I was once told by a climate alarmist (Joel Shore) that “a magnifying glass in sunlight proves that light can be concentrated”, and thus that the radiative greenhouse effect is true and that their diagrams which depict it are also true, “because the radiative greenhouse effect does the same thing.”
So, how good of a scientist and philosopher are you: Can you identify the sleight of hand there? Can you identify the sophistry?
A magnifying glass works with sunlight by undoing the inverse-square law reduction of photon density with distance from the Sun. Photons emitted from the Sun get spread over a larger and larger wave-front area as they travel away; this wave-front surface area increases as the distance from the sun, squared, because the surface area of the wave-front sphere is 4πr².
The theoretical best that a magnifying glass can do is to return the light it captures back to the density it originated from, at perfect focus. If the magnifying glass perfectly focused the light, then the absolute best that could be done is to return the light back to the density (“focus”) at which it originated. It can’t do any better than that because it can’t do better than working perfectly and focusing perfectly – perfectly is the most that it can do. And at that point, the temperature which the focused light would be able to generate under perfect conditions is the temperature of the source of the thermal radiation itself. Anything less than perfect means that only a lower temperature could be generated. The best that could be done is to achieve the spectral temperature of the source.
And so, a magnifying glass can not and does not concentrate light to induce a higher temperature than the source of the thermal radiation going though it. A magnifying glass quite specifically does not do what the radiative greenhouse effect is claimed to do.
The radiative greenhouse effect claims that thermal radiation entering into an appropriate enclosure (such as a de-Saussure device, or an atmosphere with the requisite chemical components) can be amplified to induce any final temperature desired.
In the above figure, while the input coming in from the right might be diluted sunshine at the distance of the Earth from the Sun, it could equally well be from a thermal source and radiation which has suffered no dilution at all before entering the radiative greenhouse apparatus. There are two conditions to consider here.
The first condition, the more subtle one, is where the input is from a diluted source of thermal radiation, for example thermal radiation coming from the Sun at the distance of the Earth from the Sun. While a magnifying glass concentrates sunlight by focusing it, a radiative greenhouse field would then be said to concentrate light by trapping it within enclosures causing it to pile up on itself. This is quite the recipe for sophistry because that sounds like it is the same thing as increasing the density of photons like what a magnifying glass does. It is not!
A magnifying glass increases or “re-concentrates” the planar cross-sectional spatial density of incoming photons which have a very high spectral temperature, whereas the enclosures of a radiative greenhouse field would only stack local re-generated thermal photons of the spectral temperature of the enclosure on top of each other. This is all the difference in the world.
Photons are bosons and so you can stack two photons right on top of each other and this will have zero effect upon their frequency and thus zero effect upon the subsequent temperature which they can generate. A magnifying glass does not affect the frequency of the photons either, but it does concentrate the density of incoming photons back to the density from which they originated, and if doing this perfectly than can only achieve the same thermal conditions and spectral temperature as the source. A magnifying glass can only achieve as much as the original source because it doesn’t affect the frequency of the radiation. A radiative greenhouse field, however, would be able to achieve any temperature at all, including above that of the original source, and that means that the frequency of the radiation inside a radiative greenhouse field was being increased. These are not the same things at all.
The second, less subtle condition, following on from the first, is that if the input thermal radiation to the radiative greenhouse field were not diluted, then the temperature generated inside immediately becomes higher than the source temperature.
Once again, here is the definition of heat:
“Heat is defined as the form of energy that is transferred across a boundary by virtue of a temperature difference or temperature gradient. Implied in this definition is the very important fact that a body never contains heat, but that heat is identified as heat only as it crosses the boundary. Thus, heat is a transient phenomenon. If we consider the hot block of copper as a system and the cold water in the beaker as another system, we recognize that originally neither system contains any heat (they do contain energy, of course.) When the copper is placed in the water and the two are in thermal communication, heat is transferred from the copper to the water, until equilibrium of temperature is established. At that point we no longer have heat transfer, since there is no temperature difference. Neither of the systems contains any heat at the conclusion of the process. It also follows that heat is identified at the boundaries of the system, for heat is defined as energy being transferred across the system boundary.”
from G. J. V. Wylen, Thermodynamics
This means that once the external source thermal radiation generates the temperature on an object or in an enclosure of which it is maximally capable given its spectral temperature and distance (i.e. the temperature given the spectrum of the source and the 1/r² dilution of the photon flux), then it is no longer heating and no longer sending heat and no longer able to raise the temperature of said object.
This is where the alarmists and their clandestine supporters (shills) then say that it is the object itself which causes itself to heat up some more by trapping radiation.
But no…that contradicts what they just agreed to about the heating potential of the external source. If the external source can only raise the object to the same temperature as the source temperature, and at that point heating stops because the temperatures are equal which means that heat can no longer flow, then likewise the object itself can not heat itself because the object is its own temperature! The object can not heat itself because it is its own temperature and heat does not flow between equal temperatures.
“But but but it traps heat”, they say.
No again! Firstly, there is no more heat entering the system because the only source of heat is from the external source, but it stopped sending energy as heat as soon as the temperatures became equal (or in thermal equilibrium). So, there is no more heat “to trap”. There is no more heat to trap.
And in any case, heat can’t be “trapped” because like phlogiston or caloric which came to be understood as heat, heat is only a transient form of energy and can not exist statically, can not exist as a “trapped” quantity. There is no more heat to come from the source once the target object has been induced to the temperature which the source is solely capable of producing.
So that was today’s lesson in how the climate alarmists and their shills use sophistry and pseudoscience to just basically make stuff up that is utterly false.
A magnifying glass quite specifically demonstrates that it is unable to do and does not do what the radiative greenhouse effect is claimed to be capable of. Further, to claim that the radiative greenhouse effect can do what a magnifying can not do is to 1) destroy your own original claim that a magnifying glass supports the mechanism of the GHE, and 2) violates very basic thermodynamics in the definition of heat.
We’re dealing with people who just lie and who just make whatever false analogies and re-definitions of scientific terms that they want. They just “word-salad” scientific terms together in a very clever way…in sophistry.