse effect (which, according to them, is negligible). These people are either incredible polymaths or ….
On their brand new website, they summarise their papers. In one of their summaries (archived here) they say,
This means that we should be finding a very complex temperature profile, which is strongly dependent on the infrared-active gases. Instead, we found the temperature profile was completely independent of the infrared-active gases.
This is quite a shocking result. The man-made global warming theory assumes that increasing carbon dioxide (CO2) concentrations will cause global warming by increasing the greenhouse effect. So, if there is no greenhouse effect, this also disproves the man-made global warming theory.
To be fair, this is quite a tricky concept and one that I’ve had to think about for a while before understanding myself. However, it is – I believe – roughly correct that the greenhouse effect does not influence the temperature gradient (typically called the lapse rate). What it does, though, is make the lower atmosphere opaque to outgoing long-wavelength radiation and hence makes the lower atmosphere adiabatic (As per various comments below, it’s not the atmosphere as a whole that’s adiabatic, it’s that we can treat this as a reversible adiabatic process. As parcels of air rise and fall they don’t lose any energy, but either expand and cool, or contract and heat up. This is, also, very much a simplifying assumption and the actual processes involved in setting the lapse rate are much more complicated than this simple, illustrative model). One can therefore estimate, very simplistically, the lapse rate using fairly basic physics.
For a reversible adiabatic process (isentropic),
The can be differentiated to give
The term PdV is the work done which, for an adiabatic process, is also given by -ncvdT, where n is the number of moles, and cv is the constant volume heat capacity. This allows us to write,
where I’ve used that γcv = cp (the heat capacity at constant pressure) and that if this is written in terms of mass, rather than moles, n/V is the density.
In hydrostatic equilibrium, the downward force of gravity on a gas parcel, must be balanced by an upward pressure force. Therfore,
We can combine this with the relationship between dP and dT that we derived above to get
The term g in the above is the acceleration due to gravity and is g = 10 m s-2. The specific heat capacity at constant volume is cp = 1000 J kg-1 K-1. Therefore we get that the adiabatic lapse rate is 0.01 K m-1, or 10 K km-1.
Therefore, in a fully adiabatic atmosphere (or, more correctly, one which is isentropic), the temperature should drop at 10oC for every 1 km increase in altitude. This is actually a little too high as the atmosphere will typically contain water vapour that can condense and heat the air. In this case we get a saturated adiabatic lapse rate, which is closer 5 K km-1.
So, where does the greenhouse effect come into play? Firstly, greenhouse gases in the atmosphere means that the lower atmosphere can be regarded as, approximately, adiabatic (i.e., it is opaque to outgoing radiation and hence doesn’t lose energy – directly to space – through radiative processes. It is isentropic.). Secondly, the greenhouse gases determine an effective radiative surface at which energy can escape into space via radiation (i.e., some level at which it effectively becomes optically thin). In equilibrium, the temperature at this altitude will be the temperature the planet would have if there were no greenhouse gases present. The more greenhouse gases there are in the atmosphere, the higher this radiative surface, and the higher the surface temperature will be (because of the lapse rate). So, just because the lapse rate does not appear to depend on the existence of greenhouse gases in the atmosphere, does not invalidate the greenhouse effect, although this does appear to be a common misconception.
I should say that I just worked this out this morning and may not have explained this quite as clearly as I could have. There are also almost certainly subtleties that I’ve missed that others (Tom Curtis, Eli Rabett) could probably highlight. However, I do believe that the discovery that the lapse rate does not depend on the greenhouse gas concentration is not new and does not mean that the greenhouse effect is negligible. As usual, corrections welcome through the comments.