Sorry to come back to this, but it has been bugging me for days.
Joseph Postma posted a video on YouTube. He is top man and a "climate denier" but he has sadly fallen into the Alarmist traps of:
a) ignoring clouds, and
b) assuming that the Sun warms land and oceans and that they in turn warm the troposphere from below.
So he fights the Physics deniers on their chosen territory, splitting hairs over radiation theory and thermodynamics and so on, all of which are actually largely irrelevant.
I pointed out in the comments how the Greenhouse Effect actually dictates surface temperatures (cloud temp is fixed by sunshine; add on lapse rate x altitude of clouds = surface temperature) and a self-appointed Guardian Of The Galaxy (a True Believer and regular commenter at Science of Doom) tied himself in knots trying to come up with killer arguments. Apart from the usual ad hominems and meaningless jargon/waffle, the best he could come up with was this:
"The Sun heats the Earth and the lower atmosphere is heated by the Earth's surface... No physics supports top down warming when heat naturally rises."
Let's do the last stupid statement first. In everyday life and on a small scale, sure, hot air (from a fire, for example) moves up vertically. That's only because hot air wants to expand, so becomes less dense than the surrounding air, so gravity pulls the denser air down in its place and this in turn pushes up the less dense air. It's the density that is key - you could put a helium balloon in the freezer for a bit, it will still float upwards in much warmer air.
'Heat' itself doesn't rise, and certainly not 'naturally'. 'Heat' doesn't really do anything, it just a measure of thermal energy that moves from a hot object to a cold object. Put some polystyrene between them, hey presto, much less 'heat'.
When hot or warm air rises and expands, its temperature falls. It has the same amount of energy as before, but it gains as much potential energy equal as it loses in thermal energy. That is key to this, the TOTAL energy.
People always forget potential energy (mass x altitude x gravity), because it's not much practical use. You have to convert it to kinetic energy first to be able to harness it, i.e. allow water from a high reservoir to fall through turbines to generate electrical energy.
Now the first stupid statement, "The Sun heats the Earth". The Sun warms up whatever it hits first, which is clouds for two-thirds of sunshine. And it warms them the same as anything else, you can calculate the likely end temperature (effective temperature) using the Stefan-Boltzmann equation and it's around 255K. Let's say one-third of the sunshine actually directly hits Earth at ground or sea level, plus a bit more that gets through clouds, call it half in total, This is only sufficient to warm land and ocean surface to 234K. That can't warm something that must be at least 255K, can it?
[Question: if 'back radiation', which is emitted in all directions, can significantly increase the temperature of the land and ocean surface below it, why doesn't it increase the temperature of clouds above it by a similar amount? As a result of which they'd all evaporate?]
Third stupid statement: "The lower atmosphere is heated by the Earth's surface". They are to all intents and purposes the same temperature and are both warm for the same reason.
What actually happens is that clouds are a certain altitude and the Sun warms them to a certain temperature, which of course warms the surrounding air to the same temperature. Clouds are high up, so that air also has a lot of potential energy. Energy likes to spread out evenly, so the air lower down, which has less or no potential energy, has more thermal energy to balance it out. That is the whole basis for the dry lapse rate: gravity ÷ specific heat capacity. The Gas Laws just show that low and high temperatures will never equalise. Pressure falls faster than density as you go up, so temperatures have to fall as well as you go up. Temperature is proportional to pressure ÷ density all the way up.
To use a simple maths analogy, Dave is six inches taller than Jack; Jack is six inches shorter than Dave. That doesn't tell us how tall either is. If I tell you the height of one, then you know the height of the other. The lapse rate also works in both directions; cloud temp is fixed and surface temp is simply cloud temp + their altitude x lapse rate. It would be one heck of a series of coincidences if it worked the other way round and the surface temperature magically adjusted itself to be whatever is required to give a cloud temperature that is exactly what you would expect if you calculated cloud temperature on the basis of the sunshine they receive.
The Guardian Of The Galaxy then played what he thought was another trump card, saying that clouds are below freezing (duh, I kept saying that) and so they can't warm the land or ocean surface. It's not as simple as "clouds warm the surface", it's to do with energy (in all its forms) trying to spread itself out as evenly as possible. Radiation is a side show, that's just that portion of thermal energy that can't move in a more effective way i.e. by conduction. There is a big difference between holding your hand near a hot stove and actually touching it, thermal energy moves much faster by conduction! But while I'm on the subject, they keep saying that CO2 radiates at certain wavelengths - put those wavelengths into Wien's Displacement Law and you'll see that radiation from CO2 can't warm anything to more than about 200K, well below freezing. All of which is a side-show anyway.
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Is this really so difficult to understand?
Is there a proper physicist who can see a flaw in this logic (which works even better on Venus with 100% cloud cover; if surface temperatures there were purely due to 'back radiation', its atmosphere would have to amplify upwelling surface radiation several hundred times over. Our Alarmist twat insisted, unprompted by me, that "Radiative fluxes do not add, they average" which is not only contradicts his whole thesis but is complete bollocks anyway, it is far more complicated than that.)?
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