# Venus Envy

By Steve Goddard

ESA’s Venus Express mission has been studying the planet and a basic atmospheric model is emerging.

Venus has long been the CO2 bogeyman of climate science.  In my last piece about Venus I laid out arguments against the claim that it is a runaway greenhouse which makes Venus hot. This generated a lot of discussion. I’m not going to review that discussion, but instead will pose a few ideas which should make the concepts clear to almost everybody.

If there were no Sun (or other external energy source) atmospheric temperature would approach absolute zero. As a result there would be almost no atmospheric pressure on any planet -> PV = nRT.

Because we have a sun providing energy to the periphery of the atmospheric system, the atmosphere circulates vertically and horizontally to maintain equilibrium. Falling air moves to regions of higher pressure, compresses and warms. The greater the pressure, the greater the warming. Rising air moves to regions of lower pressure, expands, and cools. The amount of warming (or cooling) per unit distance is described as the “lapse rate.” On Earth the dry lapse rate is 9.760 K/km. On Venus, the dry lapse rate is similar at 10.468 K/km. This means that with each km of elevation you gain on either Earth or Venus, the temperature drops by about 10C.

It is very important to note that despite radically different compositions, both atmospheres have approximately the same dry lapse rate. This tells us that the primary factor affecting the temperature is the thickness of the atmosphere, not the composition. Because Venus has a much thicker atmosphere than Earth, the temperature is much higher.

dT = -10 * dh     where T is temperature and h is height.

With a constant lapse rate, an atmosphere twice as thick would be twice as warm. Three times as thick would be three times as warm. etc. Now let’s do some experiments using this information.

Experiment # 1 – Atmospheric pressure on Venus’ surface is 92 times larger than earth, because the atmosphere is much thicker and thus weighs more.  Now suppose that we could instantly change the molecular composition of Venus atmosphere to match that of Earth. Because the lapse rate of Earth’s atmosphere is very similar to that of Venus, we would see little change in Venus temperature.

Experiment #2 – Now, lets keep the atmospheric composition of Venus constant, but instead remove almost 91/92 of it – to make the mass and thickness of Venus atmosphere similar to earth. Because lapse rates are similar between the two planets, temperatures would become similar to those on earth.

Experiment #3 – Let’s take Earth’s atmosphere and replace the composition with that of Venus. Because the lapse rates are similar, the temperature on Earth would not change very much.

Experiment #4 – Let’s keep the composition of Earth’s atmosphere fixed, but increase the amount of gas in the atmosphere by 92X. Because the lapse rates are similar, the temperature on Earth would become very hot, like Venus.

Now let’s look at measured data :

http://www.astro.wisc.edu/~townsend/resource/teaching/diploma/venus-p.gif

Note that at one Earth atmospheric pressure on Venus (altitude 50km) temperatures are only about 50 degrees warmer than earth temperatures. This is another indication that atmospheric composition is less important than thickness.

Conclusions : It isn’t the large amount of CO2 which makes Venus hot, rather it is the thick atmosphere being continuously heated by external sources. It isn’t the lack of CO2 on Earth which keeps Earth relatively cool, rather it is the thin atmosphere. Mars is even colder than earth despite having a 95% CO2 atmosphere, because it’s atmosphere is very thin. If greenhouse gases were responsible for the high temperatures on Venus (rather than atmospheric thickness) we would mathematically have to see a much higher lapse rate than on Earth – but we don’t.

WUWT commentor Julian Braggins provided a very useful link which adds a lot of important information.

“The much ballyhooed greenhouse effect of Venus’s carbon dioxide atmosphere can account for only part of the heating and evidence for other heating mechanisms is now in a turmoil,” confirmed Richard Kerr in Science magazine in 1980.

The greenhouse theory does not explain the even surface temperatures from the equator to the poles: “atmospheric temperature and pressure in most of the atmosphere (99 percent of it) are almost identical everywhere on Venus – at the equator, at high latitudes, and in both the planet’s day and night hemispheres. This, in turn, means the Venus weather machine is very efficient in distributing heat evenly,” suggested NASA News in April 1979. Firsoff pointed out the fallacy of the last statement: “To say that the vigorous circulation (of the atmosphere) smooths out the temperature differences will not do, for, firstly, if these differences were smoothed out the flow would stop and, secondly, an effect cannot be its own cause. We are thus left with an unresolved contradiction.”

======================================================

An update for those interested in what Venus looks like at the surface.

On March 1, 1982, the Soviet Venera 13 lander survived for 127 minutes (the planned design life was 32 minutes) in an environment with a temperature of 457 °C (855 °F) and a pressure of 89 Earth atmospheres (9.0 MPa). The photo composite above shows the soil and rocks near the lander.

Here’s another Venera image that shows a hint of yellow atmosphere. – Anthony

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kwik
May 8, 2010 2:13 pm

What disturbs me is the following;
Personally I havent given Venus much thought before reading Steven Goddards posts here at WUWT. Why should I have. I have enough other thinks to worry about on a daily basis.
But now, reading about Venus, thinking about it, the grey cells working…over at Stephen Wildes post…it stands clear to me, at least for now….that, hey, it makes sense!
And then the disturbing thought;
Surely J. Hansen must know this too? Surely? I mean, if its your job to use the grey cells on such matters?
Surely?

John caten
May 8, 2010 2:16 pm

Haha, love the title! Now I’ll go back and read the article.

Troels Halken
May 8, 2010 2:32 pm

When you compress or decompress a gas, it either warms or cools. Due to the temperature differential to the surroundings, after some time it will cool or warm by exchanging heat with the surroundings until the temperature differential is approaching zero and hence the temperature of the gas approaches that of the surroundings.
Why should Venus behave any different?

Leonard Weinstein
May 8, 2010 2:38 pm

Steve,
You are correct on all the cases you quoted, but the basic reason Venus is hot is in fact due to the presence of greenhouse gasses combined with the high pressure. It is not how much of the gas is greenhouse gasses, but the fact that there is at least some present (even <1% CO2 or water vapor and 99% N2 would do about the same). If there were no greenhouse gas at all, but the gas pressure were still high, a lapse rate would still be present (but modified due to real gas effects and greatly different temperatures), but the surface of Venus would then be the location where all of the radiation to space would balance incoming absorbed energy. This would make the surface close to Earth's temperature, and the lapse rate would result in a very cold upper atmosphere. The presence of even a small amount of greenhouse gasses moves the location of the radiation that goes to space out to the edge of the atmosphere, and the lapse rate heats the surface. The main difference is where the radiation to space occurs.

Ian l. McQueen
May 8, 2010 2:40 pm

Experiment # 1 – Atmospheric pressure on Venus’ surface is 92 times larger than earth, because the atmosphere is much thicker and thus weighs more.
I am always puzzled by the statement that the atmospheric pressure on the surface of Venus is a large multiple of that on earth.
The MW of earth’s atmosphere is about 29, and that of Venus around 44. But gravity at the surface of Venus is only 0.904 that of earth.
Atmospheric pressure is the result of the weight of a column of gas above the surface pressing down. I won’t embarrass myself by trying to calculate the effect of higher MW and lower force due gravity on Venus, and compressibility of the gas(es), but I would expect the atmosphere of Venus to extend out a large multiple of the distance that it does on earth to produce an atmospheric pressure 92X that on earth. But I have not heard that the Venusian atmosphere extends out so far…..
So, the question remains why the atmosphere is so “thick”. It is not constrained to a fixed volume, but can expand as the mass of gas is increased.
A further niggle comes from the statement: “If there were no Sun (or other external energy source) atmospheric temperature would approach absolute zero. As a result there would be almost no atmospheric pressure on any planet -> PV = nRT.”
At 0K all gases would have condensed to liquid or solid, but the mass of the gas would still be present as a layer on the surface. I would think that the liquid/solid would be as heavy (=attraction due to gravity) as the atmosphere from which it was produced, and possibly a tiny bit higher since the molecules would be concentrated at the surface instead of extending a distance above the planet and thus minutely farther from the center of attraction of the mass of the planet.

kcom
May 8, 2010 2:46 pm

It’s always been clear to me from the timeline of the discoveries on Venus and the genesis of the global warming panic that a strong argument can be made that the scare aspects of global warming (its original and most honest name) are an example of a massive case of medical students’ disease. James Hansen got his nose so deep into Venus he couldn’t see his way out. Just because it’s not real, doesn’t mean it doesn’t seem real. The mind is a powerful thing and can overwhelm logic when placed under enough stress. Ask any medical student if this has ever happened to them.

May 8, 2010 2:55 pm

Leonard Weinstein
You are correct.
Earth already has plenty of greenhouse gases, so my point is that even if earth went to 100% CO2, the maximum temperature increase would be less than 36C – nothing like Venus. (In reality, it would get cooler because of the loss of water vapour.)

May 8, 2010 2:57 pm

Ian l. McQueen
You can infer how thick the atmosphere of Venus is from this diagram:
http://www.astro.wisc.edu/~townsend/resource/teaching/diploma/venus-t.gif

May 8, 2010 2:59 pm

Ian l. McQueen
Liquids are not very compressible and don’t heat up much under pressure. Consider the bottom of a swimming pool.

May 8, 2010 3:01 pm

On Earth we have water that Venus does not have. We have a wet lapse rate that is less than a dry lapse rate because of the processes of evaporation and condensation. Condensed moisture also controls the atmospheric concentration of CO2. If we had no atmospheric moisture, CO2 concentrations could be higher and the atmosphere could be heavier. If Venus ever had water like Earth, it must of boiled off because it was too close to the Sun and not in the sweet zone that sustains life here.

May 8, 2010 3:06 pm

John caten
Title is Anthony’s idea. He also added the ESA and Venera content.

rbateman
May 8, 2010 3:29 pm

One of the great things that NASA did was the planetary explorer missions. Without comparison to other planets, there would be little hope of understanding Earth. It is unfortunate that some have hypochondriated that splendid knowledge into doomsday scenarios. Earth, like the other planets, has been as it is for at least the last billion years. The foundation for what separates Earth from the other planets is Carbon-based life that transformed the place. Else, who knows what it might have become, or not become. Better start thinking about taking care of Earth’s precious Carbon, as geologic forces are relentlessly conspiring to sequester it.
I’m thinking of a Carbon Appreciation Day.

RobJM
May 8, 2010 3:32 pm

In addition to pressure, Venus also has high concentrations of other greenhouse gasses such as carbon monoxide. If one of these gasses absorbs at the frequency corresponding to earths atmospheric window then it could have a significant effect on temp. I also wonder if atmospheric pressure could explain the faint sun warm earth paradox.

Doug S
May 8, 2010 3:36 pm

Leonard Weinstein says:
May 8, 2010 at 2:38 pm
… The presence of even a small amount of greenhouse gasses moves the location of the radiation that goes to space out to the edge of the atmosphere, and the lapse rate heats the surface. The main difference is where the radiation to space occurs.

That’s interesting Leonard. It would seem to a layman like me that a small amount of green house gas would radiate a small amount of energy back into space at the effective altitude of the gas. Are you saying that just a small amount of GHG at some altitude implies a large amount of re radiated energy is leaving the planet at that same altitude? I’m having trouble understanding that non-linear relationship between gas density and radiated energy.

Dave McK
May 8, 2010 3:40 pm

Willis- the lapse rate of earth’s atmosphere is NOT the lapse rate of a dry atmosphere.
In fact, the profile of earth’s atmosphere is that of a refrigerant system because of the working fluid water.
Venus has no such phase change gases in its atmosphere so it has the dry lapse rate.
The lapse rate of earth’s atmosphere is definitely not that of a dry atmosphere.
The are completely different- not similar at all.

IanH
May 8, 2010 3:54 pm

The modeling of Venus and earth atmospheres was reported (1,2): The authors agree adiabatic lapse rate is the crucial physical process. They point out three things
1) the adiabatic exponent for a hypothetical CO2 atmosphere replacing a nitrogen oxygen one of the same mass would result in a cooling of 6.4C.
2) Adding Carbon to oxygen in the atmosphere makes it slightly heavier, in principle resulting in tiny warming
3)Ultimately the CO2 dissolves in seas forming carbonate rocks, oxygen is thus lost from the atmosphere and atmospheric mass drops causing (tiny)cooling.
They conclude:
“Accumulation of large amounts of carbon dioxide in the atmosphere leads to the cooling, and not to warming of climate…. This conclusion has a simple physical
explanation: when the infrared radiation is absorbed by the molecules of greenhouse
gases, its energy is transformed into thermal expansion of air, which causes convective
fluxes of air masses restoring the adiabatic distribution of temperature in the troposphere.”

FWIW I am not a qualified climate scientist, take my reading with a pinch of salt.
1)
Environ Geol (2008) 54:1567–1572
Response to W. Aeschbach-Hertig rebuttal of ‘‘On global forces
of nature driving the Earth’s climate. Are humans involved?’’
by L. F. Khilyuk and G. V. Chilingar
2)
Energy Sources, Part A, 30:1–9, 2008
Cooling of Atmosphere Due to CO2 Emission
G. V. Chilingar a; L. F. Khilyuk a;O. G. Sorokhtin b
a Rudolf W. Gunnerman Energy and Environment Laboratory, University of Southern California, Los
Angeles, California, USA b Institute of Oceanology of Russian Academy of Sciences, Moscow, Russia

Mike McMillan
May 8, 2010 4:04 pm

Leonard Weinstein says:
. . . but the basic reason Venus is hot is in fact due to the presence of greenhouse gasses combined with the high pressure. It is not how much of the gas is greenhouse gasses, but the fact that there is at least some present . . .

The basic reason Venus is so darn hot is that it is so darn close to the sun. The high albedo moderates the temperature. The difference in composition affects the adiabatic lapse rate, but swapping Venus’ atmosphere with the same weight of air would give you no clouds and a much hotter planet.
The difference in lapse rates boils down to the gas molecules. Air is mainly diatomic, while Venus is triatomic CO2. The specific heat ratio Cp/Cv for air is ~1.4, CO2 is ~1.3, and that affects the temperature change as you move a parcel up and down, how much energy goes to ‘work’ as opposed to what’s left for temperature. Triatomic water vapor, our main ghg, has a Cp/Cv of ~1.3 like CO2. Methane, the next ghg suspect, also has a Cp/Cv of ~1.3. Sounds like a conspiracy.
Bottom line is that things on Venus are quite in accord with what you’d expect, no “runaway greenhouse” effect. I must acknowledge, though, that with no weather, Venus has solved the problem of climate change.

May 8, 2010 4:09 pm

Mike McMillan
There isn’t a large difference in lapse rates, and the albedo of Venus is very high, so it’s distance from the Sun has little effect on temperature.

Dr A Burns
May 8, 2010 4:09 pm

Troels,
The atmosphere is not static and conductive heat transfer to surroundings is small. Here’s a description:
“An adiabatic temperature change occurs in a vertically displaced parcel of air due to the change in pressure and volume (refer to the gas equation in section 1.2) occurring during a short time period, with little or no heat exchange with the environment. Upward displacement and consequent expansion causes cooling; downward displacement and subsequent compression causes warming. In the troposphere, the change in temperature associated with the vertical displacement of a parcel of dry (i.e. not saturated) air is very close to 3 °C per 1000 feet, or 9.8 °C / km, of vertical motion; this is known as the dry adiabatic lapse rate [DALR]. As ascending moist air expands and cools in the adiabatic process, the excess water vapour condenses after reaching dewpoint and the latent heat of condensation is released into the parcel of air as sensible heat, thus slowing the pressure-induced cooling process.”

