Friday, January 2, 2015

Why Earth is a closed thermodynamic system that must obey the 2nd Law of Thermodynamics

Some have claimed that the Earth is not defined by thermodynamics as a physically "closed system," alleging upon this false assumption that the Second Law of Thermodynamics [which is applicable to closed or isolated systems only] somehow doesn't apply to the atmosphere/greenhouse gases/total Earth climate system including the surface, atmosphere, and oceans. 

We have refuted this claim in several prior posts ranging from Why the AGW 'Hot Spot' Won't Happen (2010) all the way up to the recent series of posts on the greenhouse equation, including the post Maxwell's Demon proves why cold gases cannot make hot bodies hotter

This incorrect assumption that Earth is defined as an "open system" and not a physically "closed system" is often utilized by AGW proponents to claim that the atmosphere or Earth can rightfully violate the Second Law of Thermodynamics, such as by decreasing total entropy, transferring heat from cold to hot [which requires an impossible decrease of total entropy], warming of the surface from -18C to +15C by greenhouse gases such as CO2 (radiating at a very, very cold peak radiating temperature of -80C), and various other physical absurdities. 

While individual components of the Earth may be considered by definition an open physical system (where highly-localized decreases of entropy may intermittently occur), the Earth's climate system including land, oceans, and atmosphere in total are considered to be a closed thermodynamic system, for which the 2nd Law of Thermodynamics applies and requires total system entropy to always increase. 

Thus, the claim that greenhouse gases may violate the 2nd law to transfer heat from their very cold radiating temperatures (ranging from -80C to -18C) to warm the much warmer Earth surface by an additional 33C is absurd and physically false. Instead, the tropospheric 33C temperature gradient ["the greenhouse effect"] above and below the center of mass of the atmosphere (at ~5100 meters altitude) is maintained by the Maxwell/Carnot/Clausius gravito-thermal "greenhouse effect," as described in the recent series of posts, and is completely insensitive to changes in man-made CO2 levels. 

The physical boundary conditions of Earth's thermodynamic closed system range from the bottom of the oceans up to the top of the atmosphere at the edge of space. There is effectively no exchange of mass across any of these boundary conditions, therefore by physical definition, the total Earth system including climate system is considered a closed system which must obey the 2nd Law of Thermodynamics. 

Note the only true "isolated system" in the universe is by definition the universe itself, thus Earth is part of the isolated system of the Universe, and the "closed systems" of the Milky Way, solar system, and Earth itself. Any claims that since the universe is technically the only physically "isolated system" in existence, therefore the 2nd law of thermodynamics may be violated in total for the Earth itself, are equally absurd. 

Thermodynamic types of systems as applied to the Earth are described in this excerpt from The Physical Environment: an Introduction to Physical Geography by Michael Ritter, PhD.:

Types of systems

Systems can be classified as open, closed, or isolated. Open systems allow energy and mass to pass across the system boundary.  A closed system allows energy but not mass across its system boundary. An isolated system allows neither mass or energy to pass across the system boundary.

Open Systems

The ocean is an example of an open system. The ocean is a component of the hydrosphere and the ocean surface represents the interface between the hydrosphere and the atmosphere that lies above. Solar radiation passes through the atmosphere and is absorbed by the ocean. The absorbed energy evaporates water from the ocean. As water vapor (mass) enters the atmosphere it carries with it the heat used to evaporate the water (called latent heat) and raises the air's humidity. If the humidity is high enough, condensation occurs, latent heat is released, and clouds are created. Continued condensation creates precipitation (mass) that falls back into the ocean. Hence, energy and heat (solar radiation, latent heat) as well as mass (water vapor and precipitation) passes across the boundary between the atmosphere and hydrosphere. All of the "spheres" of the earth system are considered open systems because energy and mass is exchanged between them.

Closed Systems

Earth as a closed system
The earth system as a whole is a closed system. The boundary of the earth system is the outer edge of the atmosphere. Virtually no mass is exchanged between the Earth system and the rest of the universe (except for an occasional meteorite). However, energy in the form of solar radiation passes from the Sun, through the atmosphere to the surface. Earth in turn emits radiation back out to space across the system boundary. Hence, energy passes across Earth's system boundary, but not mass, making it a closed system.
The interface between systems is not always easy to identify, others more so. The interface between the hydrosphere and lithosphere at a shoreline is easy to recognize as a definite planar boundary between a solid and fluid. The interface between the atmosphere and hydrosphere is less easy to discern as the hydrosphere comprises both liquid water of the surface and water held in the air.

