Note: the heat from gravitational collapse is
not what I am talking about, but the distribution of pressure and temperature in a column of gas with an external energy input and acceleration due to gravity is not a mysterious concept. Potential energy and kinetic energy have a certain relationship in a gravity well, kinetic energy in a gas is a major component of the temperature of said parcel of gas, and guess where the kinetic energy is higher? Where the volume available to expand is lower, deeper inside the gravity well. Put those together and what do you get? Higher pressure, which means...
That a column of gas in a gravity well is warmest at the bottom isn't a theory, it's a fact, you can just observe it,
I did clarify that the sparse upper layers can be ridiculously hot because any given molecule is zooming around with little to lose energy against while being zapped with UV and such, as you go higher and drop below 0.1 bar you get the inversions in the chart there as density stratifications take over, direct UV deposition, even the magnetic field deforming layers plays a role in the temperatures up there. As far as creatures like us though, being adapted as we are to the bottom of an ocean of air, it's gonna be hard to tell the difference between the mesosphere and a vacuum.
If Venus had an atmosphere of, say, 99% nitrogen, it would as a matter of objective fact be cooler due to an inability to retain that level of heat.
I happened to remember seeing this worked out before, which is good, because I really don't have it in me to go back over all the studying and whatnot to make sure the math was sane before I even tried to start worrying about the calculations.
Both gases are diatomic with the same molar heat, but CO2 has higher molar mass so the specific heat used to calculate the lapse rate would be different accordingly, 44/28 means CO2 should have 1.57 times greater cooling per kilometer than N2, but that same mass ratio means it would sit about 1.57 times lower than N2, so the temperature change between the surface and the top of the adiabatic layer (a.k.a. the troposphere) should be roughly the same if you swap out CO2 for N2.
Earth probably could end up similar to Venus, millions of years after human extinction due to ecological collapse, were we to go that route. It is also possible that there could eventually be another carbon-rich period that would successfully arrest this cycle if our ultimate extinction didn't salt the Earth, but I say again, human extinction. Your hate-on for this basic comparison of how the greenhouse effect can change a planet baffles me. Nobody is seriously suggesting humans will face the threat of a 600 C surface because of climate change.
We would need to increase the mass of the atmosphere by 90 times in our death throes, this isn't something that just accidentally happens, especially with a water cycle in place busily dissolving gases out of the atmosphere and fixing them into sediments and so on.
Do you or do you not agree that the presence of carbon dioxide in a planetary atmosphere directly correlates with the heat retention of that atmosphere?
Well, Venus has something like 3000 to 5000 times as much CO2 (dealers choice, molar or mass percentage) at 92 times the pressure, so call it 270,000 to 460,000 higher concentration? According to Wolframalpha that's about 2
18 for either value, so what effect would 18 CO2 doublings have? If 2xCO2 gives a rise of 1.5 K that's 27 K warmer than here? Even if you proposed an outlandish value of 5 K per doubling we're still only looking at 90 K!
Does anybody wanna get behind the temperature increase per CO2 doubling being 22 K? Cause
that will get you 400 K warmer than here, so that seems to be something of a pickle, doesn't it?
Sorry for the late reply, had to make sure I was out of rant mode and wouldn't start trying to convince anyone of anything, but questions with such interesting answers just beg for a response.
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Topic: SCIENCE, Gravitational waves, and the whole LIGO OST! (Read 490790 times)