George Turner
May 8, 2010 4:10 pm

Ian l. McQueen
Yep. I think the pressure going to zero argument is an oopsie. The pressure is determined by mass and gravity, and so is fixed (except for some small dynamic effects due to weather). It’s the volume and temperature of the atmosphere that vary.

May 8, 2010 4:11 pm

Another great post. I have been trying to go through similar ideas in the Climate Sceptics group for a while myself.
May I suggest a couple of interesting links:
(1) UTexas teaching notes about why there is an adiabatic lapse rate at all (hint: there is no mention of any GH effect)
(2) From the New Mexico State University a table about lapse rates in various atmospheres in the Solar System (and showing that composition might matter, alongside gravity)
In particular, the lapse rate is roughly g/Cp, where g is the acceleration due to gravity and Cp is the atmosphere’s specific heat at constant pressure (cp) divided by the molecular weight. It would be interesting to find out why exactly Cp for Venus would only be 85% of Earth’s.

May 8, 2010 4:11 pm

Forgot to close the hyperlink in previous comment. Apologies.

Jacob
May 8, 2010 4:14 pm

Why is the atmosphere on Venus 92 times more dense than on Earth? That is the big question, that I don’t understand.
Now, if the atmosphere is denser – it means there are 92 times more molecules of gas in the same volume (or layer) of the atmosphere, therefore they would absorb 92 time more outgoing radiation (much more anyway). So, the heat on Venus’ surface is caused by the greenhouse effect after all, by the fact that the greenhouse effect is much stronger there, due to the density of the atmosphere, and not necessarily due to it’s composition (Co2).
If pressure alone could cause heating – why isn’t the bottom of the oceans very hot?

Savant
May 8, 2010 4:21 pm

Steve,
You have almost got it now — here is the relevant question:
For Earth and Venus (as you note) the adiabatic lapse rate is similar; For Earth and Venus, the planetary equilibrium temperature is similar (Venus is closer to the sun but has a higher albedo). So now the question: To what altitude does the atmosphere mix vertically from the surface close to the adiabatic lapse rate (note on Earth that the true lapse rate is ~6.5o/km, e.g. the atmosphere is slightly stable)? You assume in your posts that it must be to the same pressure — but where does this assumption come from? On Earth, the temperate at 50 km is ~250K, if your 10K/km held to this altitude, the surface of Earth would be 750K — clearly something amiss. The answer is that at the tropopause OLR balances the incoming solar: outgoing energy (emission) from the atmosphere by cooler greenhouse gases and from the warmer surface (in the IR windows) balances the solar headed down.
So the important question for Venus is why is the tropopause at 60Km? You make the assumption that it is because this is (approximately) the same pressure as the tropopause on Earth. But there is no physical reason why the tropopause must be at the same pressure on other bodies. As on Earth, the tropopause is where the atmosphere must mix vertically to achieve thermal balance (e.g. read very nice discussion of radiative-convective models by Manabe). If instead of being made of IR absorbing constituents, the atmosphere was made only of N2 (even if it was as massive), the surface temperature would be much colder (and there would be a large day-night difference).
There is not much to this (at zeroth order) beyond the first law of thermodynamics in a compressible (nearly-ideal) gas.

Andrew W
May 8, 2010 4:26 pm

“In my last piece about Venus I laid out arguments against the claim that it is a runaway greenhouse which makes Venus hot. This generated a lot of discussion.”
The accepted view is that present day Venus is a result of a runaway greenhouse, she got too warm, her oceans boiled, the resultant water vapour created a super GH effect, which melted the planets crust, the oxygen released from ionize H2O combined with crustal carbon to create CO2. The planets surface is hot because of its present atmosphere, its atmosphere is a product of a runaway greenhouse.
“we have a sun providing energy to the periphery of the atmospheric system”
Not sure what you mean by this, the sun’s EM radiation is absorbed by atmospheric constituents throughout the depth of the Venusian atmosphere, not at the “periphery”.
“If there were no Sun (or other external energy source) atmospheric temperature would approach absolute zero. As a result there would be almost no atmospheric pressure on any planet”
The surface pressure is almost entirely independent of the temperature, assuming that all the atmospheric constituents remain suspended.

Dave
May 8, 2010 4:28 pm

Again, the height of the tropopause will change with the composition of the atmosphere: therefore, even if the lapse rate stays constant and the temperature at the tropopause stays constant, if reducing the amount of CO2 in the atmosphere causes the tropopause to decrease in height the surface will decrease in temperature. (And note that the troposphere in Venus contains a much larger percentage of the atmosphere than the troposphere on Earth, which would be consistent with a higher CO2 level pushing the tropopause upwards).
(also, while I agree that a runaway greenhouse on Earth is almost certainly not going to happen, I think that your back-of-the-envelope calculation of the effect of 100% CO2 atmosphere is wrong because the logarithmic forcing relationship isn’t going to hold above a couple thousand ppm CO2, and you are underestimating the potential for CO2 to lead to temperature increases at those extreme concentrations)

Stephan
May 8, 2010 4:32 pm

OT: One gets the distinct impression from recent posts here, at CA, and RC etc, that interest in the subject (AGW), is finally waning. Would be interesting to follow the sites statistics recently, to confirm/deny this. Basically the skeptics/deniers were right.. weather, aka climate is not changing due to AG. AGW news stories have certainly dipped. We can all go back and get a life instead of looking at graphs of temps, ice, polar bears, anxiety due to AGW, etc.. Of course a few diehards will keep banging away at it until they too, just give up, a good ol hahaha and LOL!

1DandyTroll
May 8, 2010 4:34 pm

Sometimes I figure GISS should’ve been named after you, sometimes not so much.
What defines atmospheric temperatures and what drives those temperatures? Is it just the proximity of a star? How about gravitational pul from say a black hole? Or just from being close to a gas giant like saturn and its gravitational pul?
But sure, get rid of all the stars and everything would’ve a temperature of absolute zero…. that doesn’t even compute.

Bob_FJ
May 8, 2010 4:38 pm

For anyone still believing that CO2 GHG is the fundamental reason for high surface temperatures, please consider this, (adapted from my comment in the earlier thread):
Here is an authoritative extract from the ESA, (my bold), so let’s examine it, particularly as to why Venus has a uniform average temperature everywhere. (over 117 earth days, and see link below)
“…[1] On Venus there are no day and night variations of the surface temperature. The heat is globally ‘trapped’ under the carbon-dioxide atmosphere, with pressure 90 times higher than on Earth.
[2] Instead, the main temperature variation is due to topography. Just like on Earth, mountain tops are colder, whereas the lowlands are warmer. The ‘only’ difference is that on Venus ‘cold’ means 447º Celsius, while ‘warm’ means 477º Celsius. Such high temperatures are caused by the strongest greenhouse effect found in the Solar System…”

[1a] When facing the sun, she is said to receive at the surface about 10% of sunlight. Whether this is a midday or total facing area average, or the effects of scattering, I don’t know, but whatever, the surface receives SOME solar energy. This energy amount must be lost back to space because the planet is apparently in thermal equilibrium. The fundamental process for this should be convection and conduction. Additionally, since infrared photography etc of the surface has been accomplished there is at least one window for some infrared to directly escape to space.
[1b] At nightime she no longer receives any solar energy, but has capability to lose heat in the same way as on the daylight side, over a period 117 times longer than on Earth. What is more, because the upper atmosphere is no longer heated by solar infrared, (~40% of sunlight), the temperature gradient of the atmosphere should increase, inferring increased conductive/convective cooling. Yet, there is no change in surface temperature! Such a condition would require an impossible perfect insulation layer, and no geothermal energy, but clearly, this is not the case.
[2] This part of the extract supports Steven’s hypothesis, but see also my comment in the earlier thread concerning the strange and unexplained dynamics of the atmosphere, according to the ESA. (that may have an astonishing “mixing” effect).

May 8, 2010 4:40 pm

Dave
You are ignoring the fact that Venus has almost 100% CO2 and it’s lapse rate is the same as Earth’s up to 60 km. The empirical evidence does not agree with your theory.

Jeff Green
May 8, 2010 4:40 pm

(kcom says:
May 8, 2010 at 2:46 pm
The mind is a powerful thing and can overwhelm logic when placed under enough stress. Ask any medical student if this has ever happened to them.)
James Hansen came to his conclusions based on observations. If you can prove him wrong you win. Do ou have a better explanation?

May 8, 2010 4:44 pm

Dave McK
Dry lapse rate means unsaturated (less than 100% humidity.)
Most of the troposphere is unsaturated.
http://www.physics.umt.edu/borealis/RH%2520Lab%2520Report_06.pdf

May 8, 2010 4:48 pm

George Turner
Gas pressure P = nRT/V
There is no term for either mass or gravity.

el gordo
May 8, 2010 4:54 pm

Stephan
Over at Deltoid its all political science these days, rarely do they discuss ‘graphs of temps, ice, polar bears, anxiety due to AGW, etc.’

wayne
May 8, 2010 4:55 pm

Steve, I don’t see how they get the lapse rate for Venus you mention. I tried three ways and each is much lower. Assuming 740K for the surface temp per Wiki, the top graph has two possibilities:
(740K-260K)/58km = 8.3 K/km
(740K-310K)/52.5km = 8.2 K/km
The lower graph, assuming Earth’s mean surface temp at 290K, based on pressure, not temperature is:
(740K-290K)/49.5km = 9.1 K/km
All of these are between the surface and to the point where ~90% of the mass of the atmosphere is lower.
Do you think their 10.468 K/km rate is more accurate? As you were saying, if co2 has it’s hand in it then the lapse should be much higher than the lapse rate of earth and I come up lower, not higher by the equally valid graphs (they tend to mirror what you read in Wiki).

May 8, 2010 4:55 pm

Andrew W
If that is the “accepted view” then I have even less respect for the perpetrators of this nonsense. Basalt melts at 1300 C.

MaxL
May 8, 2010 4:55 pm

As Kwik mentions I really have not given much thought to the atmosphere of Venus either. However, this discussion has been interesting and gets one to thinking. A couple of points need more fleshing out. The statement “If there were no Sun (or other external energy source) atmospheric temperature would approach absolute zero. As a result there would be almost no atmospheric pressure on any planet -> PV = nRT.” The ideal gas law has 3 variables, T, P and V. If you decrease T, as suggested, you can do this by keeping P constant, in which case V (volume) will decrease, you can keep V constant and decrease P or a combination of both. So it is not so simple as saying there would be no pressure if there was zero temperature. The gas molecules would still be there and have the same weight. This introduces another problem, namely the hydrostatic equation which states that the pressure of a column of air is solely a result of the weight of the air above. This applies most of the time to our atmosphere on Earth and is one of the fundamental equations in numerical weather models. Offhand, however, I am not sure how well it applies to Venus.
Another problem is the discussion of lapse rates and the adiabatic process. This requires the combination of both the “First principle of Thermodynamics” which relates heat to temperature, pressure and volume, plus the idea gas equation (PV = nRT). For an adiabatic process (no heat added or subtracted), when you combine these you get Poisson’s equations. The one most familiar is the equation relating temperature and pressure: T1/T2 = (P1/P2)^k
where k is found to be 0.286 for our atmosphere.
This is the equation for the dry adiabatic lines found on Skew-T or tephigram
diagrams. You can use this to find out what the temperature here on Earth would be at be at 9000 hPa given the temperature at 1000 hPa is about 293 K.
It is difficult on a blog to go into much more detail but I hope this helps out a bit.

kwik
May 8, 2010 4:56 pm

Stephan says:
May 8, 2010 at 4:32 pm
Yes, Stephan, but:
They are now promoting new scary stories.Acidification of the osceans seems to be the new big thing. In Norway there has been several stories in the news lately.And lo and behold, after a few months camaign a new research institute is now planned to study this.

Robin Kool
May 8, 2010 4:59 pm

In the end there is simply the warmth given by the sun plus the warmth produced inside Venus, and the warmth radiated into space.
My opinion:
It is the heat the atmosphere gets from the planet surface that determines how far the atmosphere expands into space, not the other way around.
It is not the distance the atmosphere expands into space that determines the temperature at the surface.
The air receives heat on the planet surface, expands, rises and cools down, and falls back. As it falls back and contracts, it warms up again, but it will not gain more heat than it has lost by expanding. As it has also lost heat that is radiated out to space, it will arrive at the surface of the planet cooler than it left it.
My reasoning:
1. OK. For the moment, let’s forget the green house effect and let’s start with a very cold atmosphere, contracted very close to the surface of Venus.
2. You say: “Because we have a sun providing energy to the periphery of the atmospheric system, the atmosphere circulates vertically and horizontally to maintain equilibrium.”
The energy of the sun must go through the atmosphere and warm the surface of the planet, which then warms the lower layers of the atmosphere for circulation to start happening.
(The sun providing energy to the periphery (= outside) of the atmosphere, means the periphery warms up. The air there expands and wants to rise, not sink, thus no circulation. The word periphery is usually used for ‘outside’ and seems misplaced here.)
3. OK, when such a dense atmosphere is heated up, the resulting upward force is greater that of the thinner Earth atmosphere heated up to the same temperature. This makes the Venus atmosphere spread out further into space than Earth’s.
4. And yes, when the expanding gas has reached the outer layer, and has cooled down, it will fall and contract and heat up, but it will not gain more heat than it has lost by expanding. As it has also lost heat that is radiated out to space, it will arrive at the surface of the planet cooler than it left it. (Otherwise it would be a perpetuum mobile).
5. As Venus has no oceans and no biosphere, it has a hell of an urban heat island (UHI) effect.
The energy that the sun radiates on the surface heats up a thin layer of surface to very high temperatures. The whole planet is one big heat island.
None of it is spread over a huge body of water like our oceans or converted into plant growth.
I would expect that to be the most important reason the surface temperature of Venus is so much higher than that of the Earth.
Plus, of course, that Venus is closer to the Sun and receives more heat per square meter or foot than Earth.
6. The much denser atmosphere is much better at absorbing the heat of the planet’s surface, than Earth’s thinner atmosphere. Giving it a huge upward, expansive force, that expands it far out into space.
But the extend to which it spreads out is determined by the heat it receives on the surface, so that after the hot air has reached the cold space and – cooled down – falls back, it does warm up, but not to higher temperatures than it had when it started at the surface of the planet.
In other words, it is the heat content of the atmosphere – heat it gets from the planet surface – that determines how far the atmosphere expands into space, not the other way around.
It is not the extend to which the atmosphere expands into space, that determines the temperature at the surface.
7. The heat content of the atmosphere if Venus is so high, because of the massive UHI effect and because the dense atmosphere is so efficient at absorbing heat from the surface.
(8. I imagine that without oceans there is no thunderstorm belt that transports massive amounts of heat to the highest layers of the atmosphere, bypassing the greenhouse effect – the thermostat Earth has in the tropics.)

u.k.(us)
May 8, 2010 5:03 pm

I’m in way over my head here, but doesn’t the “solar wind” change the depth of our atmosphere. Which would cause pressure and temperature changes?

George Turner
May 8, 2010 5:05 pm

I’d like to suggest another experiment for Steve.
To simulate the effects of an IR blocking atmosphere on a very dim planet, build a greenhouse. The glass for the greenhouse should be selected for absolute IR opacity across the band, and it can even be triple-paned and argon-filled to limit convection losses. To best mimic the dim light on the surface of Venus, build the greenhouse deep in the forest and wait for a very dark, overcast day. Sit inside with a good thermometer and see if the temperature approaches 900 degrees F.

