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Post by steve on Feb 13, 2009 15:47:32 GMT
Still, if the IPCC models are correct, shouldn't Mars be much warmer than it apparently is given its relatively high atmospheric carbon dioxide content? No. The expected amount of warming is probably no more than 10 or 20 degrees based on the expected impact of a similar amount of CO2 in the earth's atmosphere. And, as with Venus, it is probably not sensible to extrapolate due to other differences between the planets.
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Post by donmartin on Feb 14, 2009 1:36:45 GMT
So, if the carbon dioxide proportion of the Earth's atmosphere was 95% it would increase the surface and atmospheric temperature of the Earth 10 to 20 degrees C?
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Post by socold on Feb 14, 2009 19:34:07 GMT
Below are some properties of mars relative to Earth (ie Earth=1 in all cases). Some calculated, some from wikipedia: Distance from Sun: 1.51 Greenhouse effect: 0.33 Amount of co2: 12 Amount of water vapor: 0.00036 Sunlight reaching orbit: 0.44 Sunlight absorbed: 0.59 "sunlight absorbed: 0.59" means Mars absorbs 59% as much sunlight as Earth absorbs. The amount of co2 is based on Mar's thinner atmosphere and on it having 95% co2 while Earth only has 0.038% co2. From en.wikipedia.org/wiki/Atmosphere_of_Mars: "[Mar's atmosphere has] a total mass of 25 teratonnes, compared to Earth's 5148 teratonnes" So (25 * 0.95) / (5148 * 0.00038) = ~12 Water vapor is calculated similarly. Sunlight reaching orbit is the difference between the solar constant on Earth and the solar constant on Mars, which is based on the distance of the planets from the sun. Greenhouse effect is based on the difference between each planet's effective temperature and it's actual temperature. I don't know how much of the 11C greenhouse effect of mars is covered by the small amount of water vapor vs the large amount of co2. If it's virtually all due to the co2, what does that tell us? I can't see anything obvious other than on it's own a lot of co2 can cause a lot of warming. It's not obviously compariable to earth though where a lot of water is alongside a little co2.
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Post by donmartin on Feb 14, 2009 21:36:07 GMT
Socold: thank you.
Before I use my rudimentary analytical skills, and they are rudimentary, I will postulate intuitively: atmospheric density, not atmospheric composition, determines atmospheric and surface temperature; the greater the density of atmosphere, the higher and more stable will be the the atmospheric/ surface temperature; change in atmospheric/surface temperatures corresponds directly with solar activity such that after 1970 the atmospheric temperature of Mars increased .05C as did the atmospheric temperature of Earth. Both are now in process of cooling.
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Post by donmartin on Feb 23, 2009 7:48:48 GMT
I may be incorrect, but heat and temperature are not the same. Heat is determined by both density and temperature. Temperature measures the velocity of particles. Heat is a measurement of the quantum of particles. Heat is a product of density, not temperature. In an environment without parameters, temperature can determine density : density and heat are inversely proportional to temperature.
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Post by steve on Feb 23, 2009 10:50:25 GMT
Socold: thank you. Before I use my rudimentary analytical skills, and they are rudimentary, I will postulate intuitively: atmospheric density, not atmospheric composition, determines atmospheric and surface temperature; the greater the density of atmosphere, the higher and more stable will be the the atmospheric/ surface temperature; change in atmospheric/surface temperatures corresponds directly with solar activity such that after 1970 the atmospheric temperature of Mars increased .05C as did the atmospheric temperature of Earth. Both are now in process of cooling. It sounds reasonable that a more dense atmosphere will have more stable temperature due to thermal mass. ie. while the CO2 is good at radiating energy away from the planet, as soon as it gets rid of energy it is quickly reexcited by all those warm O2 and N2 molecules. But the difference in temperature response when the sun goes down between cloudy and/or humid climates and clear dry skies shows that the density is less important in determining the average temperature of an atmosphere. Every time I've had an ice build-up in my tent when camping in the mountains, I've got up to a beautifully clear sky, whereas warmer nights usually correlate with a rapid cloud build-up once convection starts.
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Post by nautonnier on Feb 23, 2009 11:08:11 GMT
Socold: thank you. Before I use my rudimentary analytical skills, and they are rudimentary, I will postulate intuitively: atmospheric density, not atmospheric composition, determines atmospheric and surface temperature; the greater the density of atmosphere, the higher and more stable will be the the atmospheric/ surface temperature; change in atmospheric/surface temperatures corresponds directly with solar activity such that after 1970 the atmospheric temperature of Mars increased .05C as did the atmospheric temperature of Earth. Both are now in process of cooling. It sounds reasonable that a more dense atmosphere will have more stable temperature due to thermal mass. ie. while the CO2 is good at radiating energy away from the planet, as soon as it gets rid of energy it is quickly reexcited by all those warm O2 and N2 molecules. But the difference in temperature response when the sun goes down between cloudy and/or humid climates and clear dry skies shows that the density is less important in determining the average temperature of an atmosphere. Every time I've had an ice build-up in my tent when camping in the mountains, I've got up to a beautifully clear sky, whereas warmer nights usually correlate with a rapid cloud build-up once convection starts. Which is what you would expect as the humidity is higher and water vapour is considerably more effective at radiative forcing than CO 2 - This also shows how little the CO 2 radiative forcing effect is on its own.
