The Anthropogenic Global Warming Controversy
by Professor Karl Erdman*
Introduction
The simple estimation of the temperature of the surface of the earth assuming the earth behaves as a black body, and using the measured value of the radiation arriving from the sun, averaged over the total surface area of the earth, gives a value of –18°C at the necessary average radiative equilibrium at which the temperature is neither rising or falling.
To raise the temperature from this calculate value, to the actual measured average of +14.5°C of the surface it has been postulated that the infrared radiation emitted by the surface is inhibited from leaving the earth by being captured by infrared absorbing gases in the atmosphere. This energy is subsequently emitted by these so called “greenhouse” gases back to the surface (backradiation) as well as into outer space. The radiation going back to the earth is postulated to raise the temperature of the surface to its measured value. The validity of this theory is in dispute as the process contravenes both the 1st and 2nd laws of thermodynamics.
CO2 has the second largest cross section of the gases in the atmosphere for the absorption of the radiation emitted from the surface, although its absorbing power is only a tenth of that due to the much larger concentration of water vapor. The concentration of the CO2 has increased by 50{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} since the 1940s due to the burning of carbonaceous compounds for the production of energy. It has been postulated that this increase in the concentration of the CO2 has produced a rise in the temperature of the earth causing the melting of glaciers and a rise in the level of the oceans, and unless the production of CO2 is curtailed an environmentally catastrophic increase in the temperature of the climate will result.
The scenario has been given the name Anthropogenic Global Warming (AGW). The transfer of the energy in the theory is postulated to be done by radiation. A detailed description of the process and a criticism of the theory was given by Joseph E. Postma in March of 2011 under the title: Understanding the Thermodynamic Atmosphere Effect. The paper can be found on the internet.
This short note is an overview of how the energy arrives, is converted to heat in the atmosphere and eventually leaves as infrared radiation. It is distributed throughout the atmosphere as heat according to well known thermodynamic rules discussed by Claes Johnson in his paper: Climate Thermodynamics (also available on the internet). The distribution of the heat is mostly done by conduction and convection. The energy eventually leaves the atmosphere as radiation in the final conversion process that takes place at the altitude in the atmosphere where the radiation leaving the earth has been measured to have the temperature corresponding to the calculated black body value.
A more detailed discussion of the controversy can be found in the book titled: Slaying the Sky Dragon: Death of the Greenhouse Gas Theory.
A General Assessment of the Global Warming Controversy
The study of the variation of the average temperature of the surface of the earth as a function of time on the time scale determined by its history as revealed in the geological record indicates that there were large fluctuations in the temperature. There were long periods when the continents were largely covered with ice and snow and shorter periods when the temperature was much higher than at the present. Tropical forests existed on what is now the continent of Antarctica. As the distribution of the land masses has changed drastically due to continental drift it is difficult to give an exact picture as to the relationship between the variations in the temperature and the position of the poles.
Excellent data as to the changes in temperature over the last ½ million years is available and theories about the possible causes of these temperature changes has resulted in a belief that the latest rise in temperature is due to a man made increase in the concentration of so called greenhouse gases in the atmosphere. Although the physical mechanism proposed is not possible as it contravenes both the first and second laws of thermodynamics it has been appropriated by climatologists and used by the politicians to control the use of coal and oil as energy sources and unnecessary and costly regulations have been implemented to combat the “perceived” catastrophe that their continued use is expected to cause.
It is important to first get a general picture of how the temperature of the solid surface of the earth arises. Beginning at the center of the earth we discover that it is at a high temperature, far above the melting temperature of all of the elements that make up the periodic table. The central region behaves as a solid due to the high temperature. The temperature begins to decrease as we move toward the surface but due to the decrease in pressure becomes liquid about 1/3 of the way to the surface and after we have travelled about 6,300 km has cooled sufficiently to become solid. In the remaining 10 km the temperature has decreased to approximately 30°C. In the remaining few km to the surface the manner in which the temperature changes depends on whether the surface is covered by water (2/3 of the surface) or land. The remaining few kilometers of what constitutes our planet is a gaseous mixture, beginning with a density of about 1.3 kg per cubic meter and rapidly decreasing so that at the altitude of the highest point on the surface (about 8 km) is already ½ of what is at the nominal surface. Most of what we call our weather (the variations in the local climate) take place due to what happens in this thin surface layer.
The surface of the earth receives its heat from two sources. Both sources are radioactive.
The major source is of course the sun where Hydrogen is fusing to form Helium and other elements in the periodic table as far as iron. This occurs in the center of the sun and it takes ½ million years for the heat from the reactions to diffuse to the surface so energy we receive as sunshine today began its journey a long time ago. We are only beginning to understand the behavior of this energy source since we have set up experiments on the space station and have a set of circumsolar satellites so that we can view all sides to the sun simultaneously. Also we can measure the rate of the reactions in the center of the sun by studying the neutrino flux which travels at the speed of light so that the neutrinos that we measure are only 8 minutes instead of ½ million years old.
