An understandable explanation of CO2 and how it will not saturate:
"So, if a skeptical friend hits you with the "saturation argument" against global warming, here’s all you need to say: (a) You’d still get an increase in greenhouse warming even if the atmosphere were saturated, because it’s the absorption in the thin upper atmosphere (which is unsaturated) that counts (b) It’s not even true that the atmosphere is actually saturated with respect to absorption by CO2, (c) Water vapor doesn’t overwhelm the effects of CO2 because there’s little water vapor in the high, cold regions from which infrared escapes, and at the low pressures there water vapor absorption is like a leaky sieve, which would let a lot more radiation through were it not for CO2, and (d) These issues were satisfactorily addressed by physicists 50 years ago, and the necessary physics is included in all climate models"
http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument/
http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument-part-ii/
Showing posts with label co2 saturation. Show all posts
Showing posts with label co2 saturation. Show all posts
2010/02/19
2009/10/18
CO2 and IR absoption
TomVonk:
October 16th, 2009 at 4:03 am
Re: thefordprefect (#186),
"From what I have seen the logarithmic effect is usually explained by the absoption bands getting full - ie. no more radiation can be absorbed. Radiation is then absorbed by smaller absorptions bands and and by the under used width of the CO2 bands.
And the CO2 GH effect is vastly lessened by many of the bands falling within the H20 bands."
.
I don't konw where you have seen that but this explanation is not even wrong .
It is absolutely and totally forbidden that a band , any band gets "full" or "saturated" .
The population that is in an excited state is a CONSTANT for a given temperature (f.ex the CO2 15ยต excited state represents 5 % of the total CO2 population at room temperatures) . This is prescribed by the MB distribution of the quantum states .
It doesn't depend on the number of molecules , the intensity of radiation or the age of the captain . Only temperature .
So whatever amount of IR you throw at a CO2 population , they will absorb it all and REEMIT .
They can't do anything else because they must do whatever it takes to keep the percentage of excited states constant .
.
Imagine a dam (CO2 molecules) and a lake whose level (percentage of excited states) is exactly at the top of the dam .
If you increase the flow in the lake (absorbed radiation) all that will happen is that the flow over the top of the dam (emitted radiation) will increase by exactly the same amount .
If you increase the height of the dam (temperature) , the level of the lake will go in a transient untill it gets to the new top and then it's again exactly like described above .
There is no "saturation" .
October 16th, 2009 at 4:03 am
Re: thefordprefect (#186),
"From what I have seen the logarithmic effect is usually explained by the absoption bands getting full - ie. no more radiation can be absorbed. Radiation is then absorbed by smaller absorptions bands and and by the under used width of the CO2 bands.
And the CO2 GH effect is vastly lessened by many of the bands falling within the H20 bands."
.
I don't konw where you have seen that but this explanation is not even wrong .
It is absolutely and totally forbidden that a band , any band gets "full" or "saturated" .
The population that is in an excited state is a CONSTANT for a given temperature (f.ex the CO2 15ยต excited state represents 5 % of the total CO2 population at room temperatures) . This is prescribed by the MB distribution of the quantum states .
It doesn't depend on the number of molecules , the intensity of radiation or the age of the captain . Only temperature .
So whatever amount of IR you throw at a CO2 population , they will absorb it all and REEMIT .
They can't do anything else because they must do whatever it takes to keep the percentage of excited states constant .
.
Imagine a dam (CO2 molecules) and a lake whose level (percentage of excited states) is exactly at the top of the dam .
If you increase the flow in the lake (absorbed radiation) all that will happen is that the flow over the top of the dam (emitted radiation) will increase by exactly the same amount .
If you increase the height of the dam (temperature) , the level of the lake will go in a transient untill it gets to the new top and then it's again exactly like described above .
There is no "saturation" .
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