Is a Back Radiation Greenhouse Effect of 33 Kelvin Possible? Ross McLeod, Assoc. Diploma Health Surveying, B. Tech. (Engineering) May

Transcription

1 Is a Back Radiation Greenhouse Effect of 33 Kelvin Possible? Ross McLeod, Assoc. Diploma Health Surveying, B. Tech. (Engineering) May Updated August ABSTRACT This paper seeks to demonstrate an important principle of radiation physics. This principle is fundamental to the claims made about the back radiative greenhouse effect. This paper uses a simple experiment which has the obvious conclusion that the arithmetic sum of 2 discrete sources of radiant energy cannot be used to calculate a valid temperature using the Stefan- Boltzmann equation in the manner claimed by climate science introductory lectures as taught in University. Obviously this has important ramifications for many of the claims about future temperature increases, the ability to even make such predictions and the relevance of any computer program where this untested hypothesis is used in the source code. To the author s knowledge the affirmation of the claim has not been performed before. Extensive internet searching failed to locate any reference to this experiment having been undertaken previously. As the claim is fundamental to contemporary climate science the fact it has never been verified is simply astounding. Again this paper is not disputing any of the well-established scientific laws of radiative physics. It is simply questioning a previously untested hypothesis that cannot be claimed as a fundamental truth stemming from the work of the physicists that established these scientific laws. I believe it is demonstrated as invalid. I also propose a rule for summing radiation fluxes in an atmosphere that produces valid results that are consistent with logic. It is simply called the Stefan-Boltzmann law - H net = A ξ σ (T 4 T o 4 ).

2 Is a Back Radiation Greenhouse Effect of 33 Kelvin Possible? CONTENTS 1. The basic claim for the Greenhouse Effect. 2. Experimental Procedures. 3. Experimental Results. 4. Discussion of Results. 5. References.

3 1. The basic claim for the Greenhouse Effect. The greenhouse effect is credited with raising the Earth s theoretical temperature of about 255 Kelvin or about minus 18 degrees C to the observed average of about 288 K or about plus 15 degrees C. Here is Wikipedia s definition of the greenhouse effect :- The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases. Below is just one of hundreds of examples of how the basic physics of the greenhouse effect is taught in Universities. Figure The greenhouse effect is claimed to be caused by radiation absorbed by greenhouse gases which in turn heats the gases so that they radiate a portion of this energy back to the Earth s surfaces causing extra heating of the surfaces instead of the circumstances established where this energy were simply to escape to space.

4 Another claim as illustrated in the diagram above is that it is valid to sum various individual irradiative fluxes arithmetically and use that result to calculate a temperature from the Stefan-Boltzmann equation. The Stefan-Boltzmann equation is accepted as a scientific law of physics and is widely used in climate science. A consequence of this law is that raising the temperature expressed in Kelvins of an object by a factor of the fourth root of 2 causes that object to emit double the irradiative flux of the original temperature. The converse of this law implies that doubling the power of radiation heating an object will cause the temperature to increase by a factor equal to the fourth root of 2. This is clearly shown in the final line of the above diagram 2 equal radiative fluxes are summed and that sum is converted to a temperature. It is obvious that equal It is a consequence of the Stefan-Boltzmann equation that Watts per square metre is the flux emitted by an object at 303 K. It is also generally accepted that an object heated by a radiative flux equal to 479 Watts per square metre at the surface of the object being heated will cause the object to heat to 303 K. The missing link in climate science is actual proof that 2 discrete sources of radiant energy each of which produce a radiant flux at the surface of an object will combine as climate science assumes. To test this hypothesis I conducted an experiment. The procedure is simple, I believe it to be scientifically sound and relies on nothing more than observed temperatures and a simple application of the Stefan-Boltzmann equation. 2. Experimental Procedures. The experimental procedure could not be simpler. Anyone can replicate this experiment for themselves. I would have preferred more sophisticated equipment but the principle being tested does not demand it. I placed a simple thermometer on a simple stand. I placed some black tape over the bulb of the thermometer.

5 Figure 2. Experimental apparatus. The arrangement is shown in Figure 2 on the next page. This photograph was taken after the experiment had concluded as can be verified by the time shown on the clock. I used the thermometer to check the temperature each light could induce on its own. I placed a clock next to the thermometer to record time. I placed each light individually in various positions until I was able to achieve a temperature response as shown by the thermometer. I allowed significant time until it appeared no further increase in temperature occurred. This is to give some data to work with. It is important to note this crucial point about my initial starting temperatures. If one believes my starting temperatures are too low that is the initial thermometer reading may have increased had I left it longer this can only serve to further strengthen what I claim as the result of this experiment. This is because I measure the temperature the 2 lights combined can induce and compare this to the starting temperatures. If my starting temperatures are in error that is too low this merely serves to strengthen my claim that the combined temperature difference must be lower in this circumstance!

