Heh. In response to a ridiculous claim making the rounds (I get comment bombed at WUWT daily with that nonsense) which I debunked here: A misinterpreted claim about a NASA press release, CO2, solar flares, and the thermosphere is making the rounds
Dr. Roy Spencer employs some power visual satire, that has truth in it. He writes:
How Can Home Insulation Keep Your House Warmer, When It Cools Your House?!
<sarc> There is an obvious conspiracy from the HVAC and home repair industry, who for years have been telling us to add more insulation to our homes to keep them warmer in winter.
But we all know, from basic thermodynamics, that since insulation conducts heat from the warm interior to the cold outside, it actually COOLS the house.
Go read his entire essay here. <Sarc> on, Roy!
UPDATE: Even Monckton thinks these ideas promoted by slayers/principia/O’Sullivan are ridiculous:
Reply to John O’Sullivan:
One John O’Sullivan has written me a confused and scientifically illiterate “open letter” in which he describes me as a “greenhouse gas promoter”. I do not promote greenhouse gases.
He says I have “carefully styled [my]self ‘science adviser’ to Margaret Thatcher. Others, not I, have used that term. For four years I advised the Prime Minister on various policy matters, including science.
He says I was wrong to say in 1986 that added CO2 in the air would cause some warming. Since 1986 there has been some warming. Some of it may have been caused by CO2.
He says a paper by me admits the “tell-tale greenhouse-effect ‘hot spot’ in the atmosphere isn’t there”. The “hot spot”, which I named, ought to be there whatever the cause of the warming. The IPCC was wrong to assert that it would only arise from greenhouse warming. Its absence indicates either that there has been no warming (confirming the past two decades’ temperature records) or that tropical surface temperatures are inadequately measured.
He misrepresents Professor Richard Lindzen and Dr. Roy Spencer by a series of crude over-simplifications. If he has concerns about their results, he should address his concerns to them, not to me.
He invites me to “throw out” my “shredded blanket effect” of greenhouse gases that “traps” heat. It is Al Gore, not I, who talks of a “blanket” that “traps” heat. Interaction of greenhouse gases with photons at certain absorption wavelengths induces a quantum resonance in the gas molecules, emitting heat directly. It is more like turning on a tiny radiator than trapping heat with a blanket. Therefore, he is wrong to describe CO2 as a “coolant” with respect to global temperature.
He invites me to explain why Al Gore faked a televised experiment. That is a question for Mr. Gore.
He says I am wrong to assert that blackbodies have albedo. Here, he confuses two distinct methods of radiative transfer at a surface: absorption/emission (in which the Earth is a near-blackbody, displacing incoming radiance to the near-infrared in accordance with Wien’s law), and reflection (by which clouds and ice reflect the Sun’s radiance without displacing its incoming wavelengths).
He implicitly attributes Margaret Thatcher’s 1988 speech to the Royal Society about global warming to me. I had ceased to work with her in 1986.
He says that if I checked my history I should discover that it was not until 1981 that scientists were seriously considering CO2’s impact on climate. However, Joseph Fourier had posited the greenhouse effect some 200 years previously; Tyndale had measured the greenhouse effect of various gases at the Royal Institution in London in 1859; Arrhenius had predicted in 1896 that a doubling of CO2 concentration would cause 4-8 K warming, and had revised this estimate to 1.6 K in 1906; Callender had sounded a strong note of alarm in 1938; and numerous scientists, including Manabe&Wetherald (1976) had attempted to determine climate sensitivity before Hansen’s 1981 paper.
He says, with characteristic snide offensiveness, that I “crassly” attribute the “heat-trapping properties of latent heat to a trace gas that is a perfect energy emitter”. On the contrary: in its absorption bands, CO2 absorbs the energy of a photon and emits heat by quantum resonance.
He says the American Meteorological Society found in 1951 that all the long-wave radiation that might otherwise have been absorbed by CO2 was “already absorbed by water vapor”. It is now known that, though that is largely true for the lower troposphere, it is often false for the upper.
The series of elementary errors he here perpetrates, delivered with an unbecoming, cranky arrogance, indicates the need for considerable elementary education on his part. I refer him to Dr. Spencer’s excellent plain-English account of how we know there is a greenhouse effect.
