Vincent J. Curtis
27 Sept 23
Let me begin by offering my thanks and gratitude to the Tom Nelson Podcast and his guest on podcast #98, Tom Shula. It brought me back to my early days at the Ontario Research Foundation and to my work in the Glass & Ceramics Department. We had big, high-vacuum furnaces. These were large, heavy steel chambers that could be pumped down to 10-6 Torr; inside the chamber were large, graphite heating elements that could easily run up to 2200℃. The high vacuum was necessary to protect the heating element from oxidation, and to keep the power requirements modest. At high vacuum, despite the high temperatures inside, the outer part of the chamber was cool. The size of a furnace necessary to reach temperatures of 2200℃ in open air would have rivaled a rotary cement kiln in size. But that lack of heat transfer efficiency of a high vacuum is actually relevant to this story.
You had to be able to measure the pressure inside the chamber in order to know when it was safe to begin heating. I didn’t know it at the time, but the device used to measure vacuum pressures was called a Pirani gauge, and Tom Shula explained how one worked. The device uses a high resistance filament in a Wheatstone Bridge arrangement, and the device measure the amount of power required the keep the filament at a fixed temperature.
According to Shula, the filament temperature runs between 50℃ and 100℃, depending upon the range of pressure you’re going to be measuring. There are three modes of heat transport: radiation, conduction, and convection. Radiation is the passage of electromagnetic photons through space. Conduction is the transport of heat through a body, and the passage of heat through a metal rod heated at one end through to the other is an example of heat conduction. The heating of a pot of water on a hot plate requires heat conduction from the plate to the pot, and from the pot to the water. Convection is the movement of matter within a fluid body carrying heat with it; and the boiling of water in the pot is an example of convection. Forced air heating or air conditioning in a building is another example of convection, by artificial forcing.
Back to the Pirani gauge. The heated filament can lose heat by radiation, conduction, convection, and by “end losses,” which is a heat loss by conduction into the body of the gauge. What is actually measured is the amount of power, or electric current, required to keep the filament at temperature. Under high vacuum, only radiant heat transfer is available as a mechanism of heat loss, and as we saw in the case of the big furnaces, it is the least efficient. At the highest vacuum, the least amount of power is required to keep the filament warm. As more and more air is let into the chamber, the power required to keep the filament warm increases. This is because air molecules collide with the filament, absorb heat, and depart the collision at a higher speed than then entered into it. Higher molecular speeds equate to higher temperatures. Air molecules are highly efficient at taking heat from the filament; on a macro scale, this is heat loss by the filament through convection and conduction.
Tom Shula gave a little example of the
relationship between radiative and convection/conduction mechanisms of heat
transfer in a chart somewhat like the following:
Pressure
(Torr) Radiative Convection/Conduction
Contribution Contribution
% %
760
(sea level) 0.4 99.6
10/(110,000
ft) 0.7 99.3
0.02/(250,000
ft) 50.0 50.0
Climate
models 95.5 4.5
Shula gave a little context by providing some actual power readings: The radiative and end losses at high vacuum amounted to 0.4 mW; at 760 Torr pressure, the device require 100 mW of power to maintain filament temperature. In sum, the IR losses amounted to 0.4 mW, while that lost to gas was 99.6 mW.
The figures in the chart are representative; the last line is the allocations of heat transfer ratios made by the climate models. The Greenhouse Effect is based upon the idea that radiation is the primary means of heat transport within the atmosphere, and that trapped IR radiation in the lower troposphere is the cause of global temperature rise. Shula argues convincingly that his results clearly show that radiation is insignificant as a means of heat transfer in the lower troposphere. (This, in fact, was the burden of my post on “Carbon dioxide saturation and global warming” 16 Sept 23: Blackbody IR is completely absorbed by CO2 with 10 m of the surface, and is immediately thermalized.) The surface of the earth is cooled by thermal conduction to the atmosphere in contact with it, and the air in contact with the earth is constantly kept cool by convection currents. It is only in the upper atmosphere, above 250,000 ft altitude, that radiation becomes the predominant mode of heat transfer; and this is how the earth radiates heat into outer space.
Shula gave molecular beam epitaxy as an example of where a heated substrate can be kept at very hot for a long time without external heating by simply keeping it in a high vacuum. The admission of a little air cools the substrate rapidly.
From this work, Shula concludes that the climate models, being based on radiative heat transfer, are unphysical, and therefore invalid, being based upon a false assumption. There is no scientific basis for anthropogenic global warming. Greenhouse “forcing” doesn’t represent the real dynamics of heat transfer in the lower atmosphere.
Shula said that the potential for massive
government funding and the creation of a continuing crisis permitted the AGW
concept to enter the mainstream; and in this opinion I heartily agree.
-30-
Shula made use of the IPCC AR4 global energy budget in his presentation, and I have the one from AR5. The numbers are pretty close. Concerning how the surface of the earth cools, the budget claims that the earth’s surface emits 398 W/m2 on average in blackbody, i.e. infra-red radiation, and loses a further 20 W/m2 by conduction/convection, which the IPCC refers to as “sensible heat.” Thus 398 + 20 = 419 total heat loss; 100 x 398/419 = 95 % lost by radiation, and 100 x 20/419 = 5 % lost by conduction/convection. Shula says these proportions are wildly unphysical.
The energy budget also has 342 W/m2 being emitted by the atmosphere back to the earth’s surface, and this is the so-called greenhouse effect: the earth’s atmosphere is considered to be a black body that emits IR radiation. Since nitrogen and oxygen are not IR active, IR active gases, particularly water vapour and carbon dioxide, are primarily responsible for trapping this IR radiation and re-emitting it in all directions. The earth’s atmosphere is considered to be a big IR trap, or, to coin a phrase, a greenhouse.
Shula argues that the cooling mechanism proposed by IPCC is wildly unphysical. The primary mechanism of the cooling of the earth’s surface is by conduction/convection, and not by the emission of IR blackbody radiation. He further argues that the earth’s atmosphere simply cannot be considered as a blackbody. Hence, there can be no greenhouse effect of any consequence in the earth’s atmosphere: the primary means of heat transport in the atmosphere is convection/conduction, and not IR radiation.
In my post of 16 Sept 23, entitled “Carbon
dioxide saturation and global warming” I show that all of the IR radiation
emitted from the earth’s surface is captured by atmospheric CO2 within the
first 10 m of the surface, and that this is all thermalized, i.e. converted
into sensible heat. Shula shows that the
radiative heat transport mechanism on which the climate models rely is unphysical,
and hence invalidating of the model.
There can be no greenhouse effect.
I show that even if you accept the IPCC model of IR blackbody radiation
of from the earth’s surface as correct, there can be no greenhouse effect
because all that IR radiation is thermalized, and hence subject to the physics
of conduction/convection. There can be
no greenhouse effect in the earth’s atmosphere.
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