6 I then turned both lights on and recorded the thermometer s temperature over a period of time until it was apparent that any further increase was unlikely to be significant. Obviously I claim no real precision in measurements, my equipment is simple and not of the same standard of laboratory equipment, but I do claim a fundamental principle is demonstrated. I performed several experiments over a period of a week and the fundamental principle is verified every time. I invite anyone to try this. Whilst not as dramatic as heating a light bulb with mirrors or other similar flawed experiments it provides a real effect that is verifiable, provides real data and is based on simple sound scientific principles. I used 2 spotlights with a rated electrical power of 150 W. One was a new one purchased on Saturday 18 May, the other I have had for more than 10 years. The older spotlight has an accumulation of dust etc. material on the glass of the bulb which I left in place as I had already used it in that condition for previous experiments. As a result of this and perhaps age the new spotlight is slightly hotter. It is irrelevant to this discussion. 3. Experimental Results. Figure 3. Verifying Spotlight 1.

7 Figure 4. Verifying Spotlight 1. It was approximately 10:10 when I turned on the spotlight. At approximately 10:18 the thermometer is reading 30 degrees C 303 Kelvin. The fact that it is spotlight one alone providing this energy can be verified by the illumination on the left side of the tape on the thermometer bulb only. Figure 5. Verifying Spotlight 2.

8 Figure 6. Verifying Spotlight 2. It was approximately 10:19 when I turned off the first spotlight and turned on the second spotlight. At approximately 10:29 am the thermometer is reading 36 degrees C 309 Kelvin. The fact that it is spotlight two alone is verified by the illumination on the right side of the tape on the thermometer bulb only and the shadow on the thermometer on the clock. Figure 7. Commence experiment.

9 I then turned both lights on. The time is clearly 10:33 am. All that remains to do is to keep the room closed to avoid drafts interfering as much as possible. What follows is a series of photographs indicating the thermometers temperature in response to the combined heating effect of the 2 spotlights. The time is clearly 10:48 am. Figure 8. - First Reading. The temperature is clearly 45 degrees C 318 Kelvin clearly less than 46 degrees c 319 Kelvin. The time required to produce this increase in temperature is demonstrably 15 minutes. The final time for the last temperature reading is almost an additional 2 hours 12:45 pm. I am satisfied that any additional heating ought to be accomplished in this additional time.

10 The time is clearly 11:25 am. The temperature is clearly 46 degrees C 319 Kelvin. The time required to produce this increase in temperature is demonstrably about an extra 33 minutes. You can clearly see the illumination on both sides of the tape demonstrating both lights are on. Figure 9. - Second Reading. The time is clearly 11:50 am. The temperature is clearly 46 degrees C 319 Kelvin. This corresponds to negligible increase in temperature in 25 minutes. You can clearly see the illumination on both sides of the tape demonstrating both lights are on. Figure10. Third Reading.

11 The time is clearly 12:45 pm. The temperature is clearly 46 degrees C 319 Kelvin. This corresponds to a negligible increase in temperature in 80 minutes in total since 11:25 am. You can clearly see the illumination on both sides of the tape demonstrating both lights are on. Figure 11. Final Reading. 4. Discussion of Results. I claim no real precision in any of my measurements I have no measure of the accuracy of the thermometer other than to compare its measurement of indoor air temperature to an electronic weather station. There was broad agreement between these two devices at various temperatures over a range of 18 to 25 degrees C. But I never set out to be precise I set out to test a principle. The principle I sought to test is:- Can the combination of 2 or more irradiative fluxes be arithmetically summed as shown in Figure 1 and that result used to calculate a realistic temperature for that sum? In all the tests I performed this was not observed. Whilst no precision is claimed it is evident that summing irradiative fluxes gives a completely different result from what my experiments demonstrate. The temperatures I measure are so significantly lower than the result obtained by an arithmetic sum of irradiative fluxes that the precision of my temperature measurements make no difference to the result.