May 8, 2010 5:09 pm
Jeff Green
May 8, 2010 5:10 pm

(http://en.wikipedia.org/wiki/Atmosphere_of_Venus#Structure_and_composition
The large amount of CO2 in the atmosphere together with water vapor and sulfur dioxide create a strong greenhouse effect, trapping solar energy and raising the surface temperature to around 740 K (467°C), hotter than any other planet in the solar system, even that of Mercury despite being located further out from the Sun and receiving only 25% of the solar energy Mercury does.[11])
Based on AGW theory if venus’s atmosphere were nitrogen, then infrared would continue back out into the space without being reactive to the nitrogen. The gas in the atmosphere does make a difference as to how much heat is held in.

May 8, 2010 5:12 pm

MaxL
Gas pressure is created by the motion of molecules. As you approach absolute zero, molecules cease to move. So there is no pressure.
Volume has to remain above zero, because the molecules have a finite size. So yes, it is that simple.

suricat
May 8, 2010 5:14 pm

Ian l. McQueen says: May 8, 2010 at 2:40 pm
“I am always puzzled by the statement that the atmospheric pressure on the surface of Venus is a large multiple of that on earth.”
If you blow away many of the lighter elements of a planet’s atmosphere with the ‘solar wind’ and continue to warm it, the heavier elements will stay there in the atmosphere to provide a greater surface pressure.
Having said that, I’m sure you realise that the heavier gasses should form a shorter altitude distance for any change in pressure. It’s curious that the lapse rate of both Venus and Earth are similar, but is this more to do with the similar orbital distance from Sol than the atmospheric makeup of these planets?
Well I think this is possible, but perhaps it’s more to do with the natural progression of (and here’s a new term) ‘nature’!
We have the ‘nature’ of Earth, and we have the ‘nature’ of Venus.
The history of Venus has led it to its current situation, and ditto for Earth. Although Venus has a lower gravity field than Earth it has lost many of its lighter elements. Thus, Venus’s troposphere contains compounds that are much heavier than those incorporated within Earth’s troposphere and this reflects in its higher surface pressure.
Best regards, Ray Dart.

wayne
May 8, 2010 5:14 pm

I ought to correct the percentage I noticed in my comment above, at ~50-55km altitude about 99% of the mass is below this point, not 90%. Technical, but to be as accurate as possible…

William Sears
May 8, 2010 5:21 pm

The adiabatic lapse rate argument works best with heating from below. This might be caused by geothermal activity since the atmosphere of Venus, unlike earth, is opaque. I believe that a number of scientists have studied the strange geology of Venus’ “not quite plate tectonics” and no doubt have already made this same suggestion. Popular knowledge dies hard though, even among scientists, and the runaway greenhouse analogy lives on.

GeoFlynx
May 8, 2010 5:28 pm

[snip – try rewording that, there’s no reason to hurl insults]

May 8, 2010 5:34 pm

William Sears
Whether the source of heat is geothermal or absorbed SW, the lapse rate is the similar on both planets – indicating that greenhouse effect is less important on Venus than advertised.

Jeff Green
May 8, 2010 5:37 pm

(http://en.wikipedia.org/wiki/Atmosphere_of_Venus#Structure_and_composition
The atmospheric pressure at the surface of Venus is about 92 times that of the Earth, similar to the pressure found 910 metres below the surface of the ocean. The atmosphere has a mass of 4.8 × 1020 kg, about 93 times the mass of the Earth’s total atmosphere.[1] The pressure found on Venus’s surface is high enough that the carbon dioxide is technically no longer a gas, but a supercritical fluid. The density of the air at the surface is 67 kg/m3, which is 6.5% that of liquid water on Earth.[1])
The carbon dioxide is so thick that it has more the properties of fluid rather than a gas. There are all kinds of studies and observations showing co2 blocks infrared energy.

Ian L. McQueen
May 8, 2010 5:38 pm

Stephan says:
May 8, 2010 at 4:32 pm
OT: One gets the distinct impression from recent posts here, at CA, and RC etc, that interest in the subject (AGW), is finally waning. Would be interesting to follow the sites statistics recently, to confirm/deny this. Basically the skeptics/deniers were right.. weather, aka climate is not changing due to AG. AGW news stories have certainly dipped. We can all go back and get a life instead of looking at graphs of temps, ice, polar bears, anxiety due to AGW, etc.. Of course a few diehards will keep banging away at it until they too, just give up, a good ol hahaha and LOL!
Staphan, in an ideal world you would be right. But, unfortunately, many governments have accepted the IPCC reports as gospel truth and have enacted legislation designed to reduce CO2 emissions. They will do nothing for the climate but WILL do great harm to the economy. It is as if we were on a hill overlooking a railway line on which a train is headed at high speed for a bridge that is no longer there. We know that a trainwreck is inevitable, but there is nothing that we can do to stop it.
IanM

May 8, 2010 5:45 pm

Jeff Green
There is no question that CO2 absorbs infrared.

Ian L. McQueen
May 8, 2010 5:47 pm

stevengoddard says:
May 8, 2010 at 4:48 pm
George Turner
Gas pressure P = nRT/V
There is no term for either mass or gravity.
Steven-
The term “R”, the gas constant, has units of 8.314472(15) J·K-1·mol-1

Ian L. McQueen
May 8, 2010 5:48 pm

stevengoddard says:
May 8, 2010 at 4:48 pm
George Turner
Gas pressure P = nRT/V
There is no term for either mass or gravity.
Steven-
The term “R”, the gas constant, has units of 8.314472(15) J·K-1·mol-1
To me, “mol” implies “mass”, and in a gravitational field it will have weight. Doesn’t this contradict your statement?
IanM

George Turner
May 8, 2010 5:52 pm

Steven,
Gravity doesn’t appear in PV=nRT, but it does appear in F=ma. The mass is the mass of the atmosphere and the acceleration is due to gravity. That gives the downward force an atmosphere exerts on the surface (minus a small error because gravitational acceleration decreases with altitude).
Given a planet’s surface area S, the average surface pressure must be F/S = mg/S.
Venus atmophere’s mass is approximately 4.8×10^20 kg and its surface gravity is 8.87 m/sec^2, so the force it exerts on the surface is 4.26×10^21 Newtons. This is spread across a surface area of 4.6×10^8 square km, or 4.6×10^14 m^2, so the pressure is 4.26×10^21 N/4.6×10^14 m^2 = 9.26×10^6 N/m^2 (Pascals), which is 1343 psi or 91.4 atmospheres.
Even if the atmosphere condenses to a liquid or freezes to a solid, the pressure on top of the rocks is still going to be 91.4 atmospheres.
🙂

May 8, 2010 5:53 pm

Ian L. McQueen
Joules is a unit of energy
Degrees Kelvin is a unit of temperature
moles is a non-dimensional number – 6.022 x 10^23 molecules
None of these are units of mass or gravity.

Jbar
May 8, 2010 6:00 pm

Steve,
I agree with your claim about the lapse rate explaining in part why the surface of Venus is so hot, but the lapse rate does not disprove the existence of a greenhouse effect, and I believe it is only part of the story about the high surface temperature.
First, a technicality – your dry lapse rate only applies for an adiabatic process where there is no condensation or heat transfer. It is an upper limit. The actual lapse rates on both Earth and Venus are lower than their dry lapse rates.
In your previous post “Hyperventilating on Venus”, you presented this plot (http://www.globalwarmingart.com/wiki/File:Atmospheric_Transmission_png) showing the transmissivity of various gases in Earth’s atmosphere. It shows that the 380-some ppm of CO2 in Earth’s atmosphere is enough to block all infrared radiation from 13 microns to 17 microns wavelength. Combined with the infrared opacity of Earth’s water vapor, that still leaves a broad window of atmospheric transparency to infrared between 8 microns and 13 microns, enough to keep the Earth at its current comfortable temperature range.
However, on Venus, the CO2 concentration is the equivalent of 89 million ppm, relative to Earth’s atmosphere, or 234,000 times the optical thickness of CO2 on Earth. As a result, the atmospheric transmissivity to infrared on Venus is quite different from the plot linked above.
I got into this Venus argument with a friend last year and to satisfy myself of the effect of CO2, I subscribed to Spectralcalc.com for a month to run some numbers. I was able to replicate the CO2 curve in the Atmospheric Transmission plot for Earth, and I found that for Venus, the absorptive range of the gas broadens so much to other wavelengths that the Venutian atmosphere is opaque to infrared from below 2 microns up to 28 microns except for three relatively narrow windows of transparency at 2.3, 3.4, and 5.7 microns, even for only 5 kilometers of atmospheric depth (near the surface). Also, my sources indicate there is enough water vapor in the Venutian atmosphere (somewhere above 50 km altitude) to effectively block infrared emissions above 28 microns.
This shows the Venutian atmosphere is way more opaque to infrared than Earth’s atmosphere and does indeed reveal a strong greenhouse effect on Venus. Even the lower atmosphere, while efficiently passing infrared from 28 microns and higher (because there is virtually no water vapor below the clouds) is still almost opaque from 2 to 28 microns and presents a substantial impediment to radiative cooling of the surface.
As I said in the beginning, I agree with your claim that the lapse rate helps to explain partly why the Venutian surface is so very hot, but I think that lapse rate is not the whole story. With the surface receiving only 1/6th the sunlight that the Earth’s surface receives, something has to act as a barrier to slow the rate of radiation from the surface to the much cooler haze layer at 30-50km altitude, and I think that something is the CO2 infrared opacity. I’m no atmospheric scientist or physicist and I lack the tools to model this, but I suspect that if CO2 were transparent to infrared the Venutian surface would be a lot cooler than it is, but still substantially hotter than the upper atmosphere thanks to the lapse rate.
Heat from below ground cannot possibly explain the high surface temperature as some have suggested. On Earth, the heat radiating from the ground is only 1/10th of a watt per square meter, and even if it is ten or 100 times that on Venus, this is still dramatically less than the visible light reaching the surface.
[Interesting factoid: On Earth, refraction or bending of sunlight makes the horizon light during dusk and dawn even though the sun is not up. Well according to one source, on Venus the refractive effect from the thick atmosphere is so much stronger than on Earth that even the darkest region of the dark side still gets some glow from the sunlit side.]

Mike M
May 8, 2010 6:01 pm

I disagree on the PV=nRT analysis Steve. Assuming the gas remains a gas, the pressure remains constant at the surface because we must obey conservation of mass. Given a control column of a given mass of atmosphere, open at the top to vacuum space, the pressure at the surface will not change** with temperature, (** ignoring, as another poster above rightly pointed out, differences in gravity WRT altitude), because it’s weight remains the same. So it’s ‘V’ that changes not ‘P’. As temperature decreases, the height of the column will decrease thus decreasing the volume.

Mike M
May 8, 2010 6:08 pm

Speaking of radiation… How much of Venus’s heat is coming from it’s own core? Given its formation closer to the Sun, I would surmise that Venus might have a greater proportion of heavier/more unstable elements at its core than Earth. ?

George Turner
May 8, 2010 6:11 pm

I need to amend my previous comment.
If the CO2 on Venus froze it would form dry ice about 2000 feet deep, on average, and would of course form glaciers, thus increasing the pressure in the lowlands and leaving the mountain tops in a vacuum.
As a side note, the black body spectrum at 735 Kelvin starts emitting at around 700 nm, in the visible spectrum, peaks at about 3.9 microns, then tapers off towards 15 microns.
blackbody calculator
Since very little energy makes it down to the surface, successfully maintaining Venus’ temperature purely due to IR blocking would require trapping 99% of the energy emitted between 1 to 15 microns. I don’t think CO2 alone is going to accomplish it.

DesertYote
May 8, 2010 6:11 pm

The whole idea of a runaway greenhouse effect causing the dense atmosphere of Venus is so silly that it could only have been as created in the minds of Marxist brainwashed pseudo-scientists with a political agenda. The Universities have been pushing the nonsense for so long that even some real scientists have been hood winked by it. It is not that Venus has an unusually high atmospheric density for its size and location, its that the Earth has an unusually low density. That density can be quite adequately be attributed by that absurdly big ball we call the Moon.
Why are so many so confused by the relationship of temperature and density. Gas is compressible so its density is highly related to pressure. Energy will distribute evenly through the mass. The more mass per volume, the more kinetic energy per volume, the higher the temperature. It is not pressure causing heating. Sheesh! Liquid is not a compressible fluid so its density is not very related to pressure. The behaviour of the Earth’s oceans tells us nothing about the behaviour of an atmosphere. So bringing up the thermal characteristics of the Ocean is meaningless.

May 8, 2010 6:18 pm

Jeff Green, please educate yoursel on how little of the infrared band is active with CO2 even at the higher pressure and temp of the lower Venusian atmosphere.
IF all of the IR was concentrated in the tiny active bands of CO2 (which it isn’t, see black body and grey body emisssions), then CO2 could have a higher influence on temperature in the system. As it is the MASS of CO2 has a much larger effect than its GHG properties.

CRS, Dr.P.H.
May 8, 2010 6:24 pm

This is, without a doubt, the most authoritative description of the planet Venus and its environment: http://www.feedbooks.com/book/2482.pdf

SeanH
May 8, 2010 6:32 pm

With regards to the atmospheric pressure comment, it appears as though he is talking about the pressure by the gaseous envelope surrounding the planet, the atmosphere. If the temperature were dropped to 0K, the gases would solidify, leaving the planet without an atmosphere. Hence, no atmospheric pressure.

May 8, 2010 6:32 pm

There’s a basic fallacy here which Leonard Weinstein has covered fairly well. Yes, the adiabatic lapse rate is as described. With a gas in motion and under gravity, there will be a temperature difference across any layer approx as determined by the ~10 K/km figure.
But that’s a difference. It doesn’t tell you how hot it will be at top or bottom. The analogy is a battery. There’s a 1.5V difference end to end, but the actual voltage depends on how it’s connected. Where it is earthed.
A 9.2 MPa atmosphere of nitrogen will have a big temperature difference, top to bottom, but it is not “earthed” at the top. No heat is exchanged there. The temperature at the bottom is entirely determined by the radiative balance there. That’s why the bottom, in Venus conditions, couldn’t be at 700K. The 12000 W/m2 IR emitted at 700K would escape unhindered. The surface would have to cool until balance with avaible sunlight was restored. The whole column of N2 would cool with it, maintaining the lapse rate. The top would cool at the same rate as the bottom.
This is what the greenhouse effect does. It “earths” the system at TOA. CO2 emits to space at the top, not at the bottom. The radiative balance sets the temperature there. About 164 W/m2 (less than Earth) has to be emitted there to balance net sunlight absorbed (after albedo) and than determined the temperature there. The lapse rate then determines the temperature at the surface, and makes it hot. Just as on Earth, except that with our smaller GHG component, Earth also has significant emission from the surface at atmospheric window frequencies.

Stephan
May 8, 2010 6:40 pm

Well to those who replied above all I can say is Australia is out.. looks like the USA is gonna be out too.. I don’t think the French or Germans really care anymore. The British government will be much less interested that the Laborites.. and so on.. In fact it looks like Bolivia and the UN is now taking over the AGW cause. In fact I think the next Winter in both SH and NH (because that is the only thing the ordinary fellow/fellaw in the street really understands), is going to be so so cold…Good luck to ol Evo Morales Hahaha. BTW I think it is the actual weather that determines whether the ordinary person on the street will decide whether AGW is happening or not and most of the shift is due to that (ie very cold winters is Europe and USA this year). They are having doubts….

May 8, 2010 6:43 pm

Nick Stokes,
“CO2 emits to space at the top, not at the bottom.”
Which side of the molecule is the TOP??
HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA
In case any one listens to you, CO2 emits to space from tropopause out to the edge of the atmosphere here on earth and a similar depth on Venus. You are being simpleton again and more confusing than informative.

Steve Goddard
May 8, 2010 6:48 pm

I’m not sure where anyone got the idea that I am suggesting that there isn’t a greenhouse effect on Venus. It certainly wasn’t from anything I have written. This is a discussion of relative magnitude.

