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The Mystery of Tau – Miskolczi – Part Three – Kinetic Energy

Posted in Basic Science, Commentary, Debunking Flawed "Science" on April 26, 2011| 123 Comments »

In Part One we looked at the calculation of total atmospheric optical thickness.

In Part Two we looked at the claim that the surface and atmosphere exchanged exactly equal amounts of energy by radiation. A thermodynamics revolution if it is true, as the atmosphere is slightly colder than the surface. This claim is not necessary to calculate optical thickness but is a foundation for Miskolczi’s theory about why optical thickness should be constant.

In this article we will look at another part of Miskolczi’s foundational theory from his 2007 paper, Greenhouse Effect in Semi-Transparent Planetary Atmospheres, Quarterly Journal of the Hungarian Meteorological Service.

For reference of the terms he uses, the diagram from the 2007 paper:

From Miskolczi (2007)

Figure 1

On pages 6-7, we find this claim:

Regarding the origin, E_U is more closely related to the total internal kinetic energy of the atmosphere, which – according to the virial theorem – in hydrostatic equilibrium balances the total gravitational potential energy. To identify E_U as the total internal kinetic energy of the atmosphere, the E_U = S_U / 2 equation must hold.

Many people have puzzled over the introduction of the virial theorem (note 1), which relates total kinetic energy of the atmosphere to total potential energy of the atmosphere. Generally, there is a relationship between potential energy and kinetic energy of an atmosphere so I don’t propose to question it, we will accept it as a given.

By the way, on the diagram S_U = S_G, i.e. S_U = upwards radiation from the surface. And E_U = upwards radiation from the atmosphere (cooling to space).

Kinetic Energy of a Gas

For people who don’t like seeing equations, skip to the statement in bold at the end of this section.

Here is the equation of an ideal gas:

pV = nkT (also written as pV = NRT) [1]

where p = pressure, V = volume, n = number of molecules, k = 1.38 x 10^-23 J/K = Boltzmann’s constant, T = temperature in K

This equation was worked out via experimental results a long time ago. Our atmosphere is a very close approximation to an ideal gas.

If we now take a thought experiment of some molecules “bouncing around” inside a container we can derive an equation for the pressure on a wall in terms of the velocities of the molecules:

pV = Nm<v_x²> [2]

where m = mass of a molecule, <v_x²> = average of v_x², where v_x = velocity in the x direction

Combining [1] and [2] we get:

kT = m<v_x²>, or

m<v_x²>/2 = kT/2 [3]

The same considerations apply to the y and z direction, so

m<v²>/2 = 3KT/2 [4]

This equation tells us the temperature of a gas is equal to the average kinetic energy of molecules in that gas divided by a constant.

For beginners, the kinetic energy of a body is given by mv²/2 = mass x velocity squared divided by two.

So temperature of a gas is a direct measure of the kinetic energy.

The Kinetic Error

So where on earth does this identity come from?

..To identify E_U as the total internal kinetic energy of the atmosphere..

E_U is the upwards radiation from the atmosphere to space.

To calculate this value, you need to solve the radiative transfer equations, shown in Understanding Atmospheric Radiation and the “Greenhouse” Effect – Part Six – The Equations. These equations have no “analytic” solution but are readily solvable using numerical methods.

However, there is no doubt at all about this:

E_U ≠ 3kT_A/2 [5]

where T_A = temperature of the atmosphere

that is, E_U ≠ kinetic energy of the atmosphere

As an example of the form we might expect, if we had a very opaque atmosphere (in longwave), then E_U = σT_A⁴ (the Stefan-Boltzmann equation for thermal radiation). As the emissivity of the atmosphere reduces then the equation won’t stay exactly proportional to the 4th power of temperature. But it can never be linearly proportional to temperature.

A Mystery Equation

Many people have puzzled over the equations in Miskolczi’s 2007 paper.

On p6:

The direct consequences of the Kirchhoff law are the next two equations:
E_U = F + K + P (M5)
S_U − (F⁰ + P⁰ ) = E_D − E_U (M6)

Note that I have added a prefix to the equation numbers to identify they as Miskolczi’s. As previously commented, the P term (geothermal energy) is so small that it is not worth including. We will set it to zero and eliminate it, to make it a little easier to see the problems. Anyone wondering if this can be done – just set F’ = F⁰ + P⁰ and replace F⁰ with F’ in the following equations.

So:

E_U = F + K (M5a)
S_U − F⁰ = E_D − E_U (M6a)

Please review figure 1 for explanation of the terms.

If we accept the premise that A_A = E_D then these equations are correct (the premise is not correct, as shown in Part Two).

M5a is simple to see. Taking the incorrect premise that surface radiation absorbed in the atmosphere is completely re-emitted to the surface: therefore, the upward radiation from the atmosphere, E_U must be supplied by the only other terms shown in the diagram – convective energy plus solar radiation absorbed by the atmosphere.

What about equation M6a? Physically, what is the downward energy emitted by the atmosphere minus the upward energy emitted by the atmosphere? What is the surface upward radiation minus the total solar radiation?

Well, doesn’t matter if we can’t figure out what these terms might mean. Instead we will just do some maths, using the fact that the surface energy must balance and the atmospheric energy must balance.

First let’s write down the atmospheric energy balance:

A_A + K + F = E_U + E_D [10] – I’m jumping the numbering to my equation 10 to avoid referencing confusion

This just says that Surface radiation absorbed in the atmosphere + convection from the surface to the atmosphere + absorbed solar radiation in the atmosphere = energy radiated by the atmosphere from the top and bottom.

Given the (incorrect) premise that A_A = E_D, we can rewrite equation 10:

K + F = E_U [10a]

We can see that this matches M5a, which is correct, as already stated.

So first, let’s write down the surface energy balance:

F⁰ – F + E_D = S_U + K [11]

This just says that Solar radiation absorbed at the surface + downward atmospheric radiation = surface upward radiation + convection from the surface to the atmosphere.

Please review Figure 1 to confirm this equation.

Now let’s rewrite equation 11:

S_U – F⁰ = E_D – F – K [11a]

and inserting eq 10a, we get:

S_U – F⁰ = E_D -E_U [11b]

Which agrees with M6a.

And as an aside only for people who have spent too long staring at these equations – re-arrange the terms in 11b:

Su – Ed = F0 – Eu; The left side is surface radiation – absorbed surface radiation in the atmosphere (accepting the flawed premise) = transmitted radiation. The right side is total absorbed solar radiation – upward emitted atmospheric radiation. As solar radiation is balanced by OLR, the right side is OLR – upward emitted atmospheric radiation = transmitted radiation.

Now, let’s see the mystery step :

In Eq. (6) S_U − (F⁰ + P0 ) and E_D − E_U represent two flux terms of equal magnitude, propagating into opposite directions, while using the same F0 and P0 as energy sources. The first term heats the atmosphere and the second term maintains the surface energy balance. The principle of conservation of energy dictates that:
S_U − (F⁰) + E_D − E_U = F⁰ = OLR (M7)

This equation M7 makes no sense. Note that again I have removed the tiny P0 term.

Let’s take [11b], already demonstrated (by accepting the premise) and add (E_D -E_U) to both sides:

S_U – F⁰ + (E_D – E_U) = E_D – E_U+ (E_D -E_U) = 2(E_D -E_U) [12]

So now the left side of eq 12 matches the left side of M7.

The M7 equation can only be correct if the right side of eq 12 matches the right side of M7:

2(E_D -E_U) = F⁰ [13] – to be confirmed or denied

In concept, this claim is that downward radiation from the atmosphere minus upward radiation from the atmosphere = half the total planetary absorbed solar radiation.

I can’t see where this has been demonstrated.

It is not apparent from energy balance considerations – we wrote down those two equations in [10] and [11].

We can say that energy into the climate system = energy out, therefore:

F⁰ = OLR = E_U + S_T [14] (atmospheric upward radiation plus transmitted radiation through the atmosphere)

Which doesn’t move us any closer to the demonstration we are looking for.

Perhaps someone from the large fan club can prove equation 7. So many people have embraced Miskolczi’s conclusion that there must be a lot of people who understand this step.

Conclusion

I’m confused about equation 7 of Miskolczi.

Running with the odds, I expect that no one will be able to prove it and instead I will be encouraged to take it on faith. However, I’m prepared to accept that someone might be able to prove that it is true (with the caveat about accepting the premise already discussed).

The more important point is equating the kinetic energy of the atmosphere with the upward atmospheric radiation.

It’s a revolutionary claim.

But as it comes with no evidence or derivation and would overturn lots of thermodynamics the obvious conclusion is that it is not true.

To demonstrate it is true takes more than a claim. Currently, it just looks like confusion on the part of the author.

Perhaps the author should write a whole paper devoted to explaining how the upwards atmospheric flux can be equated with the kinetic energy – along with dealing with the inevitable consequences for current thermodynamics.

Update 31st May: The author confirmed in the ensuing discussion that equation 7 was not developed from theoretical considerations.

References

Greenhouse Effect in Semi-Transparent Planetary Atmospheres, Miskolczi, Quarterly Journal of the Hungarian Meteorological Service (2007)

Notes

Note 1 – A good paper on the virial theorem is on arXiv: The Virial Theorem and Planetary Atmospheres, Victor Toth (2010)

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The Mystery of Tau – Miskolczi – Part Two – Kirchhoff

Posted in Basic Science, Commentary, Debunking Flawed "Science" on April 25, 2011| 87 Comments »

In Part One we looked at the usefulness of “tau” = optical thickness of the atmosphere.

Miskolczi has done a calculation (under cloudless skies) of the total optical thickness of the atmosphere. The reason he is apparently the first to have done this in a paper is explained in Part One.

The 2010 paper referenced the 2007 paper, Greenhouse Effect in Semi-Transparent Planetary Atmospheres, Quarterly Journal of the Hungarian Meteorological Service.

The 2010 paper suggested an elementary flaw, but referenced the 2007 paper. The 2007 paper backed up the approach with the same apparently flawed claim.

The flaw that I will explain doesn’t affect the calculation of optical thickness, τ. But it does appear to affect the theoretical basis for why optical thickness should be a constant.

First, the graphic explaining the terms is here:

From Miskolczi (2007)

Figure 1

The 2010 paper said:

One of the first and most interesting discoveries was the relationship between the absorbed surface radiation and the downward atmospheric emittance. According to Ref. 4, for each radiosonde ascent the
E_D = A_A = S_U – S_T = S_U(1− exp(−τ_A)) = S_U(1− T_A ) = S_U.A (5)
relationships are closely satisfied. The concept of radiative exchange was the discovery of Prevost [17]. It will be convenient here to define the term radiative exchange equilibrium between two specified regions of space (or bodies) as meaning that for the two regions (or bodies) A and B, the rate of flow of radiation emitted by A and absorbed by B is equal to the rate of flow the other way, regardless of other forms of transport that may be occurring.

Ref. 4 is the 2007 paper, which said:

According to the Kirchhoff law, two systems in thermal equilibrium exchange energy by absorption and emission in equal amounts, therefore, the thermal energy of either system can not be changed. In case the atmosphere is in thermal equilibrium with the surface, we may write that..

What is “thermal equilibrium“?

It is when two bodies are in a closed system and have reached equilibrium. This means they are at the same temperature and no radiation can enter or leave the system. In this condition, energy emitted from body A and absorbed by body B = energy emitted from body B and absorbed by body A.

Kirchhoff showed this radiative exchange must be equal under the restrictive condition of thermal equilibrium. And he didn’t show it for any other condition. (Note 2).

However, the earth’s surface and the atmosphere are not in thermal equilibrium. And, therefore, energy exchanged between the surface and the atmosphere via radiation is not proven to be equal.

Dr. Roy Spencer has a good explanation of the fallacy and the real situation on his blog. One alleged Miskolczi supporter took him to task for misinterpreting something – here:

With respect, Dr Spencer, it is not reasonable, indeed it verges on the mischievous, to write an allegation that Miskolczi means that radiative exchange is independent of temperature. Miskolczi means no such thing. To make such an allegation is to ignore the fact that Miskolczi uses the proper laws of physics in his calculations. Of course radiative exchange depends on temperature, and of course Miskolczi is fully aware of that.

and here:

..Planck uses the term for a system in thermodynamic equilibrium, and the present system is far from thermodynamic equilibrium, but the definition of the term still carries over..

I couldn’t tell whether the claimed “misinterpretation” by Spencer was of the real law or the Miskolczi interpretation. And this article will demonstrate that the proper laws of physics have been ignored.

And I have no idea whether the Miskolczi supporter represented the real Miskolczi. However, a person of the same name is noted by Miskolczi for his valuable comments in producing the 2010 paper.

Generally when people claim to overturn decades of research in a field you expect them to take a bit of time to explain why everyone else got it wrong, but apparently Dr. Spencer was deliberately misinterpreting something.. and that “something” is very clear only to Miskolczi supporters.

After all, the premise in the referenced 2007 paper was:

According to the Kirchhoff law, two systems in thermal equilibrium exchange energy by absorption and emission in equal amounts, therefore, the thermal energy of either system can not be changed. In case the atmosphere is in thermal equilibrium with the surface, we may write that..

Emphasis added.

So if the atmosphere is not in thermal equilibrium with the surface, we can’t write the above statement.

And as a result the whole paper falls down. Perhaps there are other gems which stand independently of this flaw and I look forward to a future paper from the author when he explains some new insights which don’t rely on thermodynamic equilibrium being applied to a world without thermodynamic equilibrium.

