Incompetence & Confusion of ‘Climate Experts’ Watts & Spencer
I must admit I am completely confused by the apparent contradictory and unphysical claims of Dr Roy Spencer and Anthony Watts (WUWT). The source of this confusion is twofold and explained below.
- Is glass “opaque” to infra-red radiation as is often quoted by these two experts writing articles on the “greenhouse effect”?
- What does glass is “opaque” to IR even mean?
One simplistic claim that one hears with regular monotony is that because “Glass is transparent to visible light, but not to infrared light…” therefore glass enclosures “trap” IR radiation.
So I did some research on the matter. Firstly let me present some public statements from Spencer and Watts readers should verify for themselves:
“The way an actual greenhouse works is by trapping infrared radiation. Glass is transparent to visible light, but not to infrared light, as we see below.”
“Mr. Gore was attempting to demonstrate this effect in his setup, but there’s an obvious problem: he used infrared heat lamps rather than visible light lamps. Thus, it seems highly likely that the glass jars would block the incoming infrared, and convert it to heat. That being the case, the infrared radiative backscattering effect that makes up the greenhouse effect in our atmosphere couldn’t possibly be demonstrated here in the Climate 101 video. By itself, that would be enough to declare the experiment invalid, but not only will I show the problem of the experimental setup being flawed, I’ll go to full on replication.”
- http://wattsupwiththat.com/2011/10/18/replicating-al-gores-climate-101-video-experiment-shows-that-his-high-school-physics-could-never-work-as-advertised/
- “A real greenhouse physically traps warm air, preventing convective air currents from carrying warm air out of the greenhouse, which would then be replaced by cooler air coming into the greenhouse.”
“In contrast, the infrared atmospheric greenhouse effect instead slows the rate at which the atmosphere cools radiatively, not convectively.”
http://www.drroyspencer.com/2009/04/in-defense-of-the-greenhouse-effect/ - Comments:
Anonymous says:
August 8, 2010 at 12:39 PM
“You prevented convective cooling just like in a real greenhouse. Not much to do with radiation. Just an analogy I suppose.”
Roy W. Spencer, Ph. D. says:
August 8, 2010 at 1:24 PM
“NO. Do not confuse the two. A real greenhouse uses solar, and its glass windows are opaque to IR transfer. I’m talking about nighttime radiative cooling through an IR-transparent aperture.”
http://www.drroyspencer.com/2010/08/help-back-radiation-has-invaded-my-backyard/
Do Spencer and Watts not know what they really mean and is there any hope they will find common understanding of radiative physics? At the moment, it seems confusion reigns supreme.
Anthony Watts says:
“The way an actual greenhouse works is by trapping infrared radiation. Glass is transparent to visible light, but not to infrared light, as we see below.”
Dr Roy Spencer disagrees:
“A real greenhouse physically traps warm air …”
But Dr Roy Spencer also agrees – thus disagreeing with himself :-
“NO. Do not confuse the two. A real greenhouse uses solar, and its glass windows are opaque to IR transfer. I’m talking about nighttime radiative cooling through an IR-transparent aperture.”
So – what does the statement – “its glass windows are opaque to IR transfer” even mean?
Well let’s try to shed some light on the matter.
Firstly we need make it clear that it is a meaningless generalisation and educated people should know better than to make public statements that are incorrect.
Glass is definitely not “opaque” to all wavelengths of “IR light”
The curves show the transmittance of “soda-lime”, “Pyrex”, “UV” and “Fused Silica” glass.
Even I can see that below 4 micrometres all of the glass has a high transmittance of wavelengths that correspond to infra-red. Soda-lime glass from the manufacturer that supplied the transmittance curve shown allows over 30{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} transmittance over 4 micrometres wavelengths.
Anthony Watts has so confused the belief that –
“Glass is transparent to visible light, but not to infrared light ..” –
to completely incorrectly conclude that –
“By itself, that would be enough to declare the experiment invalid,…” –
He implies, incorrectly, it is impossible for IR to be the cause of any heating effect on the CO2 contained in the glass jars.
This is, of course, not supported by real science and is simply another misguided generalisation. Of course the IR from the “IR heat lamps” used in Al Gore’s Physics 101 can penetrate the glass bell jars and heat the CO2 inside by IR radiation absorption.
I know this is entirely possible – a real analysis says it is possible – so here goes.
Carbon dioxide absorbs infrared radiation (IR) in three narrow bands of frequencies, which are 2.7, 4.3 and 15 micrometres (µM).
Using Wien’s law we calculate the temperatures of λpeak for each wavelength
2.7 µM – Wien’s law λpeak is at temperature of 800.18 degrees C.
4.3 µM – Wien’s law λpeak is at temperature of 400.8 degrees C.
15 µM – Wien’s law λpeak is at temperature of -80 degrees C.
I have absolutely no doubt that the filament of an infra-red “heat” lamp is easily capable of producing the temperatures necessary to emit the 2.7 µM and 4.3 µM radiation wavelengths that CO2 strongly absorbs. We’ll ignore the 15 µM band as unlikely for many obvious reasons.
Thus Anthony Watts’ claim – “Thus, it seems highly likely that the glass jars would block the incoming infrared” and that this “By itself, that would be enough to declare the experiment invalid” depends entirely on whether glass is “opaque” at the frequencies necessary to cause any radiation absorption heating of CO2 contained in the glass jars.
Simple perusal of the transmittance curves clearly shows that wavelengths close to 2.7 µM pass through various types of glass at levels of 50{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} or more – it seems only fused silica glass is “opaque” at this frequency. Some of the 4.3 µM is transmitted significantly for the “soda-lime” glass.
I’m not implying that Anthony Watts’ analysis of Al Gore’s Physics 101 experiment did not establish there were irregularities.
I am saying however that his generalised statement about glass preventing any IR heating effect because glass blocks IR is not supported by fact. The evidence presented here indicates it is entirely possible to observe an IR heating effect of CO2 contained in a glass jar and crude generalisation statements such as –
“Glass is transparent to visible light, but not to infrared light ..” – are not helpful to any public discussion as they give a false impression.
And this leads to – What does glass is “opaque” to IR even mean?
We have seen from the transmittance curves above that most types of glass absorb wavelengths above 4 – 5 µM.
But does this mean that glass “traps” infra-red radiation?
Of course not and again the proponents of this nonsense have made a gross misrepresentation of the facts. A simple search of the values for the emissivity coefficient values for glass demonstrates this radiation “trapping” ability is sheer nonsense.
The Engineering Toolbox lists the following:
Glass smooth 0.92 – 0.94
Glass, pyrex 0.85 – 0.95.
Hell, for the wavelengths where glass is “opaque” to the transmission of IR the stuff is almost a damn blackbody!
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