And by this engineering brief:

What is a Thermodynamic System?

written by: Haresh Khemani • edited by: Swagatam • updated: 5/4/2010

The term thermodynamic system is used frequently in the subject of thermodynamics. Let us see what thermodynamic system is and its various types.


The word system is very commonly used in thermodynamics; let us know what it is. Certain quantity of matter or the space which is under thermodynamic study or analysis is called as system. Let us say for example we are studying the engine of the vehicle, in this case engine is called as the system. Similarly, the other examples of system can be complete refrigerator, air-conditioner, washing machine, heat exchange, a utensil with hot water etc.

Now, let us suppose that we have to analyze the performance of engine in different conditions. Here, we will feed the engine with fuels of different grades and load it with different loads to find out its efficiency. We will also find its performance during idling, acceleration, varying speed, slow speed and high speed. A thorough analysis of the engine is carried out; hence it is called as system.

The system is covered by the boundary and the area beyond the boundary is called as universe or surroundings. The boundary of the system can be fixed or it can be movable. Between the system and surrounding the exchange of mass or energy or both can occur.

Types of Thermodynamic Systems

There are three mains types of system: open system, closed system and isolated system. All these have been described below:

1) Open system: The system in which the transfer of mass as well as energy can take place across its boundary is called as an open system. Our previous example of engine is an open system. In this case we provide fuel to engine and it produces power which is given out, thus there is exchange of mass as well as energy. The engine also emits heat which is exchanged with the surroundings. The other example of open system is boiling water in an open vessel, where transfer of heat as well as mass in the form of steam takes place between the vessel and surrounding.

2) Closed system: The system in which the transfer of energy takes place across its boundary with the surrounding, but no transfer of mass takes place is called as closed system. The closed system is fixed mass system. The fluid like air or gas being compressed in the piston and cylinder arrangement is an example of the closed system. In this case the mass of the gas remains constant but it can get heated or cooled. Another example is the water being heated in the closed vessel, where water will get heated but its mass will remain same.

3) Isolated system: The system in which neither the transfer of mass nor that of energy takes place across its boundary with the surroundings is called as isolated system. For example if the piston and cylinder arrangement in which the fluid like air or gas is being compressed or expanded is insulated it becomes isolated system. Here there will neither transfer of mass nor that of energy. Similarly hot water, coffee or tea kept in the thermos flask is closed system. However, if we pour this fluid in a cup, it becomes an open system.

Related Reading

What is Thermodynamics

First law of Thermodynamics

Second law of Thermodynamics

Third law of Thermodynamics

Zeroth law of Thermodynamics

Types of Thermodynamic Systems and Important Terms Related to Thermodynamics - Part 1

And by this overview of Thermodynamics Laws and Systems 


  1. Another great post in a long series of great posts. Thanks for all the hard work.

    I have a question that may well be off-topic for this post but is on the theme at least. I have read that the surface of the the moon gets to about 123C (253F) at its hottest. Is this true? And how does that compare to how hot the earth gets at its hottest? (I assume at the equator at high noon)

    Now it is true that the slow rotation of the moon compared to the 24 hour rotation of the earth would have some effect on the difference in maximum temperatures; but would not the atmosphere be the vast majority of the difference?

    Thanks in advance for any thoughts on this issue. ~Mark

    1. Yes, the Moon gets much hotter during the day as you said, and also much colder at night (-233C). A huge range in temperature of 123+ 233C = 356C between day and night, as compared to Earth's diurnal range of of only 10 degrees between night and day. The main reasons are that water vapor evaporation and clouds cool the earth during the day and the Maxwell gravito thermal greenhouse effect keeps the surface at all times night and day ~33C warmer than if earth didn't have an atmosphere. The length of day also is an important factor next in importance.

    2. Thanks for the reply. We agree on the gravitation/mass explanation by you and Maxwell.

      What interests me is that Jim Hansen and crew keep saying that CO2 warms the planet, but since the moon's surface is about 123C and the earth's surface is said to be about 66C at maximum (I need to verify that 66C figure some more) then it looks to me like the lower atmosphere is all about cooling at the tropics and distributing the heat around the system.

      It would seem that anyone could look at that 123C vs. 66C and see that the Jim Hansen inspired CO2 will fry us idea just does not make much sense.