Thermodynamic Equilibrium and the Second Law of Thermodynamics

If you put two bodies, A & B, at two different temperatures, T_A and T_B, into a closed system then over time they will reach the same temperature.

Let’s suppose that T_A > T_B. Therefore, A will radiate more energy towards B than the reverse. These bodies will reach equilibrium when T_A = T_B (note 1).

At this time, and not before, we can say that ” ..two systems in thermal equilibrium exchange energy by absorption and emission in equal amounts”. (Note 2).

Obviously, before equilibrium is reached more energy is flowing from A to B than the reverse.

Non-Equilibrium

Let’s consider a case like the sun and the earth. The earth absorbs around 240 W/m² from the sun. The sun absorbs a lot less from the earth.

Let’s just say it is a lot less than 1 W/m². Someone with a calculator and a few minutes spare can do the sums and write the result in the comments.

No one (including of course the author of the paper) would suggest that the sun and earth exchange equal amounts of radiation.

However, they are in the condition of “radiative exchange”.

The Earth’s Surface and the Atmosphere

The earth’s surface and the bottom of the atmosphere are at similar temperatures. Why is this?

It is temperature difference that drives heat flow. The larger the temperature difference the greater the heat flow (all other things remaining equal). So any closed system tends towards thermal equilibrium. If the earth and the atmosphere were left in a closed system, eventually both would be at the same temperature.

However, in the real world where the climate system is open to radiation, the sun is the source of energy that prevents thermal equilibrium being reached.

The bottom millimeter of the atmosphere will usually be at the same temperature as the earth’s surface directly below. If the bottom millimeter is stationary then it will be warmed by conduction until it reaches almost the surface temperature. But 10 meters up the temperature will probably reduce just a little. At 1 km above the surface the temperature will be between 4 K and 10 K cooler than the surface.

Note: Turbulent heat exchange near the surface is very complex. This doesn’t mean that there is confusion about the average temperature profile vs height through the atmosphere. On average, temperature reduces with height in a reasonably predictable manner.

Energy Exchanges between the Earth’s Surface and the Atmosphere

According to Miskolczi:

A_A = E_D [4]

Referring to the diagram, A_A is energy absorbed by the atmosphere from the surface, and E_D is energy radiated from the atmosphere to the surface.

Why should this equality hold?

The energy from the surface to the atmosphere = A_A+ K (note 3), where K is convection.

The energy absorbed in total by the atmosphere = A_A + K + F, where F is absorbed solar radiation in the atmosphere.

The energy emitted by the atmosphere = E_D + E_U , where E_U is the energy radiated from the top of the atmosphere.

Therefore, using the First Law of Thermodynamics for the atmosphere:

A_A + K + F = E_D + E_U + energy retained

i.e., energy absorbed = energy lost – energy retained

No other equality relating to the atmospheric fluxes can be deduced from the fundamental laws of thermodynamics.

In general, because the atmosphere and the earth’s surface are very close in temperature, A_A will be very close to E_D.

It is important to understand that absorptivity for longwave radiation will be equal to emissivity for longwave radiation (see Planck, Stefan-Boltzmann, Kirchhoff and LTE), therefore, if the surface and the atmosphere are at the same temperature then the exchange of radiation will be equal.

Where does the atmosphere radiate from, on average? Well, not from the bottom meter. It depends on the emissivity of the atmosphere. This varies with the amount of water vapor in the atmosphere.

The atmospheric temperature reduces with height- by an average of around 6.5 K/km – and unless the atmospheric radiation was from the bottom few meters, the radiation from the atmosphere to the surface must be lower than the radiation absorbed from the surface by the atmosphere.

If radiation was emitted from an average of 100 m above the surface then the effective temperature of atmospheric radiation would be 0.7 K below the surface temperature. If radiation was emitted from an average of 200 m above the surface then the effective temperature of atmospheric radiation would be 1.3 K below the surface temperature.

Mathematical Proof

For people still thinking about this subject, a simple mathematical proof.

Temperature of the atmosphere, from the average height of emission, T_a

Temperature of the surface, T_s

Emissivity of the atmosphere = ε_a

Absorptivity of the atmosphere for surface radiation = α_a

If T_a is similar to T_s then ε_a ≈ α_a (note 4).

(In the paper, the emissivity (and therefore absorptivity) of the earth’s surface is assumed = 1).

Surface radiation absorbed by the atmosphere, A_A = α_aσT_s⁴ .

Atmospheric radiation absorbed by the surface, E_D = ε_aσT_a⁴ .

Therefore, unless T_a = T_s, A_A ≠ E_D .

If Roy Spencer’s experience is anything to go by, I may now be accused of deliberately misunderstanding something.

Well, words can be confused – even though they seem plain enough in the extract shown. But the paper also asserts the mathematical identity:

A_A = E_D [4]

I have demonstrated that:

A_A ≠ E_D [4]

I don’t think there is much to be misunderstood.

Two bodies at different temperatures will NOT exchange exactly equal amounts of radiation. It is impossible unless the current laws of thermodynamics are wrong.

As a more technical side note.. because ε_a ≈ α_a and not necessarily an exact equality, it is possible for the proposed equation to be asserted in the following way:

A_A = E_D if, and only if, the following identity is always true, α_a(T_s)σT_s⁴ = ε_a(T_a)σT_a⁴ .

Therefore:

T_s/T_a = (ε_a(T_a)/α_a(T_s))^1/4 [Equation B]

– must always be true for equation 4 of Miskolczi (2007) to be correct. Or must be true over whatever time period and surface area his identity is claimed to be true.

Another quote from the 2007 paper:

The popular explanation of the greenhouse effect as the result of the LW atmospheric absorption of the surface radiation and the surface heating by the atmospheric downward radiation is incorrect, since the involved flux terms (A_A and E_D) are always equal.

Emphasis added.

Note in Equation B that I have made explicit the dependence of emissivity on the temperature of the atmosphere at that time, and the dependence of absorptivity on the temperature of the surface.

Emissivity vs wavelength is a material property and doesn’t change with temperature. But because the emission wavelengths change with temperature the calculation of ε_a(T_a) is the measured value of ε_a at each wavelength weighted by the Planck function at T_a.

It is left as an exercise for the interested student to prove that this identity, Equation B, cannot always be correct.

The “Almost” Identity

In Fig. 2 we present large scale simulation results of AA and ED for two measured diverse planetary atmospheric profile sets. Details of the simulation exercise above were reported in Miskolczi and Mlynczak (2004). This figure is a proof that the Kirchhoff law is in effect in real atmospheres. The direct consequences of the Kirchhoff law are the next two equations:

EU = F + K + P (5)
SU − (F0 + P0 ) = ED − EU (6)

The physical interpretations of these two equations may fundamentally change the general concept of greenhouse theories.

From Miskolczi (2007)

Figure 2

This is not a proof of Kirchhoff’s law, which is already proven and is not a law that radiative exchanges are equal when temperatures are not equal.

Instead, this is a demonstration that the atmosphere and earth’s surface are very close in temperature.

Here is a simple calculation of the ratio of A_A:E_D for different downward emitting heights (note 5), and lapse rates (temperature profile of the atmosphere):

Figure 3

Essentially this graph is calculated from the formula in the maths section and a calculation of the atmospheric temperature, T_a, from the height of average downward radiation and the lapse rate.

Oh No He’s Not Claiming This is Based on Kirchoff..

Reading the claims by the supporters of Miskolczi at Roy Spencer’s blog, you read that:

Miskolczi is not claiming that A_A = E_D by asserting (incorrectly) Kirchhoff’s law
Miskolczi is claiming that A_A = E_D by experimental fact

So the supporters claim.

Read the paper, that’s my recommendation. The 2010 paper references the 2007 paper for equation 4. The 2007 paper says (see larger citation above):

..This figure is a proof that the Kirchhoff law is in effect in real atmospheres..

In fact, this is the important point:

Anyone who didn’t believe that it was a necessary consequence of Kirchhoff would be writing the equations in the maths section above (which come from well-proven radiation theory) and realizing that it is impossible for A_A = E_D.

And they wouldn’t be claiming that it demonstrated Kirchhoff’s law. (After all, Kirchhoff’s law is well-proven and foundational thermodynamics).

However, it is certain that on average E_D < A_A but very close to A_A.

Hence the Atmospheric Window Cooling to Space Thing

From time to time, Miskolczi fans have appeared on this blog and written interesting comments. Why the continued fascination with the exact amount of radiation transmitted from the surface through the atmospheric window?

I have no idea whether this point is of interest to anyone else..

One of the comments highlighted the particular claim and intrigued me.

Yes, indeed, that’s right: Simpson discovered the atmospheric window in 1928. It was not till the work of Miskolczi in 2004 and 2007 that it was discovered that practically all the radiative cooling of the land-sea surface is by radiation direct to space.

Apart from the (unintentional?) humor inherent in the Messianic-style claim, the reason why this claim is a foundational point for Miskolczi-ism is now clear to me.

If exactly all of the radiation absorbed by the atmosphere is re-radiated to the surface and absorbed by the surface (A_A = E_D) then these points follow for certain:

radiation emitted by the atmosphere to space = convective heat from the surface into the atmosphere + solar radiation absorbed by the atmosphere
total radiative cooling to space = radiation transmitted through the atmospheric window + convective heat plus solar radiation absorbed by the atmosphere

A curiosity only.

Changing the Fundamental View of the World

Miskolczi claims:

The physical interpretations of these two equations may fundamentally change the general concept of greenhouse theories.

He is being too modest.

If it turns out that A_A = E_D then it will overturn general radiative theory as well.

Or demonstrate that the atmosphere is much more opaque than has currently been calculated (for all of the downward atmospheric radiation to take place from within a few tens of meters of the surface).

This in turn will require the overturning of some parts of general radiative theory, or at least, a few decades of spectroscopic experiments, which consequently will surely require the overturning of..

Conclusion

How is it possible to claim that A_A = E_D and not work through the basic consequences (e.g., the equations in the maths section above) to deal with the inevitable questions on thermodynamics basics?

Why claim that it has fundamentally changed the the general concept of the inappropriately-named “greenhouse” theory when it – if true – has overturned generally accepted radiation theory?

Perhaps α(λ) ≠ ε(λ) and Kirchhoff’s law is wrong? This is a possible consequence. (In words, the equation says that absorptivity at wavelength λ is not equal to emissivity at wavelength λ, see note 4).
Or perhaps the well-proven Stefan-Boltzmann law is wrong? This is another possible consequence.

Interested observers might wonder about the size of the error bars in Figure 2. (And for newcomers, the values in Figure 2 are not measured values of radiation, they are calculated absorption and emission).

As already suggested, perhaps there are useful gems somewhere in the 40 pages of the 2007 paper, but when someone is so clear about a foundational point for their paper that is so at odds with foundational thermodynamic theory and the author doesn’t think to deal with that.. well, it doesn’t generate hope.

Update 31st May – the author comments in the ensuing discussion that Aa=Ed is an “experimental” conclusion. In Part Four I show that the “approximate equality” must be an error for real (non-black) surfaces, and Ken Gregory, armed with the Miskolczi spreadsheet, later confirms this.

References

Greenhouse Effect in Semi-Transparent Planetary Atmospheres, Miskolczi , Quarterly Journal of the Hungarian Meteorological Service (2007)

The Stable Stationary Value of the Earth’s Global Average Atmospheric Planck-Weighted Greenhouse-Gas Optical Thickness, Miskolczi, Energy & Environment(2010)

The Theory of Heat Radiation, Max Planck, P. Blakiston’s Son & Co (1914) : a translation of Waermestrahlung (1913) by Max Planck.

Notes

Note 1 – Of course, in reality equilibrium is never actually reached. As the two temperatures approach each other, the difference in energy exchanged is continually reduced. However, at some point the two temperatures will be indistinguishable. Perhaps when the temperature difference is less than 0.1°C, or when it is less than 0.0000001°C..

Therefore, it is conventional to talk about “reaching equilibrium” and no one in thermodynamics is confused about the reality of the above point.

Note 2 – Max Planck introduces thermodynamic equilibrium:

Note 3 – Geothermal energy is included in the diagram (P⁰). Given that it is less than 0.1 W/m² – below the noise level of most instruments measuring other fluxes in the climate – there is little point in cluttering up the equations here with this parameter.

Note 4 – Emissivity and absorptivity are wavelength dependent parameters. For example, snow is highly reflective for solar radiation but highly absorbing (and therefore emitting) for terrestrial radiation.

At the same wavelength, emissivity = absorptivity. This is the result of Kirchhoff’s law.

If the temperature of the source radiation for which we need to know the absorptivity is different from the temperature of the emitting body then we cannot assume that emissivity = absorptivity.

However, when the temperature of source body for the radiation being absorbed is within a few Kelvin of the emitting body then to a quite accurate assumption, absorptivity = emissivity.

For example, the radiation from a source of 288K is centered on 10.06 μm, while for 287 K it is centered on 10.10 μm. Around this temperature, the central wavelength decreases by about 0.035 μm for each 1 K change in temperature.

An example of when it is a totally incorrect assumption is for solar radiation absorbed by the earth. The solar radiation is from a source of about 5800 K and centered on 0.5 μm, whereas the terrestrial radiation is from a source of around 288 K and centered on 10 μm. Therefore, to assume that the absorptivity of the earth’s surface for solar radiation is equal to the emissivity of the earth’s surface is a huge mistake.

This would be the same as saying that absorptivity at 0.5 μm = emissivity at 10 μm. And, therefore, totally wrong.

