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The simple is the seal of the true.[13]

Why CO2 cools the Surface of the Earth  

Dr. Theo Eichten, München;  Professor Dr.-Ing. Vollrath Hopp[2], Dreieich; Dr. Gerhard Stehlik[1], Hanau; Dr.-Ing. Edmund Wagner, Wiesbaden; © January 2014

NASA[3] published the most realistic graphical representation of the annual energy fluxes from Sun to Earth and from Earth to space (Figure 1). A similar representation is available from IPCC[4]. Qualitatively, the measured flux values from NASA and IPCC do not really differ. Moreover, the differences between the numerical values from NASA and IPCC are not relevant for our proof that CO2 cools the surface of the Earth.

Figure 1:

The yellow and ochre arrows in Figure 1 show all solar radiation fluxes (in per cent) to Earth and their different components. Three fluxes (yellow) are reflected (6% + 20% + 4% = 30%). Three others (ochre) are absorbed by the atmosphere or by the surface of the Earth (16% + 3% + 51% = 70%). The two ochre arrows are shown as long horizontal arrows. One of them (16%) heats the upper atmosphere. The other one (3%) heats the clouds. Any absorption of solar radiation by the atmosphere or by the surface is factor in heating the Earth. All heat fluxes (red) go upward. None goes downward.

The warming of the Earth by the Sun is elementary and undisputed, as is the location of the solar radiation in the electromagnetic spectrum (Figure 2). It is obvious as well that the Earth cannot heat itself. Consequently, no chemical substance can heat itself[5]. That applies for CO2, too. If CO2 warms up, the energy must be supplied from somewhere else.

Figure 2:

Solar radiation is the only source of warming. In contrast, cooling of the Earth involves not only thermal (electromagnetic) radiation, but also mechanical heat transfer and evaporation of water. Therefore, the factors of cooling are more complicated. Three energy fluxes (red) flow from the surface of the Earth towards space as shown in Figure 1.[6] 

The cooling of the Earth starts at the surface with the following three upward fluxes: The first flux (7%) represents mechanical heat transfer including upward thermal movements. The second and most important flux (23%) represents cooling through water evaporation. The third flux (21%) represents cooling through upward thermal radiation. This flux is split into two distinct fluxes, one (15%) is emitted in the atmosphere and the other (6%) is directly emitted into space. The sum of the three cooling factors (51%) at the surface is equal to the warming of the surface by the Sun.

Sun radiation always flows downwards (70%) except for the three reflections (30%). Thermal radiation always flows upwards: 64% into the atmosphere and 6% into space. A downward thermal radiation originating in the atmosphere does not exist. A greenhouse effect of +33°C would require such a downward flux of thermal radiation.

The upward thermal radiation flux (15%) from the surface into the atmosphere (position 2) is the key argument that CO2 cools the surface of the Earth. Since this thermal radiation flows away from the surface of the Earth it cannot be a factor in warming the surface.

In the following, the different molecular chemical properties of the most important constituents of the atmosphere (CO2, H2O, N2 and O2) will be discussed. Subsequently, the cooling effect of CO2 will be deduced from these different properties.

There are some relevant scientific laws describing energy fluxes. One elementary scientific law is the law of the conservation[7] of the sum of energy. This law is valid for all compartments of the Earth, but not for the Sun as producer of energy and not for the space as infinite sink of energy. Thus, this law is only valid for energy exchange between the surface and the atmosphere of the Earth. Another fundamental scientific law says that a body gets colder when it releases energy and gets warmer when receiving energy. Radiation energy can only be converted into heat energy with the cooperation of matter. The second Law of Thermodynamics states that heat energy cannot be completely converted into useful energy (‘work’). All these laws are relevant only for the horizontal exchange of energy on Earth, but not for the upward and downward energy fluxes between Sun, Earth and space shown in Figure 1.

Heating by radiation is only possible if the radiation is absorbed and not just passed through a body as in the case of transparent materials like glass or water. As will be discussed below, the main constituents of the atmosphere, nitrogen (N2) and oxygen (O2), let almost all of the downward solar radiation[8] pass through to the surface of the Earth and let all the upward thermal radiation from the surface pass through into space. They are heated neither by solar radiation nor by thermal radiation, because they cannot absorb it. Emission and absorption of thermal radiation involve movements (vibration, rotation) of atoms and molecules getting faster (and warmer) by absorption or getting slower (and colder) by emission. In general, N2 and O2 cannot absorb or emit thermal radiation because they have no dipole moment (see below).