The Viscount Monckton of Brenchley (April 18, 2013)
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
I wrote a comment on the original Spencer article describing how most people misinterpret the S-B equation in Climate Alchemy. It’s because the atmosphere is semi-transparent so cannot be considered a grey body. This is one of the three mistakes made by Houghton. The others are to fail to understand you can’t apply the two-stream approximation at an optical discontinuity and the Earth does not emit IR as if it were an isolated black body in a vacuum.
Also, there is no net surface IR from the Earth’s surface in the main GHG IR bands. This means there can be no CO2-AGW from this cause. There is no ‘back radiation’ [because for a normal temperature gradient it is annihilated at the surface]. Pierrehumbert does a good job of saving the blushes of Climate Alchemy by his argument about the ‘CO2 bite’ in OLR. However, this heating, ~3 W for doubled CO2 is offset by a process involving clouds. I’m writing a paper on this.
The Earth’s climate is controlled by a negative feedback control system involving the optical properties of clouds so temperature is independent of CO2 concentration. Forget surface IR, that is mostly irrelevant for CO2.
peterg says:
April 24, 2013 at 10:52 pm
“I do find all this denial of basic radiative physics fairly boring.”
———————————————————————————–
The reason the AGW hypothesis fails is not because of any problem with radiative physics. The radiative physics is fine* The problem is that the fluid dynamics of the atmosphere and the surface to atmosphere conductive flux were modelled incorrectly.
Radiative gases are critical to tropospheric convective circulation, without which our atmosphere would heat dramatically due to surface conduction.
The reality of an atmosphere in a gravity field in which the gases are free to move is that the surface is far better at conductively heating the atmosphere than it is at cooling it.
*Except for that little mistake of assuming that the oceans could have their cooling rate slowed by incident LWIR. Not a huge mistake, only 71% of the earth’s surface, probably nothing to worry about 😉
Rosco says (April 24, 2013 at 9:13 pm): “At least this “slays” Willis’ steel greenhouse completely !”
Eh? The problems described are in complete agreement with the “Steel Greenhouse” article. Far from “slaying” the steel greenhouse, this reference work vindicates Willis completely.
Check out Figure 1 here:
http://wattsupwiththat.com/2009/11/17/the-steel-greenhouse/
The shell (approximately the same size as the planet) radiates–gasp!–exactly half as much as the planet, just as problem 1023 says it should! Coincidence? 🙂
Konrad says (April 24, 2013 at 10:26 pm): “Dr Spencer and other lukewarmers are wrong. Radiative gases cool our atmosphere at all concentrations above 0.0ppm.”
So that would mean that, just as absence of positive correlation between temperature and CO2 argues against a significant warming effect, the absence of a negative correlation between temperature and CO2 argues against a significant cooling effect?
Konrad;
The problem is that the fluid dynamics of the atmosphere and the surface to atmosphere conductive flux were modelled incorrectly.
>>>>>>>>>>>>>>>>
So you’re saying that the satellite temperature data is wrong?
Greg House said: “Again, this is not what the IPCC supports. You can invent whatever effect you want, but only the IPCC’s one is politically relevant, because governments and agencies refer to the IPCC reports and recommendations, not to davidmhoffer or Steven Mosher.”
The IPCC AR4 WG1 glossary defines the Greenhouse Effect thus: “Greenhouse gases effectively absorb thermal infrared radiation, emitted by the Earth’s surface, by the atmosphere itself due to the same gases, and by clouds. Atmospheric radiation is emitted to all sides, including downward to the Earth’s surface. Thus greenhouse gases trap heat within the surface-troposphere system. This is called the greenhouse effect. Thermal infrared radiation in the troposphere is strongly coupled to the temperature of the atmosphere at the altitude at which it is emitted. In the troposphere, the temperature generally decreases with height. Effectively, infrared radiation emitted to space originates from an altitude with a temperature of, on average, –19°C, in balance with the net incoming solar radiation, whereas the Earth’s surface is kept at a much higher temperature of, on average, +14°C. An increase in the concentration of greenhouse gases leads to an increased infrared opacity of the atmosphere, and therefore to an effective radiation into space from a higher altitude at a lower temperature. This causes a radiative forcing that leads to an enhancement of the greenhouse effect, the so-called enhanced greenhouse effect.”