Note 5: What exactly is meant by average emitting height? Emitted radiation varies as the 4th power of temperature and as a function of emissivity, which itself is a very non-linear function of quantity of absorbers. Average emitting height is more of a conceptual approach to illustrate the problem.

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Things Climate Science has Totally Missed? – Convection

Posted in Commentary, Debunking Flawed "Science" on December 7, 2010| 122 Comments »

With apologies to my many readers who understand the basics of heat transfer in the atmosphere and really want to hear more about feedback, uncertainty, real science..

Clearing up basic misconceptions is also necessary. It turns out that many people read this blog and comment on it elsewhere and a common claim about climate science generally (and about this site) is that climate science (and this site) doesn’t understand/ignores convection.

The Anti-World Where Convection Is Misunderstood

Suppose – for a minute – that convection was a totally misunderstood subject. Suppose basic results from convective heat transfer were ridiculed and many dodgy papers were written that claimed that convection moved 1/10 of the heat from the surface or 100x the heat from the surface. Suppose as well that everyone was pretty much “on the money” on radiation because it was taught from kindergarten up.

It would be a strange world – although no stranger than the one we live in where many champions of convection decry the sad state of climate science because it ignores convection, and anyway doesn’t understand radiation..

In this strange world, people like myself would open up shop writing about convection, picking up on misconceptions from readers and other blogs, and generally trying to explain what convection was all about.

No doubt, in that strange world, commenters and bloggers would decry the resulting over-emphasis on convection..

First Misconception – Radiation Results are All Wrong Because Convection Dominates

There are three mechanisms of heat transfer:

radiation
convection
conduction

Often in climate science, people add:

latent heat

In more general heat transfer this last one is often included within convection, which is the movement of heat by mass transfer. Although sometimes in general heat transfer, heat transfer via “phase change” of a substance is separately treated – it’s not important where “the lines are drawn”.

Update note from Dec 9th – I leave my poorly worded introduction above so that readers comments make sense. But I should have written

In fact in atmospheric physics we almost always see the breakdown like this:

-radiation
-latent heat
-sensible heat

Latent heat being the movement of heat via evaporation – convection – condensation. Sensible heat being the movement of heat via convection with no phase change. Conduction is actually also included in sensible heat, but is negligible in atmospheric physics.

Therefore when convection is written about it is both sensible and latent heat. That is, heat transfer in the atmosphere is via either convection or via radiation.

End of update note

Let’s look at conduction, safe from criticism because it is largely irrelevant as a form of heat transfer within the atmosphere. Conduction is also the easiest to understand and closest to people’s everyday knowledge.

The basic equation of heat conduction is:

q =- kA . ΔT/Δx

where ΔT is the temperature difference, Δx is the thickness of the material, A is the area, k is the conductivity (the property of the material) and q is the heat flow. (See Heat Transfer Basics – Part Zero for more on this subject).

Notice the terms in this equation:

the material property (k)
the thickness of the material (Δx)
the temperature difference (ΔT)
the area (A)

Where are the convective and the radiative terms?

Interestingly, conduction is independent of convection and radiation. This is a very important point to understand – but it is also easy to misunderstand if you aren’t used to this concept.

It doesn’t mean that we can calculate a change in equilibrium condition – or a dynamic result – only using one mechanism of heat transfer.

Let’s suppose we have a problem where we know the temperature at time = 0 for two surfaces. We know the heating conditions at both surfaces (for example, zero heat input). We want to know how the temperature changes with time, and we want to know the final equilibrium condition.

The way this problem is solved is usually numerical. This means that we have to work out the heat flow from each mechanism (conduction, convection, radiation) for a small time step, calculate the resulting change in temperature, and then go through the next time step using the new temperatures.

For many people, this is probably a fuzzy concept and, unfortunately, I can’t think of an easy analogy that will crystallize it.

But what it means in simple terms is that each heat transfer mechanism works independently, but each affects the other mechanisms via the temperature change (if I come up with a useful analogy or example, I will post it as a comment).

So if, for example, convection has changed the temperature profile of the atmosphere to something that would not happen without convection – the calculation of conduction through the atmosphere is still:

q = -kA . ΔT/Δx

And likewise the more complex equation of radiative transfer (see Theory and Experiment – Atmospheric Radiation) will also rely on the temperature profile established from convection.

So – an ocean surface with an emissivity of 0.99 and a surface temperature of 15°C will still radiate 386 W/m², regardless of whether the convection + latent heat term = zero or 10 W/m² or 100 W/m² or 500 W/m².

Second Misconception – Atmospheric Physics Ignores Convection

This is a common claim. It’s simple to demonstrate that the claim is not true.

Let’s take a look at a few atmospheric physics text books.

From Elementary Climate Physics, Prof F.W. Taylor, Oxford University Press (2005):

Extract from Elementary Climate Physics, F.W. Taylor (2005)

From Handbook of Atmospheric Science, Hewitt & Jackson (2003):

From Handbook of Atmospheric Science, Hewitt and Jackson (2003)

From An introduction to atmospheric physics, David Andrews, Cambridge University Press (2000):

David Andrews, Atmospheric Physics (2000)

In fact, you will find some kind of derivation like this in almost every atmospheric physics textbook.

Also note that it is nothing new – from Atmospheres, by R.M. Goody & J.C.G. Walker (1972):

Both convection and radiation are important in heat transfer in the troposphere.

Lindzen (1990) said:

The surface of the earth does not cool primarily by infrared radiation. It cools mainly through evaporation. Most of the evaporated moisture ends up in convective clouds.. where the moisture condenses into rain..

..It is worth noting that, in the absence of convection, pure greenhouse warming would lead to a globally averaged surface temperature of 72°C given current conditions

Note the important point that convection acts to reduce the surface temperature. If radiation was the dominant mechanism for heat transfer the surface temperature would be much higher.

Convection lowers the surface temperature. However, it only acts to reduce the effect of the inappropriately-named “greenhouse” gases. And convection can’t move heat into space, only radiation can do that, which is why radiation is extremely important.

The idea that climate science ignores or misunderstands convection is a myth. This is something you can easily demonstrate for yourself by checking the articles that claim it.

Where is their proof?

Do they cite atmospheric physics textbooks? Do they cite formative papers that explained the temperature profile in the lower atmosphere?

No. Ignorance is bliss..

Third Misconception – Convection is the Explanation for the “33°C Greenhouse Effect”

Perhaps in a later article I might explain this in more detail. It is already covered to some extent in On Missing the Point by Chilingar et al (2008).

As a sample of the basic misunderstanding involved in this claim, take a look at Politics and the Greenhouse Effect by Hans Jelbring, which includes a section Atmospheric Temperature Distribution in a Gravitational Field by William C. Gilbert.

If you read the first section by Jelbring (ignoring the snipes) it is nothing different from what you find in an atmospheric physics textbook. No one in atmospheric physics disputes the adiabatic lapse rate, or its derivation, or its total lack of dependence on radiation.

Clearly, however, Jelbring hasn’t got very far in atmospheric physics text books, otherwise he would know that his statement (updated Dec 9th with longer quotation on request):

T is proportional to P and P is known from observation to decrease with increasing altitude. It follows that the average T has to decrease with altitude. This decrease from the surface to the average infrared emission altitude around 4000 m is 33 oC. It will be about the same even if we increase greenhouse gases by 100%.

– was very incomplete. How is it possible not to know the most important point about the inappropriately-named “greenhouse” effect with a PhD in Climatology? Or even no PhD and just a slight interest in the field?

What determines the average emission altitude?

The “opacity” of the atmosphere. See The Earth’s Energy Budget – Part Three. Clearly Jelbring doesn’t know about it, otherwise he would have brought it up – and explained his theory of how doubling CO2 doesn’t change the opacity of the atmosphere – or the average altitude of radiative cooling to space.

Gilbert adds in his section:

I was immediately amazed at the paltry level of scientific competence that I found, especially in the basic areas of heat and mass transfer. Even the relatively simple analysis of atmospheric temperature distributions were misunderstood completely.

Where is Gilbert’s evidence for his amazing claim?

Gilbert also derives the equation for the lapse rate and comments:

It is remarkable that this very simple derivation is totally ignored in the field of Climate Science simply because it refutes the radiation heat transfer model as the dominant cause of the GE. Hence, that community is relying on an inadequate model to blame CO2 and innocent citizens for global warming in order to generate funding and to gain attention. If this is what“science” has become today, I, as a scientist, am ashamed.

I’m amazed. Hopefully, everyone reading this article is amazed.

The derivation of the lapse rate is in every single atmospheric physics textbook. And no one believes that radiative heat transfer determines the lapse rate.

And the important point – the Climate Science 101 point – is that the altitude of the radiative cooling to space is affected by the concentration of “greenhouse” gases.

Actually understanding a subject is a pre-requisite for “debunking” it.

Conclusion

Many people read blog articles and comments on blog articles and then repeat them elsewhere.

That doesn’t make them true.

Science is about what can be tested.

What would be a worthwhile “debunking” is for someone to take a well-established atmospheric physics textbook and point out all the mistakes. If they can find any.

It would be more valuable than just “making stuff up”.

References

Elementary Climate Physics, Prof F.W. Taylor, Oxford University Press (2005)

Handbook of Atmospheric Science, Hewitt & Jackson, Blackwell (2003)

An introduction to atmospheric physics, David Andrews, Cambridge University Press (2000)

Atmospheres, R.M. Goody & J.C.G. Walker, Prentice-Hall (1972)

Some Coolness Regarding Global Warming, Lindzen, Bulletin of the American Meteorological Society (1990)

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Do Trenberth and Kiehl understand the First Law of Thermodynamics? Part Three and a Half – The Creation of Energy?

Posted in Basic Science, Debunking Flawed "Science" on December 4, 2010| 12 Comments »

I’m in the process of writing a couple more in-depth articles but have been much distracted by “First Life” in recent weeks.. sad and unfortunate, because writing Science of Doom articles is much more interesting..

While writing a new article – What’s the Palaver? – Kiehl and Trenberth 1997 – I thought that I should separately explain a few things which related to the earlier article: Do Trenberth and Kiehl understand the First Law of Thermodynamics? Part Three.

I know that many readers already get the point. But clearly some people find the model – and real life – so controversial that they will find many ways to claim “real life” wrong. Stefan-Boltzmann, who was he? Pyrgeometers– clearly a fake product that should be investigated by the Justice Department? And so on.

One of the problems is that radiant heat transfer is not something in accord with everyday life and so – as we all do – people draw on their own experience. But people also draw on confused ideas about the First Law of Thermodynamics to make their case.

In this article, two ideas.

First, is the Atmosphere Made of PVC?

In the original article – Do Trenberth and Kiehl understand the First Law of Thermodynamics? – I used a simple heat conduction problem to demonstrate that temperatures can be much higher inside a system than outside a system, when the system is heated from within.

One commenter explained the link between this and the atmosphere, although perhaps my attempts at humor had slightly back-fired. I had disclaimed any relationship between PVC spheres and the atmosphere..

Well, I confirm the atmosphere is not made of PVC, and that conduction is not important for heat transfer through the atmosphere.

But there is relevance for the atmosphere. Where is the relevance?

Solar radiation heats the climate system “from within”. The atmosphere is mostly transparent to solar radiation so the solar energy initially heats the surface of the earth. Then the surface of the earth heats the atmosphere. Finally the atmosphere radiates energy back out to space.

If it were true that the first law of thermodynamics – the conservation of energy – was violated by a simple “lagged pipe” model – well, that would be the end of an important branch of thermodynamics.

The model showed that the temperature of an inner surface can be higher than an outer surface – and, therefore, radiation from an inner surfaces can be higher than the radiation to space from the outer surface.

The reason for providing the model of the PVC sphere – much simpler than the atmosphere – was to demonstrate that simple point.

Second, What if the Radiation from an Inner Surface CANNOT be Higher than from an Outer Surface

Many people write entertainingly inaccurate articles about this subject (see Interesting Refutation of Some Basics for one example). Apparently, if the radiation from the atmosphere/surface into space is 239 W/m² then the radiation from the inner surface itself cannot be more than 239 W/m². A confusion about the First Law of Thermodynamics.

To be specific, the actual claim from the believers in the Imaginary First Law of Thermodynamics (IFTL) is that the total radiation from the earth’s surface cannot be higher than the total radiation from the climate system into space.

This, according to the IFLT, is not allowed.

Let’s consider the consequences and calculate the results. All we need to connect the two values – when we have the W/m² for both surfaces – is the ratio of surface areas.

If E₁ is the radiation in W/m² from inner surface A₁, and E₂ is the radiation from the outer surface, of area A₂:

E₁A₁ = E₂A₂

The area of a sphere is proportional to its radius squared (A = 4πr²), so the above equation becomes:

E₁r₁² = E₂r₂²

a) The Earth and Climate System

In the case of the Earth and climate system, the radius of the earth and the radius of the “climate system” are almost identical..

The radius of the earth, r₁ = 6,380 km or 6.38 x 10⁶ m.

The radiation to space takes place from an average height of around 6km from the surface, so the radius of “the climate system”, r₂ = 6.39 x 10⁶ m (at most).

The total radiation to space, E₂ = 239 W/m² (measured by satellite).

If the IFTL believers are correct then E₁r₁² = E₂r₂²

Therefore, E₁ = 239 x (6.39 x 10⁶)² / (6.38 x 10⁶)² = 240 W/m²

Unsurprisingly, this surface radiation value is almost the same as the radiation into space because the two areas are almost identical.

