## torsdag 11 augusti 2011

### How to Fool Yourself with a Pyrgeometer

CO2 alarmism feeds on an idea of massive backradiation or Downwelling Longwave Radiation DLR from the atmosphere to the Earth surface, about 330 W/m2 to be compared with 170 W/m2 absorbed shortwave radiation from the Sun.

DLR thus triples the radiation from the Sun to an alarming 500 W/m2 hitting the Earth surface. This should make it possible to boil eggs on the bare ground, but since this does not work out, we ask: What is the evidence that there is massive DLR?

The answer by a CO2 alarmist is: DLR exists because you can measure it, e.g. it by a pyrgeometer:

• a device that measures the atmospheric infra-red radiation spectrum that extends approximately from 4.5 µm to 100 µm.
Here is how it works according to Wikipedia:

The atmosphere and the pyrgeometer (in effect the earth surface) exchange long wave IR radiation. This results in a net radiation balance according to:

$\ E_{net} = { \ E_{in} - \ E_{out} }$
Where:
Enet - net radiation at sensor surface [W/m²]
Eout - Long-wave radiation emitted by the earth surface [W/m²]
The pyrgeometer's thermopile detects the net radiation balance between the incoming and outgoing long wave radiation flux and converts it to a voltage according to the equation below.
$\ E_{net} = { \ U_{emf} \over \ S}$
Where:
Enet - net radiation at sensor surface [W/m²]
Uemf - thermopile output voltage [V]
S - sensitivity/calibration factor of instrument [V/W/m²]
The value for S is determined during calibration of the instrument. The calibration is performed at the production factory with a reference instrument traceable to a regional calibration center.[1]
To derive the absolute downward long wave flux, the temperature of the pyrgeometer has to be taken into account. It is measured using a temperature sensor inside the instrument, near the cold junctions of the thermopile. The pyrgeometer is considered to approximate a black body. Due to this it emits long wave radiation according to:
$\ E_{out} = { \sigma * \ T^4}$

Where:
Eout - Long-wave radiation emitted by the earth surface [W/m²]
σ - Stefan-Boltzmann constant [W/(m²·K4)]
T - Absolute temperature of pyrgeometer detector [kelvins]
From the calculations above the incoming long wave radiation can be derived. This is usually done by rearranging the equations above to yield the so called pyrgeometer equation by Albrecht and Cox.
$\ E_{in} = { \ U_{emf} \over \ S }+ {\sigma * \ T^4}$
Where all the variables have the same meaning as before.
As a result, the detected voltage and instrument temperature yield the total global long wave downward radiation.

So now we now how DLR is measured. Does this mean that DLR exists as a physical transfer of energy from atmosphere to Earth surface? No, it does not as explained as myth of backradiation or DLR. We recall:
A pyrgeometer measures a net transfer and then invents DLR by adding the net to outgoing radiation according to Stefan-Boltzmann for a blackbody emitting into a void at 0 K.

We see that a pyrgeometer does not measure DLR directly but invents it from the formula
• E_in = E_net + E_out,
which is supposed to result from E_net = E_in - E_out expressing a Stefan-Boltzmann law of the form
• E_net = sigma Ta^4 - sigma Te^4,
where Ta and Te are the temperatures of atmosphere and Earth surface. But Stefan-Boltzmann's law is not described this way in physics literature, where it instead takes the form
• E_net = sigma (Ta^4 - Te^4),
which does not allow extracting DLR as sigma Ta^4.

DLR and backradiation is thus fiction invented from an ad hoc formula without physical reality, which is not described in the physics literature. Nevertheless there are companies selling pyrgeometers at price of 4.000 Euro, but of course selling fiction can also serve as a business idea. But is it legal to sell fiction as science? As science fiction?

To sum up: Working with fictional differences of massive gross flows feeds alarm, while physically correct net flow does not.

