I am delighted to present to you a scientific paper that illustrates how our atmosphere interacts with the Sun and how the temperatures throughout the atmosphere as well as on the surface are in perfect harmony with basic physics and the laws of thermodynamics.
Not only is our Earth's atmosphere and its ground temperature explained, planet Venus is also shown to comply with the same laws of physics and thermodynamics.
Understanding the Thermodynamic Atmosphere Effect
by Joseph Postma.
This article began as a brief two-page summary of the theoretical development of the “Greenhouse Effect”. After having several discussions with colleagues, it became apparent that its theoretical basis was not widely understood, even though the theory appeared to be believed in implicitly. In a scientific institution it is generally expected that individuals understand the theories they support and believe in, rather than simply being aware of them and believing in them. Therefore it was curious that there seemed to be so little academic understanding of the theory of the Greenhouse Effect, as opposed to simple awareness of it.
It should be pointed out immediately that the “Greenhouse Effect” is indeed a theory - it is not a benign empirical fact, such as the existence of the Sun, for example. As a theory it has a scientific development which is open to inspection and review. It is extremely curious, from a scientific standpoint, that the word “theory” is almost never associated with the term “Greenhouse Effect” in public and academic circles.
Undoubtedly, this fact is related to why even academics are unfamiliar with the theoretical development, let alone the general public‟s awareness of the theory. Therefore from this point on, the “Greenhouse Effect” will be referred to as the “Greenhouse Theory”, indicative of the fact that it is a proposition which needs to be supported by observation and which also needs to agree with other well-established laws of physics. This is analogous to the theory of gravity: just like the atmosphere, no one questions that gravity exists, obviously. What we do question is the theory that describes how it works, and just like Einstein‟s theory of gravity which breaks down and fails under certain conditions, and isn‟t compatible with some other branches of physics, we can examine if the Greenhouse Theory also breaks down and fails under the conditions it is supposed to describe. This distinction needs to be stressed because many scientists, who really should know better, will make the claim that the effect of the Greenhouse Theory is a “scientific fact”, when in reality a scientist should understand that there is no such thing as a scientific fact, but only scientific theories. These are created with the intention to explain or describe the workings and behaviour of otherwise benign empirical data. For example, again, it goes without question that the Earth has an atmosphere, that the weather changes, and that some force pulls things down to the ground; these are facts of reality, and there is absolutely no need to qualify them with the adjective “scientific”.
No one questions these things. These facts belong to and are acknowledged by everyone everywhere, independent of science. What scientists attempt to do is create theories which can describe the way these facts of reality work, in a logical way, and in a way consistent with other scientific theories. For example, you may often witness a person insinuate that, if you question the theory of gravity, then you should test it by jumping out a window. This is an extremely anti-scientific thing to say, because indeed, scientists question the theory of gravity one-hundred percent! We don‟t question that gravity exists, but we do question the scientific theory which describes how it works. And so what we are similarly concerned with here is questioning the Theory of the Greenhouse Effect.
The Greenhouse Theory is the proposition that the atmosphere warms the surface of the Earth to a temperature warmer than it would otherwise be without an atmosphere, via a process called “back-scattered infrared radiative transfer”. This is just a fancy way of describing the idea that greenhouse gases act like a blanket around the Earth which traps infrared radiation, with the radiation causing it to be warmer than it otherwise would be, and this is supposed to be loosely analogous to how a botanist‟s greenhouse works. We will examine the proposition of the Greenhouse Theory and see if it is a theory which satisfactorily can explain our observations of the temperature of the surface of the Earth.
The word “radiative” in “radiative transfer” means “of or pertaining to light”; “transfer” is referring to transfer of energy. So radiative transfer means the transfer of energy by light. In this article the word radiative will sometimes be replaced with the word “radiation”, but the type of radiation it will be referring to is always “radiative” radiation, again simply meaning light. It is not the type of radiation you would associate with nuclear radioactivity, for example. In physics, light is also called radiation because it “radiates energy away” from its source, be it light-energy from a match, or a star.he reason why it is important to examine the Greenhouse Theory is because it fundamentally underpins the concern over “global warming”, sometimes called “anthropogenic (i.e.human) climate change”. These two terms are generally used interchangeably, but are somewhat mutually ambiguous. Anthropogenic climate change can mean any type of change in the climate, be it warming, cooling, more rain, less rain, etc, caused by humans for any reason. Of course, natural climate change has been ongoing at all times throughout Earth‟s history, and so anthropogenic climate change needs to be distinguished from this. In fact the only constant of climate is that it is constantly changing, for there have been no identifiable periods of climate stasis in Earth‟s geologic history.
