## Venus Is Hot – Mars Is Not

Both planets have atmospheric CO2 concentrations around 95%. Earth’s atmosphere has only 0.04% CO2. The density of CO2 in both planet’s atmospheres is much higher than Earth’s atmosphere.

Temperatures on Venus average a balmy 467°C, but temperatures on Mars average a nippy −63 °C. Why the big difference?

According to the “runaway CO2 greenhouse” theory, both planets should be really hot. Mars is twice as far away from the Sun, so its top of atmosphere receives only 25% of the solar radiation as Venus. But clouds on Venus reflect 75% of the sunlight – so the SW radiation flux at the surface is similar on the two planets.

So why is Venus hot and Mars cold? Simple – it is the atmospheric pressure.

The pressure on Venus is nearly one thousand times higher than on Mars. As the atmosphere convects, descending gases warm and ascending gases cool. The amount of warming is determined primarily by the increase in pressure.

Ever used a bicycle pump? Why does it get hot?

Answer : Because you are doing work to the gas when you compress it. Similarly, solar radiation transfers energy to the atmosphere, causing convection and heating of sinking air. If there was no Sun, the atmosphere would be very cold and would in fact freeze.

The runaway greenhouse theory makes little sense. If it were true, the Earth would experience it from water vapour, not CO2. H2O is a much stronger greenhouse gas than CO2, is much more abundant than CO2 and gets released from the oceans very easily and often – particularly as the planet heats up.

Just having fun
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### 16 Responses to Venus Is Hot – Mars Is Not

1. Scott says:

Using your temperatures above and the 95% concentrations you along with pressures of 0.636 kPa on Mars and 90 atm for Venus, I get the following numbers for mol CO2/L:

Mars = 3.46 e-4
Venus = 1.41

I also calculated it for Earth assuming T = 13 C, P = 1 atm, and C = 390 ppm.

Earth = 1.66 e-5

So while it’s true that “The density of CO2 in both planet’s atmospheres is much higher than Earth’s atmosphere.”, Mars has a surface CO2 density ~21x of Earth’s, while Venus’s value is ~85000x that of Earth’s. The higher pressure on Venus does cause more collisional broadening in the absorption spectrum, however, which surely increases the amount of IR absorption (relative to both Earth and Mars).

Also, a bicycle pump gets hot because you’re compressing the guess with work. It doesn’t stay hot even though it remains at high pressure.

-Scott

• Convection is work driven by solar energy. That is what maintains the adiabatic gradient. If there was no sunshine, temperatures would approach absolute zero.

• cmb says:

Venus’s temps are largely the result of a runaway greenhouse effect.

http://www.esa.int/esaMI/Venus_Express/SEMFPY808BE_0.html

This is well known throughout the world.

Re: your last paragraph – where I come from, whenever there’s too much water vapor for a certain temperature, it falls out as rain, trying to equilibrate. CO2 does no such thing, and stays in Earth’s atmosphere some 50-100 years.

That’s why we have increased our atmospheric CO2 by around 37%, but water vapor almost none. It rains. =)

• Have you ever followed a CO2 molecule around?

The whole point of CAGW is the feedback of water vapour. CO2 by itself can’t have much effect on temperature.

• cmb says:

Why, have you?

CO2 doesn’t need to have much of an effect on temperature to produce major impact. Without it and other GHGs, water vapor on Earth would be a solid.

BTW, what is CAGW?

• Catastrophic global warming

The vast majority of the greenhouse effect is the result of water vapour, not CO2.

http://stevengoddard.wordpress.com/2010/09/05/quantifying-the-greenhouse-effect-in-the-tropics/

• cmb says:

True (well, around 3/4 to 1/4), but not a rebuttal, just an interesting side fact. Changes in CO2 are quite sufficient to change atmospheric temperatures. More CO2 means more change. It works, as they say, every time it’s tried.

• My experiments with radiative transfer models indicate that CO2 has a much smaller effect than 25% – when there is water vapour present.

• cmb says:

• The results and methods are here
http://stevengoddard.wordpress.com/2010/09/05/quantifying-the-greenhouse-effect-in-the-tropics/

• cmb says:

That is an editorial. Let’s see the paper.

2. JanS says:

Steve Goddard has a good point in this post:

The vertical temperature profile (the lapse rate) in planetary atmospheres is largely a result of thermodynamics where the sun heated surface is cooled by heat transport from the surface to higher altitudes by sun-driven convection, evaporation/condensation, etc. and where radiation plays a subordinate role. The ascending warm air is cooled by adiabatic processes, resulting from pressure changes governed by the gravitation of the planet (Earth, Venus, Mars, etc.).