Before investing in pyrgeometer you may ask yourself what in fact such a device is measuring: fiction or reality? Or maybe it does not matter? To help to an answer you may take a look at:

#### 29 kommentarer:

1. The pyrgeometer is far from the only instrument that can measure DLR - it doesn't provide the spectral resolution that you see in most measurements, it is just a lumped total flux. If you want to claim DLR is a fiction you need to critique *all* instruments that measure it, not just pick one.

Nevertheless, even your critique of this simple instrument is in error. The T of the pyrgeometer is controlled by the experimenter, and need not be the same as T_e of the local Earth's surface - most likely it will not be. The pyrgeometer equation applies for all values of T. If that equation produces the same E_in value while the T of the pyrgeometer itself varies, how do you explain that E_net keeps changing while E_in is constant, in your model of things?

Also note that the DLR spectrum as measured by instruments that actually do resolve the different frequencies (see for example the many curves in the "measured spectra" section of this post: http://scienceofdoom.com/2010/07/24/the-amazing-case-of-back-radiation-part-two/ ) is NOT a black-body spectrum, and does not represent an energy flux sigma T_a^4 unless you arbitrarily assign some T_a value to match the flux. What determines T_a in your model?

2. OK, which other instrument do you want me to decode? Of course the temp of the pyrgeometer can be different from that of the Earth surface. I took them to be the same for simplicity.

3. Any infrared spectrometer, for instance. Wikipedia has diagrams and descriptions of several types here:

http://en.wikipedia.org/wiki/Infrared_spectroscopy

On the temperatures, you agree the temp of the pyrgeometer can change. So you have a situation where you are observing a physical system (energy coming from the atmosphere, according to the standard theory), and varying a temperature T. The measured net flux E_net changes as T changes. But the E_in calculated from the pyrgeometer formula stays constant. Most people would interpret that as indicating that E_in really does have a physical reality, so why do you insist it is "fictitious"?

4. There is no connection to DLR on your infrared-spectroscopy link. I take as additional evidence that DLR is fiction and not reality. Of course E_net will change with T, but that does not prove that E_in is real.

5. Huh? I earlier pointed you to a page at ScienceOfDoom that has half a dozen different infrared spectroscopy measurements of DLR, and you say it's a fiction because Wikipedia doesn't link to it? Here's the ScienceOfDoom link again.

Those measurements were made by pointing an infrared spectrometer up at the sky and seeing what the spectrum of DLR was. Do you deny these measurements exist?

6. I don't deny that you can design an instrument which is sensitive to IR light. It is the connection to transfer of heat energy which I doubt based on evidence I present.

7. Huh? By summing up DLR(lambda) over the wavelengths measured you get a total incoming energy E_in which matches what the pyrgeometer sees. That same constant value that's independent of the T of the pyrgeometer. You can call it a fiction if you like, but an invariant quantity observed many different ways independent of the measuring instrument is normally regarded as something with real physical reality.

8. When reality does not correspond to the map (models), of course reality must be wrong... [irony]

To be honest, I'm a little freaked over contributing to this professors salary (I'm a Swedish citizen).

9. I think that the improper use of the pyrgeometer and/or any other room temperature antenna unquestionably shows the total and contextual misunderstanding of the metrology and of the thermal radiation.
The aforesaid tools are simple dynamic calorimeter, i.e., devices that measure instantaneously the output electric property induced by the difference between the sensor temperature and the room temperature and hence the heat flux that the sensor exchanges with the optically sighted region.
Until now, all that is correct for the physics and the metrology.
But here starts the fairy. The heat flux is assumed as NET FLUX due to the difference between the incoming and outgoing long wave radiation flux and that allows to compute the incoming flux.
This is neither a physic measure nor a proof. I think it is only a banal trick!
Michele

10. Yes, we agree.

11. Neither a pyrgeometer nor the Earth's surface are anything like a perfect blackbody. A blackbody is assumed to be one surrounded by a vacuum, eg the whole Earth+atmosphere system surrounded by space. There can be no means of energy transfer other than radiation. In other words, the blackbody is perfectly insulated.