The heat from the center of the earth comes from the radioactive decay of the elements in the periodic table which have long half lives, the main one being K-40, of which there are approximately 14 mg in the body of the average person decaying at a rate of 4,400 disintegrations per second. There has also been the suggestion that nuclear fission from the Uranium and Thorium in the core may be taking place and the spikes of heat in the climate of the earth that occurs at intervals of 100,000 years may be due to sudden changes in the reactivity of these natural reactors. The contribution due to the heat at the surface coming from the internal heat source is small compared to the heat that arrives from the sun.
As a hot body situated in empty space the earth loses energy by emitting electromagnetic radiation. Energy is carried away in the electromagnetic fields produced in various physical processes involving the acceleration of charges when hot atoms and molecules collide, or when atoms or molecules that have been excited to higher energy states, de-excite. Simple descriptions of the processes in terms of radiation emitted by a “black body” can be used to calculate the rate of energy flow from a body whose energy content we measure in terms of its temperature, which is a measure of the kinetic energy possessed by the atoms or molecules in the body. Since the rate of energy loss per unit area from a black body is only a function of the temperature the effective temperature of the earth can be calculated and corresponds to the temperature in the atmosphere at an average altitude of 5 km.
The radiation is being emitted from a gas whose density is decreasing as a function of its altitude. The percentage of its constituents varies as a function of the height and temperature, the concentration of water vapor is greatest near the solid and liquid surface. Tthe relative constituents are Nitrogen(75{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}), Oxygen(20{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}), Water vapor(4{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}), Argon(1{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}), Carbon Dioxide(0.04{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}), Methane, and Nitrous oxide. The principal absorbers and hence emitters of the infra red radiation emitted by the planet are Water vapor and Carbon dioxide of which Water vapor is the most important as 95{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} of the absorption is due to the water vapor and only 3.6{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} to the Carbon Dioxide.
The atmosphere is fairly transparent to the incoming radiation from the sun but only about 50{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} reaches the surface as 20{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} to30{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} is reflected by clouds and another large fraction is scattered and absorbed by the atmosphere as is all of the radiation in the far infra red. Of the energy that reaches the surface, 60{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} is transported into the atmosphere by conduction and convection and 40{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} leaves the surface as infra red radiation and only 1/3 of the 40{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} that leaves the surface in this fashion is emitted into space. The rest of the infra red radiation that leaves the surface interacts with the infra red absorbing gases and excites the molecules into higher energy states. The collision rate between these molecules and the molecules comprising the rest of the atmospheric gases is so high that the energy in the excited states is transferred to the Oxygen and Nitrogen molecules where it increases the kinetic energy and hence heats the atmosphere which now becomes part of the energy transport system to the higher altitudes.
The hot atmosphere rises and cools by adiabatic expansion at the appropriate lapse rate depending on the level of the water vapor that it contains but as it rises the pressure decreases and so does the collision rate because of the decrease in density of the gas, but also the velocity has decreased because the temperature has dropped. As a result, the competition in the transfer of energy from one molecule to another by collision or its loss by de-excitation by the emission of radiation becomes the more favorable for the de-excitation process and the energy being exchanged between molecules transfers the energy stored as heat in the oxygen and nitrogen back to the excitation of the water molecule and the preferential direction of the emission is in the direction of decreasing density, into the cosmos.
The process does not depend how the energy is supplied to the system as the thermodynamics of the atmosphere guarantees the directionality of the energy flow. Moreover the process is simple physics and as is generally the case if there are two competing explanations for a physical process the simpler is usually the best description and measurements can be taken to differentiate between the two processes.
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*Dr. Karl L. Erdman: Professor Emeritus Physics, University of British Columbia, Canada. Karl Erdman is an experimental nuclear and particle physicist who at the beginning of his career was involved in measuring the cross sections for energy production in the sun. His studies in nuclear structure led to his involvement in the design of both accelerators and detectors of various types from DC machines such as Van de Graaf accelerators to high current, high energy cyclotrons. During the course of his career he worked at Cambridge University, the ETH in Switzerland and at CERN where he was also a CERN fellow in the early study of the properties of proton-antiproton interactions.
He was a designer and builder of the TRIUMF negative ion cyclotron, one of the 3 meson factories, where he subsequently was an associate director in charge of the technical division.
After his retirement from the University he was the one of the founders of the pioneering Advanced Cyclotron Systems Inc. a company that recently hit the headlines for their breakthrough in the field of cancer treatment. Erdman’s company designs and builds isotope production cyclotrons and accelerator systems delivering milliampere beams of protons. Their 30 MeV cyclotrons are major suppliers of accelerator produced isotopes for medicine and industry. The company is now the principal supplier of accelerators for the production of Tc99m for medical imaging and has constructed and installed proprietary 24 MeV systems in Canada, Russia, Europe, China, Japan, and USA.
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