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31 October 2012

The Fallacy of the Greenhouse Effect 3


(Index)

In this part I rebut Joseph Fourier's 1827 paper Dissertation on the Temperature of the Terrestrial Globe and the Planetary Spaces, often attributed as being the first mention of an atmospheric greenhouse effect. 

Fourier does not in fact claim an atmospheric greenhouse effect for the earth; rather he offers a thought experiment that if our atmosphere were to have something like a layer of glass high in it, it would have a greenhouse effect.  The mention is very brief and the idea that such dense layers in the atmosphere could exist is not substantiated and is not pursued any further by Fourier, presumably because the notion is clearly unrealistic. 

Fourier did, though, contribute to the general notion of a greenhouse effect, by being (apparently) the first person to misinterpret how an actual greenhouse works.  In Fourier's opinion a glass greenhouse is heated by two mechanisms:

1) The blocking of convection.

2) The one way valve action of letting light in but trapping IR EMR on the way out (the "greenhouse effect").

In fact the first of Fourier's two mechanisms, the blocking of convection, is the only source of increased temperature in a greenhouse.  The second mechanism, the internal flux of EMR in an object, is unimportant to the energy content of it -- it cannot warm it.  In regards to EMR only the EMR emitted or received on the outside can change the temperature of an object.  

Thus there is no temperature gain from a greenhouse effect [1]. The top layer of glass emits as much EMR down as it absorbs up from the inside of the greenhouse.  There's no multiplication of energy by reverberating or from recycling EMR.

Consider two thermometers placed in the sun on the surface of the earth.  Over one thermometer place a plane of glass.  Over the other place none.  By not putting walls around the glass pane the warming due to the lack of convection in a greenhouse can be removed.  This leaves the heat-trapping/backradiation/greenhouse-effect part to be measured.




Figure 1: Thought experiment: two thermometers are placed in the sun.  One has a slight shadow over it due to the glass pane placed above it.  Which one will be warmer?
According to greenhouse theory the thermometer on the left will be warmer than the one on the right due to the backradiation/greenhouse-effect.  In reality the one on the right is warmer, thus proving that the blocking of convection is the only mechanism of warming in a greenhouse, not the alleged "greenhouse effect".

Does the thermometer with the glass pane over it become warmer than the one without a glass pane?  No it doesn't.  In fact the covered one is slightly cooler than the uncovered one due to the light that reflects off the glass.

The backradiation from the glass down to the thermometer doesn't multiply anything.  The glass's EMR is no more than the backradiation from the atmosphere; or the clouds; or the trees; or a park bench; or the grass for that matter.  

Mutual exchanges of EMR within any volume do not raise or lower the overall energy of that volume.  At this point in time, 1827, the laws of thermodynamics had not yet been formalised, so Fourier may have been unaware that the greenhouse mechanism he had proposed would be later regarded as being against both the first and second laws.

The greenhouse effect is against the first law because the temperature increase, often alleged to be 33C, entails getting extra energy.  In thermodynamics to get more heat, it means more energy and for that you need an energy source.  E.g. you would need: nuclear, solar, battery, or fossil fuel power; with these things you can get heat because of a definitely identified power source.  Greenhouse gases on the other hand, being passive, have no such energy source, so they can't raise the temperature of anything, earth included.

The universe came with a certain amount of energy built in.  No greenhouse gas can add to this energy; it can't trap energy or multiply it.  Over time the universe's potential energy is converted into other forms, especially EMR, and will eventually be evenly dispersed throughout.  This transition can be called an increase in entropy and is related to the second law.  

One interpretation of the second law is that EMR from a cooler object cannot be made to warm a warmer one[2].  In order to avoid the infinite heat death of the universe through mutual EMR, that is EMR which is exchanged between objects, mutual EMR must be considered to cancel, not to add.  In greenhouse theory,  the amount of EMR leaving the surface and the amount given back from the sky in "backradiation" are considered to add, not to subtract as they should.


 Figure 2: By counting recycled EMR twice you get magical free energy!


The EMR that originally came from the sun is absorbed by the ground and re-radiated upward.  This then gets trapped by greenhouse gases and comes down again to do more work, to be recycled.  Unfortunately for greenhouse theorists, it doesn't work that way.

