gslack
Senior Member
- Mar 26, 2010
- 4,527
- 356
I have explained this dozens of times, in a variety of ways, to you and your ilk. I cannot help but think that you are too dense to just pick it up easily and too obstinate to actually read for comprehension.
over and over and over again I have said that it is the sun that warms the surface, with atnospheric conditions adjusting the final equilibrium temperature. the net flow of energy and heat is always outwards towards space.
there are two types of backradiation. the first is temperature dependent blackbody radiation that would be present even without greenhouse gases. the second is GHG dependent by which certain wavelengths of surface IR radiation are stopped from exiting directly into outer space because they are absorbed and re-emitted in random directions, dispersing the energy into the atmosphere where it returns to the surface/finally escapes to space/or is added to the temperature of the atmosphere where it simply becomes part of the blackbody radiation. is that simple enough for you gslack? the atmosphere will always send backradiation to the surface because it is warm and gives off blackbody radiation. GHGs just add to that existing backradiation.
the surface gives off blackbody radiation according to its temperature. if there was no atmosphere it would simply exit into space, relative to (Tsur^4 - Tspa^4), where Tsur is surface temp and Tspa is space temp. if there is an atmosphere in place then the surface would give off radiation relative to (Tsur^4 - Tatm^4). because Tatm >> Tspa the power dissapated is much less. that difference is taken up into the heat sinks of the surface and atmosphere until the energy flowing out again matches the solar input but the surface is now at a higher equilibrium temperature.
planck curves somewhat representative of surface and atmosphere temperatures. the surface is emitting more radiation and at a slightly higher energy wavelengths. when it absorbs the radiation from the lower curve, the area between the two curves is the energy available to go through the atmosphere and exit into space. it is a visual explanation of the second law of thermodynamics, it shows why heat always goes from warm to cool. there is more radiation from the warmer body to the cooler body.
is this a complete or even a good model? not really, especially if the atmosphere was only N2 and O2. the surface radiation would mostly escape, but a significant amount of heat would still be passed to the atmosphere by conduction, which would be spread by convection. it is only when GHGs are added that surface radiation starts being dispersed and substantially removed from radiation loss. water is the main GHG but it also adds a new method of transporting latent heat above the near surface bottleneck by increasing convection as heat pipes (humid air is ligher and therefore rises, until it is cool enough for the water to change phase releasing heat which can now escape). CO2 takes another bite out of the planck curve, dissapating 15 micron IR and returning some to the surface.
it does not matter that the surface and especially the atmosphere are not true blackbodies. we are concerned only with disturbances to the equilibrium, the equilibrium that has already been in place using heat sinks, convection, conduction, latent heat, and radiation.
with no atmosphere heat transport and energy loss is 100% radiation driven. as you add an atmosphere conduction and convection become increasingly important in heat transport. when you add GHGs the ratios between conduction, convection, latent heat, and radiation change again. the radiation blocked by doubling CO2 does not necessarily all go into raising the surface equilibrium temperature, it is likely that much of it is just diverted into other transport mechanisms to get it high enough to escape. Trenberth's cartoon already shows that the minority of low altitude energy escapes as radiation, especially if you take out the 10micron atmospheric window. only 26W/m2 pinball through the lower atmosphere now, closing it down even further is not making a huge change.
just to be specific about gslack's statement that I am backpedalling on back radiation....all the radiation from the atmosphere directed at, and reaching, the surface is absorbed and used to offset the outward radiation from the surface, a la planck curves. because the net radiation is almost always towards the atmosphere, the movement of heat is away from the surface. the surface temperature may rise incrementally with addition of GHGs but that is only because the solar input is not being fully balanced by surface output reaching outer space. like I have said dozens of times but gslack never seems to be able to comprehend the idea of equilibriums being being based not only on inputs but outputs as well. that is why he and SSDD and others have so much trouble understanding why solar input is only 160W but surface output via heat sink is 400W (surface output not top of the atmosphere output, which is in balance with solar input).
Sorry I didn't respond till now. I'm doing my roof so I had zero free time till now...
LOL, so if it's now that back-radiation does not warm the surface further, even though you believe in its existence, what difference does it make? If it's there but does nothing to warm the surface, than it's a moot point Ian...
So which is it now? Seriously dude you're waffling big time.. Before you stated it's role in warming the planet as fact minus the extremists claims, hence your luke-warmer status. Now you claim it's their but ineffectual in warming the surface more...