This seems to be exactly what Mosher and Hoffer have been saying. The backradiation and the ERL arguments are equivalent and both are explicitly endorsed by the IPCC.
tjfolkerts says, April 24, 2013 at 9:07 pm:
“Yes, I’m talking about the same examples. Specifically, 1026 says …”
http://books.google.no/books?id=dQGC0ifkE34C&pg=PA24&lpg=PA24&dq=concentric+sphere+black+body&source=bl&ots=Zh6N1e35jc&sig=m-7nVWch4_zv-l3ISR5k7bluSUQ&hl=en&sa=X&ei=_ldYUd7EFZLU9ATVzYHoDw&redir_esc=y#v=onepage&q=concentric%20sphere%20black%20body&f=false
What Problem 1026 is telling us is specifically that if R ~ r, the Q = Q’ + Q”. This is the exact equivalent to the Carnot cycle: W = Qh – Qc, where Q=Qh, Q”=Qc and Q’=W:
http://i1172.photobucket.com/albums/r565/Keyell/Carnot_zps4049e783.jpg
At any point in time, the heat flux leaving the surface of the sphere (Q) corresponds directly to (depends on) its specific emission temperature, which in turn depends fully and solely on (is set by) the heat flux provided to it by its heat source (so Q equals the heat input).
Q then goes half into warming the shell and keeping up its equilibrated temperature (Q’), half from the new layer to space (Q”): Q = Q’ + Q”. The entire flux comes from the sphere. It is simply split up upon absorption by the shell.
No need to invent secondary heating of the sphere to achieve radiative balance, beyond what the input from its heat source can manage on its own. Before the shell was emplaced, the power from the sphere’s heat source went into warming the sphere only (one object). After, the same amount of power goes into warming the sphere AND the shell (two separate objects). Hence the smaller flux to space. It’s that simple … Q is not reduced. The radiative flux to the cold reservoir (the surroundings) (before, Q, after, Q”) is reduced. This does not increase the surface temperature of the sphere. It maintains the temperature of the shell (Q’).
If the sphere were held at a constant temperature it would be because it received a constant energy supply from its heat source. With a variable heat source, the temperature would not be constant.
Let’s compare Problem 1026 with Problem 1023:
http://i341.photobucket.com/albums/o396/maxarutaru/bunnytaru/lol%20censorship/heatsourceinshellatequilibrium_zps1c9d662a.png
1023 specifically asks: “(…) what is the effect of the shell on the total power radiated to the surroundings?“
As you can see, J (Q) doesn’t change. J is simply replaced by J1 as ‘the total power radiated to the surroundings’ as the shell is put around the sphere. The only thing that changes is that ‘the total power radiated to the surroundings’ is halved. The rest goes into heating and maintaining the temperature of the shell, something that J didn’t have to do before the shell was emplaced. Perfect radiative balance: Q = Q’ + Q” — J = (J – J1) + J1.
The sphere/shell is also specifically likened to a star and a surrounding dust cloud (b). A star is pretty constantly heated, isn’t it?
There are more examples of course showing the exact same thing, that the source of the shell’s or the insulating layer’s incoming (warming) radiative heat flux (across a vacuum) does not heat up some more when surrounded or covered by the shell/insulating layer. The ‘insulating effect’ simply amounts to reducing ‘the total power radiated to the surroundings’ (Q –> Q”). There is no energy ‘piling up’ at the surface of the sphere/inner layer. Q (J) remains unchanged.
But we can get back to those later …
@Konrad
The greenhouse effect can heat or cool depends on the energy input and outputs and I am not sure any scientist ever said anything different.
I can also make a laser beam which has an extremely high temperature heat or cool things depending on how we up the relationship and frequency of the beam..
The problem with classic physics it is familiar only with heat only heating and so you struggle with the problem because your understanding of temperature is sort of simplistic and wrong. Roy is trying to bring a QM effect back into sort of classic physics so you can understand it but at some point you can’t.
Try understanding laser cooling and reading about it because sort of shows your problem and understanding of heat and temperature.
@Gary Young
The cooling effects of changing CO2 levels from 0.03 to 0.04 percent would be unmeasurable with current technology.
Konrad says (April 25, 2013 at 12:35 am): “The cooling effects of changing CO2 levels from 0.03 to 0.04 percent would be unmeasurable with current technology.”
Heh. I suppose the same could be said of the alleged warming effect. 🙂
LrB, the childishness was you slinging terms like ignorant around when you don’t seem to recognize the problem with your own argument.
