Greenhouse effect on Venus

[trent_julie]

G'day Forum,
I got hit with a question at work today which I can't answer, and I hope someone here might be able to help me with an answer. The question was "Why isn't Venus getting hotter?", I guess there is the assumption that Venus is somehow regulating its temperature, or is the assumption wrong and Venus is actually continuing to heat...

Help!

Trent

[michaellxv]

Good question.

But,
Why do they think it should be getting hotter?
What measurements have been taken to say it is getting hotter/colder/stable?

[mswhin63]

like most planets they usually regulate themselves based on the distance they are from the Sun.

[trent_julie]

The question was more to do with global warming, now saying that I'm not interested in sparking a debate, but thier argument seemed valid given that Venus is no longer heating (assumed I gather), thus the greenhouse effect on Venus cannot be a truely positive feedback cycle as heat is getting lost somehow.

So what I would like to know in that case is how it is losing/regulating its heat? could it be possible that the IR wavelength changes that much that it ia not absorbed by the CO2 anymore?

Or has the assumed fact drifted away from realtity?

I'm not looking for any other information other than whats happening on Venus, as I do understand that this is a hotly contested issue at the moment,

Trent

[mswhin63]

Venus can't be used as a example of our own conditions. All planets with an atmosphere must have a form of greenhouse otherwise there is no atmosphere.

For obvious reasons Venus very close to the Sun, and with a well established atmosphere it is going to be fairly obvious to scientific community that its greenhouse is going to get excessive.

There is a simple analogy with regards to our solar system both Venus and Mars are out of the Goldilocks zone. it will be expected from any other Exoplanets as well.

The issue of Venus has been used by the non-scientific community as an example of the way the earth is going to go, it is pure speculation and is intended purely just too frightened community into believing their way.

The correct term that should be used for the issues facing earth at the moment would be climate change, and this can be either natural or man-made.

[michaellxv]

I can find plenty of references to how it got like we see it today (runaway greenhouse effect). Most say that it has now stabalised but do not go on to say how.

I saw a figure of 65% of sunlight is reflect away so no doubt that is one factor.

I did find this (http://www.terrapub.co.jp/journals/EPS/pdf/5203/52030197.pdf) which discusses it. Not a light read and I have not read it fully. It would appear that your very good question is still open for study and debate.

[Shiraz]

Hi Trent.
As I understand it, every planet reaches an equilibrium temperature and stays there unless something changes. Equilibrium occurs when the total energy coming in from the sun, combined with any internal energy percolating up from the core, is exactly balanced by the thermal IR energy being radiated back out into space. If the planet does not have an atmosphere, all of the IR energy is radiated by the surface and the temperature is a pretty straightforward function of the distance from the sun. If there is an atmosphere with greenhouse gases, then some of the energy heading outwards from the surface is absorbed by the atmosphere and re-radiated into space by it's upper layers. But the atmosphere also radiates energy back downwards as well, so the temperature at the surface ends up being higher than it would otherwise be. On Venus the temperature is MUCH higher because the atmosphere is very greenhouse active, but it is still in equilibrium and it will stay essentially constant unless something changes - as far as I know, the only planet currently undergoing a change that could affect it's equilibrium temperature is the earth.

[Waxing_Gibbous]

Venus is a scientifically poor example of the greenhouse effect on Earth as its atmosphere is 90% CO2 whereas Earth's atmosphere contains only 0.04%.
There are no perfect insulating systems and heat escapes from the Venusian atmosphere just as it does Earth's - only more slowly :). Also even Venus has a nightside which accelerates heat dispersion.

[gregbradley]

I imagine the reason why is once the heat builds up to the point where the atmostphere can contain it before it leaks out back into space. The more energy the harder it would be to contain it. Lower temps I presume are easier to keep the energy locked in. Higher temps would leak more as there is more energy and the difference between the atmosphere temp and space temp would be a larger difference giving more motive.

Greg.