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Old 02-01-2014, 04:29 PM   #2307062  /  #1
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Old 02-01-2014, 04:30 PM   #2307063  /  #2
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Old 02-01-2014, 04:32 PM   #2307056  /  #3
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This is a continuation thread, the old thread is [split]61772[/split]
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Old 02-01-2014, 04:32 PM   #2307057  /  #4
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With a black planet and no atmosphere, the incoming solar radiation will warm the planet until it is radiating the same amount of energy out as is coming in. If the planet is rotating relative to the sun, in the evening, the outgoing energy will exceed the incoming energy as the planet radiates the heat it absorbed during the day, while in the morning, the incoming energy will exceed the output as the cool surface is re-warmed by the sun.

So there will be a lagged response, but the mean over the cycle will be energy in = energy out.

Add an atmosphere, and the equations are the same, except the lag is more complicated, and there's a lot of scattering, reflection, absorption and re-radiation going on in the atmosphere, all part of feedback loops that may both increase and reduce albedo.

But the bottom line of energy in = energy out over a cycle is going to stay the same, and if there is an increase in atmospheric absorption of outgoing radiation, then the mean global temperature will climb until equilibrium is restored.
But a more energetic system will lead to increased loss of atmosphere, especially the lighter bits like hydrogen from water vapour being broken down by UV high up in the column. Eventually, water stocks are going to dry up unless replenished by an ice comet or underground reserves. Then "Hello Venus"
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Old 02-01-2014, 04:54 PM   #2307092  /  #5
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But a more energetic system will lead to increased loss of atmosphere, especially the lighter bits like hydrogen from water vapour being broken down by UV high up in the column. Eventually, water stocks are going to dry up unless replenished by an ice comet or underground reserves. Then "Hello Venus"
The Earth has been a much warmer place than it is now for most if its history. Ice caps are relatively rare things yet did the atmosphere and all the water disappear into space while the atmosphere was so much more 'energetic' over all those aeons? Also, have a look at the atmosphere of Venus. It sports a surface atmospheric pressure two orders of magnitude higher than Earth and > 96% of it is CO2, so I don't think Earth/Venus comparisons are going to be very useful here.
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Old 02-01-2014, 05:11 PM   #2307112  /  #6
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But a more energetic system will lead to increased loss of atmosphere, especially the lighter bits like hydrogen from water vapour being broken down by UV high up in the column. Eventually, water stocks are going to dry up unless replenished by an ice comet or underground reserves. Then "Hello Venus"
The Earth has been a much warmer place than it is now for most if its history. Ice caps are relatively rare things yet did the atmosphere and all the water disappear into space while the atmosphere was so much more 'energetic' over all those aeons? Also, have a look at the atmosphere of Venus. It sports a surface atmospheric pressure two orders of magnitude higher than Earth and > 96% of it is CO2, so I don't think Earth/Venus comparisons are going to be very useful here.
Yeahbuut it is much closer. Can't remember exactly, but much more insolation per unit area than earth. Something went wrong with tectonics on Venus. Vulcanism can produce cloaking effects which if severe, can help reduce temps maybe even down to iceball conditions, depending on the arrangement of continents.
Warm, wet conditions will increase photosysnthesis, and this will put a higher O2 conc in the air, but it may also cause fires. But high O2, low Co2 also tends temps down. High albedo of white clouds, ice also will cool the system. Take away our ocean and will will not be "Venus" , but pretty close to it.

Likewise, if you pump Mars full of greenhouse gases, it will never be as warm as Earth, because GG's can only do so much -how much insolation is important too. of course, you would have to restock the oceans, but it is basiscally unstable because of the low grav. One would have to maintain the system by chucking ice-comets at it all the time. Add nitrogen from Neptume etc....
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Old 02-01-2014, 05:21 PM   #2307128  /  #7
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Another article. What do you all make of this? Not uber technical.

http://www.lrnit.com/GreenH_Eff.pdf

What is it saying, both collision and emission, or is it unclear?
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Old 02-01-2014, 05:25 PM   #2307136  /  #8
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No one is taking away your ocean - so I wouldn't sweat it.