A laser is not a spontaneous transfer from hot to cold, thermal radiation is a spontaneous transfer from hot to cold.
A laser involves doing work, and the production of waste heat.
Look into the Clausius statements of the laws of thermodynamics, as well as Carnot efficiency before calling others ignorant, perhaps?
___________
“The shell (approximately the same size as the planet) radiates–gasp!–exactly half as much as the planet, just as problem 1023 says it should! Coincidence? 🙂” ~Gary
The shell in 1023 does this without the implication that the inner body would increase in temperature.
Essentially it demonstrates that the steel greenhouse involves these steps:
1. Get an internally heated body
2. Add a shell around it which radiates half as much inward and outward as the inner body
3. A wizard does something
4. The temperature of the internally heated body increases
I cannot agree that radiation would quickly escape to space if GHGs did not slow the process.
It is inconceivable that greenhouse gases at minus 18 degrees C and trace concentrations could radiate as powerfully as the solid hot Moon surfaces.
NASA have clearly demonstrated that the heated Moon’s surface radiating effectively into a vacuum loses energy at a slow rate. From 390 K at lunar noon to 220 K at lunar sunset is a 170 K change in temperature in approximately 177 Earth hours – a rate of 1K per hour.
The Moon cools far more slowly once the Sun sets – from 220 K to about 100 K in 354 Earth hours.
Although there is less data for Mercury, the night on Mercury is some 2111 Earth hours long so cooling from ~740 K to ~90 K is easily understood.
There is no quick reduction in temperature of heated surfaces radiating into a vacuum.
Surely we observe a similar phenomenon here on Earth ?
The poles receive the least direct Solar radiation of anywhere on Earth and it is the fact that zero direct solar radiation is received for some months that is surely responsible for the extreme cold.
These are observable facts – there is no need of convoluted arguments to explain simple truths.
Anywhere in the Universe that is cold is so because of low levels of radiation. There is evidence that cooling from a warm state to a cold state by radiating to space takes significant time – NASA says so.
I believe them.
Besides the vacuum space at the Earth’s orbit cannot by any stretch of the imagination be thought of as cold with ~1370 W/sq m of solar radiation continually emitted by the Sun.
NASA prove the cold Earth orbit space myth in their “When we left the Earth” series when the solar panels and “parasol” – NASAs words – fitted to Skylab failed to deploy.
The astronauts that arrived to fix the problems found the temperature inside Skylab exceeded 70 degrees C.
Joseph E Postma wrote, “In any case, you can shine a flashlight at the Sun and the the beam will be there. But the flashlight doesn’t heat the Sun.”
Joseph, I have trouble with the idea that “the beam will still be there”. Does that imply that the source will lose energy (now in the beam?) and thus cool. In which case, where does the energy go? I find it easier to envisage that the beam will not be there and thus the source gets warmer as it sheds energy at a lower rate.
BTW, I’m not sure that shining a flashlight at the sun is a good thought experiment. I’d assume that some energy would probably be absorbed by the sun, just based on the color of the light from the flashlight. Pointing a finger at the sun might be a better example.
@David
There are few problems with Dr Spencers method of measuring the microwave emissions from O2 molecules. It is far more accurate than surface station data.
This system may however start to over read as global cooling occurs over solar cycle 25. Reflection from increasing snow and ice cover may be an issue. However correlation with radiosonde balloons during overpass is an eazy fix.
The other thing I want to comment on is the explanation given by people about what happens when you place some sort of insulation over a heat source – commonly putting a lid on a pot of boiling water.
They claim the back-radiation increases the heat.
Well I say bunkum – you can agree or disagree but at least consider the following :-
Exposed to the conduction/convection of the atmosphere no heat source will ever achieve its heating potential. Reduce that energy loss by effective insulation and the heat source will achieve near its potential. Radiation loss reduction may or may not contribute to this effect.
We know, or should know, that “trapping” warmed air close to our bodies, by reducing convective loss of that warmed air, is the principal manner in which we stay warm.
I see people saying stupid things like the back-radiation from the ice of igloos keeps the occupants warm.
I say rubbish.
The igloo traps the warmer air inside, maybe even warming it enough to melt the ice a little. The occupants do not shed all their clothing and romp inside naked.