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Post by steve on Feb 23, 2009 11:33:33 GMT
Which is what you would expect as the humidity is higher and water vapour is considerably more effective at radiative forcing than CO 2 - This also shows how little the CO 2 radiative forcing effect is on its own. Yes, water vapour probably provides 1/2 to 2/3 of the enhanced greenhouse effect. But CO2 is not a variable in this experiment, so it doesn't tell you anything about the radiative forcing of CO2. Of course if the theory is bogus, someone with a decent spectrometer and some spare airmiles could easily destroy the whole theory in a couple of weeks *and* have a few nice holidays at the same time.
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Post by ron on Feb 23, 2009 17:13:39 GMT
Of course if the theory is bogus, someone with a decent spectrometer and some spare airmiles could easily destroy the whole theory in a couple of weeks *and* have a few nice holidays at the same time. Can we at least agree that anyone with a decent spectrometer and a bunch of spare air miles wouldn't have either at the end of a trip with that delicate instrument on our commercial airlines?
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Post by donmartin on Feb 23, 2009 18:26:56 GMT
"...quickly re-excited by all those warm O2 and N2 molecules."
This is where I got somewhat lost. As I understand, a little, molecules may, eg, "absorb" a photon (energy), but same is immediately emitted in conservance of energy and momentum. The Zeeman and Stark effects go someway in describing this. The kinetic energy (temperature) (1/2Mvsquared) (I don't have a little "two"), after its initial state will find a lower equilibrium value according to laws of thermodynamics. I cannot see how a change in atmospheric temperature can cause warming which in fact is a function of density. Two atoms traveling at the speed of light in an area the size of the Pacific Ocean will have almost infinite high temperature, but there will be no heat due to absence of density. Indeed, it would be a very long time, approaching infinity, before equilibrium would be reached - if ever, given there are only two particles.
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Post by donmartin on Feb 24, 2009 1:23:58 GMT
If you pitched your tent on Mars, the temperature could drop as much as 100degC overnight. Due to lack of density, Mars is heated only by direct solar energy.
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Post by steve on Feb 24, 2009 10:25:30 GMT
"...quickly re-excited by all those warm O2 and N2 molecules." This is where I got somewhat lost. As I understand, a little, molecules may, eg, "absorb" a photon (energy), but same is immediately emitted in conservance of energy and momentum. The Zeeman and Stark effects go someway in describing this. The kinetic energy (temperature) (1/2Mvsquared) (I don't have a little "two"), after its initial state will find a lower equilibrium value according to laws of thermodynamics. I cannot see how a change in atmospheric temperature can cause warming which in fact is a function of density. Two atoms traveling at the speed of light in an area the size of the Pacific Ocean will have almost infinite high temperature, but there will be no heat due to absence of density. Indeed, it would be a very long time, approaching infinity, before equilibrium would be reached - if ever, given there are only two particles. Not quite sure I follow this. As I see it the earth's atmosphere comprises mostly (>96%) O2/N2 which are a thermal mass whose molecules don't emit or absorb much radiation. Within it are a few molecules of greenhouse gas (GHG) such as water vapour or CO2. GHGs are good at absorbing IR, but equally (Kirchoff's law) they are good at emitting IR. Roughly 96% of the atmosphere's "heat content" is held by the non-GHG. The GHGs warm the atmosphere by absorbing IR from the surface after which the energy is transferred thermally to other molecules through collision. They also cool the atmosphere by being collisionally excited by a warm N2 or O2 molecule and then lose the energy by radiating it into space. At night, the IR drops quickly as the ground cools, but the CO2 takes a long time to cool the atmosphere as the O2 and N2 hold 96 times the energy held by the CO2. On Mars, there is 8 or 9 times the CO2 but not much else. So while the CO2 is absorbing the IR effectively, it is also emitting IR into space just as effectively. As the sun goes down, the IR drops and the net emission to space goes up. Without the thermal mass of atmosphere, the CO2 emissions can more rapidly cool the Mars atmosphere. In short, there should be a greenhouse effect on Mars, but other differences in the Martian atmosphere may mean that it is not easy to apply analogies with earth's atmosphere.
