Sunday, June 27, 2010

The AGW Myth of Back Radiation

Prior posts have shown intuitive examples that the theory of back radiation from greenhouse gases causing warming is fictitious, that NASA's Earth energy budget does not include back radiation at all (in stark contrast to the IPCC which shows it to be unidirectional and 95% of the solar input), and that at least 28 other analyses of the physics agree that back radiation can not cause additional increase in global temperature. The IPCC Earth energy budget was created by Kevin Trenberth, author of the climategate email stating "The fact is we can't account for the lack of warming at the moment and it is a travesty that we can't". Most likely, the reason the Trenberth/IPCC Earth energy budget can't account for the lack of warming is because warming from greenhouse gas back radiation doesn't exist.

Claes Johnson, professor of applied mathematics, KTH Royal Institute of Technology, Sweden, has a blog for those interested in the mathematics & physics of the atmosphere, and has a new post today which also finds the conventional greenhouse gas theory of back radiation or reradiation causing global warming to be fictitious:

AGW Myth of Reradiation:

AGW alarmism is  based on an idea of "reradiation" from an atmosphere with greenhouse gases, but the  physics of this phenomenon remains unclear. 

To test if  "reradiation" is a real phenomenon, we suggest the following experiment: On a night with moon-light so feeble that you can cannot read a newspaper, place yourself in front of a mirror letting the moonlight reflect from the newspaper to the mirror and back again, and check if you can now read. You will probably find that the paper is still unreadable as if the "reradiation" does not give more light.
To give this experiment theoretical support we consider the mathematics of wave propagation from a source at x=0 (Earth surface)  to a receiver at x=1 (atmospheric layer) described by the wave equation:

U_tt - U_xx = 0 for x in the interval (0,1)

with solution U(x,t) being a combination of waves traveling with velocity +1 and -1 along the x-axis, and with subindices indicating differentiation with respect to space x and time t. The boundary condition at the receiver may take the form

AU_t(1,t) + U_x(1,t) =0

with a positive coefficient A signifying:
  • A = 0: soft reflection with U_x(1,t) = 0
  • A large : hard reflection with U_t(1,t) = 0
  • A = 1: no reflection: transparent absorption of all incoming waves at x = 1.
The basic energy balance is obtained by multiplying the wave equation by U_t and integrating 
with respect to x to give:

K_t + AU_t(1,t)^2 = -U_x(0,t)U_t(0,t) = Input Energy.

where K(t) is the energy of the wave over the interval (0,1). Assuming that K(t) stays constant so that energy is no accumulating, we have that 

Output Energy = A U_t(1,t)^2 = Input Energy.

In particular, with soft reflection with A = 0, the Input Energy is also zero. We learn that  it is not possible to "pump the system" by reflection at x = 1: If you change from transparency with A = 1 to reflection with A = 0, the system reacts by refusing to accept Input Energy.

Ergo: Reflection/reradiation cannot increase the insolation to the Earth surface. 

[added note: insolation refers to the radiation energy received on a given surface area in a given time.]


  1. Take a look at the measurements of "back radiation", also known as DLR (downward longwave radiation):

    And at the spectrum of "back radiation":

    The "earth energy budget" has been the subject of papers for around a 100 years, it wasn't created by Kiehl and Trenberth.

    And for a simple explanation that everyone can understand, take a look at:

  2. Science of Doom,
    Thanks for your comment, and BTW I appreciate your website and its non-condescending tone to "dissenters."

    Now to address your comment, the fact that DLR can be measured by a sensor [which is most likely colder than the earth] does not refute the fundamental principle of the 2nd law of thermodynamics that a cold body cannot warm a hot body. Yes, this is difficult quantum "spooky action at a distance," but it is nonetheless fundamental to both 19th and 20th century physics.

    As to the violations of both the 2nd law and 1st law shown in multiple earth energy budgets, I welcome your point by point rebuttal of each example noted in the post:

    As to the last post you mentioned, Dr. Claes Johnson states:

    The math/physics of Dr. Phillips is simple and correct (without backradiation). If the transfer through the wall is by conduction only, then radiation through the wall is not an issue, only from the outside into emptiness.

    Alan Siddons also adds:
    I’d just point out that if you look at his various downwelling charts and compare them to your spreadsheet's values, you’ll see that radiation from the sky is less than what the surface would be radiating. DLR peaks when surface temperature peaks and reaches its nadir when the surface is coldest. Like I say, DLR is a distorted mirror image of surface radiance, a mirage. There can be exceptions, as when warmer air is brought in from another zone. That will affect what a detector sees. But on another day, the surface can be hot while the air above is cold, and that will affect what a detector sees too. The point is, a colder body cannot heat a warmer body - neither by conduction nor by radiation. Heating via back-radiation is a myth. What the earth radiates to space is equal to what it acquires from the sun. There’s no evidence of a layer (like a pane of glass) that separately emits equal quantities of radiation up and down. It's all going up.

  3. MS:

    You requested comment on the article you referenced.

    Violation of the 1st law:
    Assumes that GHGs can perpetually recycle IR from the earth’s surface and thereby ADD energy or work input to the system. Take a look at this University course diagram showing 239.7 W/m2 solar input, but somehow the GHGs are then capable of radiating 239.7 W/m2 BOTH UP AND DOWN FOR A TOTAL OF 479.4 W/m2!!!

    I created a simple example using radiation and conductivity which so far no one has even attempted to criticize. It's early days of course, and you are welcome to point out its flaws..

    You can see this at Do Trenberth and Kiehl understand the First Law of Thermodynamics?.

    In this simple example there is a heat source within a hollow sphere (out in space) of 30,000W and thick walls of PVC. The outer walls radiate 30,000W - of course - once equilibrium is reached. And yet the inner walls are hotter. In the specific example the inner walls radiate over 1,800,000W.