But the Earth's surface (including oceans) is nothing like perfectly insulated. It can gain or lose thermal energy both from the atmosphere and the sub-surface. Indeed it does this every day when SW radiation is converted to thermal energy and then conducted into deeper layers of the surface, only to exit again that night. Neither the surface nor the instrument needs to emit all the thermal energy by radiation. Hence any application of SBL is doomed to be significantly inaccurate. What a joke that assumed -18 deg.C surface temperature is. And what a joke are the "measurements" of backradiation.

12. For calibration of pyrgeometers using other instruments see http://www.arm.gov/publications/proceedings/conf16/extended_abs/stoffel_t.pdf

13. You want to be a "Professor of Applied Mathematics" and can't transform
E_net = sigma Ta^4 - sigma Te^4
to
E_net = sigma (Ta^4 - Te^4)?

So you fail at mathematics for 8th grade pupils, you also fail to grasp simple physical concepts like conservation of energy and get lost in simple sums by making them unnecessarily complicated.

14. You are confusing algebra with physics. An algebraic manipulation does not necessarily have physical meaning. Your conception is too simplistic.

15. I find the idea that physicists won't perform an algebraic operation available to them quite hard to swallow. I find the idea that you think one can't perform an algebraic operation unless you already find it that way in the physics literature astounding.

In any case, here's a link. Look at equations 1 and 2. You can see them go between the two forms with T4 in and T4 out. Note who the authors are. Turns out, Mahan wrote the book on Radiative Heat Ransfer.

http://www.arm.gov/publications/proceedings/conf09/extended_abs/haeffelin_m.pdf

1. Again: Just because a certain algebraic operation seems to be possible, that is to write
the heat transfer Q between two black bodies of temperature s T_h > T_c given as Q = sigma * (T_h - T_c) as the net transfer from hot to cold, formally as Q = sigma * T_h - sigma * T_c, does not mean that physically there is a two transfer of energy between hot and cold with in particular sigma *T_c the heat transfer from cold to hot.

Again: Physics only concerns net transfer of heat energy from hot to cold, while two-way heat transfer is fiction, and a dangerous fiction because heat transfer from cold to hot violates the 2nd law.

If you say that the heat transfer from cold to hot is conditional with always larger transfer from hot to cold, then you have to give the mechanism guaranteeing this condition to be satisfied, since it is not described in the literature. So whats is then your explanation of this mechanism?

2. Again: Physics only concerns net transfer of heat energy from hot to cold, while two-way heat transfer is fiction, and a dangerous fiction because heat transfer from cold to hot violates the 2nd law.

Another dangerous thing is to use sloppy terminology and ambiguous definitions.

What exactly is heat energy? Heat is not energy. Do you understand the distinction?

3. Your input is not constructive and of no interest. Please direct your energy to something else.

16. Obviously heat transfer from cold to hot does not violate the second law because my refrigerator does it.

The second law applies to a closed system in aggregate. Within that closed system, under some local partition, heat can indeed flow from cold to hot.

But, if what you are saying is that not every algebraic expression one can form from the equations of physics has a physical manifestation, I agree with that. For a pyrgeometer, the physical interpretation is obvious. You don't like it, but it's obvious.

17. Also, your logic doesn't make sense to me. Let's take two stars, which are about the closest things we have to black bodies. Wolf 359 has a temperature of 2800 Kelvin, our Sun 5778. since they exist in the same universe, heat via radiation must be flowing between them. By your logic, since Wolf 359 is colder, it must not be emitting any heat (and therefore radiation) in our direction.

18. Read my book or web-site on black body radiation and you find my arguments and then reconsider your questions.

19. Where do you get that zero Kelvin from?

"pyrgeometer measures a net transfer and then invents DLR by adding the net to outgoing radiation according to Stefan-Boltzmann for a blackbody emitting into a void at 0 K."

A blackbody does not know or care about the temperature of its surroundings.. As stated in Wikipedia and links there

"The radiation has a specific spectrum and intensity that depends only on the temperature of the body."

Furthermore, all objects - regardless of temperature - emit and absorb energy.

Yes, a colder object sends energy (photons) to a warmer body which absorbs them.

