From Physics Today HT/Leif Svalgaard
Martin S. Singh and Morgan E O’Neill , “Thermodynamics of the climate system”, Physics Today 75, 30-37 (2022) https://doi.org/10.1063/PT.3.5038
Here is the introduction:
Throughout its history, Earth has experienced vastly different climates, including “snowball Earth” episodes, during which the planet is believed to have been entirely covered in ice, and hothouse periods, during which prehistoric alligators may have roamed the Arctic. Recent anthropogenic greenhouse gas emissions are the cause of modern, rapid climatic change, which poses a growing hazard to societies and ecosystems.
The climate system comprises the fluid envelopes of Earth: the atmosphere, oceans, and cryosphere. Those constituents, along with the evolving surface properties of the solid lithosphere, are responsible for reflecting some and absorbing most radiation received from the Sun. The climate system is close to an energy balance at all times. The total energy doesn’t significantly fluctuate in time because terrestrial radiation is emitted to space at approximately the same rate at which solar energy is absorbed.
Being in nearly exact energy balance with the universe allows Earth to have a relatively familiar climate tomorrow and a century from now. But over time, small deviations from a strict energy balance can induce massive changes in climate. Such small deviations are due to the diurnal and seasonal cycles, orbital variations— the Milankovitch cycles, for example (see the article by Mark Maslin, Physics Today, May 2020, page 48)—and internal forcings, such as anthropogenic emissions of carbon dioxide.
Another characteristic of Earth’s climate—indeed, any planetary climate—is that it evolves irreversibly. Imagine watching a 10-second video of a field with a leafy tree on a sunny day. Would you notice if that video had been shown in reverse? Maybe not. Now imagine watching a 10-second clip of the same field and tree during a windy rainstorm. You could probably immediately assess whether the clip was run forward or backward in time. Some obvious tells stand out: Rain should fall toward the ground, and leaves should separate from, not attach to, the tree.
The climate system contains myriad irreversible processes, and on both a calm day and a stormy day they produce entropy. Like energy, entropy is a property of any thermodynamic system, and it can be calculated if one knows the state of the system. But unlike energy, entropy is not conserved. Rather, it is continuously produced by irreversible processes. Although physicists often consider ideal, reversible processes, all real physical processes are irreversible and therefore produce entropy.
In accordance with the second law of thermodynamics, irreversibility in the climate system permanently increases the total entropy of the universe. As in the case for total energy, though, the total entropy in the climate system is relatively steady. That’s because the climate is an open system that receives much less entropy from the Sun than it exports to the universe (see box 1). The difference between what is imported and what is exported is produced locally, through friction, mixing, or irreversible phase changes.
Although the climate is approximately steady, it is far from thermodynamic equilibrium, which would be a very cold and boring state with no motion. Instead, the climate system may be thought of as an engine, fueled by the unequal distribution of solar radiation incident upon it. It is those gradients in energy, and the resulting gradients in temperature and pressure they produce, that allow the wind to blow.1
https://physicstoday.scitation.org/doi/10.1063/PT.3.5038
The article then moves on through the Climate System as a Heat Engine
But how do climate scientists characterize the work performed by the planetary heat engine? Earth cannot push on any external body, and in the framework of a classic heat engine, its work output is identically zero! The oceans and atmosphere do, however, perform work on themselves and each other, and that work generates the familiar winds and ocean currents that scientists observe. For climate scientists, useful work is that used to drive atmospheric and oceanic circulations.
Then drilling down with sections on Irreversible Processes,
The resultant cycle of energy production and dissipation, beautifully described in 1955 by Edward Lorenz,4 implies a balance between work and frictional dissipation in the climate system.
drivers of Global Circulation,
On global scales, the atmospheric circulation is driven by the differential heating associated with the Sun’s angle. It manifests as large overturning cells and jet streams. All planets in orbit around a star are heated most strongly at any given moment at the substellar point, where the planet’s surface is directly perpendicular to the star’s radiation.
modeling irreversibility,
Indeed, analysis of the entropy budget of climate models has allowed scientists to probe the climate system’s irreversibility far beyond what observations alone would allow. Such studies have shed light on the role played by moist processes in governing how Earth’s planetary heat engine may respond to climate change.
and beyond classical thermodynamics,
How can climate scientists reconcile a conceptual model of a planetary heat engine, which requires a temperature gradient to induce an overturning circulation, with the fact that observed large-scale vortices can be predicted by models that forbid temperature gradients? Tropical cyclones certainly have an important overturning circulation that responds to surface heating and upper-level cooling, but the much larger stratospheric polar vortex does not: It is a 2D phenomenon that is amenable to description using Boltzmann entropy. The most useful interpretation of the second law of thermodynamics is evidently feature-dependent in the climate system.
