The issue is that the effective radiating layer for a planet with a greenhouse atmosphere is much higher than the surface, on Earth for example it's in the stratosphere, so the temperature is much colder and the outgoing flux is less (this is a simplification). Venus works the same way, it's atmosphere cools as you go up, and because it is so dense the radiating layer is very high. In contrast, on Mars, if you do the math, you will see that the surface flux is very nearly equal to the incoming solar flux because the atmosphere is thin so the greenhouse effect is very small. The Moon, with no atmosphere, has the surface flux (on average) identically equal to the incoming flux (on average).
Water vapor has nothing to do with radiative equilibrium on Venus. My impression of the science is that because of differences between Earth and Venus (e.g., a magnetosphere that saves water vapor in the stratosphere from being destroyed), so long as the solar constant remains in the range it is today a runaway greenhouse on Earth isn't possible.
It is very close to radiative equilibrium. Obvioulsy, when the Sun heats up and cools down, it does effect Venus. Since the Sun has been cooling for over 50 years, Venus has been radiating slightly more energy than it has been recieving.from the Sun during this time.
http://www.woodfortrees.org/plot/sidc-ss...
And the notion that Venus is hot because the pressure is high is absolute nonsense. Yes, air is hot when it comes out of a compressor, but the same air quickly cools down if it remains in the tank. If somehow, a huge amount of gas were suddenly dropped on a planet, and for simplicity, let's say the gas is nitrogen, which is not a greenhouse gas, the planet would get very warm. And then it would be in a state of radiative disequilibruim, until it cools back down.
Do we actually know that Venus once had such a capability, or is it what people call, "just a theory"?
The dense white atmosphere of Venus prevents solar heat entering or surface heat heat escaping, I am not sure that radiative equilibrium is the correct term, I prefer thermos flask effect.
Venus is big, has a dense atmosphere that prevents cooling and is pretty much the same temperature now as when it formed, I expect Venus will stay as it it is until our sun expands into a red giant and swallows it up.
Hi Geff Venus has NO magnetic field lines (no internal dynamo effect) to create the greenhouse ceiling http://www.nasa.gov/mission_pages/sunear...
Edit Kano Venus white atmosphere is because of the plasma created between the bow shock and the surface, it has a ionosphere that would extend down to the surface. This plasma interacts with particles emitted by volcanism and would create an affect much like a fluorescent light bulb. If you watch that video in that link I provided you will see how Venuses atmosphere works, you see the blue band that's plasma and the orange to red is heat (inferred) escaping to space Venus is not a closed system like earth. I hope you get it as well Jeff.
I don,t know if your seen the movie about the day Earth stopped rotating and they saved us by exploding nucles and got it rotating again, Well we could do that to venus if we could make the vehicle they used to get them to the core. When you whack a iron bar hard enough you turn it into a magnet. The reason earth is different to our closest neighbours is because earth iron core got impacted enough to create a magnetic field. And this is were the atmosphere comes into it, I see the atmosphere extending out from the core not the surface and each layer is held in place by some sought of resistance created from above this proses extends right out to the bow shock. 50% of the earths energy is produced by earth it's self by radioactive decay in the UP direction and the other half is created by the sun radioactive decay in the down direction. Each layer can exchange energy through a point charge either positive or negative. This process can be see through viewing SPRITES and plasma above thunder storms. The atmosphere above the surface through its electrochemical effect helps strengthen our electromagnetic field lines, as long as the sun stays plugged in that is.
What are you going to do? Have us all pony up to save Venus now?
Venus has a geometric albedo of 0.67 and a bond albedo of 0.9. The atmosphere contains 96.5% Carbon Dioxide and 3.5% Nitrogen and has a diurnal temperature range of ~0 and an average temperature of 737K.
http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html
There also isn't much variation between daytime and night time temperatures due to the planet trapping heat so effectively.
http://www.uni.edu/morgans/astro/course/Notes/section4/new18.html
Given this and the data in the links above, is Venus in radiative equilibrium? It is once thought that water was a major component of the planet which has since evaporated and separated. Water vapour now only consists of 20ppm in the Venetian atmosphere. Can you explain the processes Venus took to reach the point it is at now and where do you see the atmosphere of planet headed in the future?
