Merged Global Warming Discussion II: Heated Conversation
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r-j
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You can be sure it has not. In fact, the question has never been asked before.
No, the answer does not appear in the link http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap7.html
r-j
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We all know that. It's what makes it hard to describe "what is happening", because most of the air is N2 and O2, when I say "the air", in regards to the atmosphere, I am talking about the non-greenhouse gases.
But even that doesn't completely solve the communication problem. If CO2 just re-radiates the IR, can you say it has warmed? If it keeps a steady temperature, rather than "keeping the heat", (which I know isn't a scientific term), then it isn't warming. If it does warm, rather than re-radiating the energy, then it will rise, as it now is warmer than the surrounding "air". So it can't be somehow warming more than the O2 and N2, or it wouldn't be a well mixed gas.
It's all very complicated, especially for somebody as slow as myself.
aleCcowaN
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You missed one thing and the chart may have led you to some misunderstanding.
r-j is stuck in CO2, IR and greenhouse effect and moving the goalposts to say that "the important thing" is farther in the physical path of the re-emitted IR -take into account that his story will evolve accordingly to which part shows any motion and where a spanner (monkey wrench) is needed to be thrown-. In that analysis, nothing have to do IR emissions as a consequence of short-wave radiation passing through the atmosphere.
The chart is an oversimplification. "Radiation is converted to heat energy, causing the emission of long-wave (IR) radiation back to the atmosphere" is meant as a process that happens in land and ocean, not in the atmosphere. Of course, there are several processes by which short-wave radiation is absorbed in the atmosphere and re-radiated as IR. Let's then talk about them as they are not depicted in that figure.
Short-wave radiations is absorbed in the atmosphere mainly in these three ways:
Ozone in the stratosphere absorb a deal of ultraviolet and a tiny part of visible in the range of about 5100 to 6800 Angstroms. That happens mainly when the sunbeams enters the atmosphere and only residually with the part reflected.
Water vapour in the troposphere absorbs in the end of visible and near infrared (about 7000 to 40000 Angstroms). Not all of it is absorbed, but there's a great deal of absorption.
Most of aerosols -dust, soot particles, etc.- are heated by the sunbeams they intercept and these particles re-radiate IR into the atmosphere and out into space. In this case, the effect is mostly with incoming short-wave radiation and the result is more a dimming effect than a warming one. You can "perceive" this effect of aerosols by watching the reddened skies at dawn showing the scattered rays, and imagining the portion of that energy that is not reflected into that redness and you're not seeing but it is absorbed as sensible heat.
To avoid any confusion in the future be sure we're are speaking of the greenhouse effect and the IR comes from the surface or the atmosphere itself -clouds, aerosols- and not from the Sun itself. Keep in mind that water vapour acts both in the incoming and outgoing spectra, but with a quite different distribution of energy densities.
r-j
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Oh that's just great! Now you have me thinking about the entire thing from the other side. If CO2 only re-radiates IR, and doesn't heat the surrounding "air" (N2 and O2 molecules), then that means it is causing the incoming IR from the sun to be re-radiated back into space, just as it causes the surface generated IR to be re-radiated back towards the surface.
An increase in CO2 would mean less IR from the sun will even make it to the surface. So there will be less IR to start with, heating the surface of the earth. So less warmth from incoming sunlight, but more warmth from outgoing IR.
Which sounds completely insane.
OK excuse me, my head is going to explode now.
citizenzen
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Thank you for the clarification.
Looking further into the question of how various air molecules react to IR I found ...
This would not appear to be the case. Please see quote above.
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r-j
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OK now I am even more confused. If CO2, or water vapor absorbs IR coming from the earth, it would also absorb it coming from the sun. Since about half the sun's energy reaching the stratosphere is IR, then CO2 is going to play much more of a role in the absorption of IR coming in, as water vapor is virtually non existent at that altitude, while CO2 can keep increasing there.
So CO2, and especially an increase will have more of an effect on incoming IR than any change in water vapor.
Damn it, my head is going to explode again.
r-j
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That certainly seems to say that CO2 causes warming of N2 and O2 by kinetic energy transfer!! Which means CO2 warms the air around it, it doesn't just re-radiate the IR away.
Nice find there!
citizenzen
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Hey, just a quick question. Just to preface it, I mostly lurk in this thread because I'm learning more than I'm teaching here, and don't pretend to be an authority on AGW.
On another board, I'm talking to someone who's asked what the origins are of the nearly 100% (can't recall if it's 93% or 97%) figure cited (we've all seen the figure) of climate scientists who accept AGW, versus those who challenge it. The poster is trying to prove that anyone - like me - who brings up the number is appealing to authority, and that the consensus doesn't matter.
Does anyone know how that number was calculated?
On another board, I'm talking to someone who's asked what the origins are of the nearly 100% (can't recall if it's 93% or 97%) figure cited (we've all seen the figure) of climate scientists who accept AGW, versus those who challenge it. The poster is trying to prove that anyone - like me - who brings up the number is appealing to authority, and that the consensus doesn't matter.
Does anyone know how that number was calculated?
