The Earths Energy Balance

I will now introduce a popular diagram showing the Earth’s Energy Budget [4].

You can see the 342 W/m2 incoming solar radiation in the top-centre of the picture.

We will now look at he next points in the CSIRO’s explanation.

Point 1

“Sunlight passes through the atmosphere, warming the earth’s surface.”

This point  is further expanded in another CSIRO information booklet [2] as follows:-

“The atmosphere (including its GHGs) is largely transparent to the Sun’s energy, most of which arrives in the form of light.”

This is a bit misleading. The implication is that Sunlight passes through the atmosphere un-impeded. This is obviously not true.

Of the 342 units of Sunlight reaching the Earth, 77 (or 22.5%) are reflected by the atmosphere – mainly by clouds. As well 67 units, or about 20%, are absorbed by the atmosphere (once again – mainly by clouds). This energy does not reach the surface of the Earth. 30 units or about 9% are reflected at the surface.

Of the original 342 units only 168 is available for “warming the earth’s surface.” The atmosphere is hardly “transparent to the Sun’s energy”.

Point 2:

In turn, the land and oceans release heat, or infrared radiation, into the atmosphere, thus balancing the incoming energy.

NO – once again this is misleading. The incoming 168 units of energy is balanced by outgoing convection and radiation. According to Kiehl and Trenberth’s model, 102 units of energy are released from the surface due to convection (air flow and latent heat), and 66 units by radiation. (This is obfuscated in the diagram – there is 350 + 40 upwards and 324 downwards = 66 upwards).

More heat is released from the surface of the Erath by convection then by radiation. this is important, why is it over looked?

Point 3:

Water vapour, carbon dioxide and some of the other trace gases absorb part of this radiation, allowing it to warm the lower atmosphere, while the remainder is emitted to space.

‘Part of this radiation’ that is ‘absorbed’ by GH gasses, means part of the 66 units radiated from the surface, (see above) not the 102 units of energy flow from the Earth by convection. This energy is not absorbed by these GH gasses.

It is not clear what is meant by “allowing it to warm the lower atmosphere”. There seems to be a common view that heat can flow from a cold atmosphere and warm the warmer surface of the Earth.  This proposition defies the second law of thermodynamics. Surely scientists at our leading scientific bodies understand basic thermodynamics?

A consequence of the second law of thermodynamics is that heat flows from a hot body to a cold body. Heat exchange between two bodies will cause the hotter body to cool and the colder body to warm until some equilibrium is reached. It is that simple; there is no known observation of heat flow causing cold bodies to increase the temperature of a hot body. This is a fundamental law.

Why then do we have this climate model where it is proposed that heat flowing from the cold atmosphere somehow raises the temperature of the warmer Earths surface. I have seen and read many wonderful explanations of how this happens. Usually it is something like the following:

“…the greenhouse gases in the atmosphere absorb some of the outgoing terrestrial (infrared) radiation and re-radiate infrared energy in all directions. There is thus now more radiant energy (short wave plus long wave) being absorbed by the ground and so it heats up further, by some tens of degrees, until the upward infrared emission just balances the total downward infrared and solar radiation…”[5] (BOM Publication, The Greenhouse Effect and Climate Change)

This reasoning shows a misunderstanding of heat flow and energy flow. It is probably easier to understand if we were to consider heat flow by convection.

Have you ever stood in front of an air-conditioner on a hot day. The surface of the air conditioner is cold. Air is forced over the surface and is blown toward you, cooling your face. Now, in this process the cold surface of the air conditioner warms, your warm face cools. Heat flow is from your face to the air-conditioner. But air flow is in the opposite direction. The air obviously has quite a bit of internal and kinetic energy. Air flows from cold to hot but the hot surface cools and the cold surface warms. The effective heat flow is in the opposite direction.

Lets look at an illustration from the Energy Budget diagram above. In the lower centre of the diagram are the arrows indicating heat flow by convection or air flow (Thermals and evapo-transpiration). But as everyone knows this mass flow is not just upwards. Rain and hail is one example of mas flow, and therefore energy flow, downwards. Does hail warm the surface of the Earth? No! Does hail have energy? Yes! So why doesn’t this energy increase the temperature of the Earth?

Unlike convection it is harder to comprehend exactly what radiation is. Can we picture radiation energy as photons, little balls of energy like miniature hail-stones? Or is it a wave like waves on the oceans or in a slinky spring like we used in high-school? All these ideas are just models to help us picture and maybe predict the behaviour of radiation. Whatever the model there is no reason to assume that it will not obey the second law of thermodynamics. “Cold” photons may flow downwards but heat will flow from hot to cold.

The statement “There is thus now more radiant energy (short wave plus long wave) being absorbed by the ground and so it heats up further” is fundamentally and demonstrably wrong.

Why is this flawed argument used by our ‘leading’ scientific bodies?

Are these the arguments that have convinced government to spend billions to curb “climate change”?

Next, I will look at what controls the temperature of the Earth

.

References

1. CSIRO Marine and Atmospheric Research, “The greenhouse effect Information Sheet”  accessed at http://www.cmar.csiro.au/e-print/open/holper_2001b.html

2. CSIRO publication “Climate And Greenhouse Gases, By Michael Raupach and Paul Fraser” accessed at http://www.publish.csiro.au/?act=view_file&file_id=CSIRO_CC_Chapter%202.pdf

4. Kiehl, J. T. and Trenberth, K. E., 1997 Bull. Amer. Meteor. Soc., 78, 197-208.

5. BOM Publication, The Greenhouse Effect and Climate Change, http://www.bom.gov.au/info/GreenhouseEffectAndClimateChange.pdf

4 Responses to The Earths Energy Balance

  1. markus says:

    Thank you W Stannard. I have only just discovered you and I really like your site. Science and cars too, love it.