    Is energy created? No.
    It just appears so to people who haven't quite grasped what the first law really says.

    You see the energy into the system (in my example) is 30,000W.
    The energy out of the system is 30,000W.
    Therefore, no energy is created.

    But inside the system, an inner wall is much hotter and is therefore radiating at a much higher level.

    The reason why I expect much less criticism of it is everyone can see that it doesn't violate any physical laws because people are much more familiar with conductivity.

    The equations are all laid out there and are uncontroversial (very basic) thermodynamics.

    Well, it's not the earth's surface and atmosphere but joining the dots together is pretty simple.

    If you can criticize the K&T diagram for violating the 1st law of thermodynamics then you can criticize my example for the same violation.

    Take a look at the example, and the maths and see what you think.

    Then we can look at your 2nd law explanation..

  4. SoD,
    There are no problems with the mathematics of the analogy you chose. The problems, as I see it, are:

    1. The atmosphere cannot both behave like a PVC blackbody and an ideal gas
    2. A cold body still cannot heat a warm body. Your example merely calculates the inner wall radiation from the PVC blackbody and does not prove that this causes the central heat source to become hotter.
    3. The analogy is also inappropriate since the energy source is inside the blackbody, rather than outside the so-called atmospheric blackbody like the sun. One common misconception is that incoming sunlight does not contain significant IR, but in fact about 45% is IR and absorbed by GHGs before reaching the earth, which is another shortcoming of the energy balance diagrams.

    Also, do you have an explanation as to why the first simplified energy budget diagram I linked to (out of many similar examples) shows that the GHGs are capable of radiating twice the energy input from the sun?

  5. Let's stay on the 1st law of thermodynamics and let's review my example.

    The system in my PVC hollow sphere example receives 30,000W of energy and radiates out 30,000W of energy.

    And yet the inner wall radiates 1,800,000W - how can it generate this radiation? It must be violating the first law of thermodynamics and creating energy.

    Q1. Do you accept that my PVC hollow sphere is sound? (It sounds like you do but I would like to confirm it)

    Q2. If you accept that my PVC hollow sphere is sound then you are comfortable with a system which receives X W/m^2 and yet in an inner surface radiates 3X W/m^2 ?

    In your point 3 you say the analogy is inappropriate.

    The first law of thermodynamics isn't concerned with where the energy comes from when you consider a system. It just says energy can't be created or destroyed. Whether I have a tiny nuclear power source inside my sphere or an electric cable running through the wall - doesn't matter.

    You also said "One common misconception is that incoming sunlight does not contain significant IR, but in fact about 45% is IR and absorbed by GHGs before reaching the earth, which is another shortcoming of the energy balance diagrams."

    A common misconception of whom? If you are talking about the general public I'm sure you are right.
    But everyone in atmospheric physics knows this. It's in all the books.

    Take another look at the energy balance diagram. You will find that about 1/3 of the solar energy is absorbed by the atmosphere.

  6. Doom,
    1. what do you mean by "sound"? that the math is correct?
    2. where do you show that a surface that receives X Wm-2 radiates 3X Wm-2?
    3. my last point #3 was to show that the analogy is also inappropriate because the sun is external to the earth atmosphere system a slightly less absurd analogy would be to put the 30000W heat source outside the PVC cavity and put a clump of earth in the center and calculate the temp of that earth. Just goes to show that the atmosphere is not a one-way radiation valve or blackbody. As to your claim that the energy balance diagrams show 1/3 of incoming solar energy being absorbed by the atmosphere - the KT diagram shows it is only 67 Wm-2 or 19.6%, a far cry from the 45% IR content of incoming sunlight.

  7. I did think that your core argument was that a system receiving X W/m^2 couldn't have an internal surface radiating 3X W/m^2.

    I thought that an example showing that this can occur - in an easier to understand environment - would illustrate that your core claim was wrong.

    But I realize you are right. As my example is made out of PVC and the atmosphere is made out of gas the example shows nothing useful.

    Just to tidy up on a minor point - the average absorbed radiation from the sun in the climate system is 239W/m^2. The amount absorbed by the atmosphere is around 70W/m^2. How did Trenberth and Kiehl arrive at this?

    Because we measure it. We measure the spectrum of received radiation at the surface. And we see the amount of energy >0.7um. Of course, there isn't a large network of FTIR equipment so there is some uncertainty as to how this varies across the surface or the earth and through the seasons.

    Just because 50% of solar radiation is >0.7um doesn't mean that only 50% makes it to the surface.

    Take a look at the solar spectrum received at the earth's surface in-
    The Sun and Max Planck Agree

  8. SOD tries to justify CO2 as a major forcing gas and even claims it can back radiate to a hotter surface but this guy shows otherwise using the same tool that SOD does:

    Carbon Heat Trapping: Merely A Bit Player in Global Warming1
    Richard J. Petschauer, Senior Member IEEE

    Then there's this paper that has the Wood's experiment and a laser experiment that shows the same thing.

    The Greenhouse Effect: Origins,
    Falsification, & Replacement

    I've read reports of weather stations showing virtually no warming in the high polar latitudes when the IPCC claims there should be accelerated warming occurring thus the hype of melting polar ice. And the computer generating hot spot has not materialized in the equatorial areas that the IPCC 3rd or 4th AR predicted. The only global warming I've noticed it the heated hype from the mainstream media on weather and climate anomalies that probable went unnoticed before the age of modern media coverage.

    When the empirical data doesn't support the computer predictions it's time to go back to the chalk boards and analyze the real data, not the massaged or hyped data that GISS and CRU continually generate.