Richard Sharpe
May 8, 2010 6:55 pm

DesertYote at May 8, 2010 at 6:11 pm said:

Why are so many so confused by the relationship of temperature and density. Gas is compressible so its density is highly related to pressure. Energy will distribute evenly through the mass. The more mass per volume, the more kinetic energy per volume, the higher the temperature. It is not pressure causing heating. Sheesh!

Wikipedia defines temperature as the average kinetic energy of particles in matter. You seem to be talking about energy density. While Wikipedia often contains things I disagree with, there seems to be a disconnect here.

Steve Goddard
May 8, 2010 7:01 pm

George Turner
Your explanation is correct in that gravity is the cause of the pressure, which drives the temperature.

George Turner
May 8, 2010 7:03 pm

Well Steve, I just thought it was assumed. Since Venus is totally devoid of vegetation, the idea of a greenhouse on it is rather silly. ^_^
Anyway, given the little F=ma thing, imagine if we reduced Venus’ surface gravity by a factor of 90, to about 0.01G or so (Vulcan terraformers probably do this all the time). Then we have a planet with the same amount of CO2, the same clouds, the same basic atmospheric structure (just stretched way up), but a surface pressure that’s Earth normal. If GHG completely drives Venus’ temperature then the dramatic change in surface pressure wouldn’t matter in the long term, and it would still be 700K+. If adiabatic heating is largely responsible then the change should produce a much cooler surface.

DesertYote
May 8, 2010 7:15 pm

Nick Stokes
May 8, 2010 at 6:32 pm
“The top would cool at the same rate as the bottom.”
No it would not unless the density was constant which it would not be.

May 8, 2010 7:26 pm

Steve Goddard
“I’m not sure where anyone got the idea that I am suggesting that there isn’t a greenhouse effect on Venus. It certainly wasn’t from anything I have written. This is a discussion of relative magnitude.”

Well, Steve, what then is your point? Relative magnitude of what? The fact that the lapse rate creates a temperature difference between where GHG’s emit (high) and the surface has always been an essential part of the greenhouse effect.

Steve Goddard
May 8, 2010 7:27 pm

Mole is a non-dimensional number. A mole of H2 weighs much less than a mole of UF6

Keith Minto
May 8, 2010 7:30 pm

The heat MUST be created by planetary forces, see http://www.esa.int/esaSC/SEMUKVZNK7G_index_0.html .
It has long been recognised that there are simply not enough craters on Venus. Something is wiping the planet’s surface clean. That something is thought to be volcanic activity……..
and “Now we have strong evidence right at the surface for recent eruptions,” says Sue Smrekar, a scientist at NASA’s Jet Propulsion Laboratory in California. They do say They estimate that the flows are possibly as geologically recent as 2 500 000 years – and likely much less, possibly even currently active. In other words they don’t know, but something must be bringing heat from the interior of the planet to lava flow the surface. This must be the major phase change going on in ‘Her’. Recent laval surface remodelling seems to me to be the cause of the night/day hot surface temperatures, the sun’s role on the surface heat seems minor. The (relatively) waterless atmosphere without significant convective
forces seems to be keeping the heat in.
This enormous heat must be coming from the planet itself, the atmosphere is merely a blanket, the adiabatic lapse rate is too limp to explain such persistent high night /day heat.

DocMartyn
May 8, 2010 7:45 pm

Just why are there clouds? Sunlight hits the top of cloud, some scattered, some absorbed, clouds evaporate.
Why does Venus have clouds during the day time? For clouds to form a liquid must have been heated, evaporated, rose up through the atmosphere and then cooled as the pressure drops.
So, why are there clouds?

Leonard Weinstein
May 8, 2010 7:50 pm

I want to point out that the oceans of the Earth hold about 40 times as much Carbon compounds as the atmosphere, and that came from dissolved CO2. In addition, the carbonate compounds in the solid land surface and sea floor of the Earth contain about 40,000 times as much Carbon as the atmosphere, and that Carbon came from life on early Earth forming Carbonate shells and organic debris (and oil and coal) from early CO2, and that this debris was sequestered on the bottom of oceans and on land. The waste product of plants taking in CO2 is Oxygen. This implies that there was once mostly CO2 in early Earth atmosphere, and much was removed over time by living organisms. Additional atmospheric material was probably removed in the collision between Earth and another planet that resulted in the formation of the Moon. There is no big mystery why Earth has little CO2 and both Venus and Mars are mostly CO2. The differences in quantities depend mainly on the size of the planets and formation details.

George Turner
May 8, 2010 7:54 pm

An experiment:
We drop a spherical probe onto Venus, weighted on the bottom so it rolls right-side up. The probe is a hollow ball well insulated with asbestos (gotta use that stuff somewhere!) and with a large IR transparent window on top. The window is insulated against convection and conduction by having multiple panes, argon filled from a high-pressure canister and a pressure regulator.
The temperature on Venus’ surface is in balance, so the heat gained from downward radiation plus the heat gained from the atmosphere by convection equals the heat lost to upward radiation and the heat lost to convection.
The internal temperature of the well-insulated probe will stabilize to a value determined only by the radiant energy balance. If the probe is cooler than the outside atmosphere then the surface is losing more radiant energy than it’s gaining, which means Venus surface must gain heat from atmospheric convection. If the probe runs hotter than the outside atmosphere then the surface must be losing heat to the atmosphere by convection. The probe’s results should allow some numbers to be placed on the surface radiation balance.
Unfortunately, finding funds for a probe that might remove Venus’ status as a dire warning to Earthlings, and thus cause us to defund all future Venus missions, might be a bit difficult.

George Turner
May 8, 2010 7:59 pm

I’ll consult with the local florist, but I’m pretty sure that huge pressure differences don’t come included in the standard greenhouse package.
Hehehehe.

George Turner
May 8, 2010 8:00 pm

Darn it. That was in reply to Nick Stokes

DesertYote
May 8, 2010 8:00 pm

Richard Sharpe
May 8, 2010 at 6:55 pm
I was under the impression that it is average kinetic energy within a volume.

May 8, 2010 8:40 pm

DesertYote
Yes, you’re right – the dry lapse rate wouldn’t change, but would operate over a shorter distance as the gas cooled and contracted. But it doesn’t change my point that a N2 atmosphere would cool as the surface cooled in a way that just tracks that cooling. It doesn’t constrain the surface temperature.

J.Hansford
May 8, 2010 8:41 pm

Ian l. McQueen says:
May 8, 2010 at 2:40 pm
“……A further niggle comes from the statement: “If there were no Sun (or other external energy source) atmospheric temperature would approach absolute zero. As a result there would be almost no atmospheric pressure on any planet -> PV = nRT.”
At 0K all gases would have condensed to liquid or solid, but the mass of the gas would still be present as a layer on the surface. I would think that the liquid/solid would be as heavy (=attraction due to gravity) as the atmosphere from which it was produced, and possibly a tiny bit higher since the molecules would be concentrated at the surface instead of extending a distance above the planet and thus minutely farther from the center of attraction of the mass of the planet.”
———————————————————————————
At absolute zero…. No molecule is in a gasseous state…. It is solid and inert…. even with no pressure…. This is a theoretical limit of course…. for Absolute zero has never been observed….. So a planet with a 100 percent nitrogen atmosphere would have a surface of solid nitrogen at 0K. There would be no sublimation… Because no molecule has any energy left.
That’s my understanding anyway.

Dave McK
May 8, 2010 8:42 pm

stevengoddard says:
Steve- check out a basic HVAC manual- there is a reason nobody designs a heat pump with a gas that doesn’t change phase.
Next, calculate the enthalpy of the constituents of air = be generous and assume 1% h20 and 500ppm co2 – do the math and see who carries the joules. The water does more than 50,000 times the work of the co2. Nevertheless, co2 does a tiny bit of work- and that only increases the efficiency of the heat flow from boiler to radiator.
Examine the profiles of earth – overlay the charts with precipitation and IR radiation.
If you don’t know the difference between the lapse rate of dry air and the actual measured lapse rate on earth which is much different, then look it up. Dithering on distractions doesn’t change these 2 fundamental facts:
Earth has a heat pump with water as the working fluid.
Any increase in efficiency of the working fluid in a heat pump (like adding some heat capacity the way CO2 does) only slows the flow for the same work. Measure and calculate the work.
At least understand that thermodynamics is about heat and that is not measured in degrees. Heat is NOT measured in degrees and there is no way to convert degrees to watts. NOT possible.
You want to study heat, you have to actually speak about heat. This has been hugely ignored for a reason.
Meanwhile- every time you suggest that the CRU and the rest are unscientific- let me clear this up once and for all:
They are brilliant psychologists and have the best and brightest marketing psychologists money can buy. You only imagine they aren’t scientific because the sad sorry truth is that you have been, are being and will keep on being duped because they are smarter than you where it matters in this game. You just haven’t really got a grip on what the game is. You’ve been outsmarted and never really stood a chance. You still argue about weather.
Strut and fret and in the end – you get shafted because you weren’t watching the pea, you were watching TV.
Troposphere, shmoposphere – clouds, rain, snow.
Once it was ‘don’t talk about religion or politics’ and it was safe to talk about the weather because nobody got offended and everybody knew something to say.
Admit that it was a brilliant maneuver to suck common man into war over the most innocuous topic. Look at the ROI. Look how well it worked and continues to work.
No, sir, they are extremely scientific and the science is valid – the results prove it.
How long ago was venus a molten ball, man? And how many trillions will it cost to play make-believe?
You don’t need a weatherman to know which way the wind blows – Dylan.
Sorry for the long winded rant. It’s been building up. Nothing personal – I’m looking at where the train is about to go dig a dirt road and the passengers chat and gossip and that bothers me because I did my Dostoevsky period long ago and didn’t want to revisit it in america, in real time.
Hugo Chavez is a piker compared to the creeps stealing america. But hey- some evolution is about to happen and guess who will get the darwin awards- it won’t be Hansen, Schmidt and Jones. Who’s the unscientific one? Well, who has the whose money?
I think I can rest my case.

May 8, 2010 8:50 pm

Steve Goddard says:
May 8, 2010 at 7:27 pm
Mole is a non-dimensional number. A mole of H2 weighs much less than a mole of UF6

The mole is the SI unit of the amount of substance, it is not non-dimensional, a mole of a substance has a mass equal to the substance’s molecular weight.

GaryW
May 8, 2010 8:56 pm

Steve Goddard
I usually agree with your postings. This one I am having trouble with. Adiabatic Lapse Rate is about temperature changes as air masses move up and down in altitude. Environmental Lapse Rate is what I think you are trying to describe. That is the temperature lapse rate with altitude. That is what you get when the air is not moving. Yes, I realize the atmosphere of Venus is probably moving up and down. However, that movement balances out producing a net neutral effect with respect to pressure change.
Consider a tall column of perfectly insulated gas. Given sufficient time for temperatures to stabilize in the column, there will be no difference in temperature top to bottom. Though at a higher pressure, the bottom of the column will not be warmer than the top. Physics show us that the gas at the bottom is at a higher energy level because of the greater potential energy associated with the higher pressure. That does not mean, however, that the gas molecules at higher pressure exhibit greater kinetic energy than the those at lower pressure.
For planetary atmospheres, the Environmental Lapse Rate is a function of the energy lost versus gained from radiation and conduction at a given altitude. Pressure figures in only in the density of the molecules available to absorb and release energy and whatever phase or chemical changes may occur.
We should actually be calling what is happening on Venus a “blanket” effect, not a “greenhouse” effect.

May 8, 2010 9:02 pm

Dave McK
You can stop hyperventilating now. The average measured lapse rate on Earth is a little lower than the dry lapse rate. About 6.5. On Venus the average measured lapse rate is also a little lower than the dry lapse rate at 8.5. Not much difference.
Your argument doesn’t provide much useful information about why Earth is 20C and Venus is is 485C.

J.Hansford
May 8, 2010 9:06 pm

Jacob says:
May 8, 2010 at 4:14 pm
Why is the atmosphere on Venus 92 times more dense than on Earth? That is the big question, that I don’t understand.
Now, if the atmosphere is denser – it means there are 92 times more molecules of gas in the same volume (or layer) of the atmosphere, therefore they would absorb 92 time more outgoing radiation (much more anyway). So, the heat on Venus’ surface is caused by the greenhouse effect after all, by the fact that the greenhouse effect is much stronger there, due to the density of the atmosphere, and not necessarily due to it’s composition (Co2).
If pressure alone could cause heating – why isn’t the bottom of the oceans very hot?
————————————————————————————-
You are confusing gasses and liquids Jacob… Seems a few others are doing the same. Gasses are compressible, liquids are not….. Compress a gas enough, and it becomes a liquid…..
Compressing a solid or liquid results in a crystalline structure I believe, but only under immense pressure…..(?)

George Turner
May 8, 2010 9:23 pm

Gary W,
If the atmosphere on Venus stopped circulating, then I agree that the compression effects would dissipate. But the atmosphere there is constantly rotating in two giant Hadley cells. The air rises near the equator, moves to the poles, descends, and moves to the equator again, so it is always undergoing cycles of compression and expansion. This means it is also undergoing cycles of adiabatic heating and cooling.

Dave
May 8, 2010 9:29 pm

“You are ignoring the fact that Venus has almost 100% CO2 and it’s lapse rate is the same as Earth’s up to 60 km. The empirical evidence does not agree with your theory.”
I am not saying that the temperature contribution of GHGs comes from changing the lapse _rate_. I am pointing out that to use the lapse rate to determine the surface temperature, you have to know both the temperature at the tropopause and the altitude of the tropopause. GHGs (and the resulting optical thickness/depth/opacity) change the altitude at which the atmosphere emits to space. Once you know that altitude, and the temperature at that altitude, _then_ you can use the lapse rate to calculate the surface temperature.
A totally transparent atmosphere will result in a planet that emits to space from the surface, and therefore the temperature of the surface will be in radiative balance with the incoming radiation from the sun. As you add GHGs, the height at which the atmosphere emits to space will increase, and the temperature of the surface increases. There is not some magic concentration of GHGs at which Venus suddenly jumps from -46 degrees C (the temperature of the surface given the existing albedo and no greenhouse effect at all: yes, this requires assuming clouds that exist at that temperature and reflect incoming light but don’t trap outgoing light, but this is a thought experiment) to 450 degrees C.
Replacing 90% of your CO2 with Folgers Crystals (I mean, N2) would change the optical thickness, and therefore the height at which you emit to space, and therefore the surface temperature EVEN IF THE LAPSE RATE REMAINS CONSTANT.
“Mars is even colder than earth despite having a 95% CO2 atmosphere, because it’s atmosphere is very thin.”
No, Mars is even colder than earth despite having more CO2 than earth because it is a lot farther from the Sun, and the additional radiative forcing from the CO2 is not enough to make up for the lower solar radiation.
Look: there are now two models of the Earth + Venus that we’re discussing: the “Standard Model” which depends on GHGs, and the “Goddard Model” which apparently requires some non-zero amount of GHGs but mostly depends depends on pressure. Why do I prefer the Standard Model, if both models apparently get the surface temperature right? I prefer the Standard Model because using the same set of physical laws it can also explain the mesospheric, stratospheric, and thermospheric temperature profiles. It can explain why the tropopause changes altitude and temperature depending on latitude. Effectively, it is a sophisticated model that has been used by atmospheric and planetary scientists for decades and survived all their tests. Is it perfect? Well, it doesn’t, for example, tell us what Climate Sensitivity should be, but for problems like explaining Venusian, Terran, and Martian temperature profiles given existing GHG concentrations, clouds, solar radiation, etc. it does really well – whereas the Goddard Model can only explain temperatures from the surface to the tropopause, and only if you tell it where the tropopause is and what temperature the tropopause is.