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Old 02-01-2014, 06:42 PM   #2307220  /  #9
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Another article. What do you all make of this? Not uber technical.

http://www.lrnit.com/GreenH_Eff.pdf

What is it saying, both collision and emission, or is it unclear?
It's not entirely clear to me and looks like a pretty confused article - which isn't to say its wrong. The main message relevant to this discussion seems to be that absorption by unexcited CO2 molecules is unlikely and that we should think of it in terms of IR photon absorption in coincidence with molecular collisions. They describe that as a complex three body problem, which are mostly pretty intractable analytically, so they use precise spectroscopic lab measurements instead to inform their radiative transfer model inputs.

They say that absorbed photon energy is immediately transferred to the surrounding gas through collisions and that collisions excite molecular vibrational modes - ~ 5% at room temperature and it is these which radiate IR photons.

All up its trying to describe something complex in simple terms and winds up seeming a bit confused and contradictory.
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Old 02-02-2014, 03:52 AM   #2307462  /  #10
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Well I guess yer happy now, eh Febble? Lets go for a double.
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If the greenhouse effect was actually like the diagrams or crazy theory you hear about, you could just measure the amount of IR from every point in the sky, and show people what is happening. Especially at night, when it is clear and cloud free, when all that radiant energy is simply beaming out into space. You measure the IR from the surface, and then you measure it from a portion of the sky, multiply that by the amount of sky, and bingo, you have proof positive of how CO2 is re-radiating IR back to the surface.
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You aren't making any sense.
If you said, "I don't understand any of that", then your comment would be true. They actually do this, measure the radiation from a black body, exposed to the sky, shielded from the sun's direct rays, and calculate the amount of "back radiation", or IR coming from the clear sky. It's complicated, but the calculation shows how much energy is coming from the sky, re-radiated or radiated towards the surface. If that amount increases over time, it means there is more greenhouse effect happening.

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All up its trying to describe something complex in simple terms and winds up seeming a bit confused and contradictory.
Yeah, well welcome to climate science 101.
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Old 02-02-2014, 04:12 AM   #2307502  /  #11
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Quote:
Originally Posted by SR71 View Post
http://www.lrnit.com/GreenH_Eff.pdf

What is it saying, both collision and emission, or is it unclear?
Is there ANYTHING about this that is simple and clear?
Quote:
The molecules/atoms that constitute the bulk of the atmosphere; oxygen (O2), nitrogen (N2) and argon; do not interact with infrared radiation significantly. While the oxygen and nitrogen molecules can vibrate, because of their symmetry these vibrations do not create any transient charge separation. Without such a transient dipole moment, they can neither absorb nor emit infrared radiation.
So once again, with no greenhouse gases the "air" can heat up by direct contact with the surface, but it would be unable to emit any IR, so it would keep heating up forever, since warm air rises. The top of the atmosphere would be constantly warm. Clearly.

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thus carbon dioxide molecules can absorb IR radiation. Collisions will immediately transfer this energy to heating the surrounding gas. On the other hand, other CO2 molecules will be vibrationally excited by collisions. Roughly 5% of CO2 molecules are vibrationally excited at room temperature and it is this 5% that radiates.
Once again, that sounds like greenhouse gases directly warm the "air" they are mixed with. But only a few are radiating away energy from the other non greenhouse gases. Oh yeah, that really clears things up.
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Old 02-02-2014, 04:50 AM   #2307507  /  #12
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... what you don't get, while sitting the shade, is heating from the clear sky around you. In other words, there isn't heat coming from the sky, like an infrared mirror that sends heat your way.
Quote:
Originally Posted by Febble
... a little is re-radiated terrestrial IR from ghgs.
No, and this is something that is easy to measure, it you have never encountered it before. Point an IR sensor at a clear dry sky, and you will not get even a farction of the IR that comes from either the sun, or the heated surface. Dry air does not radiate "heat", and empty space is not sending IR from every part of the sky at you.

Of course something like this is easy to prove.
"Not even a farction" [sic]. I.e. ZERO. ZIP. NADA. ZILCH..., right?

But wait!
What's this?

