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Discussion > GHG Theory step by step

Radical rodent, Supertroll

Physics lesson

Look at any published planetary energy budget. Convection transfers 17W/m^2 from surface to atmosphere.

Watts are a measure of energy flow rate in Joules per second. 1 Watt transfers 1 joule each second. Multiply the wattage by the number of seconds in a year to get the total energy transferred in one year.


For seawater

Change in temperature is the difference between the initial and final temperature. ∆T is in C or K.

Specific heat is the amount of heat needed to produce a change of temperature.For seawater that is 3985 Joules per kilogram per degree C.

Thermal expansion is the change in volume with changing temperature. The coefficient of thermal expansion is the relative volume change per degree C. For seawater this is 1.5 × 10^-4/C .

Volume of oceans is 1.34× 10^21 litres. Mass is 1.4 × 10^21kg.

The three ocean variables are the change in volume due to temperature change, the change in average temperature and the change in ocean heat content.


If you know the ∆T

change in energy content = ∆T × mass × specific heat

change in volume = ∆T × volume × coefficient of expansion


If you know the change in energy

∆T = change in energy/mass × specific heat

change in volume = ∆T × volume × coefficient of expansion


If you know the change in volume
∆T = change in volume/ volume × coefficient of expansion

change in energy content =∆T × mass × specific heat

supertroll

If your geothermal temperature gradient had it's cold end at the surface or in the oceans it was set up by GHGs.

Aug 11, 2017 at 8:38 PM | Unregistered CommenterEntropic man

Don't believe I asked for an explanation.

Just for amusement purposes if I give you the ocean heat content (x) tell me the temperature and ocean heat content and thermal expansion. Don't you at least need to know the salinity, ice content and ocean volume? I'm sure others here may be able to suggest other requirements you will require. I haven't never claimed your mathematical prowess.

Aug 11, 2017 at 8:52 PM | Unregistered CommenterSupertroll

EM Our posts crossed. My first impression is to wonder what you're now blathering on about. You make a bold statement that "Changes in ocean temperature, ocean heat content and thermal expansion are linked through specific heat and the coefficient of expansion. Measure one and you can calculate the other two", but now you are writing about "planetary energy budgets". Please get what you are arguing about straight.

Aug 11, 2017 at 9:04 PM | Unregistered CommenterSupertroll

EM. "If your geothermal temperature gradient had it's cold end at the surface or in the oceans it was set up by GHGs".

Well all geothermal gradients have their cold ends at the surface, pray tell me what GHGs occur (or occurred) within a granite?

This seems to be you at your most bizarre.

Aug 11, 2017 at 9:10 PM | Unregistered CommenterSupertroll

Supertroll

I am trying to discuss gravity theories with RR, geological temperature gradients with you and volume, energy content and temperature in liquids with both of you. No wonder we are getting tangled.

RR specifically asked the origin of the value I gave for the amount of energy convecting from a typical square metre of surface. That is where the reference to planetary energy budgets came in.

I learned about specific heat and thermal expansion in liquids at school. I also learned about Watts and Joules and energy flow. It is routine and uncontested physics, as is most of what I use for calculation. Since the energy content of a liquid and it's volume both vary predictably with temperature, you can easily calculate the effect of a change in one on the values of the other two. This works for a beaker of water or an ocean.

I am surprised that RR and yourself contest such basic physics.. Did you not do A Level Physics? I would have thought that the physics of energy flow and the thermal behaviour of fluids were areas of physics you would have needed to do meaningful geology.


The surface of an outcrop of granite is exchanging energy with the atmosphere, exposed to incoming radiation and radiating IR. The temperature of the granite surface is higher than if the atmosphere did not contain GHGs. Yes, GHGs do influence the temperature of granite.

Aug 11, 2017 at 10:50 PM | Unregistered CommenterEntropic man

What gravity theories? As I have stated before: to the best of my knowledge, there are no theories, yet, to explain the observations of the phenomenon.

Where did you get your magic figure for thermal expansion of seawater? The first link I found points out that thermal expansion varies according to salinity and pressure… you’re not using another average are you (as you are with the specific heat of seawater, too… oh dear…)?