The Stefan-Boltzmann law says that radiation from a surface, E = εσT⁴

The “currently believed” average value from the earth’s surface is 396 W/m². This is due to the emissivity of the earth’s surface being very close to 1.

So there are three simple choices for why the “believed value” of 396 W/m² is so much higher than the believers in the IFLT appear to claim:

The Stefan-Boltzmann law is wrong
The emissivity of the earth’s surface, for the wavelengths under question, is an average of 0.61
The surface temperature has been massively over-estimated and the “average” temperature of the earth’s surface is actually around -18°C (see note 1).

The 3rd choice should not be ruled out. Perhaps Antartica is a lot larger than measured, or a lot colder. How many temperature stations are there on Antarctica anyway? Maybe there is some cartographical error in estimating the area of this continent from when planes have flown over Antarctica and satellites have crossed the poles.

Perhaps the Gobi desert is a lot colder than people think. No one really makes an effort to measure this stuff, climate scientists just take it all for granted, sitting in their nice warm comfortable offices looking over the results of supercomputer climate models. No one does any field research.

Quite plausible really. It’s not too hard to make the case that the average temperature of the earth is much much much colder than is generally claimed.

b) The PVC Sphere

Let’s review the very simple hollow PVC sphere model. In the original article, the inner radius was 10m and the outer radius was 13m.

Let’s look at what happens as the inner radius is increased up to 10,000m while the wall thickness stays at 3m.

Instead of keeping the internal energy source of 30,000W constant, we will keep the internal energy source per unit area of inner surface constant. In the original example, this value was 23.9 W/m².

Real First Law

With the equations provided in the maths section of Part One, and an energy source of 23.9W/m², here is the temperature difference from inner to outer surface as the inner radius increases:

Note that the x-axis is a log scale. The initial value, 10¹ (=10) was the value from the original example, and the temperature difference was 290K.

As the sphere becomes much larger (and the wall thickness stays constant) the temperature difference tends towards 377K.

Now that is a very interesting number that we can check.

When the wall thickness becomes very thin in comparison to the sphere it is really approximating a planar wall. The equation for heat conduction (per unit area) through a planar wall is:

q = k . ΔT/Δx

where q = W/m², k = conductivity (0.19 W/m.K), ΔT = temperature difference, Δx = wall thickness, m

So for a 3m thick planar PVC wall conducting 23.9 W/m², let’s re-arrange and plug the numbers into the equation:

ΔT = 23.9 x 3 / 0.19 = 377 K

Correct.

So this is a very simple test. There is no other way to link heat conduction and temperature difference. The simple equations that anyone can check support the PVC sphere model results.

Imaginary First Law

Let’s find out what happens under the imaginary first law. It will be quite surprising for the supporters of the theory.

I couldn’t check the imaginary first law in any textbooks, because it’s.. anyway, as far as I can determine, here are the steps:

1. The radiation from the inner surface must be 23.9 W/m². This means (for an emissivity, ε = 0.8 that has already been prescribed for this model) that the inner surface temperature, T₁ = 151.5K (E = εσT⁴)

2. The inner and outer surface radiation values are related by the equations provided earlier:

E₁r₁² = E₂r₂²

3. Therefore, we can calculate the outer surface temperature and therefore the temperature difference.

Here is the graph of temperature difference as the radius increases:

Note the important point that as the radius increases the temperature difference reduces to almost nothing – this is the inevitable consequence of the (flawed) argument that inner surface radiation has to equal outer surface radiation.

Because when r1=10,000m, r2=10,003m, therefore, the areas are almost identical.

Therefore, the radiation values are almost identical, therefore the temperatures are almost identical.

Ouch. This means that somehow 23.9 W/m² is driven by heat conduction across 3m of PVC with no temperature difference.

How can this happen? Well – it can’t. To get 23.9 W/m² across a planar PVC wall 3m thick requires a temperature difference of 377 K.

When r1 = 10,000 m, ΔT = 0.02 K according to my IFTL calculations – and so the conducted heat per unit area, q = 0.0013 W/m². The heat can’t get out, which means the temperature inside increases.. and keeps increasing until the temperature differential is high enough to drive 23.9 W/m² though the wall.

Hopefully, this makes it clear to anyone who hasn’t already made a total nana of themselves that the imaginary first law of thermodynamics, is .. imaginary.

Notes

Note 1 – The concept of an average temperature is not really needed to actually do this calculation. Averaging temperatures across different surface materials like oceans, rocks, deserts clearly has some problems – see for example, Why Global Mean Surface Temperature Should be Relegated, Or Mostly Ignored.

All that is really required is to calculate the average radiation value instead. Just find the temperature at each location and calculate the emitted radiation. Then average up all the numbers (area-weighted).

As a note to the note.. To get 240 W/m² with an emissivity close to 1, the “average temperature” can be at most -18°C. With a wider day/night and seasonal variation than we actually experience on earth the “average temperature” would then be lower than -18°C.

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Do Trenberth and Kiehl understand the First Law of Thermodynamics? Part Three – The Creation of Energy?

Posted in Basic Science, Debunking Flawed "Science" on November 14, 2010| 123 Comments »

When I wrote Do Trenberth and Kiehl understand the First Law of Thermodynamics? I imagined that (almost) no one would have a problem with the model created. Instead, I thought perhaps some might question its relevance to climate.

It was a deliberate choice to use conduction to demonstrate the point – the reason is that radiation is less familiar to most people, while conduction is more straightforward and easier to understand.

Here is the model from that article – a heat source in a hollow PVC sphere, located in the depths of space:

Many people have experienced a lagged hot water pipe. The more lagging (insulation), the higher the temperature rises. It seems straightforward.

However, the conceptual barrier that some people have is so large that anything – literally – will be put forward to make the model fit their conceptual idea. In case the case of one blog, claiming that energy can be destroyed in an effort to get the “right” result. A delicious irony that the first law of thermodynamics is cast aside to protect.. the first law of thermodynamics.

The reason this PVC sphere model appears so wrong to many people is for similar reasons that the famous Kiehl & Trenberth diagram seems wrong – the radiation “internally” (earth surface) is higher than the external radiation to space. (Note that the radiation values in the K&T diagram can be measured).

Explaining How the Result is Calculated

..in simple terms.

Solving the maths for the model above is straightforward (refer to the first article for the actual maths). Here is the solution in simple terms:

For the steady state condition the energy radiated from the outer surface must equal the energy source in the center (30,000 W). Otherwise the system will keep accumulating energy.

Given the surface area and the stated emissivity the outer surface temperature (T2) must be 133K (to radiate 30,000 W).

The only way that heat can be transferred from the inner surface to the outer surface is through conduction. This means 30,000 W is conducted through the PVC.

Given the (low) thermal conductivity of PVC and the dimensions, the temperature difference must be 290K, making T1 = 423K.

If the temperature differential is any lower then less than 30,000W will be conducted through the wall. And if that was the case then heat would be accumulated at the inner surface – increasing its temperature until eventually 30,000W did flow through.

Conversely, if the temperature was higher than 423K then more than 30,000W would be conducted through the sphere. This would start to reduce the temperature until only 30,000W was conducted.

Simple really. However, when the result doesn’t seem right, people begin their mental gyrations to get the “right” result.

This article is not written to convince people who have their minds made up. It’s written to help those who are asking the legitimate question:

Haven’t you just created energy? And can’t I use that to run a small power station?

Good question.

This article is not about proving what has already been demonstrated, it’s about helping with mental models.

The equations of heat transfer have already been clearly explained in Part One. So far, the arguments against that have been put forward consist of:

the argument from incredulity
3m of PVC can transmit radiation straight through (no it can’t)
energy disappears under the right circumstances (that was just the first of many flaws in that person’s argument..)

Of course, if someone comes up with yet another alternative calculation of the heat transfer I will be happy to look at it.

In the meantime, let’s create a mental model..

The Power Station

A few people have jubilantly claimed that the model I created, if correct, can run a power station of 1.8 MW, from a source of only 30,000 W.

That’s what it might seem like on the surface. But strangely, the model results were derived by conserving energy. That is, no energy was created or destroyed..

In the steady state condition:

30,000 W is produced from the internal source
30,000 W is conducted through the PVC “wall”
30,000 W is radiated from the outer surface

Energy is not being created or destroyed. Where is the energy accumulation in this model? Where is the usable energy being stockpiled?

If you want to understand the subject, this point is the one to focus on and think about
If you don’t want to understand the subject say “he’s created 1.8 MW of energy from 30,000W – ridiculous”, and move on (it sounds good)

The inner surface of the sphere has an area of 1,257 m² (4πr²). Consider one square meter of internal surface, we’ll call it “A” – these kind of models always have catchy names for different components of the model.

Each second, A receives 23.9 W/m² from the internal heat source (30,000W / 1,257 m²).
Each second, A conducts 23.9 W/m² through the wall.
Each second, A absorbs 1,452 W/m² radiated from the rest of the inner wall.
Each second, A re-radiates 1,452 W/m².

This is another way of saying that no energy is being created or destroyed. Where is the energy to run this power station?

All that happens if we start drawing power out of this system is the temperature internally reduces very quickly.

How Does the Sphere Heat Up?

In my efforts to understand the conceptual problems people have, I believe that this might help. I can’t be certain – this article is about mental models.

Let’s picture the scene when the PVC sphere is “started up”.

Outside it is 0K. Inside it is 0K. Chilly. Very chilly.

Now the 30,000 W heat source is fired up. 30,000 J every second gets radiated out from this source. Every second, 80% of this 30,000 J gets absorbed by the inner surface (with 20% reflected).

At this stage almost no energy is conducted through the PVC sphere. It can’t – because the temperature differential is not nearly high enough. Conduction requires a heat differential. So instead, the energy goes into heating up the inner surface of the sphere.

As the inner surface heats up it begins to conduct heat through to the outer surface – but most of the energy still goes into heating the inner surface.

A necessary consequence of the inner surface being heated up is that it radiates. All of this radiation is absorbed by the rest of the inner surface AND THEN re-radiated. Energy is not being created. This energy can’t be “tapped off” to do anything useful.

A small supply of energy is simply being “bounced around” (not really “bounced” but it might be a useful way to think about it)

This energy is simply the energy that has been accumulated by the inner surface during the initial heating process. It keeps being accumulated until finally the temperature is high enough to conduct the full 30,000 W through to the outer surface.

Now we have reached equilibrium! On our journey to equilibrium, while the inner surface was heating up, it accumulated heat, and this accumulated heat is now radiated, absorbed, re-radiated, absorbed…

You can connect it to a power station and very quickly you will draw down this accumulation of energy. The maximum you can draw out long term will be 30,000 W.

Conclusion

This article is all about mental models – explaining why the actual results for this model don’t violate the First Law of Thermodynamics. The results were calculated from the very simple and standard heat transfer equations.

Analysis of this model, with the results that I have presented (in part one), demonstrates that energy is conserved.

At first glance it might not seem like it to many people – because the inner surface radiation is so high. But the energy is just re-radiated from the energy absorbed. It’s like a small stockpile of energy that is being “bounced around” from wall to wall.

There is only one (legitimate) way to solve the heat transfer equations for this model. Other approaches invent /destroy physics in an attempt to get a low enough value for the radiation emitted from the inner wall.

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The Three Body Problem

Posted in Basic Science, Debunking Flawed "Science" on November 5, 2010| 174 Comments »

With apologies to my many patient readers who want to cover more challenging subjects.

Many people trying to understand climate science have a conceptual problem.

I have written (too) many articles about the second law of thermodynamics – the real and the imaginary version. Resulting comments on this blog and elsewhere about those articles frequently contain comments of this form:

So if we take bucket A full of water at 80°C and bucket B full of water at 10°C, Science of Doom is saying that bucket A will heat up because of bucket B? Right! That’s ridiculous and climate science is absurd!

Yes, if anyone was saying that it would be ridiculous. I agree. To take one example from many, in The Real Second Law of Thermodynamics I said:

Put a hold and cold body together and they tend to come to the same temperature, not move apart in temperature.

Of course, it could be that I am inconsistent in my application of this principle.

One observation on the many contrary claims resulting from my articles – not a single person has provided a mathematical summary to demonstrate that the examples provided contradict the first or second law of thermodynamics.

It should be so easy to do – after all if one of the many systems I have outlined contravenes one of these laws, surely someone can write down the equations for energy conservation (1st law of thermodynamics) or for change in entropy (2nd law of thermodynamics) and prove me wrong. We aren’t talking complex maths here with double integrals or partial differentiation. Just equations of the form a + b = 0.

And here’s the reason why – the problem that people have is conceptual. It seems wrong so they keep explaining why it seems wrong.

Conceptual problems are the hardest to get around. At least, that’s what I have always found. Until a subject “clicks”, all the mathematical proof in the world is just a jumble of letters.

So with that introduction, I offer a conceptual model to help those many people who don’t understand how a cold atmosphere can lead to a warmer surface than would occur without the cold atmosphere.

And if you are one of those people in the “firmly convinced” camp, let me suggest this reason for making the effort to understand this conceptual model. If you understand why others are wrong you can help explain it to them. But if you just don’t understand the argument of people on “the other side” you can’t offer them any useful assistance.

Model 2 – Two bodies – The Boring One that Everyone Really Does Agree With

Very quickly, to “warm everyone up”, and to once again state the basics – if we have two bodies in a closed system, and body A is at temperature 80°C and body B is at 10°C, then over a period of time both will end up at the same temperature somewhere between 10°C and 80°C. It is impossible, for example, for body A to end up at 100°C and body B at 0°C.