In a recent paper the German “super-physicists” Professors Gerhard Gerlich and Ralf D. Tscheuschner (the scientists behind the much-discussed “CO2 falsification” paper) derive, from basic physical considerations, “barometric formulas” that describe this effect. The paper is available at http://arxiv.org/abs/1003.1508 . The paper is rather theoretical, but contains an appendix that in plain English concludes that:
– Arrhenius hypothesis that CO2 will heat the earth is false
– Heating of Earths surface by “backradiation” from atmospheric greenhouse gases (CO2, H2O, etc.) is not possible and breaks against the fundamental second law of thermodynamics.
– The AGW (anthropogenic global warming) greenhouse effect on the earth therefore does not exist.
– The hypothesized “runaway” greenhouse effect on Venus does also not exist.

Only theoretical physicists actively dealing with these issues are qualified to make statements on the basic physics (radiation effects, thermodynamics, dynamics of atmospheres, etc.) governing the behavior of planetary atmospheres. Climatologists and most other scientists do not have this fundamental knowledge, which usually does not stop them from making sweeping statements (often with references to Svante Arrhenius and others historical scientists) on that the physics is settled. The basic physics is also not discussed anywhere in the IPCC documentation, except in very superficial terms (and then in terms as it was an indisputable fact), and we (policy makers, media and the general public) are supposed to believe that the hypothesis is true without providing any strict (experimental or theoretical) evidence. We would be better off if we instead listened to real physicists, who know what they are talking about.

The AGW scare builds only on one corner stone, that is, the unphysical hypothesis that infrared “backradiation” from greenhouse gases (CO2, H2O, etc.) in the (colder) atmosphere heats the (warmer) surface of the earth. Since this is a false foundation, the entire AGW “house of cards” collapses. There is nothing left – the AGW scare is dead.

• cmb says:

I’m afraid your conclusion is in serious error and is insupportable. No violation of 2ndLT in AGW. Radiant heating is an exception to 2ndLT, this has been known for a very, very long time.

http://www.jstor.org/stable/982684

“- Arrhenius hypothesis that CO2 will heat the earth is false
– Heating of Earths surface by “backradiation” from atmospheric greenhouse gases (CO2, H2O, etc.) is not possible and breaks against the fundamental second law of thermodynamics.
– The AGW (anthropogenic global warming) greenhouse effect on the earth therefore does not exist.
– The hypothesized “runaway” greenhouse effect on Venus does also not exist.”

All falsified by the real, demonstrable mechanism of radiative heating from cold objects to hot. The alternative is a body that absorbs radiant energy but does not heat – a physical impossibility, as a little research will verify.

You also write: “Only theoretical physicists actively dealing with these issues are qualified to make statements on the basic physics (radiation effects, thermodynamics, dynamics of atmospheres, etc.) governing the behavior of planetary atmospheres. ”

Nope, I am fully qualified to make such statements – I can read. You are also qualified – but wrong. You trusted charlatans. The author is also qualified, but is playing some game, as the false (indeed, impossible) total exclusion of CO2 action in his last paragraph attests. He wants to use vaporization due to a heating planet as an example, but not the resulting precipitation that keeps H2O vapor in check but does not exist at earth temperatures for CO2.

More on 2ndLT “violation” via radiative heating:

And, a few statements by scientific organizations may be in order. No scientific society or national government on the face of the earth rejects AGW theory. Many, many official statements quoted here for additional research.

http://www.post-carbon-living.com/TTHW/Documents/Climate_Change_Consensus.pdf

3. gypsy says:

Seems like emb is the one who has been taken for a ride and sees catastrophe in invisible things. Or he works for someone in a role of disinformation. I suspect the latter,

No amount of scientific bullshit can account for common sense and his common sense is either lacking or deliberately being ignored. Again the latter is most likely.

Anyway, we should probably look at your scientific bullshit. What body are you possibly referring to? The atmosphere? Or perhaps you were talking about the sun for some reason. Perhaps the atmosphere is the interfering agent that allows for this breaking of the 2ndLT in your imagination?

The IPCC has behaved criminally with deliberate deception to fuel a corporate agenda and should be prosecuted thusly.

As should you for your own lying role.

4. Peter Hanely says:

A more detailed treatment of this basic model is at http://tallbloke.files.wordpress.com/2011/12/unified_theory_of_climate_poster_nikolov_zeller.pdf Success for multiple terestrial planets, vs. demonstrated failure for greenhouse gas based theory.

5. Nikolov and Zeller said this:

“Thus, empirical evidence indicates that the lower atmosphere contains more kinetic energy than provided by the Sun. Understanding the origin of this extra energy is a key to the GHE.”

My proposition explained in detail elsewhere is that the ‘extra’ kinetic energy is coming from conversion of gravitational potential energy back to kinetic energy within adiabatically warmed descending air.

At any given moment half the atmosphere is rising and half is falling.

That returning kinetic energy cannot escape the system as radiation to space because before it can do so it is taken upwards again in the next cycle of adiabatic ascent.

The surface temperature is determined by insolation PLUS returning kinetic energy from the atmosphere.