By the way, a few things we really do not know about the oceans, yet:

We do not know the change in temperature;

We do not know the change in energy;

We do not know the change in volume… oh, and we do not know the volume, anyway, beyond an educated guess, neither do we know its mass.

So, if we do not know any of the three parameters that you are trying to establish, it is not possible to calculate what any of the other two might be.

Once again, you revert to your obsession that, somehow, the planetary budget has to be in balance. As it has never been so for any significant period throughout the history of the planet, why are you so convinced that it has to be?

Oh, and I asked for a source of your data; you have yet to provide it, other than some vague reference to planetary budgets.

Aug 12, 2017 at 12:44 AM | Registered CommenterRadical Rodent

EM. Just as you are not talking about the temperature of the ocean surface in connection with a temperature profile - a hydrographic lapse rate (I believe there are many according to salinity and how that changes vertically), I was writing about a geothermal gradient within the granite where their are few if any GHGs. Any surface effects rarely descend down for more than a couple of metres and will be swamped by any water flow in fractures.

I,ll leave the rest to RR who hourly is exposing your faux science and over-fascination with imprecisely known numbers. You'll mentioned that you were getting tangled up and were discussing temperature in liquids with both of us. Wrong there again, I was discussing heat flow in SOLID granite.

Aug 12, 2017 at 6:22 AM | Unregistered CommenterSupertroll

I've been trying to understand the N&Z gravity paper. it is reasonable to assume at first reading that gravity leads to compression of the atmosphere and this generates warming, just like the stroke of a bicycle pump. This leads to the criticism that the warming is one off and the heat soon dissipates.

I don't claim to understand the paper but I'm beginning to see that the above interpretation is not entirely correct. Forget the bicycle pump.analogy.

The gravity induced pressure creates a high density of gas molecules close to the surface. Then, when solar radiation heats the earth surface and this gas is warmed by conduction, it maximises kinetic energy in this region. The gas law PV=nRT is obeyed and the high pressure gives a high temperature. The energy is supplied by the sun, the air mass and gravity provide the conditions.

The radiative properties of greenhouse gases play their role in radiating away the heat from higher in the atmosphere but the warming effect is negligible, a conclusion being reached by more and more scientists whether through reduced climate sensitivity, increased importance of the oceans or other climate drivers such as solar cycles.

The great GHG driver is shrinking in importance as it is increasingly realised that it was simply wrong to attribute all climate change to a trace gas.

Aug 12, 2017 at 11:06 AM | Unregistered CommenterSchrodinger's Cat

Nice one, Mr Cat. Very succinctly put, and it makes a great deal of sense (even if you are exposing an embarrassing gap in my knowledge). The only flaw is that you are not using any numbers, so will fail to sway at least one of your readers (hint: make a few up that will conform to your conclusion – that should do the trick).

Aug 12, 2017 at 12:02 PM | Registered CommenterRadical Rodent

Schrodinger's cat

"The gravity induced pressure creates a high density of gas molecules close to the surface. Then, when solar radiation heats the earth surface and this gas is warmed by conduction, it maximises kinetic energy in this region. The gas law PV=nRT is obeyed and the high pressure gives a high temperature. The energy is supplied by the sun, the air mass and gravity provide the conditions."

Doesn't work. Surface pressure is determined by the mass of air in the amosphere and the strength of gravity. These are constant. You cannot extract work of heat from this static system.

Move heat into the atmosphere and you get an initial increase in pressure. With only gravity and the overlying mass of air to constrain it you then get an increase in volume. The hot air convects and air at normal pressure and lower temperature moves in from the side to replace it. The air gains energy at the surface and radiates it away at 12km. That energy flow provides the work powering convection.

You see that at all scales from thermals to Hadley cells.

Think of a conveyer belt. Material is carried up the belt and gains potential energy as work is done on it by the power unit but the potential energy of the belt itself remains constant.

The actual air movement is potential energy neutral. Rising air gains potential energy. Sinking air loses it. They cancel out. The net potential energy change is zero. There is no free lunch.