DC
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from diffreent studies and surveys.
http://en.wikipedia.org/wiki/Scient...rveys_of_scientists_and_scientific_literature
r-j
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Oh thank you! My head was exploding left and right. Now we can return to the unscientific discourse once again.
As for how much IR is reaching our atmosphere, are you kidding me? You don't know how to Google? And why wouldn't you already know this figure?
r-j
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Really? It's in the Encyclopedia Britannica, under the article on Infrared Radiation. I'm sure it's online as well.
I first found this on NASA's climate site:
http://climate.nasa.gov/scientific-consensus
It quotes the 97% consensus figure, which by itself, doesn't help me. Lots of people quote the figure. So, fortunately, they do so with a citation. Clicking on that citation links me to these three publications:
<W. R. L. Anderegg, “Expert Credibility in Climate Change,” Proceedings of the National Academy of Sciences Vol. 107 No. 27, 12107-12109 (21 June 2010); DOI: 10.1073/pnas.1003187107.
Abstract
Although preliminary estimates from published literature and expert surveys suggest striking agreement among climate scientists on the tenets of anthropogenic climate change (ACC), the American public expresses substantial doubt about both the anthropogenic cause and the level of scientific agreement underpinning ACC. A broad analysis of the climate scientist community itself, the distribution of credibility of dissenting researchers relative to agreeing researchers, and the level of agreement among top climate experts has not been conducted and would inform future ACC discussions. Here, we use an extensive dataset of 1,372 climate researchers and their publication and citation data to show that (i) 97–98% of the climate researchers most actively publishing in the field surveyed here support the tenets of ACC outlined by the Intergovernmental Panel on Climate Change, and (ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.
P. T. Doran & M. K. Zimmerman, "Examining the Scientific Consensus on Climate Change," Eos Transactions American Geophysical Union Vol. 90 Issue 3 (2009), 22; DOI: 10.1029/2009EO030002.
N. Oreskes, “Beyond the Ivory Tower: The Scientific Consensus on Climate Change,” Science Vol. 306 no. 5702, p. 1686 (3 December 2004); DOI: 10.1126/science.1103618.
I was able to find an abstract on 1 of the 3 publications. I found the other 2 quite frequently cited by other publications, but not to such a degree that I could learn the methodology used to arrive at the number.
Can anyone here provide more help?
DC
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we could give the same answer to your questions.....
very telling....
http://curry.eas.gatech.edu/Courses/6140/ency/Chapter3/Ency_Atmos/Radiation_Solar.pdf
that is how it's done when someone asks you for a source.
DC
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r-j
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http://curry.eas.gatech.edu/Courses/6140/ency/Chapter3/Ency_Atmos/Radiation_Solar.pdf
That is a pretty good source, but it says "Of the radiant energy emitted from the Sun, approximately 50% lies in the infrared region ", which isn't the same as stating the percentage that reaches the stratosphere.
Not that it matters, the issue is what happens when CO2 (and the other GhGs) interact with the IR coming from the sun. It would seem it warms up the atmosphere is what it does.
That is a pretty good source, but it says "Of the radiant energy emitted from the Sun, approximately 50% lies in the infrared region ", which isn't the same as stating the percentage that reaches the stratosphere.
Not that it matters, the issue is what happens when CO2 (and the other GhGs) interact with the IR coming from the sun. It would seem it warms up the atmosphere is what it does.
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aleCcowaN
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It's a matter of wave length. Let me see if I can find a figure with black body spectra that simulates the sun and the earth surface... hmm ... I can't find now an figure stripped of deeper elements, but this one may suffice:
The red surface depicts the energy coming from the Sun and reaching the surface. The "amputation" on the left is mainly because of ozone. The dents are mainly because of water vapour.
The blue surface depicts the energy from the surface going out into space. Water vapour also blocks part of the spectrum, but in different wave lengths.
But carbon dioxide has a small effect in the portion of solar energy reaching the surface and a larger effect in the portion of IR trying to leave the planet into space. That's why increasing CO2 warms the planet: the more of it there is, the less energy reaches the surface, but in a more larger scale the more energy gets reflected back into the atmosphere and only can escape by changing to shorter wave-lengths, that is, the emitting surface must get warmed to achieve that.
The effect of human actions -and sometimes nature too- in increasing CO2 is widen the rightmost opaque area in the CO2 spectra, so the blue part of the figure loses a bit of the abrupt slope in its right, what in turn forces the spectra to move a tiny bit to the left and increase radiation a bit in all available frequencies, that is, warming the planet.
Of course, there's a lot of counteracting processes -and some positive feedbacks too- that moderates the result, and mainly there is a transient effect because the planet has a humongous amount of water -it could be shaped as a second moon of more than 1100 km -700 miles- of diameter. So the water in the planet would be capable of absorbing all the energy the sun gives without radiating a sole photon back into space and the oceans will warm less than 1°C per year.
CO2, already explained. It's water vapour you might want to analyse.
The problem here is you have to understand quantum physics. We can discuss it but more water vapour is not going to bounce back more incoming energy than what is going to bounce back down. In your place, I'll better bet to clouds increasing albedo. You'd have a better chance to keep a notion of a warming-not planet by following that path. I mean, you could dilate the discussion here by following that.
Take it easy!
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