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Post by nautonnier on Feb 24, 2009 16:14:18 GMT
"...quickly re-excited by all those warm O2 and N2 molecules." This is where I got somewhat lost. As I understand, a little, molecules may, eg, "absorb" a photon (energy), but same is immediately emitted in conservance of energy and momentum. The Zeeman and Stark effects go someway in describing this. The kinetic energy (temperature) (1/2Mvsquared) (I don't have a little "two"), after its initial state will find a lower equilibrium value according to laws of thermodynamics. I cannot see how a change in atmospheric temperature can cause warming which in fact is a function of density. Two atoms traveling at the speed of light in an area the size of the Pacific Ocean will have almost infinite high temperature, but there will be no heat due to absence of density. Indeed, it would be a very long time, approaching infinity, before equilibrium would be reached - if ever, given there are only two particles. Not quite sure I follow this. As I see it the earth's atmosphere comprises mostly (>96%) O2/N2 which are a thermal mass whose molecules don't emit or absorb much radiation. Within it are a few molecules of greenhouse gas (GHG) such as water vapour or CO2. GHGs are good at absorbing IR, but equally (Kirchoff's law) they are good at emitting IR. Roughly 96% of the atmosphere's "heat content" is held by the non-GHG. The GHGs warm the atmosphere by absorbing IR from the surface after which the energy is transferred thermally to other molecules through collision. They also cool the atmosphere by being collisionally excited by a warm N2 or O2 molecule and then lose the energy by radiating it into space. At night, the IR drops quickly as the ground cools, but the CO2 takes a long time to cool the atmosphere as the O2 and N2 hold 96 times the energy held by the CO2. On Mars, there is 8 or 9 times the CO2 but not much else. So while the CO2 is absorbing the IR effectively, it is also emitting IR into space just as effectively. As the sun goes down, the IR drops and the net emission to space goes up. Without the thermal mass of atmosphere, the CO2 emissions can more rapidly cool the Mars atmosphere. In short, there should be a greenhouse effect on Mars, but other differences in the Martian atmosphere may mean that it is not easy to apply analogies with earth's atmosphere. " At night, the IR drops quickly as the ground cools, but the CO2 takes a long time to cool the atmosphere as the O2 and N2 hold 96 times the energy held by the CO2." I did not realize that CO 2 had the task of cooling the atmosphere And it is the water vapor that holds the majority of the heat in the atmosphere - as is shown at night when humidity is low, atmospheric temperatures drop very fast, whereas in high humidity (even in the absence of clouds) the temperature drop is very much slower. Of course as the temperature drops to a level that water condenses out then the heat on condensation is again transferred to the atmosphere. Then as clouds form the 100% humidity of the atmosphere and the water droplets trap almost all radiated IR. Indeed the main difference between Mars and Earth atmosphere is the absence of the damping effect (sic ) of water vapor on temperature variations.
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Post by jorgekafkazar on Feb 24, 2009 17:07:49 GMT
[trim]Not quite sure I follow this. As I see it the earth's atmosphere comprises mostly (>96%) O2/N2 which are a thermal mass whose molecules don't emit or absorb much radiation. Within it are a few molecules of greenhouse gas (GHG) such as water vapour or CO2. GHGs are good at absorbing IR, but equally (Kirchoff's law) they are good at emitting IR. Roughly 96% of the atmosphere's "heat content" is held by the non-GHG. The GHGs warm the atmosphere by absorbing IR from the surface after which the energy is transferred thermally to other molecules through collision. They also cool the atmosphere by being collisionally excited by a warm N2 or O2 molecule and then lose the energy by radiating it into space. At night, the IR drops quickly as the ground cools, but the CO2 takes a long time to cool the atmosphere as the O2 and N2 hold 96 times the energy held by the CO2. On Mars, there is 8 or 9 times the CO2 but not much else. So while the CO2 is absorbing the IR effectively, it is also emitting IR into space just as effectively. As the sun goes down, the IR drops and the net emission to space goes up. Without the thermal mass of atmosphere, the CO2 emissions can more rapidly cool the Mars atmosphere. In short, there should be a greenhouse effect on Mars, but other differences in the Martian atmosphere may mean that it is not easy to apply analogies with earth's atmosphere. Sounds reasonable to me.
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Post by donmartin on Feb 24, 2009 21:00:47 GMT
Apologies, but I'm a hedgehog - slow and siple.
"Trap", "hold", "absorb"? Is there a theory within the Dalton model wherein it is convincingly concluded that an atom or molecule traps, holds, or absorbs anything. Do photons attach to neutrons and become "pheutrons"? And the wave theory of atomic structure doesn't assist because were an atom as conceived in the wave theory to "absorb" energy, then its atomic structure would change thus creating a different element - and no one has hypothesized that yet in relation to GHG.
And, again, is it not correct that temperature is a measurement of atomic velocity only, and not heat, which is a function of the aggregate number of atoms or molecules (n) within a defined space, which on Earth is a function of gravity and the dipolar magnetic field?
Just asking.
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