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Post by sigurdur on Dec 14, 2009 21:01:02 GMT
It does appear as if there is something clouding the discussion......
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Post by poitsplace on Dec 15, 2009 4:29:12 GMT
Another way to put it, I suppose would be to say that since water vapor and CO2 CLEARLY share their spectrum, their outputs MUST be proportional. Remember, the climate was already at equilibrium with these proportions before we added CO2. Water vapor outputs about 5/6 of the energy of this shared spectrum, CO2 about 1/6. The grossly oversimplified absorption math most people use as "proof" of significant anthropogenic global warming COMPLETELY ignores that water vapor is present and MUST be channeling a good portion of CO2's spectrum away. Within CO2's spectrum this works out to about 2/3 of the energy. So instead of 3.7 watts per square meter of forcing, it's more like 1.3 watts per square meter for a doubling of CO2....and you STILL have to contend with increased convection and other factors if there's any gradient change.
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Post by steve on Dec 15, 2009 9:28:22 GMT
This "channelling away" idea is a completely wrong concept, because 9,999,999 times out of 10 million, a greenhouse gas molecule is excited by thermal collision, not by absorption of an IR photon.
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Post by poitsplace on Dec 15, 2009 11:29:37 GMT
LOL...But Steve, how does that change the fact that the water vapor is the main radiator of atmospheric energy?
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Post by steve on Dec 15, 2009 12:11:11 GMT
I think it should significantly change the conceptual view you have of the processes.
Because the energy exchange is mostly by collision excitation/deexcitation, greenhouse gases throughout the whole atmosphere are continuously radiating at a rate that depends on the local temperature and pressure of their surroundings.
The same gases are absorbing at a rate that largely depends on the amount of radiation in their locality and the concentration of the gas.
Varying the sporting analogy, your conceptual view seems to draw a picture of a good basket ball team (the water vapour) nicking the ball (the energy) of a bad basketball team (the CO2) and then in a pass or two, slam-dunking it into the net of outer space.
But the presence of the water vapour does not take away the ability of CO2 to emit radiation, as it will always continue to be thermally excited (and deexcited)
Perhaps it is more like one of those fairground games where you compete to throw balls into holes. The faster and more accurately you throw, the more balls you get down the hole. A slower thrower does not score more slowly if he is playing against a faster thrower.
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Post by sigurdur on Dec 15, 2009 13:13:19 GMT
I think it should significantly change the conceptual view you have of the processes. Because the energy exchange is mostly by collision excitation/deexcitation, greenhouse gases throughout the whole atmosphere are continuously radiating at a rate that depends on the local temperature and pressure of their surroundings. The same gases are absorbing at a rate that largely depends on the amount of radiation in their locality and the concentration of the gas. Varying the sporting analogy, your conceptual view seems to draw a picture of a good basket ball team (the water vapour) nicking the ball (the energy) of a bad basketball team (the CO2) and then in a pass or two, slam-dunking it into the net of outer space. But the presence of the water vapour does not take away the ability of CO2 to emit radiation, as it will always continue to be thermally excited (and deexcited) Perhaps it is more like one of those fairground games where you compete to throw balls into holes. The faster and more accurately you throw, the more balls you get down the hole. A slower thrower does not score more slowly if he is playing against a faster thrower. OK......tell me why this excitement does not work on Mars?
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Post by steve on Dec 15, 2009 14:39:58 GMT
Because Martians aren't very good at basketball?
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Post by sigurdur on Dec 15, 2009 15:11:03 GMT
Socold and I had a discussion about co2 on Mars and why it doesn't appear to affect temperature there. I think we both came away knowing that we don't know why it doesn't.
You are a pretty smart feller, so I thought you would want to take a stab at it. There is data about the K temp on the NASA site with co2 concentrations etc.
Basketball does sound about as good a reason for no bounce as anything I guess.
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Post by steve on Dec 15, 2009 17:01:54 GMT
Sorry. My flippancy was really because the point I was making is not really controversial and doesn't relate to the greenhouse effect per se.
I think the Mars argument is as follows.
1. While there is 10 times as much CO2 in Mars' atmosphere as in earth, there is no water vapour. 2. Current earth's total greenhouse effect is about 33C 3. If earth got 10 times as much CO2 its temperature would rise a further 9C or so - to 42C. 4. If water vapour is 2/3 of the greenhouse effect, this suggests that without water vapour, the greenhouse effect would be 14C on earth. 5. This suggests that the greenhouse effect on Mars might raise its temperature 14C above the Stephan-Boltzmann expected value.
Mars has a large diurnal cycle, and big temperature gradient from equator to the pole because of the thinner atmosphere and the fact that there is so much CO2 (which therefore radiates a bigger proportion of the total energy in its atmosphere).