From the article: “Recent anthropogenic greenhouse gas emissions are the cause of modern, rapid climatic change, which poses a growing hazard to societies and ecosystems.”
Nope, there’s no evidence for that. It is pure speculation. Wild speculation. Totally unsubstantiated speculation.
One should be wary of believing things written by people like this who cannot tell the difference between evidence and speculation.
Sometimes we are distracted and are focused on the macro. CO2 is not special. This paper clearly shows that something else is at play. It is simply Earths charge field and electrons
The average temperature of Earth and Venus at 1 BAR can be calculated straight from the energy required to raise the potential of 1 electron through 1 volt. We simply sum up all the electrons in a MOLE of AIR on Earth and multiply it by the energy required to charge up each electron in a mole of air to 1 electron volt.
http://milesmathis.com/farad.pdf
Just want to point out that electrons bound to atoms in gases like nitrogen and oxygen are not free to have their energies raised at random. They are subject to the laws of quantum theory as proposed by Bohr, hence to elevate the energy of an electron in atoms the electron must absorb electromagnetic energy or thermal energy that gives them the required energy to rise to a higher energy state (orbital). .
The theory you propose would apply to free electrons in something like a battery.
I just want to point out that the energies required to raise electrons from lower shell (aka “orbital”) levels to higher shell levels (i.e., allowed electron quantum states around nuclei) in any nitrogen or oxygen molecule on on the order of 1-3 eV.
As the attached figure shows, the energy levels (in eV) corresponding to LWIR emitted from Earth’s surface are well below 1 eV.
So when discussing oxygen and nitrogen exchanging energy with LWIR-excited GHGs in Earth’s atmosphere, the energy changes occur in translational (i.e., molecule velocity) and vibrational modes of the molecular bonds, only the last of which is governed by quantum mechanics, NOT in the electron shells.
To the extent that sub-eV energy absorbed by nitrogen or oxygen gases can be partitioned between all all degrees of freedom, these gas molecules can effective have their energies “raised at random”.
Then too, given the quantum mechanical basis for radiation and the Maxwell-Boltzmann distribution of energies in any ensemble of gas molecules at any given average temperature, the thermal radiation of energy from these molecules occurs more or less randomly.
“So when discussing oxygen and nitrogen exchanging energy with LWIR-excited GHGs in Earth’s atmosphere, the energy changes occur in translational (i.e., molecule velocity) and vibrational modes of the molecular bonds, only the last of which is governed by quantum mechanics, NOT in the electron shells”.
***
Gordon…molecular bonds are electrons. A molecule is nothing more than two or more atoms bonded by shared electrons or charges produced by electrons. Vibrational modes are related to electron bonds and involved electron transitions as well..
Jopo,
Earth’s atmosphere has much more than a single mole of “air”. And what’s the basis for your calculation—wrong as it is on mass—using just a single eV of energy per electron for all electrons in one mole? Aren’t you aware that K shell electrons have different eV energy values than L shell electrons, which in turn have different eV energy values compared to M shell electrons, and so forth?
The mass of Earth’s atmosphere has been estimated to be 5.1*10^18 kg.
— https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
For air having an average molecular weight of 28.96, the weight per mole would be 28.96 grams, or 0.029 kg.
Therefore, there are approximately 1.76*10^20 moles in the atmosphere.
N.B. The relative concentrations of different gases comprising the atmosphere doesn’t change significantly until above the 100 km altitude. An altitude up to 100 km contains 99.9999% by mass of the total atmosphere, and by convention this altitude is taken to be “the top of the atmosphere (TOA)”.