20. I only got two words for ya .....

PEER REVIEW

Otherwise it's just another OPINION from a faceless blog any fool can write

21. What is then your opinion J.R. as peer?

22. (continued)

So, as explained above, the radiation that emanates from a blackbody has a frequency distribution, and Wien’s Displacement Law tells us that the peak frequency increases proportionally with the temperature. That peak frequency can be seen in the above Planck curves and we should note that the area under the curve represents the total radiative flux for the indicated temperature. But it is important to understand that not all of the electromagnetic energy in the emanating radiation actually came from thermal energy in the body itself. In the case of the Earth’s surface, much of the electromagnetic energy in the emanating radiation actually comes from the electromagnetic energy in radiation from the cooler atmosphere. This radiation is immediately re-emitted by the surface without any of its electromagnetic energy being converted to thermal energy. The incident radiation from a cooler source does, however, slow the rate of radiative cooling of the warmer target because the target does not have to use as much of its own thermal energy in order to fulfil its “quota” of radiation as is determined by the area under its Planck curve.

So, yes, the so-called “back radiation” does in fact slow down that portion of surface cooling which is itself due to radiation. However, because its energy does not go through the complicated process of being absorbed and converted to thermal energy, the back radiation can have no effect on the rate of non-radiative cooling of any planet’s surface. The only radiation that can increase the temperature of the surface must come from a hotter source, namely the Sun. Thus the Solar radiation getting through to a planet’s surface is the only radiation that plays a part in determining a planet’s surface temperature. Neither on Earth or Venus (or any other planet with a significant atmosphere) does that radiation account for the actual observed planetary surface temperatures, and this fact alone is sufficient to put to rest all the literature and “settled science” which blames global warming on back radiation from the radiating gases in the atmosphere.

The reader might be thinking that, if back radiation slows surface cooling then it leads to warmer mean temperatures. In response we ask, “Cooling from what temperature?” The point is, the whole concept that back radiation is the cause of that “33 degrees of warming” is false, because back radiation does not add to the warming effect of the Sun.

23. The equation used in the calculations are absolutely wrong as Professor Johnson has written !!!

They have mistaken the quantity E(net) for a radiation flux and of course it isn't !!

E(net) is the difference between two discrete fluxes and is not amenable to comparison with sigmaT^4.

You can easily verify this for yourself by plotting 2 temperature curves in a spread sheet using Planck's equation.

E(net) is the area between the upper and lower curve BUT you can also generate a curve by subtracting every value for wavelengths of both curves.

This generates a curve which superficially resembles a Planck curve but is not !

You can prove this by rewriting Planck's equation for temperature then plot the 3 curves.

Both of the real temperature curves plot as straight lines parallel to the x axis wavelength as a constant temperature - y axis value - no surprise here.

The curve for E(net) plots as a varying temperature value instead of a constant PROVING beyond dispute the algebraic manipulation quoted is invalid !

Remember sigmaT^4 also is the area under the Planck curve for the temperature value - it is the integral of the Planck equation !!

You can easily demonstrate that many of the algebraic manipulations performed in climate science do not produce curves that are Planck curves hence they DO NOT equal sigmaT^4 !!

If the result is not a Planck curve the integral of that curve is not a valid Stefan-Boltzmann equation relationship - UNLESS you happen to have developed some relationship which replaces Planck's equation.

Professor Johnson is totally right !!

24. Experiment design: heat an object to an exact given temperature and measure how long time it takes until temperature is equal to surroundings. repeat the experiment, but now with a second object located close holding a lower temperature. Will the cooling time for the first object increase? If so the colder object have radiated energy to the hotter object.

25. Of course surrounding cooler objects will influence how fast a warm objects cools off, but not by warming the warmer object, just slowing the cooling.

26. "but not by warming the warmer object"
Do you mean "warming" as the first object has to be gaining in temperature from the initial level? That will not happen as both object radiates energy as heat out of body and both will decrease temperature by time. Still, as the first object increase in cooling time it has got added some extra energy, hasn't it? If so, from where did it get the extra energy if not from the cooler second object?