Everyone is in agreement on this point.

Note that the “period of time” might be anything between seconds and many times the age of the universe – dependent upon the circumstances of the two bodies.

Model 3A – Three Bodies with the Third Body Being Quite Cold

Where’s Body 1? This picture is the view from Body 1, also known as “Chilly Earth”, which is a spherical solid planet.

To make the problem much easier to solve we will state that the heat capacities of Body 2 and Body 3 are extremely high. This means that whether they gain or lose energy, their temperature will stay almost exactly the same. Body 1, “Chilly Earth”, has a much lower heat capacity and will therefore adjust quickly to a temperature which balances the absorption and emission of radiation.

“Chilly Earth” doesn’t have an atmosphere.

However, for the purposes of helping the conceptual model, “Chilly Earth” reflects 30% of shortwave radiation from the Sun but at longer wavelengths absorbs 100% (reflects 0%). This means its emissivity at longwave is also 100%.

“Chilly Earth” has a very high conductivity for heat, and therefore the whole planet is at the same surface temperature. (See note 1).

“Sun” is 150M km away from “Chilly Earth”, and “Chilly Earth” has a radius of 1,000 km (a little different from the planet we call home).

Let’s calculate the approximate equilibrium temperature of “Chilly Earth”, T₁

How do we do this? By calculating the energy absorbed from Body 2 and from Body 3, and calculating the temperature of a surface that will radiate that same energy back out.

The method is simple – see below.

Energy Absorbed from Body 2, “Sun”

Radiation from “Sun” at 5780K = 6.3 x 10⁷ W/m² – near the surface of the sun. By the time the sun’s radiation reaches earth, because of the inverse square law (the radiation has “spread out”), it is reduced to 1,369 W/m². Remember that 30% is reflected, so the absorbed radiation = 958 W/m².

The surface area that “captures” this radiation = πr² = 3.14 x 10⁶ m².

Energy absorbed from body 2, E_r2 = 958 x 3.14 x 10⁶ = 3.01 x 10⁹ W.

Energy Absorbed from Body 3, “Space”

Radiation from “Space” at 3K = 4.59 x 10^-6 W/m². Apart from the very tiny angle in the sky for “Sun”, the entire rest of the sky is radiating towards the earth from all directions in the sky.

The surface area that “captures” this radiation = 4πr² = 1.26 x 10⁷ m².

Energy absorbed from body 3, E_r3 = 4.59 x 10^-6 x 1.26 x 10⁷ = 57.7W.

So energy from body 3 can be neglected which is not really surprising.

Energy Radiated from Body 1, “Chilly Earth”

For thermal equilibrium (energy in = energy out), “Chilly Earth” must radiate out 3.01 x 10⁹ W, from its entire surface area of 1.26 x 10⁷ m².

This equates to 239 W/m², which for a body with an emissivity of 1 (a blackbody) means T₁ = -18°C.

So we have calculated the equilibrium temperature of “Chilly Earth”.

Now, if we change the model conditions – the reflected portion of solar radiation, the emissivity of the earth at longwave, or the conductivity of the planet’s surface – any of these factors would affect the result. They wouldn’t invalidate the analysis, they would simply lead to a different number, one that was slightly more difficult to work out.

But hopefully everyone can agree that with these conditions there is nothing wrong with the method. (I realize that a few people will not agree..)

Model 3B – Three Bodies with the Third Body Being Somewhat Warmer

So now we are going to perform the same analysis with our new Body 1, “Warmer Earth” (a wild stab at an appropriate name).

The only thing that has really changed about the environment is that Body 3, “Crazy Background Radiation”, is now at 250K instead of 3K.

Note that the temperature of Body 3 is higher than before but lower than the equilibrium temperature of 255K calculated for “Chilly Earth” in the last model. As before, body 3 has an emissivity of 1 for longer wavelengths.

Body 1, “Warmer Earth”, still reflects 30% of solar radiation and is the same in every way as “Chilly Earth”.

What are we going to find?

We will do the same analysis as last time. Repeated in full to help those unfamiliar with this kind of problem.

Energy Absorbed from Body 2, “Sun”

The surface area that “captures” this radiation = πr² = 3.14 x 10⁶ m².

Energy absorbed from body 2, E_r2 = 958 x 3.14 x 10⁶ = 3.01 x 10⁹ W.

Energy Absorbed from Body 3, “Crazy Background Radiation”

Radiation from “Crazy Background Radiation” at 250K = 221 W/m². Apart from the very tiny angle in the sky for “Sun”, the entire rest of the sky is radiating towards the earth from all directions in the sky.

The surface area that “captures” this radiation = 4πr² = 1.26 x 10⁷ m². (See note 2).

Energy absorbed from body 3, E_r3 = 221 x 1.26 x 10⁷ = 2.78 x 10⁹ W.

In this case, energy from body 3 is comparable with body 2.

Energy Radiated from Body 1, “Warmer Earth”

Body 1 absorbs E_tot= E_r2 + E_r3 = 5.79 x 10⁹ W

For thermal equilibrium (energy in = energy out). “Warmer Earth” must radiate out 5.79 x 10⁹ W, from its entire surface area of 1.26 x 10⁷ m².

This equates to 460 W/m², which for a body with an emissivity of 1 (a blackbody) means T₁ = +27°C.

Discussion

Our two cases have revealed something very interesting.

A very very cold sky led to a surface temperature on our slightly different earth of -18°C, while a cold sky (colder than the original experiment’s planetary surface temperature) led to a surface temperature of 27°C.

Well, and here’s the thing, strictly speaking the temperature is actually caused primarily by the bright object in the middle of the picture, “Sun”. The energy absorbed from the sky just changes the outcome a little.

In both cases we calculated the equilibrium temperature by using the first law of thermodynamics (energy in = energy out).

If we do the calculation of entropy change we will find something interesting.. but first, let’s consider the conceptual model and what exactly is going on.

It’s very simple.

In a 3-body problem the temperature of the coldest body still has an effect on the equilibrium temperature of the body being heated by a hotter body.

I could make it more catchy, more media-friendly, but that would go against everything I stand for. I will call this Doom’s Law.

Entropy

The second law of thermodynamics says that entropy can’t reduce. The many cries of anguish that will now arise will claim that Model 3B has broken the Second Law of Thermodynamics. But it hasn’t.

See The Real Second Law of Thermodynamics for more on how to do this calculation. And even clearer, the article by Nick Stokes:

Change in entropy, δS = δQ / T

where δQ = change in energy, T = temperature

We will consider both models over 1 second.

Model 3A

Body 2, “Sun”, δS₂ = -3.85 x 10²⁶ / 5780 = -6.66 x 10²² J/K

Body 3, “Space”, δS₃ = 3.85 x 10²⁶ / 3 = +1.28 x 10²⁶ J/K

And finally, Body 1, “Chilly Earth”, δS₁ = 0 / 255 = 0 J/K

Total Entropy Change = δS₁ + δS₂ + δS₃ = +1.28 x 10²⁶ J/K :a net increase in entropy.

Model 3B

Body 2, “Sun”, δS₂ = -3.85 x 10²⁶ / 5780 = -6.66 x 10²² J/K

Body 3, “Crazy Background Radiation”, δS₃ = 3.85 x 10²⁶ / 250 = +1.54 x 10²⁴ J/K

And finally, Body 1, “Warmer Earth”, δS₁ = 0 / 255 = 0 J/K

Total Entropy Change = δS₁ + δS₂ + δS₃ = +1.47 x 10²⁴ J/K :a net increase in entropy.

Important points to note about the entropy calculation

Both scenarios increase entropy – by transferring heat from a high temperature source, “Sun”, to a low temperature source, “Space” in 3A, and “Crazy Background Radiation” in 3B (which is really also Space at a higher temperature).

The earth-like planet is sitting in the middle and doesn’t have a significant effect on the entropy of the universe.

In both cases the entropy of the system increases, so both are in accordance with the second law of thermodynamics.

The earth cools to space, but just at a slower rate when the background temperature of “space” is higher.

If we replaced “crazy background radiation” by an atmosphere that was mostly transparent to solar radiation, the analysis would be a little more complex but the result wouldn’t be much different.

Reasons Why It Might be Wrong

Just to be clear, these aren’t true..

1. The hotter body can’t absorb radiation from the colder body

a) see Amazing Things we Find in Textbooks – The Real Second Law of Thermodynamics for six textbooks on heat transfer which all say, yes it does. Actually, seven textbooks, thanks to commenter Bryan identifying his “non-cherrypicked” textbook by “real physicists” which also agreed.

b) see The Amazing Case of “Back Radiation” – Part Three which includes the EBEX experiment as well as a brief explanation of fundamental physics

c) see Absorption of Radiation from Different Temperature Sources – clearing up a few misconceptions on this idea

2. It’s not a real situation because the atmosphere isn’t a black body

It is true that the atmosphere is not a blackbody. But look back at model 3B. It doesn’t matter. Body 3 in this model could be a 250K body with an emissivity of 0.1 and the temperature would still increase over model 3A.

In fact, if the claim is that a colder body can never increase the temperature of a warmer body – all we need is one counter-example to falsify this theory. Now, if you want to modify your theory to something different we can examine this new theory instead.

Reasons Why It Has to be Right

1. The First Law of Thermodynamics. This neglected little jewel is quite important. Energy can’t disappear (or be created) or be quarantined into a mental box.

There is a reason why all the people disputing these basic analyses never explain where the energy goes (if it “can’t” go into changing the temperature of the hotter body that might have absorbed it). The reason – they don’t know.

2. The Second Law of Thermodynamics. This law says that in a closed system entropy cannot decrease. Despite angry claims about “no such thing as a closed system” – that’s what the second law says. Entropy is often simple to calculate.

If a solution uses simple radiation of energy (Stefan-Boltzmann’s law) and satisfies the first and second law of thermodynamics, and some people don’t like it, it suggests that the problem is with their conceptual model.

Conclusion

This is a conceptual model that is very simple.

The sun warms up the earth, and the earth cools to space. The colder “space” is, the faster the rate of net heat transfer. The warmer “space” is, the slower the rate of net heat transfer. And because the sun “pumps in” heat at the same rate, if you slow the rate of heat loss the equilibrium temperature has to increase.

The first law of thermodynamics is the key to understanding this problem. It is simple to verify that model 3A & 3B both satisfy the first law of thermodynamics. In fact, more importantly, a different result would contradict the first law of thermodynamics.

It is also easy to verify that in both 3A & 3B entropy increases.

Just to be clear on a tedious point, the earth and space do not have to radiate as a blackbody to have these conclusions. They just make the model simpler to explain, and the maths easier to understand. We could easily change the emissivity of the planet to 0.9 and the emissivity of space to 0.5 in both models and we would still find that Model 3B had a warmer planetary surface than Model 3A.

Many people will be unhappy, but this blog is not about bringing happiness. Clarity is the objective.

One more hopeless note of despair – this article uses simple theory to prove a point, which is actually a very valuable exercise. Next, some will say – “I don’t want that pointless over-theoretical theory, these people need to prove it with some experiments“.

And so I offer the series, The Amazing Case of “Back Radiation” as proof, especially Part Three. Result of Part Three was – “well, that can’t happen because it goes against theory“..

And so the circle is complete.

Notes

Note 1 – These strange conditions that don’t relate to the real world are to make the conceptual model simpler (and the maths easy). This is the staple of physics (and other sciences) – compare simple models first, then make them more complex and more realistic. If you can prove a theory with a simple model you have saved a lot of work and more people can understand it.

Note 2 – Solar radiation is from a tiny “angle” in the sky, and so the radiation is effectively “captured” by the earth as a flat disk in space. This area is the area of a disk = πr². By contrast, radiation from the sky is from all around the planet, and so the radiation is effectively captured by the surface area of the sphere. This area = 4πr². See The Earth’s Energy Budget – Part One for more explanation of this.

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Theory and Experiment – Atmospheric Radiation

Posted in Atmospheric Physics, Debunking Flawed "Science" on November 1, 2010| 106 Comments »

In New Theory Proves AGW Wrong! I said:

So, if New Theory Proves AGW Wrong is an exciting subject, you will continue to enjoy the subject for many years, because I’m sure there will be many more papers from physicists “proving” the theory wrong.

However, it’s likely that if they are papers “falsifying” the foundational “greenhouse” gas effect – or radiative-convective model of the atmosphere – then probably each paper will also contradict the ones that came before and the ones that follow after.

I noticed on another blog an article lauding the work of a physicist who reaches some different conclusions about the role of CO2 and other trace gases in the atmosphere.

This has clearly made a lot of people happy which is wonderful. However, if you want to understand the science of the subject, read on.

One of the areas that many people are confused by is the distinction between GCMs and the radiative transfer equations. Well, strictly speaking almost everyone who is confused about the distinction doesn’t know what the radiative transfer equations are.

So I should say:

Many people are confused about the distinction between GCMs and the effect of CO2 in the atmosphere

They are quite different. The role of CO2 and other trace gases is a component of GCMs.

Digression – As an analogy with less emotive power we could consider the subject of ocean circulation. Now it’s easy to prove theoretically that more dense water sinks and less dense water rises. We can do 100’s of experiments in tanks that prove this. Now if the models that calculate the whole ocean circulation don’t quite get the right answers one reason might be that the theory of buoyancy is a huge mistake.