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If you said, "I don't understand any of that", then your comment would be true.
No, not that. That's just F_X being the condescending dick that he is. I mean, what's this?
Quote:
They actually do this, measure the radiation from a black body, exposed to the sky, shielded from the sun's direct rays, and calculate the amount of "back radiation", or IR coming from the clear sky. It's complicated, but the calculation shows how much energy is coming from the sky, re-radiated or radiated towards the surface. If that amount increases over time, it means there is more greenhouse effect happening.
Why, it seems F_X may have learned something from our little discussion!
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Old 02-02-2014, 10:20 AM   #2307535  /  #13
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Quote:
Originally Posted by F X View Post
Quote:
Originally Posted by SR71 View Post
http://www.lrnit.com/GreenH_Eff.pdf

What is it saying, both collision and emission, or is it unclear?
Is there ANYTHING about this that is simple and clear?
Quote:
The molecules/atoms that constitute the bulk of the atmosphere; oxygen (O2), nitrogen (N2) and argon; do not interact with infrared radiation significantly. While the oxygen and nitrogen molecules can vibrate, because of their symmetry these vibrations do not create any transient charge separation. Without such a transient dipole moment, they can neither absorb nor emit infrared radiation.
So once again, with no greenhouse gases the "air" can heat up by direct contact with the surface, but it would be unable to emit any IR, so it would keep heating up forever, since warm air rises. The top of the atmosphere would be constantly warm. Clearly.
No. Clearly not.

For starters, air warmed by conduction from the earth also warms the air near by by conduction. In other words, by molecular collisions. As it does so, it cools. This is why you get convection currents. Air molecules near the sun-warmed surface gain translational kinetic energy which they transfer to other nearby molecules through collisions thereby losing some of their own. They will also tend to rise. As they rise they will meet more molecules to which their heat can be transferred by collision. Thus by the time they get very far up they will be considerably cooler than the stuff currently near the ground being warmed, and will tend to fall again.


So you are wrong that way for starters. And that's important, because it means that more the earth (water or land) is heated by the sun, the more the air near it is warmed, and the warmer the near-earth atmosphere becomes.

But as I understand it, I think you are wrong in a second way. Despite the fact that the translational kinetic energy of the air is dissipated (transferred to other molecules) as it rises, resulting in a net drop in temperature (second law of thermodynamics), nonetheless, air at the top of the column will be slightly warmer than it would be if the air at the bottom wasn't being heated.

And this air will indeed, as I understand it, radiate, as one of the smart guys pointed out - it will radiate at the low broad-band IR frequencies given by the translational movement of any molecular dipoles.
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Old 02-02-2014, 10:18 PM   #2307735  /  #14
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The Earth has been a much warmer place than it is now for most if its history. Ice caps are relatively rare things ...
And yet the ardent climate expert somehow knows that even a billion years ago, or 65 million years ago, a 2 million years ago, the sun was pretty much exactly the same as it is now.

And that the sun has little to do with the energy balance of the earth.
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Old 02-02-2014, 10:50 PM   #2307752  /  #15
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So what is your point, F X?

That the climate isn't warming? That it is is, but not due to human activities? That it is changing due to human activities, but not warming?

That there have been lots of changes over time, and so no reason to get worried about this one?

That actually things are getting cooler right now, and maybe we should increase our ghgs to warm it up a bit?

I'm just not sure what position you are taking here.

You seem to have got quite a lot of the science wrong, yet you seem to have some kind of overall position on the matter, and I'd like to know what that position is, and whether it has changed in light of what you have recently learned about the science?

Or do you think you haven't?
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Old 02-03-2014, 12:19 AM   #2307779  /  #16
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My position is the same one I usually take. Everybodies wrong, and shit isn't going down like anybody predicted, and people are stupid and selfish and I am skeptical of most everything.

Like this avoidance of water vapor in this thread. If it was only about CO2, then that should be the topic title. Not "greenhouse gases".

http://www.sciencedaily.com/releases...0202111055.htm

Read it and weep salty tears of joy.

Paper is here http://www.earth.huji.ac.il/data/Fil...g/GWetal13.pdf
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Old 02-03-2014, 12:53 AM   #2307781  /  #17
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Well, everybody probably is wrong, but your skepticism seems involve some pretty crass mistakes!

And no, the thread wasn't, and isn't, just about CO2, but answering the question wrt to CO2 should help with understanding the more complex case of H2O.

Are you now, at least, convinced that atmospheric CO2 re-radiates terrestrial infrared, and that this means that a little less than half of what it absorbs is returned to earth, rather than being lost to space as it would be if there were no CO2?
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Old 02-03-2014, 04:12 AM   #2307825  /  #18
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people are stupid and selfish and I am skeptical of most everything.
Except, apparently, anyone who tells you AGW is baloney.
Like Bob Carter.
Like Anthony Watts.
Like Roy Spencer.
Like Stephen Wilde.