12 The spotlight on the left in figure 3 heated the thermometer 30 degrees C or 303 K. The Stefan-Boltzmann equation says this is equivalent to the bulb of the thermometer emitting an emissive power of ~478 Watts per square metre. The spotlight on the right in figure 5 heated the thermometer 36 degrees C or 309 K. The Stefan-Boltzmann equation says this is equivalent to the bulb of the thermometer emitting an emissive power of ~517 Watts per square metre. The maximum temperature recorded was 46 degrees C or 319 K. The Stefan-Boltzmann equation says this is equivalent to the bulb of the thermometer emitting an emissive power of ~587 Watts per square metre. Now I claim this represents exactly what is claimed in the University lecture but they are wrong in their claim about the manner in which it is valid to sum radiative fluxes as is shown below. Spotlight 1 represents the solar radiation. As it heats the bulb to 30 degrees C I think it is valid to claim there is a flux of ~478 Watts per square metre induced by the action of this spotlight. Spotlight 2 represents the back radiation. As it heats the bulb to 36 degrees C I think it is valid to claim there is a flux of ~517 Watts per square metre induced by the action of this spotlight. The obvious question to ask is why 303 K, ~478 Watts per square metre did not combine with 309 K, ~517 Watts per square metre to produce the result I always see claimed in climate science University lectures that is a simple arithmetic sum of 995 Watts per square metre with a temperature of 364 K? Refer back to Figure 1 to see this is exactly the result that is claimed different figures but the same principle solar radiation back radiation combine to heat the Earth such that the Earth s surfaces heat to 303 K and emit 470 W/square metre as a result thus balancing the radiation fluxes and enabling the value for the back radiation. I assert the model taught as introductory climate science is flawed because it is not confirmed by simple experiment. I do not care about all of the arguments surrounding the claimed violations of various laws or whether a photon has no knowledge of the source that emitted it and will be absorbed. Actually that argument is spurious because of course it has knowledge of the source that emitted it it is emitted with precisely the energy level induced by the temperature of the emitter. I am solely concerned with these results.

13 A simple accounting of what is really happening here makes all of this add up in a meaningful way that is totally inconsistent to the flawed claim in the University lecture. Ambient air temperature was about 18 degrees C - ~291 K. This represents a radiative flux of the order of ~406 W/square metre. Spotlight 1 therefore induced extra heating of the order of = 72 W/square metre. Spotlight 2 therefore induced extra heating of the order of = 111 W/square metre. Summing these 406 ambient + 72 extra from spotlight extra from spotlight 2 = ~589 W/square metre and the Stefan-Boltzmann calculated temperature of ~589 W/square metre is ~319 K or 46 degrees C. I record 46 degrees C. These results clearly question the validity of summing irradiative fluxes and calculating a theoretical temperature in the manner presented by the University lecture cited. Obviously this also challenges the assertion that 2 sources of energy at much reduced temperatures than used in this experiment can combine to produce a 33 K greenhouse effect when a more modest 10 or 11 K is recorded at significantly higher power. The problem for the University lecture claim is that they have no ambient temperature to which they supply additional flux power. I would like to have tried lower temperatures but the climate here forbids this. Despite being almost winter air temperatures inside my house rarely drop below 10 degrees C overnight and are rarely less than 20 degrees C during the day. There it is I tried really hard to make sure these results were repeatable. I have performed similar experiments many times and every time the result is a temperature increase significantly less than what the practice of summing radiation fluxes and calculating temperatures for that sum as used by climate science claims. It is actually intuitive that these results are most likely valid for example combining a 30 degree C with a 36 degree C heat source to produce a resultant temperature of the order of 90 degrees C as claimed in lectures about the greenhouse effect does not seem likely. I claim no precision in this I had only crude equipment but I think it eloquently demonstrates that summing two or more radiation fluxes arithmetically and calculating a Stefan-Boltzmann equivalent temperature from that sum as described in the University lecture cited is completely unrealistic and invalid. Finally, note none of my experimental results are dependent on any form of back radiation and stand in stark contrast to the flawed University lecture model.

14 I propose that these results indicate that the only valid method to calculate the likely temperature increase by combining radiation sources in an atmosphere is not a simple arithmetic sum but actually relies on whether the value of the additional energy source being considered exceeds the value for the current ambient conditions. As I show only radiation sources with a value above ambient temperatures combine to produce realistic results. The science that is being taught ignores an initial condition and claims the results that should arise from my experiment are:- 478 W/sq.m. (303K) W/sq.m. (309K) should combine to 995 W/sq.m. resulting in a temperature of ~364 K. This is demonstrably wrong. If one added in ambient conditions the results are even more inaccurate. However if one considers ambient conditions as a starting point and considers the additional radiation sources in relation to this the sum appears to work. As has been demonstrated as realistic I propose the following series of steps as a rule for summing radiation fluxes in an atmosphere:- 1) Calculate the radiation flux for the ambient temperature; 2) Subtract the ambient flux from the additional flux; 3) If the result is positive add the difference to the value for ambient conditions and calculate the new temperature based on that flux sum. This rule is verified for all of the conditions experienced in my experiment. It is also logical. Obviously this raises the question of what to do if step 2) above results in a negative result. I claim you ignore it adding a lower value of radiation flux to a higher ambient value provides no additional heating capacity. I clearly demonstrate results that show higher radiation fluxes are required to raise temperatures a result entirely consistent with established science. I can only claim what I have shown raising the temperature of an object requires an additional energy flux that is greater than the flux responsible for ambient conditions. This casts serious doubts on whether back radiation has any heating effect at all. 5. References