But there could be other reasons as well. For example, flaws in equations for the amount of momentum transferred from the winds to the ocean, knowledge of the salinity throughout the ocean, knowledge of the variation in eddy diffusivity and tens – or hundreds – of other reasons. All we need to do to confirm buoyancy is to go back to our tank experiments.. End of digression.

Happily there is plenty of detailed experimental work to back up “standard theory” about CO2 and therefore prove “new theories” wrong.

Richard M. Goody

RM Goody was the doctoral advisor to Richard Lindzen. He wrote the classic work Atmospheric Radiation: Theoretical Basis (1964). I have the 2nd edition, co-authored with Y.L. Yung, from 1989.

Here are measured vs theoretical spectra at the top of atmosphere. Note that the spectra are displaced for easier comparison:

From Atmospheric Radiation, Goody (1989)

Click for a larger image

This extract makes it easier to see the magnitude of any differences:

From Atmospheric Radiation, Goody (1989)

Click for a larger image

Goody & Yung comment:

The agreement between theory and observation in Figs 6.1 and 6.2 is generally within about 10%. It is surprising, at first sight, that it is not better. Uncertainties in the spectroscopic data are partially responsible, but it is difficult to assign all the errors to this source. Local variations in temperature and departures from a strictly stratified atmosphere must also contribute.

The radiosonde data used may not correctly apply to the path of the radiation. The atmospheric temperatures could be adjusted slightly to give better agreement..

How was the theoretical calculation done? By solving this equation, which looks a little daunting, but I will explain it in simple terms:

Before we look in a little detail about the radiative transfer equations, it is important to understand that to calculate the interaction of the atmosphere and radiation, there are two parameters which are required:

the quantity of radiatively-active gases (like CO2 and water vapor) vertically through the atmosphere (affects absorption)
the temperature profile vertically through the atmosphere (affects emission)

If we have that data, the equation above can be solved to produce a spectrum like the one shown. The uncertainty in the data generates uncertainty in the results.

Given the closeness of the match, if a “new theory” comes along and produces very different results then there are two things that we would expect:

demonstrating the improvement in experimental/theoretical match
explaining why the existing theory is wrong OR under what specific circumstances the new theory does a better job

When you don’t see either of these you can be reasonably sure that the “new theory” isn’t worth spending too much time on.

Of course, the result from the great RM Goody could be a fluke, or he could have just made the whole thing up. Better to consider this possibility – after all, if a random person has produced a 27-page document with lots of equations it is very likely that this new person if correct, so long as they support your point of view..

Dessler, Yang, Lee, Solbrig, Zhang and Minschwaner

In their paper, An analysis of the dependence of clear-sky top-of-atmosphere outgoing longwave radiation on atmospheric temperature and water vapor, the authors provide a comparison of the measured results from CERES with the solution of the radiative transfer equations (using a particular band model, see note 1):

From Dessler et al (2008)

The authors say:

First, we compare the OLR measurements to OLR calculated from two radiative transfer models. The models use as input simultaneous and collocated measurements of atmospheric temperature and atmospheric water vapor made by the Atmospheric Infrared Sounder (AIRS). We find excellent agreement between the models’ predictions of OLR and observations, well within the uncertainty of the measurements.

Notice the important point that to calculate the OLR (outgoing longwave radiation) measurements at the top of atmosphere we need atmospheric temperature and water vapor concentration (CO2 is well-mixed in the atmosphere so we can assume the values of CO2).

For interest:

The uncertainty of an individual top-of-atmosphere OLR measurement is 5 W/m2 , while the uncertainty of average OLR over a 1-latitude 1-longitude box, which contains many viewing angles, is 1.5 W/m²

The primary purpose of this paper wasn’t to demonstrate the correctness of the radiative transfer equations – these are beyond dispute – but was first to demonstrate the accuracy of a particular band model, and second, to use that result to demonstrate the relationship between the surface temperature, humidity and OLR measurement.

So we have detailed spectral calculations matching standard theory as well as 100,000 flux measurements matching theory – at the top of atmosphere.

What about at the ground?

Walden, Warren and Murcray

In Measurements of the downward longwave radiation spectrum over the Antarctic plateau and comparisons with a line-by-line radiative transfer model for clear skies, the authors compare measured spectra at the ground with the theoretical results:

Antarctica - Walden (1998)

As you can see, a close match across all measured wavelengths.

I don’t remember seeing a paper which compares large numbers of DLR (downward longwave radiation) measurements vs theory (there probably are some), but I hope I have done enough to demonstrate that people with new theories have a mountain to climb if they want to prove the standard theory wrong.

Whether or not GCMs can predict the future or even model the past is a totally different question from Do we understand the physics of radiation transfer through the atmosphere? The answer to this last question is “yes”.

The Standard Approach – Theory

Understanding the theory of radiative transfer is quite daunting without a maths background, and as many readers don’t want to see lots of equations I will try and describe the approach non-mathematically. There is some simple maths for this subject in CO2 – An Insignificant Trace Gas? Part Three.

Consider a “monochromatic” beam of radiation travelling up through a thin layer of atmosphere:

Monochromatic means “at one wavelength”.

The light entering the layer at the bottom will be partly absorbed by the gas, dependent on the presence of any absorbers at that wavelength. The actual calculation of the amount of absorption is simple. The attenuation that results is in proportion to the intensity of radiation and in proportion to the amount of absorbers and a parameter called “capture cross section”. This last parameter relates to the effectiveness of the particular gas in absorbing that wavelength of radiation – and is measured in a spectroscopy lab.

There are complications in that the capture cross section of a gas is also dependent on pressure and temperature – and pressure varies by a factor of five from the surface to the tropopause. This just makes the calculation more tedious, it doesn’t present any major obstacles to carrying out the calculation.

That means we can calculate the intensity of radiation at that wavelength emerging from the other side of the slab of atmosphere. Or does it?

No, the problem is not complete. If a gas can absorb at a wavelength it will also radiate at that same wavelength.

Energy from radiation absorbed by the gas is shared thermally with all other gas molecules (except high up in the atmosphere where the pressure is very low) and so all radiatively-active gases will emit radiation. However, at the wavelength we are considering, only specific gases will radiate.

So the calculation for the radiation leaving the slab of atmosphere is also dependent on the temperature of the gas and its ability to radiate at that wavelength.

To complete the calculation we need to carry it out across all wavelengths (“integrate” across all wavelengths).

That calculation is then complete for the thin slab of atmosphere. So finally we need to “integrate” this calculation vertically through the atmosphere.

If you read back through the explanation, as it becomes clearer you will see that you need to know the quantity of CO2, water vapor and other trace gases at each height. And that you need to know the temperature at each height in the atmosphere.

Now it’s not a calculation you can do in your head, or on a pocket calculator. Which is why the many people writing poetry on this subject are usually wrong. If someone reaches a conclusion and it isn’t based on solving the equations shown above in the RM Goody section then it’s not reliable. And, therefore, poetry.

The Standard Approach – Doubling CO2

Armed with the knowledge of how to calculate the interaction of the atmosphere with radiation, how do we approach the question of the effect of doubling CO2?

In the past many people had slightly different approaches, so usually it is prepared in a standard way – explained further in CO2 – An Insignificant Trace Gas? Part Seven – The Boring Numbers.

The most important point to understand is that the atmosphere and surface are heated by the sun via radiation, and they cool to space via radiation. While all of the components of the climate are inter-related, the fundamental consideration is that if cooling to space reduces then the climate will heat up (assuming constant solar radiation). Which part of the climate, at what speed, in what order? These are all important questions but first understand that if the climate system radiates less energy to space then the climate system will heat up. See The Earth’s Energy Budget – Part Two.

Therefore, the usual calculation of the effect of doubling CO2 – prior to any feedbacks – assumes that the same temperature profile exists vertically through the atmosphere, along with the same concentration of water vapor. The question is then:

How much does the surface temperature have to increase to allow the same amount of radiation to be emitted to space?

See The Earth’s Energy Budget – Part Three for an explanation about why more CO2 means less radiation emitted to space initially.

The end result is that – without feedbacks – the surface will increase in temperature about 1°C to allow the same amount of radiation to space (compared with the case before CO2 was doubled).

The calculation relies on solving the radiative transfer equations as explained in words above, and shown mathematically in the extract from Goody’s book.

The “New Theory”

For reasons already explained, if someone has a new theory that gets a completely different result for the effect of more CO2, then we would expect them to explain where everyone else went wrong.

There is no sign of that in this paper.

For interested readers, I provide a few comments on the paper. The author is described as “John Nicol, Professor Emeritus of Physics, James Cook University, Australia”. Perhaps modesty prevents him mentioning the professorship in his own bio – in any case, he probably knows a lot of physics – as do the many professors of physics who have studied radiation in the atmosphere for many decades and written the books and papers on the subject..

In any case, on this blog, we weigh up ideas and evidence rather than resumés..

Here is his conclusion:

The findings clearly show that any gas with an absorption line or band lying within the spectral range of the radiation field from the warmed earth, will be capable of contributing towards raising the temperature of the earth. However, it is equally clear that after reaching a fixed threshold of so-called Greenhouse gas density, which is much lower than that currently found in the atmosphere, there will be no further increase in temperature from this source, no matter how large the increase in the atmospheric density of such gases.

So he understands the inappropriately-named “greenhouse” effect in basic terms but effectively claims that the effect of CO2 is “saturated”.

The paper’s advocate claimed:

..closely argued, mathematical and physical analysis of how energy is transmitted from the surface through the atmosphere, answers all questions..

– however, the paper is anything but.

There are some equations:

Planck’s law of blackbody radiation (p3)
Stefan-Boltzmann’s law of total radiation (p2)
Wien’s law of peak radiation (p3)
spectral line width due to natural broadening, doppler broadening and collision broadening (p7 &8)
density changes vs height in the atmosphere (p6)

These are all standard equations and it is not at all clear what equations are solved to demonstrate his conclusion.

He derives the expression for absorption of radiation (often known as Beer’s law – see CO2 – An Insignificant Trace Gas? Part Three). But most importantly, there is no equation for emission of radiation by the atmosphere. Emission of radiation is discussed, but whether or not it is included in his calculation is hard to determine.

Many of the sections in his paper are what you would find in a basic textbook (although line width equations would be in a more advanced textbook).

There are typos like the distance from the earth to the sun – which is not 1.5M km (p3). This doesn’t affect any conclusion, but shows that basic checking has not been done.

There are confusing elements. For example, the blackbody radiation curve (fig 1) for a 289K body, expressed against frequency. The frequency of peak radiation actually matches a wavelength of 17.6 μm, not 10 μm. (Peak frequency, ν = 1.7×10¹³ Hz, λ=c/ν = 3×10⁸/1.7×10¹³ = 17.6 μm. This corresponds to a temperature of 2.898×10^-3/λ = 165 K).

And comments like this suggest some flawed thinking about the subject of radiative transfer:

The black inverted curve shows the fraction of radiation emitted at each frequency which escapes from the top of the troposphere at a height of 10 km and thus represents the proportion of the energy which could be additionally captured by an increase of CO₂ and so contribute to the further warming of air in the various layers of the troposphere. It thus represents the effective absorption spectrum of CO₂ within the range of frequencies shown after accounting for collisional line broadening which provides a reduced but significant level of absorption even in the very far wings of the line which is represented in Figure 3 on page 6.

Why flawed? Because the radiation emitted from the top of the troposphere is made up from two components:

surface radiation which is transmitted through the atmosphere
radiation emitted by the atmosphere at different heights which is transmitted through the atmosphere

Because other parts of the paper discuss emission by the atmosphere it is hard to determine whether or not it is ignored in his calculations, or whether the paper fails to convey the author’s approach.

One interesting comment is made towards the end of the paper:

The calculations show that doubling the level of CO2 leads to an escape of only 0.75 %, a difference of 1.8 %. Thus, in this example where the chosen value of the broadening used is significantly less than the actual case in the atmosphere, an additional 6 Watts, from the original 396 Watts, would be retained in the 10 km column within the troposphere, when the density of carbon dioxide is doubled.

Now when we consider the effect of doubling CO2 the question is what is the “radiative forcing” – the change in top of atmosphere flux. The standard result is 3.7 W/m². (This is what leads to the calculation of 1°C surface temperature change prior to feedback).

It appears (but I can’t be certain) that Dr. Nicol thinks that the radiative forcing for doubling CO2 is even higher than the calculations that appear in the many papers used in the IPCC report. From his calculations he reports that 6W/m² would be retained.

On a technical note, although radiative forcing has a precise definition, it isn’t clear what exactly Dr. Nicol means by his value of “retained radiation”.

However, it does appear to conflict which his conclusion (extract reported at the beginning of this section).

There are many other areas of confusion in his paper. The focus appears to be on the surface forcing from changes in CO2 rather than changes in the energy balance for the whole climate system. There is a section (fig 6, page 21) which examines how much terrestrial radiation is absorbed in the first 50m of the atmosphere by the CO2 band at current and higher concentrations.

What would be more interesting is to see what changes occur in the top of atmosphere forcing from these changes, for example:

Longwave radiative forcing from increases in various "greenhouse" gases

This graph is from W.D. Collins (2006) – see CO2 – An Insignificant Trace Gas? – Part Eight – Saturation.

Note the blue curve. This graph makes clear the calculated forcing vs wavelength. By contrast Dr. Nicol’s paper doesn’t really make clear what surface forcing is considered – how far out into the “wings” of the CO2 band is considered, or what result will occur at the surface for any top of atmosphere changes.

It is almost as if he is totally unaware of the work done on this problem since the 1960’s.