However, as shown in Figure 1, two fluxes of solar radiation (16% and 3%) are absorbed by the atmosphere and clouds. This raises the question of which molecules actually absorb this radiation?

The flux labelled as ‘position 1’ (16%) corresponds to the UV radiation of the Sun. It is absorbed by the O2 molecule and converted into heat via the following two ozone processes:

As before the ozone processes, O2 and O3 molecules exist unchanged after the ozone process, too. This is called a chemical equilibrium. Therefore, the ozone process in total is nothing more than the 100% conversion of UV radiation from the Sun into heat of the atmosphere. The ozone process does not correspond to Planck's radiation law.

The 3% flux of the solar radiation absorbed by clouds represents the IR radiation of the Sun that is absorbed by the liquid water droplets of the clouds. Due to the high density of molecules in the liquid state, the IR absorption rate of liquid water is much stronger than that of gaseous H2O molecules.

Now, we return to our key argument concerning the cooling by CO2. This requires a closer look at the thermal radiation flux from the surface of the Earth into the atmosphere (position 2). This flux exists because the emission rate of CO2 into space is always higher than the absorption rate of radiation coming upward from the surface of the Earth.

Initially, we noted that the Earth and thus all chemical substances on Earth can’t heat themselves. In contrast, nearly all materials can cool down in the sense of Newton's Law of Cooling by irreversible emission of thermal radiation into the space. However, there are some exceptions that include a few chemical molecules, which cannot cool in the sense of Newton's Law of Cooling. This is because a prerequisite of emission (or absorption) of electromagnetic radiation is that the vibrations (and/or rotations) of the molecule must involve a change of its dipole moment. The molecules of N2 and O2 are symmetric and completely non polar, thus they don’t possess an electric dipole moment[9]. Without such a dipole moment, the thermal motions of the molecules can neither emit nor absorb electromagnetic radiation, neither from Sun nor from Earth. Nitrogen and oxygen constitute about 97% of the atmosphere. Consequently, ~97% of the atmosphere can’t cool itself. This is very important for the CO2 discussion.

Nevertheless, the atmosphere near the surface shows a nocturnal cooling. But the atmosphere is indirectly cooled by contact to the surface. At night the surface cools strongly by upward thermal radiation emission.

In contrast to N2 and O2, Newton's Law of Cooling is valid for the less symmetric triatomic gas molecules H2O and CO2, whose chemical bonds are strongly polar, and therefore they are very IR active (see also Figure 3). Figuratively speaking, the IR inactive bulk of the atmosphere (~97%) is mixed with about 2% “usually IR active Earth material" making the atmosphere to some extent “open to the cooling by the space”. The numerical value of 2% is the sum of the average concentrations of H2O (~0% to ~4%) and of CO2 (0.04% corresponding to 400 ppm). H2O and CO2 are referred to as “normal Earth’s material" because they cool by emitting thermal radiation into space and are cooled by space in that way. However, at a height of ~2m, where the meteorological temperatures are measured, the cooling of this atmospheric layer is dominated by the indirect cooling by the surface. The direct cooling by the upward thermal radiation of H2O and CO2 is too low to be relevant due to their low concentration of only 2%.

However, the situation regarding the total energy balance of the entire atmospheric column up to the turbopause of ~75 km height is quite different. In this regard the 2% admixture of H2O and CO2 is enough to cool column in a way that it is getting colder and colder with height and vicinity to space. While the atmosphere over its entire volume up to ~75 km height is cooled from space, the area of the surface of the Earth that is cooled from space is strongly limited to a few centimetres in depth. This explains the very high cooling capacity (64%) of the atmosphere and the much lower cooling capacity (6%) of the total surface of the Earth (including land mass and ocean).

Regarding the solar radiation flux, the energy input into the atmosphere occurs not only indirectly over the surface of the Earth (51%), but additionally also by direct absorption of solar radiation (16% + 3% = 19%). Hence, the atmosphere receives 70% of the solar energy, which is more than the surface receives (51%). Nevertheless, the atmosphere is still colder than the surface of the Earth! Referred to the total cooling capacity of the whole Earth (70%), the cooling capacity of the atmospheric column (64%) is about one order of magnitude higher then the cooling capacity of the few centimetres of the surface (6%).