You also may want to consider that near Earth’s surface, the normal atmospheric potential field gradient is on the average around 100 V/m, so any free electron would only have to move a distance vertically upward of 1/100 m, less than 1/2 inch, to gain one eV in energy.
You need to read the paper again. It states the “that the energy in a Mole of charged electrons to 1 volt is also the same as the Earth’s average temperature“
You have gone somewhere where the paper does not go. Totally irrelevant. As for the Ionisation energy levels. 1st, 2nd, 3rd etc. Yes been there and done that. Do you know just using the First level also brings it extremely close. Like 289 K I think it was. So lets address the “astonishing correlation” Try and get an alarmist to provide numbers like that. Yeah right. Instead they have said. yeah it is a coincidence. I mean like really guys. Come on!
Jopo, I need go no further than this:
You state, in bold typeface no less, “the energy in a Mole of charged electrons to 1 volt is also the same as the Earth’s average temperature”.
Energy is not temperature.
And I certainly don’t need to read any paper that would state such, so thanks for the “heads up” info.
lol. you accept CO2 getting back to ground state as being energy emitted. But put your head in the sand when other gases fall back to a ground state. That is poor of you.
Please cite the specific post where I accepted “CO2 getting back to ground state as being energy emitted.”
Now, you were saying something about putting one’s head in the sand . . .
Did you know that if you sum up the numbers on all the balls on a billiard table it comes to 136. The average weighting on each ball being 8.5.
Numbers have weight?
Who knew!
And, by the way, the numbers on a standard set of billiard balls go successively from 1 to 15. (The white, cue ball does not have a number.)
The sum of 1+2+3+4 … +15 = 120, not 136.
Need I say more?
darn 15 balls shoot. you got the point though. eV are directly linked to Kelvin. You are just choosing to ignore that.
There is a serious misunderstanding of entropy in this article. Entropy was defined by Clausius as the sum of infinitesimal quantities of heat at temperature T. He produced this relationship…
ds = dq/T
That is in the infinitesimal, differential form. The definition, as a sum, claims…
S = integral dq/T
Since T is defined as a constant, it can be taken outside the integral sign as…
S = entropy = T integral dq.
It is completely obvious that entropy is a measure of heat transfer, a sum of heat transfer, and is the mathematical statement of the 2nd law.
However, Clausius also stated the 2nd law like this….”Heat can NEVER be transferred, by its own means, from a colder body to a hotter body. He later claimed that applied equally to radiation. IMHO, that is the definition of the 2nd law that should be used since it addresses the laws of heat transfer in a clear fashion.
Confusion has arisen based on another statement made by Clausius in relation to entropy. He stated that entropy is zero for a reversible process and positive for an irreversible process. He noted that most processes are irreversible and scientists seem to have confused that as entropy being a measure of irreversibility.
Entropy is not a measure of irreversible processes in general, only a measure of heat given off by an irreversible process. Natural erosion is not related to entropy unless heat is given off. Even at that, how much of that irreversible process is related to other phenomena?
Correction…S = T.integral dq should be S = 1/T.integral dq.
You have made an astute observation that, as you say, is often overlooked. Entropy changes are related to transfer of heat. In this view entropy is simply a state function and when combined with temperature is very useful for visualizing heat transfers in refrigeration and thermal power cycles. It is no different than using pressure and volume to calculate work for processes involving a gaseous working fluid.
However, entropy has a further use in looking at wasted work potential in irreversible processes. An irreversible process doesn’t require explicit heat transport to be related to a permanent entropy gain of the universe. For example, one can envision the (minimal) amount of work that would have to be expended to undo the irreversible process (put the universe back to its original state — undo the erosion if you will), divided by the dead state temperature as a measure of the minimal permanent entropy increase.
Some years ago I had an influential department colleague who lectured me about emphasizing entropy concepts and calculations in my thermodynamics course as a waste of effort that no engineer would put to good use. I could only counter that such lessons were central to engineers thinking about efficiencies of processes and machines — and ultimately the costs of such. Thermodynamics, I think, is widely misunderstood even by people who could make better use of it.