The only way to extract gravitational potential energy from a mass in a gravity field is by moving it downwards. The clocks I tinker with have suspended weights. These drop slowly through the gravity field, turning their gravitational potential energy into work to drive the clock. Again there is no free lunch. When the weights reach the floor I have to do work lifting them again.

Aug 12, 2017 at 4:00 PM | Unregistered CommenterEntropic man

Radical rodent

There you go.

Look at the figure.

Aug 12, 2017 at 4:28 PM | Unregistered CommenterEntropic man

Schrodinger's cat

You do realise that PV=nrT is energy neutral?

For a given mass of gas under adiabatic conditions, changing one of the three variables leads to changes in the others to maintain the relationship. There is no change in the energy content of the gas.

Consider a packet of gas returning to the surface after convection. It increases in pressure, decreases in volume and increases in temperature, but it's energy content does not change. You cannot get a sustained iincrease in energy content and temperature of the surface by adiabatically increasing the pressure. As I said, there is no free lunch.

Aug 12, 2017 at 4:57 PM | Unregistered CommenterEntropic man

Ah, Trenberth… “The heat is hiding at the bottom of the oceans” Trenberth. Clutching at argument from authority is a bit dodgy with this one. David Evans presents a more realistic alternative theory; to his credit, he is quite happy for others to dispute his ideas, and to enter into constructive dialogue about it. However, you should beware of raising Rhoda’s dander with this killer phrase: “These values are all globally and annually averaged…

Once more, though, the actual provenance of these figures in not particularly clear. But, even that is academic – so what if there is imbalance in the planetary energy budget? When hasn’t there been an imbalance in this oh-so-important budget?

What you do not seem to understand what Mr Cat is driving at is that the air is warmed by contact with the surface, its density is lowered, and it rises, creating a thermal. Cooler air moves in to replace it at the surface, while this displaced air loses it heat adiabatically as it rises, as well as by radiation and conduction to air around the thermal and, ultimately, radiating to space. The cooler air that has replaced it at the surface came from somewhere, and that somewhere now needs to air to replace what has gone. In this way, a convection cell is produced. On a global scale, this heating happens in the tropics, the rising air being replaced by (cooler) air from higher latitudes; in this way, the Trade Winds a formed The warmed air moves to higher latitudes in its new, higher altitudes, losing heat to space as it does so. Now cooler, it is denser, and descends, and heats by the gas laws. This is one important way in which the heat from the tropics is dispersed to higher latitudes, and how climate and weather systems are formed – the Coriolis effect caused by the Earth’s spin, and the topography and variety of surfaces mix that brew up even more! I know that this is rather complex, with no discernible numbers having been extracted to impress the more gullible, but is a more realistic scenario than just estimating figures, and averaging as many as you can find.

Aug 12, 2017 at 6:05 PM | Registered CommenterRadical Rodent

William Gilbert produced the following in a comment at Tallbloke's Talkshop.


The first law for a gaseous atmosphere can be written:

dU = dQ – dW = dQ – PdV (1)

The differential for the work term is PdV since the atmosphere is a constant pressure system and VdP = 0. The sign for PdV is negative since I am assuming that work is being performed by the system to the surroundings. Let’s also specify that all terms are expressed as intensive properties (Q is in joules per unit mass and PV is an intensive property in its self – no moles allowed here).

We can also say that dQ = CvdT so that equation (1) becomes:

dU = CvdT – PdV (2)

But this assumes that the system is only influenced by one field, the electromagnetic field (the sun). But the atmosphere is also influenced by a second field, the Earth’s gravitational field. Thus we need to add another term to the first law to reflect the gravitational field:

dU = CvdT + gdz – Pdv (3)

If we assume that the atmosphere is at static or dynamic equilibrium (and all politically correct climate scientists must – rightly or wrongly), then dU = 0 and:

CvdT + gdz – PdV = 0 (4)

If we define the system described in (4) as an air parcel, then certain things must happen if any of the terms become > or 0) and the parcel will expand (dV > 0) doing work on the surroundings. But that work energy (PdV) must come from the existing internal thermal energy (CvdT) thus leaving CvdT smaller (cooler) than it would have been if expansion did not occur. At the same time the parcel, having expanded, becomes buoyant and rises. That work energy is now converted to gravitational potential energy (gdz). The internal energy (U) of the parcel is still the same as it was when it first received heat energy from the surface but CvT is now smaller and gz is larger (an isentropic or adiabatic process). The density is also smaller because the parcel expanded (but who cares?). This process continues as long as the parcel rises.