Keith Minto
May 8, 2010 9:32 pm

George Turner says:
May 8, 2010 at 7:54 pm
George, I think you are on the right track, all you need is a downward sensor facing the crust in the shadow of the craft and an upward sensor sensing radiative energy from above and compare the two.
Willis, in the earlier thread, suggested that the surface pressure was such that a super critical fluid would occur, the images above would suggest otherwise.

Bamboozled
May 8, 2010 9:33 pm

What about the role of upper atmosphere sulfuric acid clouds? They are dense and heavy, right? Can they act like a glass of plastic film in a real greenhouse? http://astronomyonline.org/SolarSystem/VenusIntroduction.asp says “Extremely high atmospheric winds – 360 km/h – yet mild breeze near the surface”. This implies there is little heat exchange via convection near the surface. So, it’s like a car with rolled up windows in a parking lot under direct sunlight–it gets unbearably hot inside because hot air cannot escape. High atmospheric pressure and denser atmosphere is just the result of this.

May 8, 2010 9:35 pm

It is very important to note that despite radically different compositions, both atmospheres have approximately the same dry lapse rate. This tells us that the primary factor affecting the temperature is the thickness of the atmosphere, not the composition. Because Venus has a much thicker atmosphere than Earth, the temperature is much higher.
No it doesn’t, all it tells you is that the temperature gradient through the atmosphere is approximately the same. The actual temperature reached depends on the boundary condition, it doesn’t follow that the thicker atmosphere will be warmer. The composition does have a controlling role, a nitrogen atmosphere of similar pressure and thickness on Venus would result in a cold planet (surface ~230K).
With a constant lapse rate, an atmosphere twice as thick would be twice as warm. Three times as thick would be three times as warm. etc.
No, this does not follow!
Now, lets keep the atmospheric composition of Venus constant, but instead remove almost 91/92 of it – to make the mass and thickness of Venus atmosphere similar to earth. Because lapse rates are similar between the two planets, temperatures would become similar to those on earth.
No, the temperature difference from surface to tropopause would be the same, not the actual temperatures.
This and the associated thread show quite clearly that an IR-opacity of the atmosphere is the cause of atmospheric heating, i.e. ‘the greenhouse effect’.
Titan has a thicker atmosphere (mostly N2) than Earth yet is much colder, surface T 95K.

Spector
May 8, 2010 10:00 pm

To get the atmosphere on Earth as dense as Venus, I think we would ‘need’ something like a nearby supernova to flash-boil the ocean. If most of the energy received went into boiling the water, then the total mass of the planet should remain about as it was. I do not know if the atmosphere would cool and the oceans would reform after this event or if the new condition would remain stable. It would be a moot point.

Alvin
May 8, 2010 10:06 pm

Ugh, stop quoting Wiki as a source guys.

DesertYote
May 8, 2010 10:12 pm

Nick Stokes
May 8, 2010 at 8:40 pm
Got it. Sorry for not seeing the point you were trying to make to begin with.

May 8, 2010 10:26 pm

Phil.
You must have forgotten your high school chemistry.
A mole is most definitely a non-dimensional number. It is 6.023 * 10^23 molecules.
One of the interesting properties of gases (Avogadro’s law) is that they all occupy about the same volume at the same pressure and temperature, regardless of molecular weight. That is why the ideal gas law does not have a term for mass.
Avogadro’s law (sometimes referred to as Avogadro’s hypothesis or Avogadro’s principle) is a gas law named after Amedeo Avogadro who, in 1811,[1] hypothesized that “Equal volumes of ideal or perfect gases, at the same temperature and pressure, contain the same number of molecules.” Thus, the number of molecules in a specific volume of gas is independent of the size or mass of the gas molecules.

CRS, Dr.P.H.
May 8, 2010 10:35 pm

Hansen presents a dust insulation model as the cause of Venus’ high temperature in his 1967 article:
http://pubs.giss.nasa.gov/docs/1967/1967_Hansen_Matsushima.pdf

Mike McMillan
May 8, 2010 11:00 pm

stevengoddard says:
George Turner –
Gas pressure P = nRT/V . There is no term for either mass or gravity.

stevengoddard says:
MaxL –
Gas pressure is created by the motion of molecules. As you approach absolute zero, molecules cease to move. So there is no pressure. Volume has to remain above zero, because the molecules have a finite size. So yes, it is that simple.

Like special relativity, the gas pressure equation works well in the absence of gravity. Given the temperature and pressure at the surface of the earth, we should be able to calculate the volume of the atmosphere. V = nRT/P
I must be doing it wrong, because I get different volumes for toasty sea level Houston and cool mountainous Salt Lake City. I do get the same surface pressure, though.

May 8, 2010 11:11 pm

Mike McMillan
The ideal gas law works just fine, and gravity has nothing, nada, zippo to do with the accuracy of the equation.
You are comparing different temperatures and pressures in Houston, so you simply plug in different numbers into the equation. The ideal gas law works just as well in Timbuktu as it does in Salt Lake City.

jaymam
May 8, 2010 11:13 pm

Steve Goddard “If there were no Sun (or other external energy source) atmospheric temperature would approach absolute zero.”
But planets the size (or more) of the Earth and Venus have a significant internal heat source from radioactivity, which surely would heat the atmosphere.
Lord Kelvin, without knowing about radioactivity, calculated the age of the Earth as 40 million years.
In 1904 Rutherford, allowing for radioactive elements in the Earth’s core, calculated the age of the Earth in billions of years.

May 8, 2010 11:44 pm

jaymam
The amount of energy coming out of the earth is 44.2 × 10^12 W
http://www.agu.org/pubs/crossref/1993/93RG01249.shtml
The amount of energy reaching earth from the sun is 1.366 kilowatts per square meter * 510,072,000 km2 * 1,000,000 m^2/km = 69 x 10^16 W
http://en.wikipedia.org/wiki/Sunlight
The sun contributes more than 10,000 times as much energy to the atmosphere than does the internal heat of the earth.

May 9, 2010 12:11 am

Expanding on the points that Leonard Weinstein and Nick Stokes make. What is being discussed is the dry adiabatic lapse rate, which starts from the assumption that everywhere in the atmosphere the radiative energy absorbed is balanced by the energy emitted. If not, you get convective energy transport to re-balance the situation. That leaves gravitational compression, but it is not saying that radiative energy flow is negligible, just that it is balanced. As Nick and Leonard say, the lapse rate does not set the surface temperature, which is determined by the solar radiation absorbed at the surface and the IR re-emitted by greenhouse gases in the atmosphere.
What does the lapse rate determine? Looking at extremes is useful. Nick points out that if the surface is at absolute zero the thickness of the atmosphere (at least for an ideal gas) would be zero. What if the surface were at infinite temperature. Then the height of the atmosphere would be infinite also. From this, we conclude that the height of the atmosphere is determined by the lapse rate and the surface temperature
There are, of course, a few other things to consider. First, the dry adiabatic lapse rate is not 10 K/km for every atmosphere. For example it is 4.5 K/km on Mars and 2.0 K/km on Jupiter. Better put it is the ratio of the local gravitational constant divided by the specific heat (in J/(kg-K) or g/Cp. For the case of Venus, where the surface and the atmosphere are very hot, we have to account for the contribution of molecular vibrations to the specific heat, which will change with temperature and thus with altitude.

jcrabb
May 9, 2010 12:22 am

As day and night temperatures are so similar on Venus something must be maintaining the night time temperatures, especially considering the Venusian night is around 120 Earth days long, surely without the direct input of heat from the Sun over this period a significant amount of heat would be lost, unless there was a significant Greenhouse effect at work.

pft
May 9, 2010 12:46 am

On the subject of ocean depth, liquids are certainly compressible, just not as compressible as gasses. At 6 km depth for example, water would be at 600 atmospheres, density increases 3.7% and temperature would be 10 deg C above what water at 1 atmosphere AND the same heat content would be. Yet the temperature is only 3 deg C in the ocean deep. The only thing keeping water from freezing at ocean depth would seem to be waters compressibility, since little or no heat from the surface is reached at the bottom except via some convection, in fact it’s main heat source is the heat from the ocean floor and hydrothermal vents .
Air at 30,000 ft is at quite a low temperature, due to it’s low density and pressure, yet it’s heat content on a per molecule or mass basis is close to that at the surface. If it were adiabatically compressed to 1 atmosphere (ie, w/o losing heat), it’s temperature would be close to air at the surface. This points to the difference between heat and temperature.
In the upper atmosphere well above the stratosphere, temperatures reach 1000 deg C, yet air density is so low, you would feel little heat, as the mass and thus heat density is low. If you were able to survive the lack of oxygen, lethal radiation and needed no oxygen, you would quickly lose all your body heat despite the high temperatures. A real world example would be that of heating a thin needle to several hundred degrees C. It will not burn your finger since it’s heat content is so low (little mass) it dissipates quickly before it can do any damage.
Temperature of air at 2-3 meters (or 14,000 ft via satellite) or on the surface of the oceans is a very poor way to determine if our planet is heating. Temperatures can increase or decrease locally, or even in aggregate over short time periods (decades) but tell you little about if the heat content of the planet is increasing or decreasing.
The oceans are tremendous heat sinks with a heat capacity 50 times greater than the atmosphere. Heat gained by the atmosphere is quickly be absorbed by the oceans and temperature increases would be minimal as a result of evaporation and downward transport of heat due to increased salinity. In fact, the ocean surface area actually warms the atmosphere in the higher latitudes since it is at a higher temperature than the air. If not for the oceans ability to transport heat to the higher latitudes, we would be in a permanent ice age. Most of the Northern Hemisphere releases more energy to space than is received from the sun. It is only at the tropics that the energy balance is positive, and weather and the oceans then transfer this energy to the higher latitudes.
Attempts are made to determine the heat capacity of the ocean, but these are uncertain estimates and changes exceed the uncertainty of the estimates.

volauvent
May 9, 2010 12:51 am

P is given by the gravity (no gravity, the atmosphere escapes in space)
T is given by the heat equilibriums which are depending from many process including density, thus pressure… radiation and initial heating by the sun of course.
Only V could be the consequences of the others because there is no solid shell around the earth.
So you can’t prove anything from a general PV=nRT; you must go the the differential equations in each dV portion of the atmosphere (what are doing the models, but I do not say that the models are doing this well!).
Imagine that T is close to zero, with an atmosphere, PV/n is close, to zero , V/n is close to zero , so the change would be a very high density of the atmosphere. (mostly going to liquid under some temperatures; that’s happening for water, after all , with our current temperatures)
I am not sure that it is usefull to compare earth and venus as the conditions are so different, especially the content of the atmospheres and the very different temperatures.

May 9, 2010 12:56 am

Phil. said on May 8, 2010 at 8:50 pm:

Steve Goddard says:
May 8, 2010 at 7:27 pm
Mole is a non-dimensional number. A mole of H2 weighs much less than a mole of UF6

The mole is the SI unit of the amount of substance, it is not non-dimensional, a mole of a substance has a mass equal to the substance’s molecular weight.

A mole is just a number, a commonly used divisor when talking about a count of something.
You have a quantity of identical objects, be they atoms or ping-pong balls. You can describe the count in terms of thousands, millions, quadrillions, even moles. No one would argue a term like a quadrillion has a dimensional quality, in use you just take the count, divided it by a quadrillion, report that number. Exact same thing with a mole, you take the count, divide by a mole (6.02214 x 10^23), report that number.
3.28 * 10^24 = 5.45 moles. Left side is a count, an ordinary number. It has no dimensional quality. How can you argue the right side is not non-dimensional?

Troels Halken
May 9, 2010 12:58 am

Dr A Burns,
“The atmosphere is not static and conductive heat transfer to surroundings is small.”
Movement requires energy, and hence the energy must come from somewhere. After the initial compression of the gas, which releases energy in the form of heat, there has to be a heat/energy source to keep the gas warmer than the surrounding space.
I have no idea of how well insulated a planet is. Thinking about earth on a starry night, it is hardly perfect.

Dave McK
May 9, 2010 1:29 am

stevengoddard says:
May 8, 2010 at 9:02 pm
Dave McK
You can stop hyperventilating now. The average measured lapse rate on Earth is a little lower than the dry lapse rate. About 6.5.
————————————————
The adiabatic lapse rate of dry air is -9.8K/km
You are calling 2/3 ‘little’ and avoiding to name the real number.
Sir- 66% of something is significantly less than 100%.
The effect is due to water and the hadley pump that moves the working fluid from the heated surface to the infinite heat sink of space.
Don’t try to belittle me- you act like a damn climatologist.

Bob_FJ
May 9, 2010 1:30 am

George Turner Reur May 8, 2010 at 9:23 pm

[1] If the atmosphere on Venus stopped circulating, then I agree that the compression effects would dissipate.
[2] But the atmosphere there is constantly rotating in two giant Hadley cells. The air rises near the equator, moves to the poles, descends, and moves to the equator again, so it is always undergoing cycles of compression and expansion. This means it is also undergoing cycles of adiabatic heating and cooling.

[1] Yep. Any “initial point-in-time compression” of the atmosphere will result in increased T as a consequence of work done. (= mechanical energy). However, that “initial consequent heat” will be lost to the colder atmosphere above, (per thermo law 2), and for sustenance of it, equal replacement work energy in renewed air compression is necessary.
[2] At first sight that might partly explain an equatorial to poles redistribution of heat, but does not explain the reported daylight-time to night-time redistribution in terms of the ESA mapping of surface T‘s . However, how does your assertion fit in with the well reported large polar vortices, and how does it redistribute heat to mid latitudes?
Please elaborate on your assertion that Hadley cells arise at the equator and descend at the poles, (without any loss of T!!!), and provide a reference to show that these have been observed, including at what altitudes.
If you can answer that, I’ll elaborate more on the above.

Dave McK
May 9, 2010 1:37 am

The surface of Venus is dominated by volcanism. It has a crappy heat pump to lose the heat.
About 80% of the planet consists of a mosaic of volcanic lava plains, dotted with more than a hundred large isolated shield volcanoes, and many hundreds of smaller volcanoes.
Volcanoes less than 20 kilometres (12 mi) in diameter are very abundant on Venus and they may number hundreds of thousands or even millions.
Forget about greenhouse, dude. You aren’t helping.

May 9, 2010 1:52 am

I’d say there’s not too much reason to be concerned, unless global warming was too big or too small. Other than that forget about it.

Dave McK
May 9, 2010 2:36 am

http://www.engineeringtoolbox.com/spesific-heat-capacity-gases-d_159.html
Gas or Vapor kJ/kg
Air 0.287
Carbon dioxide 0.189
Water Vapor 0.462
Steam 1 psia.
120 – 600 oF
That’s what it takes to change the temperature 1 degree K.
When CO2 changes from 1 to -1 C, a change of 2 degrees C, it radiates 2(0.189 kJ/kg) = 0.378 .
http://en.wikipedia.org/wiki/Enthalpy_of_vaporization
When water vapor changes from 1 to -1 (and condenses) it radiates 2257 kj/kg + 2(0.462 kJ/kg) = 2257.853776 kJ/kg.
It does this every single time you see a cloud.
But CO2 has no phase change so it carries no heat – the numbers:
All gases at the same temperature have the same number of molecules per unit volume. (Avogadro)
Water, being light, masses 18g/mole and CO2 masses 44 g/mole
Using 1 mole of air, just to make math easy:
We lowball the water in the atmosphere at 1% of the molecules
So, in a mole of atmosphere, we have 0.01 moles of water = 0.18g
now we highball the CO2 at 500ppm which is 0.0005, or 1/2000 of a mole of CO2.
1/2000 * 44g/mole = 0.000484 moles of CO2 = 0.021296g
So in our mole of air with but 1% H2O and a generous 500ppm CO2-
the water condensing radiates 0.18g * 2257.853776 kJ/kg = 406.41367968 J
while the CO2 radiates 0.021296g * 0.378 kJ/kg = 0.008049888 J
the ratio of 0.008049888/406.41367968 = .00001980712855516645290496438242332
or as much to say that water vapor in the example carries 50486.873814890343815963650674393 times more heat than the CO2 does.
And that’s just rain. If it turns to snow- multiply by 5-6.
Meanwhile, Venus is a ball of active volcanoes with a dry heat pump to radiate it poorly.
That is why Earth’s climate doesn’t resemble that of Venus.

