by Ian Bradford
The IPCC, the Intergovernmental Panel on Climate Change, formed by the United Nations, initially declared that humans were putting carbon dioxide into the atmosphere and that was causing global warming. Then that was changed to climate change because of the embarrassment of at least 20 years of no temperature change from 1998. Then all sorts of weather events were put down to more CO2 and finally methane CH4 also became a problem.
Cows were in the firing line and it was pushed that we should give up eating meat and do away with cows. Perhaps we would have no milk, either!
The greenhouse effect
Most of the argument revolves around the “greenhouse effect.” The basic principle is that short wavelength radiation from the sun, which includes Ultra Violet A, Visible Light, and Infra Red, passes through the atmosphere and reaches the earth causing it to warm. Now the IPCC states that the earth at about 15ºC, gives off longer wavelength Infra-Red radiation (heat), and this heat is absorbed by the CO2 and CH4 in the atmosphere and then they re-radiate to warm the earth. As more CO2 and CH4 enters the atmosphere this warming increases.
A word about actual greenhouses: The same radiation from the sun strikes a greenhouse. The glass allows visible light and a small amount of shorter wavelength Infra Red to pass though. All objects within the greenhouse are heated. Like the earth, these heated objects give off infra Red Radiation, but this is of longer wavelength than that which entered. The glass will not pass this out. Consequently, the greenhouse builds up heat. However, if windows are opened, especially in the roof, much of this confined heat escapes into the atmosphere.
There is no comparison between a greenhouse and the earth/atmosphere system. In a greenhouse the hot air is confined. No such confinement takes place in the atmosphere. In this respect the term “greenhouse gas” is a misnomer.
The layered atmosphere
The atmosphere is divided into horizontal layers.
Three scientists G.V. Chilingar, L.F. Khiliyuk, and O.G. Sorokhtin, investigated the effect of CO2 emissions on the temperature of the atmosphere. The proponents of the so-called “greenhouse effect” take into account only radiation from the earth’s surface. (That’s heat travelling by electromagnetic waves). The three scientists found that in the dense troposphere the heat is mainly transferred by convection.
Convection is an actual movement of the particles and is common with gases. The three scientists found that
- convection accounted for about 67%,
- water vapour condensation in the upper troposphere accounted for about 25%,
- radiation accounted for only about 8% of the heat transfer from the earth’s surface to the troposphere.
Methane is a tiny proportion of the atmosphere
The gases near the surface of the earth warm up from the earth, and expand making them less dense. They rise up through the troposphere. Methane (CH4) is carried along with all the other gases. (At this stage that methane is only about 1800 parts per billion (ppb) in the atmosphere.) That means it makes up only 0.00018% of all the gases in the atmosphere. That’s a very tiny amount, but it is known that it is a better absorber of radiation than CO2 for example. This is confirmed by laboratory experiments. But of course only methane was in the experimental container, whereas in the atmosphere there are several gases, all mixed, two of which are in large quantities – oxygen and nitrogen.
So methane along with all other gases rise when warmed. As they rise they cool and therefore become more dense. You will note that the top of the troposphere is at about – 60 deg C. Being now more dense they then begin to fall back to the earth. This cooler air replaces the warmer air of the lower layers. The conclusion is that the temperature distribution in the troposphere has to be close to adiabatic.
An adiabatic process
What does adiabatic mean? An adiabatic process is a process in which heat does not enter or leave a system. The rising and falling of air, as above, is considered to be an adiabatic process. What does this mean then? If no heat enters the system then the air returned to earth will not have warmed above what it was when it left the earth. Therefore it cannot warm the earth. So we can rule out convection.
Here is a graph showing the temperatures in each layer. The red line is temperature.
Now what about the 8% of heat transferred by radiation? This radiation has to find one methane molecule among 500,000 other molecules. So there is a good chance the radiation will be absorbed by something else. Laboratory experiments putting successive gases in a tube, shining radiation of various wavelengths through the tube and collecting the radiation with a spectrometer, shows that “greenhouse” gases do not absorb all the radiation falling on them. They only absorb radiation of a certain wavelength.
In the case of methane it only absorbs radiation in two narrow bands centered on 3.5 microns and 8 microns. A micron is a wavelength of a millionth of a metre. The graph below gives the absorption spectra of greenhouse gases. In other words the graph gives the wavelengths of the Infra Red radiation (heat), from the earth that the molecule of that gas will absorb. (I have drawn vertical lines though the peaks of methane.)
µm is micrometres or microns
Note that the vertical lines pass through at least part of the absorption spectrum of water. Water vapour by the way means just water molecules — a gas.
The importance of water vapour
Now water vapour averages about 2% in the atmosphere. It is also a greenhouse gas — the main greenhouse gas, as it absorbs Infra Red radiation in those little shaded mountains. If there is an average amount of water vapour then there are 10,000 times more water molecules than a single molecule of methane.
So starting with a small amount of radiation to begin with, it is highly likely that all this radiation will be absorbed by water vapour (since there is so much of it), before it actually reaches a methane molecule.
It seems clear then, that methane, which exists in the atmosphere in only tiny amounts, plays virtually no part in the warming of the earth.
Reducing methane by avoiding meat and cutting down on cow numbers will make no difference to climate. A considerable reduction in meat consumption will however, increase the chance of malnutrition and nutrient deficiencies, which is something never mentioned by the anti-meat, climate alarmist disciples.
The tiny increases in methane associated with cows should not be the basis for insane regulations or national policy.
G.V. Chilinger, L.F. Khilyuk, O. G. Sorokhitin: Cooling of the Atmosphere Due to CO2 Emissions.
Watts, Anthony: Methane the Irrelevant Greenhouse Gas, April 2014
Non volatile Technologies Pty Ltd.: The Truth about Man-made Global Warming.
Tufsted, David: Why is Methane Such a Bad Greenhouse gas? Quora, August 2019.