It is also possible that I have misunderstood what he is trying to demonstrate or what he has demonstrated. Hopefully someone, perhaps even Dr. Nicol, can explain if that is the case.

Conclusion

Calculations of radiation through the atmosphere do require consideration of absorption AND emission. The formal radiative transfer equations for the atmosphere are not innovative or in question – they are in all the textbooks and well-known to scientists in the field.

Experimental results closely match theory – both in total flux values and in spectral analysis. This demonstrates that radiative transfer is correctly explained by the standard theory.

New and innovative approaches to the subject are to be welcomed. However, just because someone with a physics degree, or a doctorate in physics, produces lots of equations and writes a conclusion doesn’t mean they have overturned standard theory.

New approaches need to demonstrate exactly what is wrong with the standard approach as found in all the textbooks and formative papers on this subject. They also need to explain, if they reach different conclusions, why the existing solutions match the results so closely.

Dr. Nicol’s paper doesn’t explain what’s wrong with existing theory and it is almost as if he is unaware of it.

References

Atmospheric Radiation: Theoretical Basis, Goody & Yung, Oxford University Press (2nd ed. 1989)

An analysis of the dependence of clear-sky top-of-atmosphere outgoing longwave radiation on atmospheric temperature and water vapor, by Dessler et al, Journal of Geophysics Research (2008)

Measurements of the downward longwave radiation spectrum over the Antarctic plateau and comparisons with a line-by-line radiative transfer model for clear skies, Walden et al, Journal of Geophysical Research (1998)

Notes

Note 1 – A “band model” is a mathematical expression which simplifies the complexity of the line by line (LBL) solution of the radiative transfer equations. Instead of having to lookup a value at every wavelength the band model uses an expression which is computationally much quicker.

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Does Back-Radiation “Heat” the Ocean? – Part Two

Posted in Debunking Flawed "Science", Ocean Physics on October 23, 2010| 87 Comments »

In Part One we looked at how solar radiation and DLR (or “back radiation”) were absorbed by the ocean. And we had a brief look at how little heat would move by conduction into the deeper ocean if the ocean was “still”.

There were some excellent comments in part one from Nick Stokes, Arthur Smith and Willis Eschenbach – probably others as well – take a look if you didn’t see them first time around.

We will shortly look at mixing and convection, but first we will consider some absolute basics.

The First Law of Thermodynamics

How does the ocean sustain its (high) temperature? Every second, every square meter of the ocean is radiating energy. The Stefan-Boltzmann relationship tells us the value:

j = εσT⁴, where ε is the emissivity of the ocean (0.99), σ = 5.67 x 10^-8 and T is the temperature in K

For example:

if T = 20°C (293K), j = 415 W/m²
if T = 10°C (283K), j = 361 W/m²

Now, many people are confused about how temperatures change with heat imbalances. If, for some reason, more heat is absorbed by a system than is radiated/conducted/convected away – what happens?

More heat absorbed than lost = heat gained. Heat gained leads to an increase of temperature (see note 1). When the temperature of a body increases, it radiates, conducts and convects more heat away (see note 2). Eventually a new equilibrium is reached at a higher temperature. It is important to grasp this concept. Read it again if it isn’t quite clear. Ask a question for clarification..

Questions are welcome.

A Simple Model

Evaluating a very simple energy balance model might help to set the scene.

Here is the radiative input – solar radiation and “back radiation” from the atmosphere, with typical values for a tropical region:

The primary question – the raison d’êtra for this article – is what happens if only the solar radiation heats the ocean? And compared with if the back-radiation also heats the ocean?

It’s easy to find the basic equilibrium point using the first law of thermodynamics. All you need to know is the energy in, and the equation which links energy radiated with temperature.

For radiation, this is the Stefan-Boltzmann law cited earlier. The starting temperature for the ocean surface in this example was set to 300K (27°C). Depending on whether solar and back-radiation or just solar is heating the surface, here is the surface temperature change:

Notice the difference in the temperature trends for the two cases.

Now the model doesn’t yet include convective heat transfer from the ocean to the atmosphere (or movement of heat from the tropics to the poles), which is why in the first graph the temperature gets so high. Convection will reduce this temperature to a more “real world” value.

The second graph has only solar radiation heating the ocean. Notice that the temperature drops to a very low value (-15°C) in just a few years. Clearly the climate would be very different if this was the case, and the people who advocate this model need to explain exactly how the ocean temperature manages to stay so much higher.

By the way, if we made the “well-mixed layer”, d_mixed, of the ocean deeper it would increase the time for the temperature to change by any given amount. That’s because more ocean has more heat capacity. But it doesn’t change the fact of the energy imbalance, or the final equilibrium temperature.

The model is a very simplistic one. That’s all you need to demonstrate that DLR, or “back radiation” must be absorbed by the ocean and contributing to the ocean heat content.

Turbulence and the Mixed Layer

Let’s take a look at a slightly more complex model to demonstrate an important point. This simulation has four main elements:

radiation absorbed in the ocean at various depths, according to the results in Part One
conduction between layers in the ocean
convective heating from the ocean surface to the atmosphere, according to a simple model with a fixed air temperature

This model is not going to revolutionize climate models as it has many simplifications. The important factor – there is no convection between different ocean layers in this model.

Now conductivity in still water is very low (as explained in Part One).

The starting condition – the “boundary condition” – was for the temperature to start at 300K (27°C) for the first 100m, with the ocean depths below to be a constant 1°C.

The model is for illumination. Let’s see what happens:

The wide bars of blue and green are because the day/night variation is significant but squashed horizontally. If we expand one part of the graph to look at the first few days:

You can see that the day/night variation of the top 1mm and 10cm are significant.

Look back at the first graph which covers four years. Notice the purple line, 10m depth, the blue line, 3m depth; and the red line, 1m depth.

Why is the ocean 1-10m depth increasing to such a high temperature?

The reason is simple. This model is flawed– these results don’t occur in practice. (And yes, the ocean would boil from within..)

The equations that make up this model have used:

the radiation absorbed from the sun and the atmosphere (as described in part one)
the radiation emitted from the surface layer (the Stefan-Boltzmann equation)
conductivity transferring heat between layers

If these were the only mechanisms for transferring heat, the ocean 1m – 10m deep would be extremely hot in the tropics. This is because the ocean where the radiation is absorbed cannot radiate back out.

For a mental picture think of a large thick slab of PVC which is heated from electrical elements within the PVC. Because it is such a poor conductor of heat, the inner temperature will rise much higher than the surface temperature, so long as the heating continues..

The reason this doesn’t happen in practice in the ocean is due to convection.

If you heat a gas or liquid from below it heats up and expands. Because it is now less dense than the layer above it will rise. This is what happens in the atmosphere, and it also happens in the ocean. The ocean under the very surface layer heats up, expands and rises – overturning the top layer of the ocean. This is natural convection.

The other effect that takes place is forced convection as the wind speed “stirs” the top few meters of the ocean. Convection is the transfer of heat by bulk motion of a fluid. Essentially, the gas or liquid moves, taking heat with it.

Price & Weller (1986) commented:

Under summer heating conditions with vanishing wind, the trapping depth of the thermal response is only about 1m (mean depth value), and the surface amplitude is as large as 2ºC or 3ºC. But, more commonly, when light or moderate winds are present, solar heating is wind mixed vertically to a considerably greater depth than is reached directly by radiation: the trapping depth is typically 10m, and the surface amplitude is reduced in inverse proportion to typically 0.2ºC. Given that the surface heating and wind stress are known, then the key to understanding and forecasting the diurnal cycle of the ocean is to learn how the trapping depth is set by the competing effects of a stabilizing surface heat flux and a destabilizing surface stress.

Here are the results from a model with another slight improvement. This includes natural convection. The mechanism is very rudimentary at this stage. It simply analyzes the temperature profile at each time step and if the temperature is inverted from normal buoyancy a much higher value of thermal conductivity is used to simulate convection.

The “bumpiness” you see in the temperature profile is because the model has multiple “slabs”, each with an average temperature. This could be reduced by a finer vertical grid.

During the early afternoon with peak solar radiation, the ocean becomes stratified. Why?

Because lots of heat is being absorbed in the first few meters with some then transported upwards to the surface via convection – but while the solar radiation value is high this heat keeps “pouring in” lower down. However, once the sun sets the surface will cool via radiation to the atmosphere and so become less buoyant. With no solar radiation now being absorbed lower down, the top few meters completely mix – from natural convection.

I did have a paper with a perfect set of measurements to illustrate these points. It showed day/night and seasonal variation. Sadly I put it down somewhere. Many hours of hunting for the physical paper and for the file on my PC but it is still lost..

Note that the large variation of surface temperature (4-5°C) is just a result of the convective mixing element in the model being too simplistic and moving heat much faster than happens in reality.

Kondo and Sasano (1979) said:

In the upper part of the ocean, a mixed layer with homogeneous density (or nearly homogeneous temperature) distribution is formed during the night due to free convection associated with heat loss from the sea surface and to forced convection by wind mixing.

During the daytime, the absorption of solar radiation which occurs mostly near the sea surface causes the temperature to rise, and a stable layer is formed there; as a consequence, turbulent transport is reduced.

Daily mean depth of the mixed layer increases with the wind speed. When the wind speed is lower than about 7-8 m/s, the mixed layer disappears about noon but it develops again in the later afternoon. A mixed layer can be sustained all day under high wind speeds..

Conclusion

The subject of convection and oceans is a fascinating one and I hope to cover much more. However, convection is a complex subject, the most complex mechanism of heat transfer “by a mile”.

There are also some complexities with the skin layer of the ocean which are worth taking a closer look at in a future article.

This article uses some very simple models to demonstrate that energy radiated from the atmosphere is being absorbed in the ocean surface and affecting its temperature. If it wasn’t the ocean surface would freeze. Therefore, if atmospheric radiation increases (for example, from an increase in “greenhouse” gases), then, all other things being equal, this will increase the ocean temperature.

The models also demonstrate that conduction of heat on its own cannot explain the temperature profiles we see in the ocean. Natural convection and wind speed both create convection, which is a much more effective heat transport mechanism in gases and liquids than conduction.

Updates: Does Back Radiation “Heat” the Ocean? – Part Three

Does Back Radiation “Heat” the Ocean? – Part Four

References

Diurnal Cycling: Observations and Models of the Upper Ocean Response to Diurnal Heating, Cooling and Wind Mixing, James Price & Robert Weller, Journal of Geophysical Research (1986)

On Wind Driven Current and Temperature Profiles with Diurnal Period in the Oceanic Planetary Boundary Layer, Kondo and Sasano, Journal of Physical Oceanography (1979)

Notes

Note 1 – For the purists, heat retained can go into chemical energy, it can go into mechanisms like melting ice, or evaporating water which don’t immediately increase temperature.

Note 2 – For the purists, the actual heat transfer mechanism depends on the physical circumstances. For example, in a vacuum, only radiation can transfer heat.

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Amazing Things we Find in Textbooks – The Real Second Law of Thermodynamics

Posted in Basic Science, Debunking Flawed "Science" on October 7, 2010| 324 Comments »

Probably many, most or all of my readers wonder why I continue with this theme when it’s so completely obvious..

Well, most people haven’t studied thermodynamics and so an erroneous idea can easily be accepted as true.

All I want to present here is the simple proof that thermodynamics textbooks don’t teach the false ideas circulating the internet about the second law of thermodynamics.

So for those prepared to think and question – it should be reasonably easy, even if discomforting, to realize that an idea they have accepted is just not true. For those committed to their cause, well, even if Clausius were to rise from the dead and explain it..

On another blog someone said:

Provide your reference that he said heat can spontaneously flow from cold to hot. And not from a climate ‘science’ text.

I had cited the diagram from Fundamentals of Heat and Mass Transfer by Incropera and DeWitt (2007). It’s not a climate science book as the title indicates.

However, despite my pressing (you can read the long painful exchange that follows) I didn’t find out what the blog owner actually thought that the writers of this book were saying. Perhaps the blog owner never grasped the key element of the difference between the real law and the imaginary one.

So I should explain again the difference between the real and imaginary second law of thermodynamics once again. I’m relying on the various proponents of the imaginary law because I can’t find it in any textbooks. Feel free to correct me if you understand this law in detail.

The Real Second Law of Thermodynamics

1a. Net heat flows from the hotter to the colder

1b. Entropy of a closed system can never reduce

1c. In a radiative exchange, both hotter and colder bodies emit radiation

1d. In a radiative exchange, the colder body absorbs the energy from the hotter body

1e. In a radiative exchange, the hotter body absorbs the energy from the colder body

1f. This energy from the colder body increases the temperature compared with the case where the energy was not absorbed

1g. Due to the higher energy radiated from a hotter body, the consequence is that net heat flows from the hotter to the colder (see note 1)

The Imaginary Second Law of Thermodynamics

2a. – as 1a

2b. – as 1b

2c. – as 1c

2d. – as 1d

2e. In a radiative exchange, the hotter body does not absorb the energy from the colder body as this would be a violation of the second law of thermodynamics

Hopefully everyone can clearly see the difference between the two “points of view”. Everyone agrees that net heat flows from hotter to colder. There is no dispute about that.

What the Equations Look Like for Both Cases

Now, let’s take a look at the radiative exchange that would take place under the two cases and compare them with a textbook. Even if you find maths a little difficult to follow, the concept will be as simple as “two oranges minus one orange” vs “two oranges” so stay with me..