Dust in Mars' atmosphere has a big effect on Mars' weather. On earth, water vapour is very important. The differences in the atmosphere might make the expected greenhouse effect more than 14C or less than 14C. I suspect it is less than 14C because the planet cools so quickly. However it is not clear to me whether our knowledge of the surface temperature of the planet is known in sufficient detail to detect a variation from the Stephan-Boltzman basic calculation of even as much as 14C.
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Post by poitsplace on Dec 15, 2009 18:30:09 GMT
Wait, now higher CO2 concentrations cause the atmosphere to get cooler?
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Post by sigurdur on Dec 15, 2009 18:38:44 GMT
Sorry. My flippancy was really because the point I was making is not really controversial and doesn't relate to the greenhouse effect per se. I think the Mars argument is as follows. 1. While there is 10 times as much CO2 in Mars' atmosphere as in earth, there is no water vapour. 2. Current earth's total greenhouse effect is about 33C 3. If earth got 10 times as much CO2 its temperature would rise a further 9C or so - to 42C. 4. If water vapour is 2/3 of the greenhouse effect, this suggests that without water vapour, the greenhouse effect would be 14C on earth. 5. This suggests that the greenhouse effect on Mars might raise its temperature 14C above the Stephan-Boltzmann expected value. Mars has a large diurnal cycle, and big temperature gradient from equator to the pole because of the thinner atmosphere and the fact that there is so much CO2 (which therefore radiates a bigger proportion of the total energy in its atmosphere). Dust in Mars' atmosphere has a big effect on Mars' weather. On earth, water vapour is very important. The differences in the atmosphere might make the expected greenhouse effect more than 14C or less than 14C. I suspect it is less than 14C because the planet cools so quickly. However it is not clear to me whether our knowledge of the surface temperature of the planet is known in sufficient detail to detect a variation from the Stephan-Boltzman basic calculation of even as much as 14C. Ok....we all know about the dust on Mars. But what better place to prove co2's effect than on a climate with virtually no water vapor? This should be a slam dunk of emperical evidence. As far as being accurate on Mars temp, I do think we have that one covered. If you doubt what NASA indicates, then all satellite data including the temp of the sun etc are not accurate. It still boils down to the fact that Mars is a perfect experiment concerning co2 and temperature retention without the affects of water vapor. IF there is no appreciable effects of heat retention on Mars, with the much larger concentration, even with the diff in pressures it is larger; then that would indicate that the water vapor is the retainer of heat in the earth atmosphere as the experiment does not work on the Martian atmosphere. Correct?
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Post by itsthesunstupid on Dec 15, 2009 19:29:13 GMT
This is a sincere question: How can water vapor, which is approximately 95% of the greenhouse gases, be responsible for just 2/3 of the greenhouse effect? I apologize if this seeming contradiction has already been addressed.
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Post by donmartin on Dec 15, 2009 20:20:38 GMT
re: Mars
The proportion of CO2 in the atmosphere of Mars (@95%) is 2,500 times greater than the proportion of CO2 in the atmosphere of Earth (@.038 %). The atmosphere of Mars is less dense than that of Earth by a factor of 100. The energy/radiation per square metre is approximately 1/2 that of Earth. The question which arises is why is the atmospheric temperature of Mars not greater than Earth's by a factor of 1.2? Conversely, why is the atmospheric temperature of Mars so much lower than Earth's.
I believe Hansen inconclusively mentioned this issue a while back, although not with reference to the foregoing parameters.
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Post by nautonnier on Dec 15, 2009 22:15:34 GMT
I think that there may be a confusion between IR at the correct narrow frequency that happens to collide with a CO2 molecule and get almost immediately re-emitted (scattered) and the actual temperature of the CO2 causing radiation according to Stefan Boltzmann. This does seem to be the nub of the 'discussion' between Kiwi and Steve.
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Post by poitsplace on Dec 16, 2009 4:47:30 GMT
This is a sincere question: How can water vapor, which is approximately 95% of the greenhouse gases, be responsible for just 2/3 of the greenhouse effect? I apologize if this seeming contradiction has already been addressed. I think they're assuming that the greenhouse effect is based entirely on absorption/emission of outgoing radiation...and ignoring the fact that 30% of the earth's daytime energy input is taken entirely entirely out of that mode (as latent heat in water vapor) until later in the day when it cools. This is a lot (if not most) of what maintains the tropospheric gradient and the warming we're used to. The mars thing is a good point though...it does make me wonder why, if they're spending something in the neighborhood of 100 billion PER YEAR on this climate nonsense...they haven't lobbed a fleet of probes at mars to measure the temperature gradient of that atmosphere and the ground temperatures at various points across the surface. If they spent just 1% of that crazy climate budget on martian research we'd know a heck of a lot more about mars (probably work out to 2-10 probes PER YEAR).
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