SO wtf? Make up your damn mind already dude. This is exactly the kind of thing I talked about from you. Waffling when it doesn't fit your belief system... You know it's BS, or you know it's not, time to man up.. Pick a side and face the music, you will be right or you will be wrong. It's called a risk and everyone should be ready to take some...
If it were a simple matter of hyped-science only but a sound theory, there would be some thing made to harness this backradiation property by now, if only for the press and the ability to shut up skeptics.. It's a flawed theory and based on an incomplete one...
There IS backradiation... Has to be.. Photons don't decide where to go depending on the destination temperature. NET FLOW is upwards. Doesn't violate ANY damn principle.. The warming of the lower trop simply acts to SLOW DOWN the ENERGY transfered from the Gray Body Surface upwards.. Remember the diff between POWER (instantaneous) and ENERGY (over time).
You and ssdd are stuck on the paradigm that this means the net warming direction changes. It doesn't.. Take the sun out of the picture. Desert at night.
1) What is the surface COOLING profile (over time) on a cloudless night?
2) What is the surface COOLING profile (over time) on a cloudy night?
THere's your backradiation effect..
THe reason your backradiation oven doesn't work >>>>>>> --- there's NO NET DOWNWARD FLOW --- ever..
((OK maybe BRIEFLY LOCALLY with warmer air aloft and other weather transients. ))
Check the plug.. That's what an electronics engineer always does first..
No you are missing the point here. Net flow, or absolute, IF there is back-radiation yet it cannot warm it's source it's a moot claim as far as AGW theory goes. If the process slows heat loss as you just said, and Ian now claims (despite past claims to the contrary by him) than it's an insulator and NOT a secondary heating mechanism.
An insulator does not create more heat, it slows heat loss. Now if Ian's previous claim via Dr. Spencer and co. is to be believed, backradiation can produce additional warming of the source. IF Ian is now claiming that it doesn't warm the source more but only slows heat loss, which we claimed all along, then he is in fact backpeddling from his previous claims..
Thermal properties of gases (especially GH gases due to additional the molecular bonds), are directly effected by their temperature. Meaning more heat in, the faster it sheds that heat. Same thing in reverse, less heat in the better an insulator they are. Further, and at that same time Add heat, and convection increases, remove heat and convection decreases.
Air minus convection is a great thermal insulator, add convection and it's a great heat dissipation/transfer system. We aren't discussing solid, liquid, or a porous material with trapped air pockets inside here, we are discussing air moving relatively freely and able to convect heat away very well.
As I said before and will continue to say, the entire system is an excellent heat pump, with limited thermal insulating properties. Limited by air flow and the inherent thermal properties of gases.
Compress the gasses to the point they are near liquid, a different story. But they aren't here and so they react as gases do to heat.
You can call it "net flow" all you want, the fact remains if the "back-radiation" that is claimed is actually going on, and as you and Ian say it has no effect on the warmer source, than it's a moot claim..
All things radiate some amount of heat, yet that does not mean that radiated heat can warm it's warmer heat source. Call it phase differential, call it wavelength variance, call it magic for all I care, the point remains it doesn't effect noticeable change in it's source.
If you heat up a iron bar until it's red hot, and wrap it in a blanket, it will still cool down, slower than without the blanket, but it won't get hotter, it will cool.
That's the very reason we cannot create perfect or even near-perfect heat engines. The entire process would require infinite or near-infinite reusable energy from a source.
PS.. Before I forget again. You're forgetting the wave-like properties of EM radiation. You are doing what Ian and Spencer does and treating it as a particle only. As SSD pointed out before if it's a particle, it can flow back due to the shear space available to miss the incoming source particle. But if it's a wave than it is a wave and cannot flow back towards it's greater source. What we have in our understanding right now is wave-particle duality, meaning to our understanding it shows properties of both equally. Dismissing the wave property to suit a theory makes the theory dubious at best. As I said before, the entire system reacts and responds more like a heat pump than an insulator. The thermal properties of gases and convection alone would lead to this conclusion, add in the complete failure of climate modeling and predictions based on them, the failure of rises in GH gases to show additional warming in the last decade and a half, and then realize that 180 years of CO2 increases and we have not even a 2 degree rise in temps globally.. Yet every year in my state we go from 90 degree and up summers and 30 degree and below winters, and this drastic drop is due to our position relative to the sun. SOmething which warmers and luke-warmers claim to have less an impact on climate then a trace gas...
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