Anthropogenic global warming, on the other hand, means a general warming of the atmosphere theorized to be due to human emission of carbon dioxide (CO2), which is then theorized to cause a strengthening of the effect of the Greenhouse Theory, which is what actually causes said warming. It is this latter definition which is more fundamental and which directly relates to the Greenhouse Theory, because atmospheric warming via CO2 can be theorized to lead to various changes in the climate, such as precipitation changes, etc. And it is also possible that small-scale local cooling can take place, even though the average trend of the entire atmosphere would still be towards general warming. Therefore “anthropogenic climate change” falls under the theory of global warming caused by anthropogenic emission of CO2 and the effect of the Greenhouse Theory. To be perfectly clear, we call it “anthropogenic” global warming (AGW) in order to distinguish it from natural warming, for example from natural changes in the brightness of the Sun, and from natural emission of CO2 from the biosphere (all life, such as plants, animals and, bacteria) and lithosphere (all geologic activity, such as volcanoes, weathering of rocks such as limestone, etc). So Anthropogenic Global Warming caused by anthropogenic emission of CO2 depends upon the Greenhouse Theory to actually create said anthropogenic warming. And this is distinguished from Natural Global Warming (NGW) which could be theoretically caused by natural emission of CO2 which would also depend upon the Greenhouse Theory to actually create said natural warming. In other words, the Greenhouse Theory states that an increase of atmospheric CO2 (or any other “greenhouse” gas, but CO2 is the one we‟re most concerned with), be it human or naturally sourced, should cause global atmospheric warming on average via back-scattered infrared radiation, although there may be small-scale local cooling in some locations also. So there are two parts in the analysis of the Greenhouse Theory: Does back-scattered infrared radiative transfer act like a blanket upon, and explain the temperature of, the surface of the Earth, analogous to the way a greenhouse building works; and do changes in atmospheric CO2 drive significant changes in atmospheric temperature via this type of radiative Greenhouse Theory?
In order to answer these questions we must go through the physics and mathematical development of some basic facts about the way the Sun and the Earth work together in exchanging radiation. We are going to have to look at some mathematics in the upcoming section, but I want to stress one very important thing: I do not require the reader of this article to fully understand or follow along with the development of the math equations. When I read a scientific paper that has lots of math in it, usually I can just skip over the math parts and keep on reading the text to see what the point of it all is. Unless it is a scientific paper that is specifically about the development of some new equations that someone isn‟t sure of, it is usually sufficient simply to acknowledge that the equation has been written down and showed to you, but you are not required to work it out for yourself. You just have to keep reading along to find out what the point is.
The reason why I‟m making this point and talking to the reader in the first person here, is because I realize that not everybody reading this has a degree in physics or likes mathematics, and so I don‟t want them to stop reading along when I start discussing them. The physics involved here is what you would find in current senior-year high-school math classrooms, and first-year undergraduate physics at universities. If it‟s been decades since you did any math, or physics is your most hated class in school, don‟t worry about it! Just read along and I‟ll try to describe what‟s happening clearly enough so that those who are interested can also work it out for themselves.
One concept needs to be introduced before we continue with some math, which is called a “blackbody”. In physics, a blackbody is an extremely important conceptual tool because the behaviour of a blackbody relates to fundamental concepts in physics, such as the Laws of Thermodynamics. A blackbody is simply exactly what it sounds like: an object which is completely black. The reason why it is black is because it absorbs 100% of all the light that strikes it, and doesn‟t reflect any of it back. Therefore it appears black! This is one part of the “behaviour” we refer to when discussing blackbodies: the behaviour that it has when struck by light. And the behaviour is that it absorbs it all. It should be pointed out that in the real world, most objects will reflect some of the incident light and absorb only the rest. But even in this case many objects can still be very closely approximated by a theoretical blackbody, and you do this by factoring out the amount of radiation lost to reflection. For example, if 30% of the light is reflected, then 70% is absorbed and you can take account for this in the math.
When a blackbody absorbs the energy from light and there‟s no other heat or light sources around to warm it, then it will warm up to whatever temperature is possible given the amount of energy coming in from the light being absorbed. If the source of light is constant, meaning it shines with the same unchanging brightness all the time, then the blackbody absorbing that light will warm up to some maximum temperature corresponding to the energy in the light, and then warm up no further. When this state is reached it is called “radiative thermal equilibrium”, which means that the object has reached a stable and constant temperature equilibrated with the amount of radiation it is absorbing from the source of light. This is distinct from regular “thermal equilibrium”, which is when two objects which are in physical contact eventually come to the same temperature, if they started out at different temperatures. In radiative thermal equilibrium, the object absorbing the light will not come to the same temperature as the source emitting the light, but actually will always be cooler than it because the distance between the two objects reduces the energy flux density of the radiation from the source.