The opposite scenario can occur if an elevated parcel is cooled (from radiation to space?): the thermal energy is decreased (CpdT), the parcel is compressed (+PdV) from the mass above it and it descends, and the gravitational potential energy (gdz) decreases. But the total internal energy (U) remains constant as it descends (isentropic/adiabatic process). The density is also larger due to volumetric contraction (but who cares?).

Since CpT = CvT + PV for an adiabatic system, equation (4) can also be rewritten as:

CpdT + gdz = 0 (5)

And some quick algebra yields:

dT/dz = -g/Cp (6)

which is the classic formula for the dry adiabatic lapse rate. (This also explains why Cp and not Cv is the correct term for the Loschmidt equation).

So the thermal gradient observed in the atmosphere is nothing more than the result of the conservation of energy via isentropic processes (constant entropy) with PV work driving the processes. The Helmholtz free energy is zero and the system is at equilibrium (U = constant) even though a temperature gradient exists.

Temperature is only a measure of one form of energy in the atmosphere and thus can only be a partial descriptor of the atmospheric thermodynamics. For example, at 10 km height, gravitational potential energy accounts for 30% of the total internal energy (based on the 1976 Standard Atmosphere). And if we are dealing with a moist atmosphere, we have to include a term for the latent heat of vaporization, which can be a very sizable number in itself.

Since radiation heat transfer only deals with one term of the first law (CvT), it cannot adequately be a primary predictor of atmospheric behavior. The radiative properties of the atmosphere are a function of the non-radiative processes occurring in the atmosphere, not the other way around.

If anyone wants a more detailed treatment of this subject, my 2010 E&E paper goes into a little more detail in the Physics section (http://www.friendsofscience.org/assets/documents/Gilbert-Thermodyn%20surf%20temp%20&%20water%20vapour.pdf)”

Aug 12, 2017 at 6:31 PM | Unregistered CommenterSchrodinger's Cat

EM - You didn't read my comment about the N&Z paper correctly.

The kinetic energy (i.e. temperature)) at the bottom of the atmosphere is a consequence of the high molecular density brought about by the mass of air pressing down. The energy is supplied by the sun via the heated surface.

The warm lower atmosphere is a consequence of that atmosphere and the points made directly above. You don't need GHG to trap the heat. The atmosphere effectively does that itself.

Aug 12, 2017 at 6:43 PM | Unregistered CommenterSchrodinger's Cat

https://wattsupwiththat.com/2017/08/12/uncovered-decades-old-report-showing-climate-data-was-bad/

T.Karl said so. Should we trust him now?

Aug 12, 2017 at 8:36 PM | Unregistered Commentergolf charlie

https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-4-4-4.html

"There is greater consistency between simulated and observed differential warming in the tropics in some satellite measurements of tropospheric temperature change, particularly when the effect of the cooling stratosphere on tropospheric retrievals is taken into account (Karl et al., 2006). External forcing other than greenhouse gas changes can also help to reconcile some of the differential warming, since both volcanic eruptions and stratospheric ozone depletion are expected to have cooled the troposphere more than the surface over the last several decades (Santer et al., 2000, 2001; IPCC, 2001"

"There is greater consistency.." suggests there is below expected levels of consistency.

"...volcanic eruptions and stratospheric ozone depletion..." If in doubt, blame volcanoes, but ozone depletion assell?

Karl and Santer did not express 97% confidence in the Consensus.