Like Jerome ( ) , for that matter.
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Old 02-04-2014, 04:27 PM   #2308695  /  #19
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Quote:
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Are you now, at least, convinced that atmospheric CO2 re-radiates terrestrial infrared,
What do you mean by "terrestrial infrared"? CO2 does not absorb any radiation at all between 9 microns and 13 microns. Which is the IR range of 220K to 320 K, the temperature range of IR radiated by "the earth" that would warm the surface if re-radiated. (which is why WV is so important)

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Are you now, at least, convinced that atmospheric CO2 re-radiates terrestrial infrared, and that this means that a little less than half of what it absorbs is returned to earth, rather than being lost to space as it would be if there were no CO2?
See above.

CO2 does absorb and re-radiate at other bands, which is why it is credited with some of the greenhouse effect, but it doesn't effect the majority of IR that matters at ground level at all.

The small amount at 4.3 and 15 microns warms the upper atmosphere, not the surface. Remember the sun shines at those frequencies, and CO2 matters a lot more in the atmosphere where it is dry, due to the lack of greenhouse effect where WV is low.
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Old 02-04-2014, 05:13 PM   #2308726  /  #20
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Quote:
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Quote:
Originally Posted by Febble View Post
Are you now, at least, convinced that atmospheric CO2 re-radiates terrestrial infrared,
What do you mean by "terrestrial infrared"?
Infrared radiation emitted by the earth. Emitted because it is warmed by means of having absorbed solar radiation.

Quote:
CO2 does not absorb any radiation at all between 9 microns and 13 microns. Which is the IR range of 220K to 320 K, the temperature range of IR radiated by "the earth" that would warm the surface if re-radiated.
The spectrum of terrestrial IR radiation brackets the CO2 band.

Quote:

(which is why WV is so important)
H2O is important for many reasons.

Quote:
Quote:
Originally Posted by Febble View Post
Are you now, at least, convinced that atmospheric CO2 re-radiates terrestrial infrared, and that this means that a little less than half of what it absorbs is returned to earth, rather than being lost to space as it would be if there were no CO2?
See above.

CO2 does absorb and re-radiate at other bands, which is why it is credited with some of the greenhouse effect,
Yes.

Quote:
but it doesn't effect the majority of IR that matters at ground level at all.
[citation needed]

Quote:
The small amount at 4.3 and 15 microns warms the upper atmosphere, not the surface.
[citation needed]

Quote:
Remember the sun shines at those frequencies, and CO2 matters a lot more in the atmosphere where it is dry, due to the lack of greenhouse effect where WV is low.
Have you read this article, F X? It's very clear.
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Old 02-04-2014, 05:45 PM   #2308760  /  #21
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Quote:
Originally Posted by Febble View Post
Have you read this article, F X? It's very clear.
If it's "very clear" then you should be able to describe how it shows CO2 absorbing IR at the frequencies that earth radiates in.


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Old 02-04-2014, 05:48 PM   #2308766  /  #22
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That diagram shows clearly why CO2 is more important at high altitudes, where WV is low, or non existent.
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Old 02-04-2014, 05:57 PM   #2308771  /  #23
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Quote:
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That diagram shows clearly why CO2 is more important at high altitudes, where WV is low, or non existent.
What does this mean? What do you mean by "more important"?

CO2 is important because it is increasing as a result of human activity AND because it will result greater infrared flux at the earth's surface, resulting in greater heating of the land and oceans, and thus to warmer air, more water vapour in the air, and more energy in the troposphere.

Or do you disagree?
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Old 02-04-2014, 06:07 PM   #2308777  /  #24
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Quote:
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Quote:
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Have you read this article, F X? It's very clear.
If it's "very clear" then you should be able to describe how it shows CO2 absorbing IR at the frequencies that earth radiates in.
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Old 02-04-2014, 11:16 PM   #2309122  /  #25
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Quote:
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CO2 is important because it is increasing as a result of human activity AND because it will result greater infrared flux at the earth's surface, resulting in greater heating of the land and oceans, and thus to warmer air, more water vapour in the air, and more energy in the troposphere.
No, that is completly wrong. The effect of CO2 occurs high in the atmosphere, where water vapor is little to none.





In a moist atmosphere CO2 does almost nothing. The one place it has no overlap with WV is far too hot for any radiation coming from the surface of the earth. (recall the CO2 absorbing the candle flame heat)

The other band, where it overlaps with WV the WV overwhelms the CO2, so it is in the dry cold atmosphere that CO2 matters.
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