Figure 3[10]:

Now we come back to our key argument. The ochre arrow (position 2) in Figure 1 represents the cooling by thermal radiation (15%) from the surface of the Earth to the atmosphere. But, N2 and O2 are unable to absorb thermal radiation. Only the trace gases H2O and CO2 can absorb this thermal radiation emitted by the surface. This radiative cooling completely contradicts the hypothetical “greenhouse effect” that claims a warming of +33°C by so called “greenhouse gases”.

Moreover, the most important flux of thermal radiation from the atmosphere into space (64%), which dominates the overall energy balance of the Earth, is the thermal radiation of the whole atmosphere (Position 4), shown as a thick red arrow, which transports all energy into space that is introduced into the atmosphere. Figure 1 shows a sudden start of an arrow with a constant thickness somewhere in the atmosphere. In reality, such a sudden jump doesn’t exist. Rather the thickness of this arrow, which represents the cooling rate of the atmosphere, should increase steadily with altitude up to 75 km. The temperature of the atmospheric column decreases with altitude more than just the usual -0.6°C to -1°C per 100 meters, corresponding to the influence of gravity on density and temperature.

How can CO2 act as the main coolant of the Earth, although it only exists in trace amounts of 400 ppm in the atmospheric column? The concentration of gaseous water above ~12 km altitude decreases to ~10 ppm, because the gaseous H2O molecules condense to ice. Between ~12 and ~75 km altitude, the thermal radiation to space is emitted by the CO2 only.

Moreover, CO2 is the most important coolant of the Earth, not only proven by the energy fluxes between Sun, Earth and Space, but also because of its particularly intense IR activity. CO2 has very strong IR bands at 15 ìm and 10 ìm (Figure 4), because of the high polarity of the C=O bond. The transformation of the important cooling effect of CO2 into a warming effect due to fraud physical assumptions - called greenhouse effect - is one of the biggest mistakes made by scientists.

The most important factor for the increasing thermal radiation of the “entire atmospheric column” with altitude is the strong IR activity of H2O und CO2 that is modulated by broadening of their IR bands by pressure. At low pressure in high altitudes the IR bands are very narrow and very intense. At high pressure near the surface of the Earth the IR bands are very broad and less intense. But, thermal radiation from the flanks of the bands reach the space directly without absorption by the molecules in higher altitudes under lower pressure.

Figure 4[11]:

Further details are discussed in this book.[12]


[1] Corresponding author: Dr. Gerhard Stehlik (gerhard.stehlik@gmx.de), GDCh Senior Expert Chemist ( https://www.gdch.de )

[2] Convenor Working Group Environment Engineering, VDI Darmstadt - Frankfurt am Main ( http://www.vdi.de )

[3] NASA - National Aeronautics and Space Administration, USA ( http://upload.wikimedia.org/wikipedia/commons/4/47/NASA_Earth_energy_budget.gif )

[4] IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Frequently Asked Question 1.1 „What Factors Determine Earth’s Climate“ Page 94 [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA

[5] It seems that white phosphorus is warming itself up to self-ignition. In fact, the temperature increases due to conversion of chemical energy of white phosphorus and oxygen into heat. That's the rule at every combustion process.

[6] Position 2 is an exception.

[7] Horizontal energy fuxes parallel to the surface of the Earth like cooling an area by a cold wind and warming an area by a warm wind, both are not relevant for the energy budget of the Earth because of the Law of Conservation of energy is valid in these cases.

[8] Exception is the ozone process of UV sunlight (position 3)

[9] A chemical bond then has an electric dipole moment, if different atoms are connected to each other. Then one atom is electrically positive relative to the other one and the other is negatively charged at the same rate, so that total outward electrical neutrality is maintained. The thermal movement of the two chemically bonded atoms with a dipole moment causes the electromagnetic heat radiation.

[10] http://www.heliosat3.de/e-learning/remote-sensing/Lec7.pdf

[11] http://irina.eas.gatech.edu/EAS8803_Fall2009/Lec6.pdf

[12] Fortschritts-Berichte VDI, Reihe 15, Nr. 256, Hopp, V., Stehlik, G., Thüne, W. u. Wagner, E., Atmosphäre, Wasser, Sonne, Kohlenstoffdioxid, Wetter, Klima, Leben - Einige Grundbegriffe. ISBN: 978-3-18-325615-0.

[13] First of the ancient mottoes of the Nobel lecture, 8 December, 1983 by SUBRAHMANYAN CHANDRASEKHAR: The simple is the seal of the true. Beauty is the splendour of truth.