There is absolute proof about the fact that reducing convective heat loss is the principal means by which we stay warm – radiation trapping has little to nothing to contribute.
Animals have only one mechanism to keep warm – their fur or feathers. There is no radiation barrier to prevent radiative losses – none.
Animal fur reduces the loss of the warmed air by reducing convection – there is no other mechanism possible.
We know this is true as we understand the phenomenon of wind chill which acts to destroy the trapping of the warmed air.
As a qualified Environmental Health Officer I know I am on firm ground in discussing simple biology.
@max
And now laser cooling is not spontaneous .. please describe how you arrived at this great piece of physics another of your great theories. You and Konrad look more and more ignorant the more you comment.
If you want to talk about work so lets put the two on even footing you have this big massive energy source in the sky we call it a sun it produces energy. I have a laser unit plug into a power socket so we both have a power source to do work they are equivalent get it functionally identical.
Now going down to the exchange level the transfer in laser cooling has to be instantaneous or you couldn’t get to zero degree kelvin that is in your classic garbage world how you define ABSOLUTE ZERO. Any non instant transfer would mean you would have motion try making an exchange of energies with a collision and have absolutely no movement.
The problem I have with you whackjobs is the same as Roy you are running up against some impossible physics for anything in classic physics to challenge because QM showed that classic physics is wrong 100 years ago. Instead of listening like all pseudoscience junkies instead of listening that you keep digging looking more and more stupid as you go.
If animals were relying on reducing radiative losses, to further support Rosco’s point, then evolution would probably begin producing nearly perfect mirrors, as that is by far the best radiative insulation.
Again, LrB, I live in a universe governed by relativistic and quantum physics, I know they are experimentally confirmed, and I know I do not live in a classical universe, learn how to read, kiddo.
Let me bold it for you:
I am not operating within a classical paradigm, the universe only resembles a classical one in the weak field regime, at small scales it is quantum, at large and fast scales it is relativistic, learn how to read before you go off on a rant next time.
A laser is not a spontaneous process, I know masers form naturally, but I’ve never seen a CO2 laser randomly appear and function.
TomR,Worc,MA,USAs
At April 24, 2013 at 9:32 pm you say
I answered Noelene and you may be interested in that answer. However, you may not have seen it because it was held in moderation for an hour and the thread had moved way past it when it appeared out of moderation.
However, P*stma saw my answer to Noelene because he quoted from it at April 24, 2013 at 4:53 pm and was unjustifiably offended by it.
In case you are interested, my answer to Noelene was at April 24, 2013 at 3:42 pm and this link jumps to it
http://wattsupwiththat.com/2013/04/24/spencer-slays-with-sarcasm/#comment-1286437
Richard
Max™ says (April 25, 2013 at 1:15 am): “The shell in 1023 does this without the implication that the inner body would increase in temperature.”
Really? OK, let’s assume the inner sphere has a constant heat source, as in the Steel Greenhouse, and is in thermal equilibrium with the shell as in problem 1023. Sphere temp is at T1. We agree that the power radiated by the system to its surroundings is half the power radiated by the inner sphere, as in both problem 1023 and Willis’s Figure 1, yes? (If not, why not?)
Now snatch away the “insulating” shell, real sudden-like. The system is suddenly cooling twice as fast, as per problem 1023, but its power input is unchanged! Oh no! What happens to the temperature of the inner (now alone) sphere? Increase? Decrease? Remain the same?
Let the system come to equilibrium, sphere at temp T2. Now add the shell back. Let the system come to equilibrium. Inner sphere is now at temp T3. What’s the relationship of T1, T2, and T3?
a) T1 = T2 = T3
b) T1 = T3 > T2
c) something else (specify)
and why?
There are two different mechanisms of radiative cooling of gases: by emitting quants of wavelength corresponding to quantum resonance of moleculae and by emitting at all wavelengthes (so called blackbody radiation). The first mechanism prevails for greenhouse gases, but the second is fairly universal and applies also to nitrogen and oxigen. And even greenhouse gases such as water vapour and carbon dioxide do not necessary emit at their quantum resonance wavelength when excitated by short-range radiation but can transfer excessive energy by collisiom with moleculae of nitrogen and oxigen without emitting anything. How much energy is re-emitted by carbon dioxide and how much simply heat atmosphere without emitting anything is everybody’s guess, because quantum mechanical calculations are too cumbersome to perform even using supercomputers. And heating of atmosphere enhances convection and make convective layer depth higher, which can compensate or even overcompensate backscattering by CO2. So the real contribution of greenhouse effect to surface warming in real atmosphere with convection, evaporation, condensation and radiation cooling can not be calculated, measured or estimated by any other means. It can be arbitrary small or even negative.