    3. You're right, the highest temperature ever recorded on Earth was 136F or 58C in 1922 in Libya. The daytime moon temp is 123C. The atmosphere/albedo are a large cooling, not warming, mechanism for Earth.

  2. MS, very nice as always.

    My training did not state that an open system can ever violate the second law. Rather that when analyzing an open system it is important to recognize that energy may leave/enter as a mass of something like a combustible fuel (the energy is in the chemical bonds broken when the fuel is burned), or the latent heat in water vapor.

    Folks that demand a pass from the second law by claiming that the Earth (with atmosphere) is an open system are totally wrong on that account as well. Open or closed the second law still applies.

    For example, Helium gas does exit the Earth, it is emitted via radioactive decay from rocks. It floats upwards and exits to space, that is why there is very little in the atmosphere, it's all just "moving along". So the Earth's mass is actually getting smaller from the loss of Helium. But it is also absorbing micrometeorites all the time, so the mass of the Earth is probably nearly a constant. The Earth is very very close to a closed system, but like all human imposed constraints there is always a little bit of gray area involved.

    Nice summary and totally correct as stated.

    Cheers, KevinK

    1. Thanks Kevin for your insights as always, and we agree as usual. It's astonishing to me how folks try to weasel around entropy and the 2nd law, but as well stated by Caltech physicist Sean Carroll, the second law is "Natures most reliable law"

      I recommend his 2nd chapter titled "The Heavy Hand of Entropy" in his best-selling book "From Eternity to Here" for a great introduction to the meaning, origin, and astonishing significance of entropy/2nd law to just about everything in the universe including space-time, life, philosophy, physics, cosmology, etc. etc.

  3. Entropy in a closed system may decrease only by increasing the entropy in another system. That is what the 2nd law of thermodynamics means. It is only in an isolated system that entropy can only increase.

    Thus the entropy of system earth can decrease by increasing the entropy of surrounding space. Saying the earth is a closed system allows for this because transfer of energy can occur between earth and the rest.

    There is the continued us of this trope "cold gasses increasing the temperature of hot gasses" as if people are saying that heat flows backwards. That's not what is being said. The rate of flow of heat between two bodies of gas depends on the difference of temperature between them. The difference in temperature of the top of the atmosphere and the troposphere might be large but it's smaller than the difference between open space and the troposphere. Thus the rate of flow of heat is smaller in the former case. It's not that the cold gas is heating the warm gas, it's that the troposphere doesn't cool as fast.

    There is a tendency to get "flow of heat" mixed up with radiation. It's not exactly the same thing. Heat flow is an intellectual construct. IR radiation is one way it occurs. Saying that back radiation occurs isn't the same thing as saying that heat flows backwards. Back radiation doesn't happen without forward radiation, which is always in the direction of heat flow.

  4. Roderic & Anonymous:

    Did either of you even read this post? These are the same old tired arguments I've refuted time and again in hundreds of posts over the last six years. Put "entropy" and "2nd Law" in the HS search box to read all of these prior posts which I'm repeating in this comment.

    Then read the entire 2nd chapter of Caltech physicist Sean Carroll, about "the Heavy Hand of Entropy" in his best-selling book "From Eternity to Here" for a great introduction to the meaning, origin, and astonishing significance of entropy/2nd law to just about everything in the universe including space-time, life, philosophy, physics, cosmology, climate, etc. etc.

    After studying all of the above, if you can find any specific flaw in Carroll's or my work, then come back to comment & be very specific.

  5. Ah it is Doug Cotton as usual hiding behind "Anonymous" or the multitude of aliases.

    How many times do I have to tell you that you are permanently banned for several lifetimes of each of your aliases from ever commenting again at this site. Go away, don't ever read or comment upon any post ever again, including your aliases.

    1. Thanks to the notorious climate troll Doug Cotton continuing to waste my time removing his banned comments, from now on, all comments to this blog will be from members of the blog only, for now to eternity.

      Bye bye Douggie.

      All those who wish to become preregistered members of the blog, send an email to

  6. what about during the early years of the earth's formation when it was bombarded by asteroids, even after life took place and dinosaurs went extinct? could that be deemed as an open system?

  7. Earth loses "about three kilograms (3 kg) of hydrogen and 50 grams (50 g) of helium per second" to space (see so it is an open system according to the definition at the end of this piece.