In the introduction to his own translation of Fourier's paper, William Connelley suggests it could have been a transcription of a speech.  This could perhaps explain the repetitive nature of it; Fourier would mention a concept five or six times at various points, e.g. how when you dig a hole down into the earth the temperature rises with depth. 

Fourier's paper is primarily concerned with explaining why the earth is at the temperature it is.  If you are going to read it (be warned it's a frustrating read), I recommend Connelley's translation of it over Burgess' 1837 one.  Connelley also has a few footnotes worth reading.

Fourier's paper discusses three main causes of warming for the earth:

1)  Internal heat left over from its formation.

2)  Heat from distant stars and other celestial objects.

3)  Heat from the sun.

Fourier addresses issues like why the bottom of lakes and oceans are maintained at a temperature just above the freezing point of water, at water's maximum density of 4C.  I ask the same thing: why are the bottom of the oceans so cold?  Why doesn't it get warmer with depth like it does on land? 

Fourier proposes that the immense pressure at the bottom of such large bodies of water keeps the temperature down.  That doesn't sound right though. Why should pressure be able to destroy heat content, resulting in the lower temperature of the ocean bottoms?

In my opinion there is not an adequate explanation from Fourier, or from modern physics for that matter, for why the ocean bottoms should be in effect refrigerated.  In any event, Fourier concludes that earth internal heat makes no discernible contribution to the temperature at the surface, and is therefore dismissed.

In the case of heat from distant stars and other celestial objects, Fourier considers it to be significant, declaring the effective temperature of outer space to be -50C (-40 in octigesimal scale).  Fourier is off on this notion by about 220K. 

Modern estimates put the background temperature of space at a little above absolute zero, at 3K (-270C).  Connolley calls the Fourier space temperature claim silly (and yet he curiously buys Fourier's greenhouse story without question).  

The tone of Fourier's paper is authoritative and self-assured (again perhaps indicating it was a lecture and not a written paper).  This is surprising given that it is based on so few empirical observations.  Dig a couple of holes here and there, measure the temperature; get a bit of data from Saussure and his greenhouse experiments; and then just make up the rest and portray it as case closed.  It seems even at this early stage, poor scientific practice and belief in an atmospheric greenhouse effect, went hand in hand.

Fourier concludes that there are only two factors determining earth's temperature: 1) the -50C background radiation of space, and 2) heat from the sun.

In the end, Fourier doesn't claim that there's an atmospheric greenhouse effect.  But he does get the ball rolling on the idea because he erroneously thinks that an actual greenhouse is heated by upward flowing EMR being "trapped" on the way out by the glass ceiling.  Fourier also erroneously claims a similar heat trapping and multiplying effect for solid or liquid objects, e.g. the ocean.

Fourier started the greenhouse effect idea before the formalisation of the thermodynamic laws that negated it in 1850.  Though the concept is an egregious violation of these laws, the idea is remarkably popular even to this day.

(Index)

 

3 comments:

  1. When you drape a blanket over yourself on a chilly day - you don't add heat to your system, yet your body get's warmer.

    Following your logic that warming would be impossible
    since it would defy the Laws of Thermodynamics.

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    Replies
    1. Hi. No, the warming from an actual physical blanket, stops the dissipation of heat due to the physical, mechanical blocking of convection. Same for clouds; same for the glass ceiling of a greenhouse.

      And it depends on the fact that the human body is warmer than the outside air. If the converse situation arose, and the outside air was hotter than you, you could keep yourself cooled (for a time) with the same blanket. Can greenhouse gases work in the same way, to keep you cool?? (I suggest not.)

      A physical, human blanket blocks the movement of molecules, of convection, in two ways: "natural convection", like the Brownian motion of the air; and "current" or "thermal" convection (advection), in which currents of air flow and mingle.

      On the other hand, when EMR is trapped and re-radiated, you cannot get a similar energy trapping or multiplying effect.

      Finally, it is not my intention to use the supposedly "high and mighty" laws of thermodynamics as a club to beat over the head of true believers of the greenhouse effect. It's just that, unfortunately for believers, greenhouse theory is a not a valid method for creating energy.

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    2. In lighter term, you won't feel the cold because you're protected. But if you think the outside air is getting warmer, that is the time that you should free yourself from your cocoon. But as you said, this logic isn't possible with this issue. You're better off to be wise in the factors that contribute to the greenhouse effect.

      Sabrina @ EmeraldKnightConsultants.com

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