Aug 12, 2017 at 9:19 PM | Unregistered Commentergolf charlie

Sorry, but that is not true at all. You mistake a change in forcing for a change in temperature. That is a bridge way, way too far. What we do know is that GHGs cause increased forcing. Period.

Willis Eschenbach August 11, 2017 at 11:14 am

Aug 13, 2017 at 1:23 AM | Unregistered Commenterclipe

Schrodinger's cat

"The warm lower atmosphere is a consequence of that atmosphere and the points made directly above. You don't need GHG to trap the heat. The atmosphere effectively does that itself."

Regrettably not.

We've already discussed this. A non-radiative atmosphere without GHGs cannot trap heat. The temperature at the bottom of the atmosphere will equilibrate to the temperature of the surface. Since the surface temperature is determined by the radiation balance it is independant of atmospheric pressure or density.

Aug 13, 2017 at 11:49 AM | Unregistered CommenterEntropic man

A non-radiative atmosphere without GHGs cannot trap heat.
Surely an oxymoronic statement? A non-radiative atmosphere without GHGs cannot trap lose heat. There, fixed it for you.

The principle source of heating for any atmosphere will be the surfaces impinged upon by sunlight; the air in contact is warmed by conduction, and the heat is then dissipated by convection, which is heavily influenced by the atmospheric pressure and the planet’s gravity.

Aug 13, 2017 at 12:28 PM | Registered CommenterRadical Rodent

I am getting awfully confused by some of this. Is anyone seriously contending that GHGs don't "trap" heat, so making the surface and lowermost atmosphere warmer than it otherwise would be? Is anyone saying that GHGs are not required to "trap" this heat? If the first question is answered in the affirmative, then the second seems rather academic in that our atmosphere contains GHGs that produce some warming.

Aug 13, 2017 at 12:33 PM | Unregistered CommenterSupertroll

Since the surface temperature is determined by the radiation balance it is independant of atmospheric pressure or density. [sic]
Regrettably not.

As the simplest of measurements of two identical surfaces at the same latitude but at two different altitudes will show you, the higher surface, the surface with the lower atmospheric pressure, will have a lower temperature. This is what is often referred to as the environmental lapse rate; this is why it is cooler up a mountain than on the coast. This is why the officers live in Two Boats on Ascension Island, while the ratings live at or near the airfield.

Aug 13, 2017 at 1:01 PM | Registered CommenterRadical Rodent

Minty: your confusion is understandable. While “greenhouse” gases will “trap” heat, their contribution to warming of the atmosphere will be so negligible as to be insignificant (as can be attested on Venus). They probably play as important a role in radiating the heat to space as they do in “trapping” it within the planetary atmosphere, thus nullifying any heating effect they may have.

Aug 13, 2017 at 1:06 PM | Registered CommenterRadical Rodent

Radical rodent

Both my statement and your correction are true statements. Both make the point that without GHGs the atmosphere does not affect the average surface temperature or radiation budget.

Your second paragraph contains one error. Convection cannot dissipate heat, only move it around within the atmosphere.

To dissipate the incoming energy from the Sun, Earth must radiate an equivalent amount of energy back into space.

If we had a non-radiative atmosphere all that radiation would be emitted from the surface. In practice only 17% of the OLR is emitted from the surface via the atmospheric window. The otherv 83% of the OLR is emitted from the tropopause.

Aug 13, 2017 at 1:20 PM | Unregistered CommenterEntropic man

Radical rodent

We crossed.

Like for like, please.

You are talking about the local effect of lapse rate. I am comparing planets.

Since it seems I must be pedantic, I will rephrase.

Two identical planets have identical incoming energy, albedo and outgoing energy. Both have non-radiative atmosphere.

The only difference is that Planet A has a higher surface pressure than planet B.

Equivalent areas of the surface of both planets will have the same surface temperature, regardless of the difference in surface pressure.

The reason? A planet with a non-radiative atmosphere will radiate all OLR from the surface. It will equilibriate at such a temperature that OLR = insolation-albedo. Surface pressure is irrelevant.

Aug 13, 2017 at 1:49 PM | Unregistered CommenterEntropic man