Gareth
May 9, 2010 2:53 am

Two fascinating posts along a similar lines to this one elsewhere.
They raise an interesting idea in my head. Are our notion of ice ages wrong? An increase in glaciation (for whatever reason) reduces sea levels. As sea levels sink the temperate zone where mammals and plants can most easily thrive moves with it onto what was formerly sea floor. What happens to temperatures? If the place where you are getting your proxy data from doesn’t move it would record a dropping temperature due to the atmosphere there getting thinner but there would still be plenty of surface with a thick and warm atmosphere.
Conversely, increases in sea levels (for reasons of less glaciation or volcanic and tectonic activity displacing water) would increase the apparent temperature for any given location that stays above water. The atmosphere appears to get thicker because it is being pushed upwards.
Are sea level changes factored in to temperature reconstructions?
Troels Halken said: When you compress or decompress a gas, it either warms or cools. Due to the temperature differential to the surroundings, after some time it will cool or warm by exchanging heat with the surroundings until the temperature differential is approaching zero and hence the temperature of the gas approaches that of the surroundings.
Why should Venus behave any different?

Convection currents on Earth cause warm air to rise, expand and cool whilst pushing cool air down, compressing and warming it. If Venus has convection currents it is not behaving any differently.

kwik
May 9, 2010 3:41 am

Dave McK says:
May 8, 2010 at 8:42 pm
Dave, what was the point of that “rant”?
Did you appeal to authority? Or that “they” have more money?

Mike M
May 9, 2010 3:44 am

stevengoddard says: “The ideal gas law works just fine, and gravity has nothing, nada, zippo to do with the accuracy of the equation.”
Yes, the equation itself works fine because it has nothing to do with gravity. But in this case pressure is a function of gravity. You are ultimately implying, (as I understand you), that the mass of a given control volume of air in a gravitational field decreases with temperature; that one half the temperature will give us one half the pressure at the surface. That sir is impossible. The amount of air remains the same so its weight remains the same and so the pressure at the surface remains the same.
I have two volley balls, (the reason air exists! ;), pumped them up to the same pressure at the same temperature – they weigh the same. If I cool one off to half (K) temperature of the other, it shrinks to half the volume of the other – but they still weigh the same. Instead of volley balls, we have two columns of air as control volumes in earth’s gravitational field with rigid walls and open at the top to vacuum space. They are each 1 inch square with the same amount air at the same temperature in each. The weight of the air in each of them exerts 14.7 pounds of force at the bottom and the very top-most molecule in each of them is at the same altitude. If we cool one column to say half the temperature of the other, the altitude of its top-most molecule will decrease to roughly one half the altitude of the other, (I’m not certain of the exact height but it will be a lot less than the other one).
I submit that the pressure in each column AT THE SURFACE will remain the same. As we go up in altitude however, that’s where we see a difference in pressure bewtween the two columns. The warmer column has a higher pressure than the cooler one at any altitude above the surface. The difference is zero at the bottom and increases the higher we go until it becomes infinite beyond the top of the cooler column.
But of course there are no walls up there, the air from the warmer column, having a greater pressure at altitude than the cooler one – flows into the cooler column increasing its weight and the measured barometric pressure at the surface.

May 9, 2010 4:10 am

Dave McK
There are more than 50 active volcanoes on Earth’s land surface, not to mention hundreds under the oceans. Their tiny contribution to the energy budget is much less than the measurement error.
http://www.geo.mtu.edu/volcanoes/world.html

May 9, 2010 4:22 am

The lapse rate on Venus is constant to 60 km. On Earth it is constant to about 14 km. Surface pressure on Venus is 92 times larger than Earth.
60/14 = 4.28
ln (92) = 4.52
Those numbers seem to be pretty close together, and hint that pressure differences explain the height of the tropopause, rather than greenhouse gas concentrations.
Earth’s atmosphere is mainly opaque to IR due to water vapour. Venus atmosphere is mainly opaque to IR due to spectral broadening of CO2 under high pressure. The addition of more greenhouse gas should be a minimal effect compared to the pressure differences.

May 9, 2010 4:22 am

Gareth,
http://www.countingcats.com/?p=4745

Mike M
May 9, 2010 4:25 am

” Dave McK says: Troposphere, shmoposphere – clouds, rain, snow.”
I concur, 99% of the difference between the atmospheric temperatures of Earth and Venus is because of that amazing stuff called water. Without water I’d guess that we’d be almost as hot as Venus no matter how much CO2 there was. To me, the difference in temperature illustrates the immense power of water’s negative feedback.
People understandably have a lot of trouble wrapping their minds around the idea that something can cool off or warm up without losing or gaining heat and I therefore surmise that to be the reason so many choose to ignore the latent heat of water in vapor form being carried up adiabatically to higher altitudes.

David Bailey
May 9, 2010 4:26 am

Anthony,
I think this could be a really big nail in the coffin of climate change because it demonstrates more clearly than anything else that the normal critical processes that operate in science haven’t worked in “climate science” for some time! Can you get this published in a journal somewhere?

May 9, 2010 4:35 am

Mike M
Without water the earth would be much hotter, but not for the reasons you mention.
If there were no oceans, no limestone would have formed, and the atmosphere would be much more dense.

May 9, 2010 4:37 am

Gareth
I was thinking the same thing. Small differences in atmospheric pressure could explain the early faint sun paradox and possibly ice ages as well. Certainly something worth looking into.

Mike M
May 9, 2010 4:41 am

My prior comment, the phrase “infinite difference”, I meant ratio-metrically. (We need an edit feature!)

Jbar
May 9, 2010 5:00 am

Nick Stokes,
The 700K surface of Venus doesn’t emit 12,000 W/m2. That would be (close to) the emittance of a black body radiating at near 700K, but Venus’s surface is NOT a black body.
Venus’s surface must be 733K to remain in radiative balance with sunlight because almost the entire infrared spectrum is blocked by the CO2 atmosphere and water vapor at high altitude. When you block parts of the infrared spectrum, the Stefan Boltzmann law no longer applies. Instead of having a simple formula based on T^4, now you have to integrate over the whole emission spectrum wavelength by wavelength, excluding the wavelengths that are blocked.
When you start blocking parts of the emissions spectrum, it takes a much larger increase in temperature than given by the T^4 law to emit the same amount of energy.

Jbar
May 9, 2010 5:12 am

Doc Martyn:
There are clouds because of the atmospheric lapse rate that Steve Goddard talks about.
The lower atmosphere is too hot for certain compounds to condense, but the upper atmosphere (50-70 km altitude) is much cooler, allowing them to condense into clouds. (Example: the pressure at 50km altitude is just below 1 atmosphere and the temperature is 57C.) At the altitudes where these clouds exist, there is very likely a phenomenon of solar energy vaporizing the clouds and heating the atmosphere, the heated gas rises to a higher altitude but cools thanks to the lapse rate, forming new clouds.

May 9, 2010 5:22 am

Jbar
Night on Venus is thousands of hours long, and the temperature is the same as the day side – which doesn’t receive much SW either.
Almost all of the IR is absorbed by Earth’s atmosphere, but we seem to be able to keep temperatures below 733K.

DavidB
May 9, 2010 5:26 am

There seem to be two possibilities here:
either
(a) Steven Goddard has made a major, Nobel-worthy breakthrough in atmospheric physics
or
(b) he has fundamentally misunderstood and misapplied the ‘ideal gas law’.
As a scientific layman I am not competent to say which, though, like Quasimodo, I have a hunch.

May 9, 2010 5:29 am

Jbar says:
May 9, 2010 at 5:00 am

You’re right when the atmosphere blocks IR. I was referring to the supposed GHG-free atmosphere.
Alternatively, it is still true that the surface emits (about) 12,000 W/m2. The S-B law applies at that level. Of course, many wavelengths are than quickly absorbed in the real atmosphere. But they were emitted.

Jbar
May 9, 2010 5:30 am

Dave:
May 8 6:48 PM Steve Goddard more-or-less states that there are both lapse rate and greenhouse effect. (Steve:”I’m not sure where anyone got the idea that I am suggesting that there isn’t a greenhouse effect on Venus. It certainly wasn’t from anything I have written. This is a discussion of relative magnitude.”)
So from that I take it his opinion is that it’s just a question of what share of the high surface temperature is due to each effect. However, he doesn’t really say what % is lapse rate and what % is greenhouse. I think none of us in this forum have to tools to calculate that. (Although I’ll take a wild guess its 50/50, plus or minus 25% either way. Does that help???)

May 9, 2010 5:33 am

I’ve written a post here to try to explain the close relation between the adiabatic lapse rate and the greenhouse effect. It doesn’t make sense to say that warming is due to the lapse rate and not the GHE. They go together.

Tom in Florida
May 9, 2010 5:41 am

I have not seen any discussion as to WHY the atmosphere on Venus evolved differently than on Earth. To me that is an important question. If the evolution is different, then there there should be little fear that Earth will end up like Venus.
I understand that Venus has no magnetic field that has allowed the solar wind to strip away lighter elements including water vapor. Add in the slower, retrograde rotation and any comparison to how Earth might evolve starts to become meaningless.

Troels Halken
May 9, 2010 5:51 am

Gareth,
“Convection currents on Earth cause warm air to rise, expand and cool whilst pushing cool air down, compressing and warming it. If Venus has convection currents it is not behaving any differently.”
As I understand it, convection comes from air that is being heated (and hence expands and then rise as it is lighter that the surrounding air) either by the sunlight on the surface or by the sunlight itself or both. If we turn off the energy source the convection stops, which also happens on earth during the night. What this tells us, is that without an external energy source as the sun, the temp on the surface on the earth will drop rapidly due to energy being lost to space.

May 9, 2010 6:04 am

stevengoddard says:
May 8, 2010 at 10:26 pm
Phil.
You must have forgotten your high school chemistry.
A mole is moist definitely a non-dimensional number. It is 6.023 * 10^23 molecules.

Clearly then it is not dimensionless, as I said it is the unit that represents the amount of a substance.
One of the interesting properties of gases (Avogadro’s law) is that they all occupy about the same volume at the same pressure and temperature, regardless of molecular weight. That is why the ideal gas law does not have a term for mass.
Of course it does!
PV=mRT/M where m is the mass of the gas and M is the molar mass.

Jbar
May 9, 2010 6:07 am

Spector:
Let’s do a thought experiment. If a “supernova flash-boils the ocean” as you suggest, then you have an extremely high water vapor concentration in the atmosphere causing a surface pressure of 265 atmospheres (including N2 and O2). At that concentration, water vapor’s capacity to block infrared would turn Earth into a Venus, at least temporarily, and the oceans might never condense again. At that pressure, surface temperature would have to fall below 390C for water to condense.
On the other hand, the whole atmosphere would be enshrouded in water vapor clouds. Some clouds reflect light but others trap infrared, so whether or not this brave new world would stay stuck in “runaway greenhouse” mode or reflect more light back into space and cool back down (allowing the oceans to reform) depends on what type of clouds dominate. Even if the globe cooled enough to form oceans, there might still be enough water vapor left in the atmosphere to keep the surface at some higher pressure and temperature than today (greater than 100C), depending on the balance of cloud types and global albedo.
Either way, the intense blast of radiation from any supernova close enough to boil the oceans would directly kill every living organism on the planet instantly. Game over. Reboot.

Jbar
May 9, 2010 6:14 am

Jaymam:
Energy emissions from the Earth’s interior amount to 1/10th of a watt/m2, thousands of times less than the surface radiation from the sun. This energy source is only significant to the behavior of thousands of miles of rock with a low heat transport rate, not the atmosphere or oceans with their much higher heat transport rates.

Editor
May 9, 2010 6:24 am

stevengoddard says:
May 8, 2010 at 5:53 pm

Ian L. McQueen
Joules is a unit of energy
Degrees Kelvin is a unit of temperature
moles is a non-dimensional number – 6.022 x 10^23 molecules
None of these are units of mass or gravity.

I’m not sure what people are arguing about at this point, but let me try to set some basics right. Much of physics can be reduced to the basic units of mass, length, and time. Before the term “SI” replaced “metric”, i.e. back in my high school physics class, we talked about measuring things in CGS (centimeter, gram, second) vs. MKS (meter, kilogram, second) units. Maybe also FPS (foot, poundal, second) but let’s not go there. I’m not sure why we didn’t include temperature, probably because we were looking at static and dynamics (hanging signs, weights on massless ropes a pulleys and baseballs thrown on flat, airless planets).
So, the ideal gas law is
pV = nRT
From Wikipedia (which is a good source for some stuff like this), In SI units, p is measured in pascals; V in cubic metres; n in moles; and T in kelvins. R has the value 8.314472 J·K^-1·mol^-1.
A pascal is pressure, and is newton per meter squared. A newton is force, and its units come from F=ma, so mass times distance per time squared, or g·m·s^-2.
Therefore, a pascal is g·m^-1·s^-2 due to dividing be square meters.
Volume is m^3, n is dimensionless (a number of molecules, but granted what I call a “honorary unit” of mol), temperature just K.
R has to make the dimensions balance. Wikipedia uses Joules in its J·K^-1·mol^-1. A joule is a unit of energy, which is force times a distance (parallel to the direction of the force!). We have force above, so a joule’s dimensions are g·m^2·s^-2.
Does all this balance? pV is g·m^-1·s^-2 · m^3 = g·m^2·s^-2
nRT is g·m^2·s^-2·K^-1·mol^-1 · mol · K = g·m^2·s^-2
Yay – it balances. Mass is a basic unit in pressure and energy.
However, mass can be ignored for looking at small quantities of gas as it is compressed and expanded adiabatically. It cannot be ignored when looking at tall columns of a gas, e.g. a column of an atmosphere, because the mass above any point in the column determines the pressure at that point.
Assuming a well mixed column, as we seem to have at Venus thanks to surface heat causing convection to mix the troposphere, then given the temperature at any point in the column, we can determine the temperature when a handful of gas there is moved anywhere else in the column.

Jbar
May 9, 2010 6:27 am

jcrabb
Most of the action in Venus’s atmosphere takes place in and above the cloud layer (50-70km altitude). Here clouds absorb sunlight on the sun side and race around at high speed to emit infrared radiation on the night side, keeping the temperature of this high atmospheric layer relatively uniform in spite of the slow rotation of the surface. The uniform temperature of this high altitude zone helps to set the uniform temperature distribution of the lower atmosphere and surface. (Not sure of the details of that.)
Venus’s atmosphere is highly refractive, so that sunlight wraps around the planet from the sun side all the way to the dark side, much much more than the dawn/dusk effect on Earth (although I have no idea how much sunlight actually reaches the dark side). That provides some solar heating of the surface even on the dark side. However, I am still at a loss to explain why the surface temperature is uniform all the way around unless the high refractivity of the atmosphere makes the surface lighting uniform. (Doubtful)

Jbar
May 9, 2010 6:32 am

pft
The ocean does not freeze at the bottom because water is most dense a few degrees above freezing. It cools at the surface of the ocean and then sinks down before it freezes. It cannot freeze then because there is no mechanism to cool it to a lower temperature down there.
We’re very lucky that water works this way or ice would continue to pile up on the ocean floor until all the oceans and lakes would be entirely frozen over and our planet would be an ice ball.