“…one can envision the (minimal) amount of work that would have to be expended to undo the irreversible process (put the universe back to its original state — undo the erosion if you will)…”
Interesting way of looking at it. Clausius talked a great deal about the equivalence of heat and work.If you have not read his original work I strongly recommend it. The guy was brilliant and meticulous about his science.
I agree that thermodynamics is a poorly understood discipline. .
Most of the founders of thermodynamics were so brilliant that I am utterly puzzled about the origin of their insights. I don’t recall ever having read Clausius, and perhaps on your recommendation I will. I have read Carnot and while he was brilliantly inspired much of his musings are confused because, as you likely know, there was no first law as yet annuciated. Another thing you likely recognize is that one’s views about thermodynamics depend to a large extent on where you learned the basic concepts — chemists, physicists, engineers all look at the topic a bit differently. I have been fortunate to have first taken a course in ug physics using Zemansky’s superb text, then a graduate course in mechanical engineering, then statistical mechanics in physics graduate school, then taught it to engineers about eight times — after 47 years I am beginning to feel that I understand it pretty well…but I am also learning new things all the time.
Thanks for the reply.
The article states that “Recent anthropognic greenhouse gas emissions are the cause of modern climate change”
I believe that I can offer a simple way to REFUTE that statement, and would appreciate input from anyone wanting to comment upon it, since I may be wrong.
As I understand it, the major tenet of the greenhouse gas hypothesis is that CO2 warms the climate by retaining heat”
However water vapor is well known to be the major greenhouse gas that retains heat.
Now, consider the atmospheres over desert areas. They are hot and very dry, and contain only a small amount of water vapor. As a result temperatures plunge during the night, because there is insufficient heat retention from the small amount of water vapor present.
CO2 is a well-mixed gas in our atmosphere and is present at the same levels over deserts at noon and at night
.IFit it actually had any heat retentive properties worth considering,it would prevent temperatures from plunging.
One might speculate that temperatures might plunge even more, if there were no CO2 present. However this is testable. Cycle a metal container over a day, in a desert setting, filled with desert air from which the CO2 has been removed, and see whether the temperature within the box drops more than outside the container
.
“As I understand it, the major tenet of the greenhouse gas hypothesis is that CO2 warms the climate by retaining heat…”
***
That’s one of them, that GHGs trap heat. However, heat is a property of atoms and unless you trap the atoms defining the heat, you can’t trap heat. The glass in a real greenhouse can trap heat as rising atoms/molecules of air but molecules of air like GHGs cannot do that.
Circa 1909, R. W. Wood posited that air is heated at the surface and rises. Since the air is 99% nitrogen and oxygen, and they are both poor emitters of infrared, the N2/O2 retains the heat until it reaches an altitude where the heat dissipates naturally through a reduction of pressure. That alone could explain the so-called greenhouse effect.
A more refined aspect of the heat trapping theory is that GHGs slow the dissipation rate of heat at the surface. However, Newton’s Law of Cooling claims that the rate of heat dissipation is proportional to the difference in temperature between a body and its environment. That infers the difference between surface temperature and the atmosphere at the boundary between them.
Of course, the atmosphere and surface would normally be in thermal equilibrium, hence no heat could be transferred via conduction.However, heated air rises and is replace by cooler air from aloft and that forms a temperature differential so heat can be dissipated to the cooler air.
Since air is 99% nitrogen and oxygen, they set the temperature of the atmosphere, not trace GHGs. Therefore it has to be nitrogen and oxygen controlling the rate of surface heat dissipation.
“Produce entropy”? Absurd!
Entropy is not measured. Entropy is ‘estimated’ and assumed.
The problem is, Clausius invented entropy, defined it and named it. He defined it roughly as the sum of infinitesimal transfers of heat at a temperature T. ds = dq/t is the infinitesimal relationship and S = integral dq/T is the integral form. There is nothing in that relationship about unavailable energy or disorder, only heat.
I fear that modern scientists have taken it upon themselves to redefine the work of a scholar in thermodynamics.
The energy flow is irreversible, the state of the global climate is not irreversible, but the opinions of some climate scientists appear robustly irreversible.
Good point about the climate scientists.