In this post I will make a short description of pyrgeometers and IR-sensors that both use a thermopile as the fundamental mechanism for the function of the device. It will be clear to anyone interested that it cannot be used as proof for any radiative energy coming from a cold atmosphere that heats the earth surface.
In the blogposts over at scienceoffraud about radiation from the ass of the atmosphere, pyrgeometer measurements are used as proof of ”back-radiation”.
The thermopile (fig1) can be explained as a slightly more advanced thermometer with the difference that it measures a gradient across the material in the sensor, using a difference in voltage that depends on changes in conductivity arising from differences in the temperature of the material. It uses the difference to produce a value of heat transfer into, or out of, the device. In the case of the atmosphere it is a measured transfer from the device that is measured, the difference between the temperature of the device as a result of the surrounding temperature, to the temperature of the part exposed to the atmosphere.
Fig 1, composition of a thermopile
When used in a pyrgeometer, the device claimed to measure ”backradiation”, the thermopile is placed in a shell with a theremometer measuring the temperature of the device as a reference. The pyrgeometer is placed outside and according to Wikipedia it can at best have a range of 25 meters into the atmosphere above. In the device there is a thermopile measuring the gradient across itself as part of it is exposed to, and directed towards, the atmosphere above. The transfer of heat to the atmosphere above is calculated from the small gradient inside, that is assumed to continue into the atmosphere. In figure 2 the principle is shown for an IR-thermometer with a thermocouple inside. It is the same basic principle and here are the equations used for the function of device, shown below the picture.
Figure 2, the basic working principle for a IR-thermometer with the included equations.
In figure 3 we can see a section of a pyrgeometer and as you can see, there is nothing inside is capable of measuring IR-radiation over a distance in an atmosphere. To do that, you need a device for optical measurement, measuring photons and their wavelengths, not a net heat transfer “thermometer”.
Figure 3, a section drawing of a pyrgeometer
In figure 4 we can find a scetch of the working principle of the sensor body in the pyrgeometer, the thermopile. It is in Swedish but I think it is obvious what is shown. The text below translates as:
“The heat flow is determined by the small gradient caused, by the use of very sensitive thermo-elements. The energyflow of outgoing photons is calculated using the Stefan-Boltzmann law based on the sensorbodys measured temperature.”
In the drawing you can see red and blue arrows claimed to show in- and outgoing photons. This is not a correct description, logically it can only measure a gradient inside the sensor, as it doesn´t have any optical view beyond its own material. The blue arrows indicate what is implied as incoming photons, but in a situation where the temperature in the direction of measurement is lower than that of the device, there is only indirect indication of temperature-difference by the small internal gradient. What the device does is measure the heat transfer from the sensor, and then that difference is wrongfully claimed to be incoming radiation. I don´t say that there cannot be any incoming radiation, just that this device is definitely not capable of measuring it.
Figure 4, a drawing of the claimed measurement of incoming radiation from an atmosphere
When you see someone claiming that ”back-radiation” from the atmosphere is proven by measurements from IR-cameras or pyrgeometers, you know this person have no clue of what they are talking about. These are devices that have the “greenhouse effect” built into them, if you use them for atmospheric measurements from groundlevel. A thermopile is an excellent, sensitive device for use in other situations, but not to measure “back-radiation”, or “the ghost of the greenhouse” as I prefer to call it. To measure a small gradient over a thermopile and extend that measurement into the atmosphere claiming it to be a measurement of incoming photons, is distilled bullshit. Maybe a more refined form of bullshit, but nothing else than bullshit.
Have a nice day and don`t forget to use a lot of oil