Editor
May 9, 2010 6:33 am

stevengoddard says:
May 8, 2010 at 5:53 pm
Degrees Kelvin is a unit of temperature
<rant>
There are degrees Celcius, there are degrees Fahrenheit, there are no such things as degrees Kelvin. The term is just kelvins, lowercase! Otherwise, for consistency’s sake you’d want to talk about length meters (aren’t those rulers?), time seconds (which almost makes sense to distinguish from angle seconds), and frequency hertz (units named for people are always lower case).
If we’re going to get the basics right, lets start with the names.
</rant>

May 9, 2010 6:37 am

Jbar says:
May 9, 2010 at 5:00 am
Nick Stokes,
The 700K surface of Venus doesn’t emit 12,000 W/m2. That would be (close to) the emittance of a black body radiating at near 700K, but Venus’s surface is NOT a black body.
Venus’s surface must be 733K to remain in radiative balance with sunlight because almost the entire infrared spectrum is blocked by the CO2 atmosphere and water vapor at high altitude. When you block parts of the infrared spectrum, the Stefan Boltzmann law no longer applies. Instead of having a simple formula based on T^4, now you have to integrate over the whole emission spectrum wavelength by wavelength, excluding the wavelengths that are blocked.

Whether the atmosphere is blocked has nothing to do with the emissivity of the surface, which remains a near black body.

Jbar
May 9, 2010 6:43 am

A “mole” is shorthand for chemists to make it easier for them to do their maths.
It is a number of grams equivalent in value to the molecule’s molecular weight. Eg. one gram-mole of water = 18 grams of water (approx), same as the molecular weight of water.
A mole of any substance contains the same number of molecules – Avogadro’s number – 6.022 E23 molecules.
So if a chemist knows that one molecule of oxygen (O2) reacts with two molecules of hydrogen (H2), they know that they need one mole of oxygen (16 grams) to react with 2 moles of hydrogen (2 grams) to make 1 mole of water (18 grams).
It is much more convenient than counting molecules!
Engineers play with bigger numbers than chemists so US and British engineers like to use “pound-moles”, or the number of pounds with the same numeric value as the molecular weigh.

Editor
May 9, 2010 6:47 am

Oh – I forgot to mention a couple posts back about my “honorary” units. I’ve found them handy in some calculations and in “dimensional analysis” to give units to technically dimensionless quantities. The simplest example is pi, 3.14159….
Pi is dimensionless, so the equation circumference = 2 x pi x radius is just length on both sides. If we use the honorary units of radial meters and circumferential meters, then pi takes on units of circumference/radius and becomes easier to track. You can also thrown in units for diameter and radius lengths to keep the “2” involved in the dimensional analysis.
Dimensional analysis, by the way, is something I learned quickly in physics class, but isn’t taught very well. I remember reading an article in Science News decades ago discussing that and claiming that students taught it understood physics much better and applied various formulae correctly.
One thing I never did learn, and was in part my downfall in college physics, is the Greek alphabet. Both upper and lower case. Reading equations like “P = squiggle times squiggle-with-extra-zig divided by lambda” was not the way to learn that stuff. At least I know lambda, well, lowercase lambda anyway.

jaymam
May 9, 2010 6:56 am

The amount of energy coming out of the earth is 4.42E+13 watts
The amount of energy reaching the top of the atmosphere from the sun is 1366 watts/m2
The average albedo of the Earth is about 0.3 therefore 410 watts/m2 is not reflected
Area of Earth’s surface 510,072,000 km2 = 5.1E+14 m2
Area of Earth with the sun shining on it is 4 times less, i.e. 1.275E+14 m2
Energy from the sun is 1.275E+14 * 410 = 5.22E+16 watts
5.22E+16 divided by 4.42E+13 = 1182, or 0.085%
0.085% should not be ignored.

Doug S
May 9, 2010 7:05 am

jcrabb says:
May 9, 2010 at 12:22 am
As day and night temperatures are so similar on Venus something must be maintaining the night time temperatures, especially considering the Venusian night is around 120 Earth days long, surely without the direct input of heat from the Sun over this period a significant amount of heat would be lost, unless there was a significant Greenhouse effect at work.

The relatively small difference between day and night temps intrigues me as well. Wouldn’t a reasonable assumption be that the thick atmosphere is circulating so fast that it is distributing energy around the planet so that convective heat distribution is dominant?

Jbar
May 9, 2010 7:06 am

Dave McKay
The 380 ppm of CO2 in our atmosphere absorbs ALL the infrared radiation between 13 and 18 microns wavelength trying to leave the surface of the Earth on its way to space. The CO2 then reradiates that energy in all directions, up, down, and sideways. (Anything going sideways has to travel through so much more atmosphere than what’s going straight up that it effectively winds up getting all reabsorbed, so the net effect is for the radiation to either pass up or be reflected effectively straight down.) So the CO2 acts like a few-percent reflective mirror of infrared surrounding the Earth.
The atmosphere of Venus contains 89,000,000 ppm (relative to Earth), which is enough to block all the infrared radiation between 2 and 28 microns wavelength except for 3 narrow windows of transparency and everything longer than 28 microns. So even a few kilometers of Venus’s CO2 atmosphere absorbs the majority of radiation trying to leave the surface and reradiates it in all directions (but, effectively, 50-some% up/ 40-some% down). Then the next few km higher does it again, and the next few km, and the next, until the radiation finally gets to the top of the atmosphere and can get out freely into space. So the CO2 in Venus’s atmosphere acts like a tall stack of 40-50%-reflective infrared mirrors.
There’s water vapor high up in Venus’s atmosphere, and that water is enough to block all the infrared radiation longer than 28 microns, the big chunk that CO2 misses, adding H20-greenhouse insult to CO2-greenhouse injury.

björn
May 9, 2010 7:12 am

If the seas of Venus boiled in a runaway greenhouse meltdown, where is the water?

Enneagram
May 9, 2010 7:16 am

A different approach to Venus:
https://ssl.scroogle.org/cgi-bin/nbbwssl.cgi

Onion
May 9, 2010 7:20 am

Without greenhouse gases in Venus’s atmosphere, Venus would be hundreds of degrees cooler. That means Venus is that hot because of the greenhouse effect.
Talk about pressures and lapse rates is just dancing around the above fact.

Jack Morrow
May 9, 2010 7:50 am

Steve Goddard
I guess all those moles or co2 is causing all your cold weather in CO.

Marc77
May 9, 2010 7:55 am

Based on this text and others, it seems Venus is hot because of its thick atmosphere. The cause of this runaway-building-of-a-thick-atmosphere might be its proximity with the sun. Now it is in equilibrium because of the high albedo of its atmosphere(negative feedback).
The way I understand the adiabatic lapse, I might be wrong, is like this.
If you have a differential of pressure through a column of gas, you have more molecules on one side. I the gas is well mixed, all molecules will have the same distribution of chaotic-kinetic-energy(heat). So the side of the column with more molecules will have more heat.
Now if there was no movement, after some time I guess the warmest molecules would get on top and the coldest at the bottom.
So basically, the system has to be somewhere between those two tendencies.
I also took a look at what a supercritical fluid is. Based on wikipedia, “In addition, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties of a supercritical fluid to be “fine-tuned” “. So it seems a supercritical fluid CO2 has the compression properties of a gas, not of a liquid.
Finally, there is also a place on Earth where temps are high, under the crust. It is also possible that Venus atmosphere could be a good insulator just like Earth’s crust, so the geothermal heat could build there. Just like I believe the geothermal heat could build under a thick layer of ice on Earth, but this is another subject.

Spector
May 9, 2010 8:11 am

I have often thought that Venus, being much closer to the sun than the Earth, must intercept a larger flux of gases from the solar wind and the extreme outer layers of the solar atmosphere. Perhaps the atmosphere of Venus is as dense as it is because that planet has had a better opportunity to scoop up gases from the sun. [My speculation.] For some gases, there may be equilibrium condition where the rate at which each gas is acquired is balanced by the rate it escapes back into outer space.
If the Earth had the same surface pressures as Venus, I am sure that the ground temperatures would be much higher here also. I do not think CO2, per se, is the real problem.

Pascvaks
May 9, 2010 8:15 am

On the motion to the motion to the motion..
Everyone in favor of NASA being given the mission of diverting a comet into Venus in the next two decades (and thereby gaining the wherewithall to save us from a similar impact) and beginning the transformation of Venus into a habitable planet say YES!
Those opposed?
The motion is carried and will be open for discussion for the next session, following the Memorial Day and 4th of July Break! One hour, equally divided will be allotted to the discussion by the Committee of the House.

GeoFlynx
May 9, 2010 8:17 am

So let me get this straight, you have written two “Venus” blogs that have displayed your misunderstanding and misapplication of the ideal gas laws, and yet you wish everyone to believe that your insight on that planet trumps all the scientists at NASA and JPL?
REPLY: Still snotty and condescending but better than the last one that was snipped

Ralph
May 9, 2010 8:25 am

>>>With a constant lapse rate, an atmosphere twice as thick would
>>be twice as warm. Three times as thick would be three times as warm.
>>>etc. Now let’s do some experiments using this information.
Without wishing to stir up too much controversy (remember last time !) , this is the same argument as Willis Eschenbach’s Steel Greenhouse posting (below). Willis doubled the number of steel spheres, to do exactly the same thing – double the temperature on the surface.
http://wattsupwiththat.com/2009/11/17/the-steel-greenhouse/
Pretty obvious, really.
.

May 9, 2010 8:31 am

GeoFlynx
If you have a specific objection, please post it. There is no constructive way to respond to ad hom attacks.

May 9, 2010 8:32 am

Jack Morrow
It is nice today, but supposed to be 45 degrees for a high on Wednesday. That is close to normal for January 1.

May 9, 2010 8:35 am

jcrabb
Some greenhouse you are describing. It doesn’t lose even one degree of temperature over 1400 hours of pitch black. You should patent it. You will make a killing.

OkieSkeptic
May 9, 2010 8:37 am

Dry lapse rate looks suspiciously like ‘thermal gradient’ and this gradient shouldn’t occur without a thermal difference between the upper atmosphere (at space) and the surface. From this viewpoint, if the top of a dry atmosphere were at the same temperature as the surface, there would be a pressure difference from gravity but no thermal gradient. That gradient in the Venus example should be mostly from solar heat trapping at the bottom of the atmosphere.
One major difference between Earth and Venus is Nitrogen content and Venus would have probably have been entirely different if it had as much as the Earth’s atmosphere. The million dollar question is how Venus and Mars managed to be without it as it was abundant in the early solar system.

Squarebob Spongepants
May 9, 2010 8:37 am

DaveMcK says:
When water vapor changes from 1 to -1 (and condenses) it radiates 2257 kj/kg + 2(0.462 kJ/kg) = 2257.853776 kJ/kg.
It would be a wonderful world if it did radiate heat like that – but almost always the heat is conducted by cold surfaces (having already radiated the heat away) or transformed into kinetic energy warming supercooled gases, which have also already radiated the heat away.

May 9, 2010 8:43 am

Ralph
Actually the argument is different from what Willis posted. I’m not discussing the radiative budget – rather just the basic physics of gas warming as it moves to areas of lower pressure lower in the atmosphere. The higher the pressure, the higher the temperature.

DesertYote
May 9, 2010 9:06 am

Dave McK
May 9, 2010 at 1:37 am
OH NO! Its worse then we thought. The green house affect is melting the planet!

DesertYote
May 9, 2010 9:34 am

Tom in Florida
May 9, 2010 at 5:41 am
I have pointed out here and in another post that one really big difference between the Earth and Venus is our monstrously oversized moon which played a major role in the creation of our atmosphere and plays a major role in weather today, but no one seems to remember what was once understood science.

J.Hansford
May 9, 2010 9:41 am

OkieSkeptic says:
May 9, 2010 at 8:37 am
“……One major difference between Earth and Venus is Nitrogen content and Venus would have probably have been entirely different if it had as much as the Earth’s atmosphere. The million dollar question is how Venus and Mars managed to be without it as it was abundant in the early solar system.”
————————————————————————————
It’s always puzzled me that peculiarity….. Just why is it that Earth has 70% nitrogen in it’s atmosphere, whilst Mars and Venus barely have any?
G’dam mystery if you ask me:-)

Ralph
May 9, 2010 10:11 am

>>stevengoddard says: May 9, 2010 at 8:43 am
>>Ralph
>>Actually the argument is different from what Willis posted. I’m not
>>discussing the radiative budget – rather just the basic physics of gas
>>warming as it moves to areas of lower pressure lower in the atmosphere.
>>The higher the pressure, the higher the temperature.
Two sides of the same coin, is it not….
.

gallopingcamel
May 9, 2010 10:24 am

stevengoddard says:
May 8, 2010 at 2:57 pm
QUOTE
You can infer how thick the atmosphere of Venus is from this diagram:
http://www.astro.wisc.edu/~townsend/resource/teaching/diploma/venus-t.gif
UNQUOTE
That graph appears to support your hypothesis. It will be interesting to see what rebuttal James Hansen can come up with.
It looks as if there might be a “Goldilocks Zone” on Venus at an altitude of over 50 km!

May 9, 2010 10:45 am

With all these comments, some expanding, some disagreeing, some clarifying, I no longer know how much of the original Note stands. Would it be possible, once the Comments are closed, to modify as appropriate, with footnotes if necessary? This is, I suppose, the benefit of peer-review before publication: what remains is cleaned up and ready for distribution.