Greg House says: April 24, 2013 at 9:13 pm
(my bold).
Here you are just making an assertion without any backing.
For a simple example of how you are wrong, why are you assuming that the back radiation is from a colder source? Ground frosts at night are very common – they are caused by the surface losing energy by radiation, mostly directly to space, in which case the air close to the surface can clearly be warmer than the surface, esp. when the surface is a good radiator (e.g. a black car).
So even if you don’t believe in the “cooler can warm a warmer thing” idea, you don’t need to. Clearly GHG is providing energy to the surface.
LdB says:
April 25, 2013 at 2:23 am
You are abusing Konrad who has carried out actual experiments which he has published on various blogs, so he does know what he is talking about.
Empirical results which show that theories are wrong are the way that science is supposed to be done.
I suggest that you also take a look at TheFordPrefect’s experiments which show that if Back Radiation exists at all it is a minute amount of energy, nothing like the 50% bandied about by the climatologists.
Rosco says:
April 25, 2013 at 1:56 am
“…I see people saying stupid things like the back-radiation from the ice of igloos keeps the occupants warm.
I say rubbish.
The igloo traps the warmer air inside, maybe even warming it enough to melt the ice a little. The occupants do not shed all their clothing and romp inside naked.
There is absolute proof about the fact that reducing convective heat loss is the principal means by which we stay warm – radiation trapping has little to nothing to contribute….”
//////////////////////////////////////////////////////
I have lost count the number of times that I have pointed out that Igloos work by reducing convection and thereby by trapping heat.
The same is so of space blankets/insulatuion blankets. To have any substantial effect these need to be wrapped around the user thereby reducing convection and trapping heat. If they worked primarily by re-radiating heat, one could construct a space blanket much like a toilet roll. it could be say 6ft high and 2ft in diameter. The user could stand inside the mirrored roll and enjoy all the back radiated heat. But it would not be effective because of convection; significant heat loss would occur vertically. In fact from the radiative point of view, the diameter could be 3ft or 10ft, and the user would theoretically enjoy the same levels of re-radiated body heat, yet as the diameter size of the roll increases, it becomes less and less effective since convection plays an increasingly important roll.
Where heat can be lost through conduction or through convection or through radiation, then radiation is weak, and is overwhelmed by the other processes.
Today in sunny Spain it is cold (like most of Europe the last 3 months have been cold). I have no heating on in the house. My granite work top (in the kitchen) is cold to the touch. If I place a plastic/poluthene bag on top of the granite and place my hand on top of that bag, it does not feel cold. If I place a sheet of aluminium foil on the granite work top and place my hand on top of the foil, it feels cold.
In short, whatever miniscule radiative effect the aluminium foil has, it does not overcome conduction. The cold surface of the granite is conducted. Whereas the plastic bag is a good insulator and keeps my hand warm (even though plastic is a poor radiator)
If I suspend the aluminium foil horizontally in the air, and place my hand above it, possibly I can feel some reradiated heat when my hand is about 2mm above the foil, but the effect is so slight that I am unsure whether it is real or placebo.
But the point is that in the real world, redatiated heat (energy) is overcome by conduction and convection and this is so in the workings of the Earth’s atmosphere (not also forgetting the phase changes of water and associated latent heat).
Joseph E Postma says:
April 24, 2013 at 3:29 pm
“It’s called an incandescent flashlight.”
It is about the resistor (lets use the filament) becoming even hotter still if you shine the flashlight at a mirror. This does not increase the brightness (temperature) of the filament. Trapping the radiation does not increase the temperature of the filament.
Not my prefered item of interest (radiation… a very long time ago) but as far as I remember, if you can concentrate some of the outgoing light (including IR) via a concave mirror back onto the filament, the latter wouldn’t survive for long.
Or with an experiment: make that the outher wall of the bulb is coated with silver and test how long it takes before the filament is burned up, compared to a non-coated bulb… In the case of non-halogen bulbs, only radiation is at work, no conduction or convection.