Here is the example we will consider:

Radiant heat transfer

We will keep it very simple for those not so familiar with maths. In typical examples, we have to consider the view factor – this is a result of geometry – the ratio of energy radiated from body 1 that reaches body 2, and the reverse. In our example, we can ignore that by considering two very long plates close together.

E₁ is the energy radiated from body 1 (per unit area) and we consider the case when all of it reaches body 2, E₂ is the energy radiated from body 2 (per unit area) and we consider that all of it reaches body 1.

We define E_net1 as the change in energy experienced by body 1 (per unit area). And E_net2 as the change in energy experienced by body 2 (per unit area).

Radiation Exchange under The Real Second Law

E₁ = εσT₁⁴; E₂= εσT₂⁴ (Stefan-Boltzmann law)

E_net1 = E₂ – E₁ = εσT₂⁴ – εσT₁⁴

E_net2 = E₁ – E₂ = εσT₁⁴ – εσT₂⁴

Therefore, E_net1 = -E_net2

Under The Imaginary Second Law

E_net1 = – E₁ = -εσT₁⁴

E_net2 = E₁ – E₂ = εσT₁4⁴ – εσT₂⁴

Therefore, E_net1 ≠-E_net2 ; note that ≠ means “not equal to”

This should be uncontroversial. All I have done is written down mathematically what the two sides are saying. If we took into account view factors and areas then the formulae would like slightly more cluttered with terms like A₁F₁₂.

In the case of the real second law, the net energy absorbed by body 2 is the net energy lost by body 1.

In the case of the imaginary second law, there is some energy floating around. No advocates have so far explained what happens to it. Probably it floats off into space where it can eventually be absorbed by a colder body.

Alert readers will be able to see the tiny problem with this scenario..

What the Textbooks Say

First of all, what they don’t say is:

When energy is transferred by radiation from a colder body to a hotter body, it is important to understand that this incident radiation cannot be absorbed – otherwise it would be a clear violation of the second law of thermodynamics

I could leave it there really. Why don’t the books say this?

Engineering Calculations in Radiative Heat Transfer, by Gray and Müller (1974)

Note that if the imaginary second law advocates were correct, then the text would have to restrict the conditions under which equation 2.1 and 2.2 were correct – i.e., that they were only correct for the energy gain for the colder body and NOT correct for the energy loss of the hotter body.

Heat and Mass Transfer, by Eckert and Drake (1959)

Note the highlighted area.

Basic Heat Transfer, M. Necati Özisik (1977)

Note the circled equations – matching the equations for the “real second law” and not matching the equations for the “imaginary second law”. Note the highlighted area.

Heat Transfer, by Max Jakob (1957)

Note the highlighted section, same comment as for the first book.

Principles of Heat Transfer, Kreith (1965)

Note the highlighted sections. The second highlight once again confirms the equation shown at the start, that under “the real second law” conditions, E_net1 = – E_net2. Under the “imaginary second law” conditions this equation doesn’t hold.

Fundamentals of Heat and Mass Transfer, Incropera and DeWitt (2007)

Note the circled section. This is false, according to the advocates of the imaginary second law of thermodynamics.

And the very familiar diagram shown many times before:

From "Fundamentals of Heat and Mass Transfer, 6th edition", Incropera and DeWitt (2007)

Conclusion

There are some obvious explanations:

1. Professors in the field of heat transfer write rubbish that is easily refuted by checking the second law – heat cannot flow from a colder to a hotter body.

2. Climate science advocates have crept into libraries around the world, and undiscovered until now, have doctored all of the heat transfer text books.

3. (My personal favorite) Science of Doom is refuted because these writers all agree that net heat flows from the hotter to the colder.

4. Look, a raven.

Relevant articles – The Real Second Law of Thermodynamics

Notes

Note 1 – Strictly speaking a hotter body might radiate less than a colder body – in the case where the emissivity of the hotter body was much lower than the emissivity of the colder body. But under those conditions, the hotter body would also absorb much less of the irradiation from the colder body (because absorptivity = emissivity). And so net heat flow would still be from the hotter to the colder.

To keep explanations to a minimum in the body of the article in 1e and 1f I also didn’t state that the proportion of energy absorbed by each would depend on the absorptivity of each body.

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Does Back-Radiation “Heat” the Ocean? – Part One

Posted in Basic Science, Debunking Flawed "Science", Ocean Physics on October 6, 2010| 45 Comments »

In the three part series on DLR (also known as “back radiation”, also known as atmospheric radiation), Part One looked at the network of stations that measured DLR and some of the measurements, Part Two reviewed the spectra of this radiation, and Part Three asked whether this radiation changed the temperature of the surface.

Very recently, on another blog, someone asked whether I thought “back radiation” heated the ocean. I know from a prominent blog that a very popular idea in blog-land is that the atmospheric radiation doesn’t heat the ocean. I have never seen any evidence for the idea. That doesn’t mean there isn’t any..

See note 1 on “heat”.

The Basic Idea

From what I’ve seen people write about this idea, including the link above, the rough argument goes like this:

solar radiation penetrates tens of meters into the ocean
atmospheric radiation – much longer wavelengths – penetrates only 1μm into the ocean

Therefore, solar radiation heats the ocean, but atmospheric radiation only heats the top few molecules. So DLR is unable to transfer any heat into the bulk of the ocean, instead the energy goes into evaporating the top layer into water vapor. This water vapor then goes to make clouds which act as a negative feedback. And so, more back-radiation from more CO2 can only have a cooling effect.

There are a few assumptions in there. Perhaps someone has some evidence of the assumptions, but at least, I can see why it is popular.

Solar Radiation

As regular readers of this blog know, plus anyone else with a passing knowledge of atmospheric physics, solar radiation is centered around a wavelength of 0.5μm. The energy in wavelengths greater than 4μm is less than 1% of the total solar energy and conventionally, we call solar radiation shortwave.

99% of the energy in atmospheric radiation has longer wavelengths than 4μm and along with terrestrial radiation we call this longwave.

Most surfaces, liquids and gases have a strong wavelength dependence for the absorption or reflection of radiation.

Here is the best one I could find for the ocean. It’s from Wikipedia, not necessarily a reliable source, but I checked the graph against a few papers and it matched up. The papers didn’t provide such a nice graph..

Absorption coefficient for the ocean - Wikipedia

Figure 1

Note the logarithmic axes.

The first obvious point is that absorption varies hugely with the wavelength of incident radiation.

I’ll explain a few basics here, but if the maths is confusing, don’t worry, the graphs and explanation will attempt to put it all together. The basic equation of transmission relies on the Beer-Lambert law:

I = I₀.exp(-kd)

where I is the radiation transmitted, I₀ is the incident radiation at that wavelength, d is the depth, and k is the property of the ocean at this wavelength

It’s not easy to visualize if you haven’t seen this kind of equation before. So imagine 100 units of radiation incident at the surface at one wavelength where the absorption coefficient, k = 1:

Figure 2

So at 1m, 37% of the original radiation is transmitted (and therefore 63% is absorbed).

At 2m, 14% of the radiation is transmitted.

At 3m, 5% is transmitted

At 10m, 0.005% is transmitted, so 99.995% has been absorbed.

(Note for the detail-oriented people, I have used the case where k=1/m).

Hopefully, this concept is reasonably easy to grasp. Now let’s look at the results of the whole picture using the absorption coefficient vs wavelength from earlier.

Figure 3

The top graph shows the amount of radiation making it to various depths, vs wavelength. As you can see, the longer (and UV) wavelengths drop off very quickly. Wavelengths around 500nm make it the furthest into the ocean depths.

The bottom graph shows the total energy making it through to each depth. You can see that even at 1mm (10^-3m) around 13% has been absorbed and by 1m more than 50% has been absorbed. By 10m, 80% of solar radiation has been absorbed.

The graph was constructed using an idealized scenario – solar radiation less reflection at the top of atmosphere (average around 30% reflected), no absorption in the atmosphere and the sun directly overhead. The reason for using “no atmospheric absorption” is just to make it possible to construct a simple model, it doesn’t have much effect on any of the main results.

If we considered the sun at say 45° from the zenith, it would make some difference because the sun’s rays would now be coming into the ocean at an angle. So a depth of 1m would correspond to the solar radiation travelling through 1.4m of water (1 / cos(45°)).

For comparison here is more accurate data:

From "Light Absorption in Sea Water", Wozniak (2007)

Figure 4

On the left the “surface” line represents the real solar spectrum at the surface – after absorption of the solar radiation by various trace gases (water vapor, CO2, methane, etc). On the right, the amount of energy measured at various depths in one location. Note the log scale on the vertical axis for the right hand graph. (Note as well that the irradiance in these graphs is in W/m².nm, whereas the calculated graphs earlier are in W/m².μm).

From "Light Absorption in Sea Water", Wozniak (2007)

Figure 5

And two more locations measured. Note that the Black Sea is much more absorbing – solar absorption varies with sediment as well as other ocean properties.

DLR or “Back radiation”

The radiation from the atmosphere doesn’t look too much like a “Planck curve”. Different heights in the atmosphere are responsible for radiating at different wavelengths – dependent on the concentration of water vapor, CO2, methane, and other trace gases.

Here is a typical DLR spectrum (note that the horizontal axis needs to be mentally reversed to match other graphs):

Pacific, Lubin (1995)

Figure 6

You can see more of these in The Amazing Case of Back Radiation – Part Two.

But for interest I took the case of an ideal blackbody at 0°C radiating to the surface and used the absorption coefficients from figure 1 to see how much radiation was transmitted through to different depths:

Figure 7

As you can see, most of the “back radiation” is absorbed in the first 10μm, and 20% is absorbed even in the first 1μm.

I could produce a more accurate calculation by using a spectrum like the Pacific spectrum in fig 6 and running that through the same calculations, but it wouldn’t change the results in any significant way.

So we can see that while around half the solar radiation is absorbed in the first meter and 80% in the first 10 meters, 90% of the DLR is absorbed in the first 10μm.

So now we need to ask what kind of result this implies.

Heating Surfaces and Conduction

When you heat the surface of a body that has a colder bulk temperature (or a colder temperature on the “other side” of the body) then heat flows through the body.

Conduction is driven by temperature differences. Once you establish a temperature difference you inevitably get heat transfer by conduction – for example, see Heat Transfer Basics – Part Zero.

The equation for heat transfer by conduction:

q = kA . ΔT/Δx

where k is the material property called conductivity, ΔT is the temperature difference, Δx is the distance between the two temperatures, and q is the heat transferred.

However, conduction is a very inefficient heat transfer mechanism through still water.

For still water, k ≈ 0.6 W/m.K (the ≈ symbol means “is approximately equal to”).

So, as a rough guide, if you had a temperature difference of 20°C across 50m, you would get heat conduction of 0.24 W/m². And with 20°C across 10m of water, you would only get heat conduction of 1.2 W/m².

However, the ocean surface is also turbulent for a variety of reasons, and in Part Two we will look at how that affects heat transfer via some simulations and a few papers. We will also look at the very important first law of thermodynamics and see what that implies for absorption of back radiation.

Update – Does Back-Radiation “Heat” the Ocean? – Part Two

Reference

Light Absorption in Sea Water, Wozniak & Dera, Atmospheric and Oceanographic Sciences Library (2007)

Notes

Note 1 – To avoid upsetting the purists, when we say “does back-radiation heat the ocean?” what we mean is, “does back-radiation affect the temperature of the ocean?”

Some people get upset if we use the term heat, and object that heat is the net of the two way process of energy exchange. It’s not too important for most of us. I only mention it to make it clear that if the colder atmosphere transfers energy to the ocean then more energy goes in the reverse direction.

It is a dull point.

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Evaluating and Explaining Climate Science

Archive for the ‘Debunking Flawed “Science”’ Category

A Mystery Equation

Conclusion

References

Notes

Thermodynamic Equilibrium and the Second Law of Thermodynamics

Non-Equilibrium

The Earth’s Surface and the Atmosphere

Energy Exchanges between the Earth’s Surface and the Atmosphere

Mathematical Proof

The “Almost” Identity

Oh No He’s Not Claiming This is Based on Kirchoff..

Hence the Atmospheric Window Cooling to Space Thing

Changing the Fundamental View of the World

Conclusion

References

Notes

The Anti-World Where Convection Is Misunderstood

First Misconception – Radiation Results are All Wrong Because Convection Dominates

Second Misconception – Atmospheric Physics Ignores Convection

Conclusion

References

First, is the Atmosphere Made of PVC?

Second, What if the Radiation from an Inner Surface CANNOT be Higher than from an Outer Surface

a) The Earth and Climate System

b) The PVC Sphere

Notes

Explaining How the Result is Calculated

The Power Station

How Does the Sphere Heat Up?

Conclusion

Model 2 – Two bodies – The Boring One that Everyone Really Does Agree With

Model 3A – Three Bodies with the Third Body Being Quite Cold

Model 3B – Three Bodies with the Third Body Being Somewhat Warmer

Discussion

Entropy

Reasons Why It Might be Wrong

Reasons Why It Has to be Right

Conclusion

Notes

Richard M. Goody

Dessler, Yang, Lee, Solbrig, Zhang and Minschwaner

Walden, Warren and Murcray

The Standard Approach – Theory

The Standard Approach – Doubling CO2

The “New Theory”

Conclusion

References

Notes

The First Law of Thermodynamics

A Simple Model

Turbulence and the Mixed Layer

Conclusion

References

Notes

What the Equations Look Like for Both Cases

What the Textbooks Say

Conclusion

The Basic Idea

Solar Radiation

DLR or “Back radiation”

Heating Surfaces and Conduction

Reference

Notes

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