This leads us to the second part of the behaviour of a blackbody which makes them so great. When a blackbody has reached thermal equilibrium, it can no longer absorb more light for heating and therefore has to re-emit just as much light-energy as it is absorbing. Because the blackbody can‟t just reflect the light, it has to re-emit it as thermal radiation. The spectrum of this re-emitted light follows a very well known equation called the Planck Blackbody Radiation Law, after the German physicist Max Planck who helped discover it in the early 1900‟s. This law allows us to calculate the total amount of energy in a blackbody spectrum, and what the temperature the object actually needs to be at in order to emit that amount of energy. We can determine exactly what the equilibrium temperatures must be. For a real-world object that actually reflects some light but absorbs the rest of the light, when we factor this is into the equations we find that the object still closely approximates the ideal blackbody, and this is of course confirmed by observation. We can therefore calculate the “effective” temperature the object would need to have if it were a perfect blackbody emitting that amount of radiation.
So strictly speaking, although the blackbody absorbs all the light that strikes it, it wouldn‟t actually appear perfectly black at all wavelengths because the thermal energy it re-emits is also a form of light. But it appears black because this re-emitted light is of a much lower energy than the light being absorbed. For example if the object absorbs visible light, then it will re-emit infrared light which we can‟t see, and therefore it still appears black. The object would need to heat up to some very high temperature indeed for it to re-emit visible light; a red-hot oven element, for example, can approach 10000C (but it heats up due to the electricity being run through it). And as mentioned earlier, in the real world many objects which you wouldn‟t necessarily expect to behave like blackbodies, also act like blackbodies. Basically, everything tries to act like a blackbody as best as their physical conditions allow for. And so even entire stars like the Sun emit radiation very close to the way a blackbody does, according with the Planck Blackbody Radiation Law. You can therefore understand why the blackbody is such an important conceptual tool in physics. Rarely do you find an actual perfect blackbody in nature; but everywhere you look you find things acting very similar to one. As amazing as this sounds, the only thing that really does seem to perfectly resemble a blackbody is the entire universe itself! And probably Black Holes, but that‟s an entirely different discussion.
Lastly, there is one fundamental law of physics that relates to blackbody emission of thermal energy: it is absolutely fundamentally impossible for a blackbody to further warm itself up by its own radiation. This is actually true for all objects, but we‟ll just keep referring to blackbodies here since that‟s what the subject is about. For example, imagine a blackbody which is absorbing energy from some hot source of light like a light-bulb, and it has warmed up as much as it can and has reached radiative thermal equilibrium. The blackbody will then be re-emitting just as much thermal infrared energy as the light energy it is absorbing. However, because the blackbody doesn‟t warm up to a temperature as hot as the source of light, its re-emitted infrared light is from a lower temperature and thus of a lower energy compared to the incoming light that it is absorbing. Now here‟s the clincher: imagine that you take a mirror which reflects infrared light, and you reflect some of the infrared light the blackbody is emitting back onto itself. What then happens to the temperature of the blackbody? One might think that, because the blackbody is now absorbing more light, even if it is its own infrared light, then it should warm up. But in fact it does not warm up; it‟s temperature remains exactly the same. The reason why is very simple to understand but extremely important to physics: the blackbody is already in radiative thermal equilibrium with a hotter source of energy, the higher radiative energy spectrum light from the light-bulb. You cannot make something warmer by introducing to it something colder, or even the same temperature! You can only make something warmer, with something that is warmer! This reality is called the 2nd Law of Thermodynamics, and is so central and fundamental to modern physics it cannot be expressed strongly enough.
To make the idea more intuitive, imagine a simple ice-cube. Even though an ice-cube is at zero degrees Celsius, it is still 273 Kelvin degrees above absolute zero and therefore has quite a bit of thermal energy inside it, which it does radiate away as thermal infrared energy. Of course, we don‟t sense this radiation because we‟re warmer than the ice-cube (hopefully!), and we don‟t see it because our eyes aren‟t sensitive to that low frequency of light radiation. Could you then simply bring in another ice-cube which is also at 00C and of course also radiating its own thermal energy at that temperature, and thereby heat up the first ice-cube by placing this second one near it? Or could you heat up the first ice-cube by placing it in a freezer at -100C? In both cases, there‟s lots of thermal energy from the secondary sources which falls on the first ice-cube, so shouldn‟t this energy “go into it” and warm it up? Of course not! You could only heat up the first ice-cube by introducing it to something warmer than it, like the palm of your hand, or a glass of water at 10C, or the radiation from the Sun. Or imagine the example of a burning candle: could you use a mirror to shine the candle-light back onto the flame, and thereby make the flame burn hotter? Such conjecture is not the way reality works, and remember, these concepts are true for any object, not just blackbodies. The main point is: heat naturally always flows from hot to cold, whether through conduction, convection or radiation, and most importantly, cannot raise its own temperature even if its own radiation was to flow back into itself.
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