Simple Physics or Physics Simple?

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I often see the statement "co2 causes warming, its simple physics".

Firstly, I find it hard to believe the physics of the atmosphere are simple, physics is never simple - particularly at a planetary scale!

My understanding of the greenhouse effect is that it in fact ignores several laws of physics.

Firstly "greenhouse" is a misnomer as radiative forcing does not warm a greenhouse (even though glass absorbs infrared like co2), in fact the glass actually slightly cools a greenhouse over say panes of polished salt crystals (that don’t absorb infrared). The question is actually why is it cooler outside of the greenhouse? (greenhouse warm due to a lack of convection)

I understand the concept that Co2 in the troposphere (often incorrectly shown a blanket over the earth) absorbs a few narrow bands of infrared, and as it increases in the atmosphere it becomes more opaque to infrared until all the leaving infrared energy is eventually absorbed causing slightly increased emission (about the point we are at), but within the laws of physics this could not heat ground air, as it would have to flow against the actual heat flow. To enable co2 to warm surface air you have to essentially set thermal conductivity in the atmosphere to zero (an un-physical assumption) and assume local thermal equilibrium, ignoring the lower temperatures of the atmosphere above.

Or am I (or the IPCC) misunderstanding the effect? Common sense would actually say that as Co2 is present and greatest at the surface of the earth, the absorption would occur at or very close to the surface (rather than the troposphere) and would then be drawn upward to space via convection (as is observed in the temperature data available i.e. the surface is warming faster than the troposphere in contradiction to the IPCC models).

Co2 induced warming calculations basically assume the atmosphere is in a constant state of energy balance, but it is in fact in a constant state of flux and highly choatic.

Either way, to ignore physical effects such as radiative convection seems to me to an entirely un-physical representation of the “greenhouse” layer.

So is the “greenhouse” effect really simple physics, or is it physics simple?
Gnet, my understanding is that the atmosphere cools with altitude as the the pressure reduces with altitude
 
your grip on science is correct the 'green house,' effect is based on the emissions of the planet itself or the massive emission every hour of the day by humans, so the argument i am sure will go on and on, since there is such squabbles over the natural and the artificial.

so what is needed is the proper analysis of the amount of air bourne carbon, particulates and NOX, methane and so on and the proper test to see if heat is being repelled back to the planets surface and where all the energy that is being displaced and dissipated in the gas body or troposphere is actually going.
 
I'd have to say that the basic concept of greenhouse warming is pretty simple to understand. Of course, if you don't understand what a wavelength (wave) is or don't know the difference between infrared and visible light, then you'll have trouble understanding.

The physics goes something like this:

Solar heat reaches Earth in the form of visible and UV light. Some of this light is reflected back into space by clouds and light-scattering particles before it reaches Earth’s surface. Most of the light does reach Earth's surface, providing warmth for sunbathers and energy for photosynthesis in plants.

Once this energy warms the planet, it is then reflected off of Earth and back towards space in the form of longwave energy, or infrared light. Some of this infrared energy escapes into outer space, and some will be absorbed by molecules in the atmosphere. Most molecules in the atmosphere, such as nitrogen and oxygen, can not absorb this infrared energy. Greenhouse gases (CO2, H2O, and CH4) are "tuned" to absorb energy at infrared wavelengths. Absorbing energy "excites" these greenhouse molecules.

Because energy can neither be created nor destroyed, "excited" greenhouse gas molecules will gradually radiate its captured infrared energy as heat. Heat is radiated from "excited" greenhouse molecules into all directions; some of the energy is lost to space, some is directed downwards and warms earth's surface even more.

It is very rare that you will find someone that completely disagrees with modern physics properties such as the fact that CO2 and other gases act as greenhouse gases (capturing escaping infrared energy to then release as heat.) Earth has a natural greenhouse gas effect. It is true that if the atmosphere completely lacked greenhouse gases, then the global temperate would then be about 30°C (55° Fahrenheit) cooler. Water would be locked away as ice, and life would probably not be possible.
 
Common sense would actually say that as Co2 is present and greatest at the surface of the earth, the absorption would occur at or very close to the surface (rather than the troposphere) and would then be drawn upward to space via convection........

This would be in true in most cases, and I agree with you in the statement "Either way, to ignore physical effects such as radiative convection seems to me to an entirely un-physical representation of the “greenhouse” layer."

This "energy" so to speak that is absorbed by the CO2 layer, is the same as the energy received by photosynthetic organisms, and this is in turn translated into chemical energy, but what does this energy absorbed by the CO2 layer translate in to? If it is in fact thermal energy, then why doesn't this diffuse in turn to the upwards of our atmosphere?

In fact, the atmosphere above is cooler, and I don't remember why this is, because in sense it stands that heat rises, and heat reflected off the surface warms surface air and in turn this "heat" should warm the upper atmosphere as well. But the farther from the surface you get, the less radiance there is, therefor the less "heat" in the upper atmosphere. Also to assume that as pressure goes up, so does temperature, then the pressure of the upper atmosphere is greater than at the surface. However, the atmospheric composition changes through levels of the atmosphere. More Nitrogen composition comprises the upper atmosphere, keeping it much cooler? If this is true, should we be more worried about the amount of N in the upper atmosphere?

Ok I understand that. I was assuming pressure is GREATER with altitude, but now I do remember that pressure drops. But I am still wondering about the nitrogen composition also. While I understand a good bit of conceptual physics, I am not very knowledgeable in our atmosphere. I have studied the so called "ozone" layer some in the distant past. Global warming interests me when speaking in terms of facts, rather than just some news reporter showing a video of a once frozen tundra.

However, going by the fact that pressure is greater at the surface than to space, it makes sense that more "heat" would be present closer to the surface, and that thermal conductivity approaches a limit in relation to altitude. If you find anything else, email it to me if you be so kind. In the near future, I will try to find time on my own to research this and possibly get in touch with some old instructors for insight.

"Science is man's feeble attempt to explain the world around him"
 
why dont you try asking this question in the 'physics' section? or dont you want to have your pet theory explained away for you?
 
Pressure falls with altitude and under most conditions so does temperature. That's because lower pressure really means fewer particles to fill a given volume. Fewer particles mean more rapid heat loss. Radiative heat rises but cools as it encounters less pressure. As it rises it's replaced by cooler, descending air.

CO2 does not cause changes in temperature. In fact it's the opposite. Temperature changes lead CO2 changes, just as temperature dictates the amount (not percentage) of water vapor that the atmosphere is capable of holding. This is something that the IPCC and others have avoided talking about because it's a law that defies their logic and theory.
 
You are right it is not simple physics. There are a lot of misconceptions here and I will try to clear some of them up.

Generally the glass used in a green house (remember not all glass is equal and some have special coatings) is very reflective of IR. The purpose of the glass is to not allow radiative loss of IR. The visible and UV that is allowed in is for photosynthesis and there are additional non-radiative relaxations that cause heating. Not all heat is directly generated from the adsorption of IR.

I am not sure about your point of the troposphere. Why does the troposphere need to directly heat the ground air? Would not the increase in temperature in the troposphere mean that ground air has less ability to dissipate heat? Just using the most basic model on heat transfer, Newton's Law of Cooling, says that if the energy difference between the two regions is lower the rate of energy transfer would be lower. I see no laws of physics being broken.

I do not have knowledge of details of the atmospheric calculations. However on a global scale it would make sense that the overall system is in a state of quasi-equilibrium since we not seeing large changes in the overall average temperature on the earth. On a localized level, yes it would be chaotic. It actually sounds very similar to problems in statistical mechanics where things are random on molecular scale, but on a macro scale the properties are very predictable.
 
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