    I’m only a lay person who is interested in the science of climate, with no formal education on the subject, I troll through many climate blogs and try and keep up with the latest developments.

    Your notations on the energy budget and radiation cleared up a fair bit of unknown for me. Thank you.

    I am finding it a bit difficult to conceptualize the reflection of 30 Wm/2 from the surface and the radiation of 40 Wm/2 from the surface. Of the 198 Wm/2 that gets through the stratosphere down to the surface and then the surface reflects and radiates just under half of the 198 Wm/2. I wonder how this much energy gets reflected or radiated back through the tropopause into outer space.

    Also, back radiation is perplexing, and it is probably the hardest to calculate. I’m surprised that so much gets back radiated to the surface. I’ll keep trolling.

  2. ndcodeblue says:

    “According to Kiehl and Trenberth’s model, 102 units of energy are released from the surface due to convection (air flow and latent heat), and 66 units by radiation. (This is obfuscated in the diagram – there is 350 + 40 upwards and 324 downwards = 66 upwards).

    More heat is released from the surface of the Erath by convection then by radiation. this is important, why is it over looked?”

    Net radiation balance =/= outgoing radiation…you have right there that it is 390Wm^-2 emitted by the surface.

    “It is not clear what is meant by “allowing it to warm the lower atmosphere”. There seems to be a common view that heat can flow from a cold atmosphere and warm the warmer surface of the Earth. This proposition defies the second law of thermodynamics. ”

    No, it does not violate the second law. The second law, in this respect, holds that there cannot be a net flow of heat from a cold to hot reservoir. Photons from a “cold” source do not reroute around a hotter object. The second law would be violated if there was a net flow from the atmosphere to the surface.

    I have a nice example. What do you do when you’re trying to go to sleep and your bedroom is cold? You pull a blanket over you. The blanket is initially “cold” and you are “hot”. You see where this is going…

  3. David, UK says:

    Thanks for this – I followed your link from your comment at WUWT. You appear to have made the same error that I myself made for many years – until I read an interesting essay by Jo Nova just a few months ago. First, here is your paragraph that I refer to:

    It is not clear what is meant by “allowing it to warm the lower atmosphere”. There seems to be a common view that heat can flow from a cold atmosphere and warm the warmer surface of the Earth. This proposition defies the second law of thermodynamics. Surely scientists at our leading scientific bodies understand basic thermodynamics?

    Yes, if you have two bodies, one cooler than the other, the cooler one cannot cause the warmer one to become warmer still. Second law, as you say. HOWEVER (and this is the bit I was forgetting until recently) bear in mind: a) heat energy between the two bodies does flow in both directions. Obviously the net result is that more energy passes from the warmer body to the cooler body (than vice versa) hence we see a warming of the cooler body and a cooling of the warmer one. OK, so far so much in agreement (I hope). Then b) What if we run the experiment again, but this time the cooler body is, say a couple of degrees warmer (but still cooler than the warm body)? Obviously the warmer one will still pass more energy to the cooler one than it receives back, hence we see net warming of the cool one and net cooling of the warm one. BUT the net transference of energy will be less and slower.

    In simple terms: increased energy coming from the cooler body will slow down energy loss from the warmer body.

    So, the idea of relatively cool GHGs radiating energy back to a warmer earth “causing it to warm” – well, a more accurate description would be “causing it to cool more slowly and less” but in short it doesn’t really violate the second law. Another practical example: hold an ice cube near your face, and feel the heat rushing from your face (in return for little energy back from the cube!). Now switch a cube of room-temperature chocolate in place of the ice. The chocolate is still way cooler than your face, but because it is warmer than the ice it will (in terms of net result) sap less warmth from your face.

    I might add that none of this is cause for climate alarmism. This earth hasn’t survived the last few billion years by being ultra-sensitive to the tiniest changes. And the idea of such a minor GHG as CO2 driving such a major GHG as H2O (the positive feedback hypothesis) is, to me, nonsense, like Hansen and his tipping points.

    • wstannard says:

      Hi David and thanks for a well reasoned comment. I agree whole heartedly with your last paragraph and especially the positive feed back nonsense. I am going to write something on this soon.

      You said “heat energy between the two bodies does flow in both directions”. At his point I can see that you haven’t sat through a Thermodynamics class for some time. A lot of effort is spent trying to explain the difference between heat and energy.
      Will you consider this.. take a bucket of ice. Although ice is relatively cold it contains a lot of energy – (thermal, chemical, nuclear.. e = mc2..). If you drop this ice into a bucket of hot water what happens? Well energy has flowed from the bucket of ice to the hot water. But heat flows from the hot water to the ice…

      Otherwise I agree with you comments. The flow of heat from the surface of the Earth may be impeded by the composition of the atmosphere. This is known as the “GH effect”. However my main point is that this radiative heat flow from the surface is relatively small compared to the energy (whoops, heat) that is radiated to space by the atmosphere. The atmosphere received this energy by convection from the surface and also directly from the sun – sidestepping radiation from the surface and the GH effect! This flow to space is enhanced by “GH gasses” in the atmosphere.

      I postulate = the net result of GH gasses is to cool the Earth!

      Cheers

      Waz

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