MaxL
May 9, 2010 10:50 am

Just one final post on the subject and I will leave it at that. When we meteorologists speak of “atmospheric pressure” here is what we are referring to:
This from the AMS Glossary of Meteorology http://amsglossary.allenpress.com/glossary
“atmospheric pressure—(Also called barometric pressure.) The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the “column” of air lying directly above the point in question.”
If others have a different definition of atmospheric pressure, then that should be stated at the beginning of their thesis so that we are talking about the same things.

dr.bill
May 9, 2010 11:10 am

Steve (Goddard),
Your insistence on relating pressure to molecular motion, and heating due to pressure, is ruining what should have been a good discussion. I believe that it also impedes your understanding of your own proposal. As many others have put forth, and I will re-iterate, the atmosphere is warmed from the bottom, and only then will things start moving up. It is not the other way around. Where the surface gets its heating from is another matter. It might be simple percolation of Solar energy down to the surface, whether directly or in the form of a bit of back-radiation from the atmosphere, or it might be vulcanism, or it might be something that the Borg are doing with slipstream drives, but it is the bottom that does the heating of the atmosphere, not the other way around.
Regarding pressure, it can be caused by molecules in motion. It can also be caused by the simple weight of whatever is sitting on something else. It can furthermore be caused by the application of any force of any kind from any source to whatever is feeling the pressure. We figure out the pressure at depth in the oceans, for example, by calculating the weight of the water above that depth, and then we add the atmospheric pressure that exists at sea level, which in turn is due to the weight, not the motion, of the air molecules stacked up above that. This is basic Physics. It doesn’t matter if the atmosphere is in the form of a gas, as solid, or a slurpy. It’s just its weight that determines the pressure at ground level, or the bottom of the ocean, nothing more.
I say this as a physicist who has taught many subjects, including Thermodynamics, over many decades, but you do not need to simply take my word for it. There are 10’s of thousands of textbooks that will tell you the same thing.
Regarding your original proposal, the data you presented shows that there is no need to invoke a “runaway greenhouse” effect on Venus, any more than there is on Earth. The graph of Temperature vs Altitude that you include looks very much like that of the Earth in the bottom two regions. There is a linear “lapse rate region” up to 60km, followed by an isothermal region for about 10km, much like the bottom part of our own stratosphere.
If one can extrapolate back down to the surface using the lapse rate that can be found from the graph, it would have a temperature of about 500°C or so, purely on the basis of ordinary atmospheric dynamics, with no need for massive effects of any other kind. Note again, that by extrapolating back down to the surface, I am not saying that the atmosphere of Venus heats up because you are going down. I am purely using the apparent straight line to estimate the value at its bottom end, given what the graph shows for its top end.
The higher regions of Venus depart from Earth’s pattern, but the lowest 60km looks very much like a “regular troposphere”, albeit much thicker than our own, which only shows that it is being heated more strongly, from below, than is the case on Earth. That “thickness effect” may also be seen on our own planet. As you likely know, the tropopause in our Polar regions is only at a height of about 8km, while in the Tropics, it is generally at a height of 16km, or even a bit more above very hot places. That is not a coincidence. It is simple cause and effect, and they need to be put in the right order, which you are not doing. Umbrellas don’t cause rain.
I do not like “getting personal or confrontational”, and I generally like the things you post on WUWT, but I think it’s time you stopped being so dogged about “being right”, and accepted the valid and well-intended interventions of many other posters who have carefully explained their points of view, only to be summarily dismissed by a one-liner from you. This isn’t very respectful, there is no need for it, and it simply impedes understanding.
/dr.bill

Roger Clague
May 9, 2010 11:44 am

The Greenhouse Effect (GHE) and the thermodynamic lapse rate.
The phrase GHE muddles together the effect and the suggested cause. It suggests that the warming effect of the atmosphere is caused by the chemical structure of some of the gases in air, molecules that are made of more than one type of atom, especially CO2.
There is warming in addition to that caused by the sun, calculated using the concept of energy balance and the Stefan/ Boltzmann Law. What causes the extra warming?
Steve Goddard’s recent posts say the extra warming is explained by the pressure of the atmosphere. There is no need to consider the chemical composition. All gases create pressure, on Earth mainly N2 and O2, on Venus mainly CO2. All gases contribute to the extra warming. All of the extra warming is explained by physics. There is no need to consider the structure of these gases.

Bruce
May 9, 2010 12:29 pm

Nice post. I like the Venera images. Since it’s VE parade day in Moscow, let’s toast a Russian aptitude for Polar scientific expeditions, space exploration, and the encirclement of Axis armies.

May 9, 2010 12:32 pm

dr.bill
How is Venus “warmed from the bottom” during it’s thousands of hours long nights?

May 9, 2010 12:36 pm

Venus has no oceans, so it has no limestone. No limestone means a thick atmosphere of CO2. A thick atmosphere means high temperatures.
It took decades for science to accept the obvious fact of continental drift. Scientists can be just as bone headed as anybody else.

Nullius in Verba
May 9, 2010 12:38 pm

Here’s a paper by Carl Sagan that discusses the Venusian ‘greenhouse’.
You might be surprised by the mechanism he proposes for it.
Doesn’t it look familiar?

LarryOldtimer
May 9, 2010 1:36 pm

Since neither Mars nor Venus has any planetary magnetic field, I would expect that the solar wind carries away any lighter gases, such as H2O vapor, leaving behind the more dense gaseous molecules. With it being far to hot on Venus for carbon based life, there is no conversion of CO2 to oxygen and carbon.
Venus is vastly different from Earth in most respects. To attempt to equate the workings of the atmospheres on Venus and Earth is an exercise in futility. Too, we know very little about the charastics and composition of Venus itself.
Back when I was a lad, from what I personally read (and I had a greal of interest in things scientific), it was speculated that the temperature of Venus was about 125 degrees F, and that Venus was a “wet” world, since the dense clouds were thought to be of water. Very warm and balmy, was the scientific speculation circa 1950 or so.
“A little knowledge is a dangerous thing.” ~ Alexander Pope
To attempt to “extrapolate” only a little knowledge into a “grand theory” is one of the most dangerous of all things that can be done..

dr.bill
May 9, 2010 2:03 pm

stevengoddard:
May 9, 2010 at 12:32 pm
dr.bill
How is Venus “warmed from the bottom” during it’s thousands of hours long nights?

I don’t know Steve,
Perhaps we should try to find out.
/dr.bill

May 9, 2010 2:06 pm

I am finding this thread as baffling as the previous one about Venus. Why are the following points not obvious?
(1) The surface must support the weight of the atmosphere, regardless of its temperature. Gases have weight! Thus, the surface pressure is determined by the mass of the atmosphere and the gravity of the planet, independent of temperature.
(1′) There is a very small effect of temperature, since it does affect the depth of the atmosphere, and gravity diminishes slightly with height. This is a small effect.
(2) An atmosphere should approximately follow an adiabat — that is, pressure and temperature varying at the adiabatic lapse rate — provided the conditions are suitable for convection. This is true in the lower atmosphere of both Earth and Venus. But convection will only occur if the fluid is heated from beneath. In other words, the net heat flow in the fluid in the convective zone must be upward.
(3) If the atmosphere of Venus were heated from the top — which I gather is Steve’s theory — then there should be no upward heat flow in the lower atmosphere. Ergo, no convection. The temperature profile would be much flatter than the adiabatic lapse rate. Indeed, in the long run it should be quite flat, an isothermal atmosphere.
(4) This is not what is happening. Thus, the surface is heating the atmosphere at the bottom. Internal energy sources, volcanism and such, are orders of magnitude too small. The surface must be heated by the short-wave radiation that reaches it. That is, it must be heated by sunlight (however attenuated). This net heat input to the surface accounts for the net upward heat flow in the atmosphere.
(5) The surface is really hot, and so it radiates strongly. (Most natural surfaces are pretty good blackbodies at IR wavelengths.) In fact, the surface radiates dozens of times more IR radiation than actually emerges into space at the top of the atmosphere. So almost all of this must be absorbed by the atmosphere, and reradiated (both up and down, of course, in each layer).
So we have an atmosphere heated from below, by a surface that is getting its energy input from short-wave radiation. The thermal radiation from the surface is strongly absorbed by the atmosphere. If we turned off this absorption and made the atmosphere transparent to IR, then the planet would quickly cool off to a much lower temperature, until radiative equilibrium would be re-established. Doesn’t that pretty much define the greenhouse effect?
I keep expecting this thread to be about WHY Venus has developed such a strong greenhouse effect, and whether the term “runaway greenhouse” appropriately describes this process. Fascinating question, and present theories involve a good deal of speculation. I would probably count as a moderate AGW skeptic — a “luke-warmer” in common parlance — but the discussion here does not inspire me with confidence that this community has a firm grasp on the basic physics. Sorry to be so blunt, but the thing is pretty distressing to someone who reads WUWT regularly and with pleasure.
I’d like to see Steve respond to the points about hydrostatic equilibrium and the upward heat flow associated with the adiabatic lapse rate.

lgl
May 9, 2010 2:33 pm

If the clouds at 40-60 km height absorbs most of the LW from below, and I believe they do, then the lapse rate should make the surface at 730 K with any composition of the atmosphere below the clouds.

Nullius in Verba
May 9, 2010 2:45 pm

Here’s another clear explanation of the role of the adiabatic lapse rate in ‘greenhouse’ warming.

May 9, 2010 3:04 pm

Nullius in Verba – that’s a fantastic link you’ve posted! Thanks!
Just one last contribution to the topic. I urge everyone to take a holistic look at Venus: it’s a very peculiar planet, and the composition of the atmosphere and surface temperature are just a couple of its peculiarities. Somebody has already mentioned the extensive (apparent?) volcanism, and how young the surface is. That’s not all: Venus rotates very slowly and in the wrong direction, as if something had hit and toppled it. Such a cataclysm alone would have resurfaced it several times over. Also where is plate tectonics? What is the origin of all strange surface features that don’t appear anywhere else in the Solar System? Etc etc
I know there’s people trying hard to build a rover that would resist the inferno and I am looking forward for such a mission to take place.

Rob R
May 9, 2010 3:28 pm

Steven
Over at “The Reference Frame” Lubos Motl has a detailed dicussion of your WUWT posts on Venus temperature.
You will be interested to find that in his conclusion he is largely in agreement with you. i.e. that the greenhouse effect on Venus amounts to a few dozens of degrees C and that the very high temp at the surface relates primarily to the environmental lapse rate.

May 9, 2010 3:38 pm

Ben Schumacher
The pressure is determined by the weight of the gas above it as you said. And according to the ideal gas law, the ratio of temperature/volume is controlled by the pressure. I’m not sure what you find baffling about that.
I’m not making any attempt to explain what the heating mechanism is. Just pointing out that the temperature profile in Venus’ atmosphere indicates it is an adiabat.
The purpose of this exercise is to argue that even if earth’s atmosphere was 100% CO2, temperatures would be nothing like they are on Venus.

May 9, 2010 3:41 pm

It’s been confusing on both articles how people are talking about pressure.
Pressure is force exerted on a surface, can be expressed as pounds per square inch or even newtons per square meter. Atmospheric pressure is being discussed, which basically is the average of the forces involved from gas molecules hitting a surface.
So if the temperature drops to where all the gas molecules precipitate out, what atmospheric pressure is acting on a vertical surface? None. What if I set up a pressure gauge with a horizontal surface pointing upwards, a meter above the ground, what would it read? Nothing, as all the formerly gaseous molecules are already in a layer on the ground below the gauge. Same thing if the horizontal surface is pointing downwards, rotated to vertical, or in any position.
Yes, you can talk of pressure from a substance laying on a surface that’s not completely vertical. But that would be pressure based on gravitational force, while here atmospheric pressure (all-surrounding) is being discussed. So why all the nit-picking?

Bob_FJ
May 9, 2010 3:41 pm

Jbar Reur May 9, 2010 at 6:27 am

[1] Most of the action in Venus’s atmosphere takes place in and above the cloud layer (50-70km altitude). Here clouds absorb sunlight on the sun side and race around at high speed to emit infrared radiation on the night side…
[2] Venus’s atmosphere is highly refractive, so that sunlight wraps around the planet from the sun side all the way to the dark side, much much more than the dawn/dusk effect on Earth (although I have no idea how much sunlight actually reaches the dark side). That provides some solar heating of the surface even on the dark side. However, I am still at a loss to explain why the surface temperature is uniform all the way around unless the high refractivity of the atmosphere makes the surface lighting uniform. (Doubtful)

[1] But the downward infrared cannot heat warmer air below, per thermo law 2. Also, the temperature gradient clearly shows heating from the surface, the candidates being absorbed sunlight and geothermal.
[2] With sulphuric acid etc clouds, haze, and a dense atmosphere, scattering must be greater than on Earth, but some of the Venera photos show pronounced shadows around the rocks. Thus the effect that you propose is most unlikely to be large, assuming the photos are gen.

GeoFlynx
May 9, 2010 3:42 pm

Didn’t mean to be condecending, but using the closed volume ideal gas laws to describe atmospheric pressure, equating temperature with atmospheric pressure, and implying that gravity disappears at the lowest temperatures are your ascertions. When lucid comments are made to correct these misconceptions there is no acknowlegement nor attempt at retraction. It would therefore appear that your intent is somewhat other than achieving an understanding of the question at hand.

May 9, 2010 3:58 pm

GeoFlynx
The fact that you don’t understand something is an indication only of your own lack of understanding. You are making ridiculous straw man arguments about gravity disappearing.
CO2 freezes long before reaching absolute zero. If you turned the atmosphere of Venus into a huge chuck of dry ice at 1K, it would continue to exert the same amount of pressure downwards on the surface of Venus. At the same time the vapour pressure of CO2 would be very close to zero.

May 9, 2010 4:26 pm

If you changed the composition of Venus atmosphere to 100% nitrogen, the planet would be much colder due to the lack of absorption of IR. The atmosphere would also necessarily be much thinner (lower volume.) P = nRT/V
However, if you changed the composition of Venus atmosphere to 95% nitrogen and 5% CO2, the temperature and height of the atmosphere would not be hugely different than it is at present. Why? Because the greenhouse effect is logarithmic. After the first few percent, additional CO2 makes much less difference to the temperature.
Consider earth, where a doubling of CO2 only increases temperatures by <1 (Lindzen) to 3 (IPCC) degrees C.

May 9, 2010 4:32 pm

GeoFlynx
The pyramids of Egypt exert a lot of pressure on the ground below. If you were buried 3,000 years ago underneath the pyramid you would be crushed. However, if you were buried in a tomb inside the pyramid, your remains might survive long enough to be made fun of by Steve Martin.
Gravity has not disappeared for King Tut. There are different manifestations of pressure and stress, and your simple view of the world is inadequate for complete analysis.
Don’t mean to be condescending (note spelling.)

May 9, 2010 4:45 pm

Steven,
“If you changed the composition of Venus atmosphere to 100% nitrogen, the planet would be much colder due to the lack of absorption of IR.”
I actually agree with that last post, and I think it’s pretty much mainstream science. But how is that statement different from the Wiki:
“Without the greenhouse effect caused by the carbon dioxide in the atmosphere, the temperature at the surface of Venus would be quite similar to that on Earth.”
which in your last article you said was all wrong?

Keith Minto
May 9, 2010 5:08 pm

Ignoring composition and circulation, does it not mean, comparing height of atmosphere alone, that Earth could never have a ‘runaway’ warming?
pft May 9 12:46 said,

Air at 30,000 ft is at quite a low temperature, due to it’s low density and pressure, yet it’s heat content on a per molecule or mass basis is close to that at the surface. If it were adiabatically compressed to 1 atmosphere (ie, w/o losing heat), it’s temperature would be close to air at the surface. This points to the difference between heat and temperature.

This is similar to my thoughts in the last thread i.e. higher pressure temperature readings are higher because they are simply more efficient. This is the result of a higher molecular collision rate on the sensor, so I would suggest that some (not all) of the apparent higher temperature at the bottom of a column of air is due to a density effect…. that is, you reading the heat content of the air more efficiently.
This confuses the current rationale behind the adiabatic lapse rate slightly.

OkieSkeptic
May 9, 2010 5:17 pm

Steve:
“However, if you changed the composition of Venus atmosphere to 95% nitrogen and 5% CO2, the temperature and height of the atmosphere would not be hugely different than it is at present. Why? Because the greenhouse effect is logarithmic. After the first few percent, additional CO2 makes much less difference to the temperature.”
I have difficulty seeing this. I can understand the reason for the thick CO2 blanket since there are no water/carbonates to remove the volcanically generated CO2. However, this wouldn’t apply to nitrogen and there should still be less of it relative to Venusian gravity using earth as an example. Couldn’t the major source of heat trapping on Venus simply be because of the thick atmosphere and lack of water vapor, making vertical convective transfer to space difficult (unlike Earth)? It has already been mentioned that the ground level density of the CO2 may be in the supercritical or near liquid state, which would make vertical thermal transfer very difficult relative to that of a gas.
As covered in other comments regarding CO2 depth pressure and temperature, if one could enclose a vertical section of Venusian atmosphere in a sealed insulated tube (closed system), after a period of time the temperature would completely equalize throughout the volume through convective transfer even though the gravity pressure at the tube bottom would still be 93 atmospheres. If this insulated tube of CO2 where originally in space and dropped into Venus’ gravity field, there would be immediate heating at the ‘bottom’ from the pressure increase but this would be cause by mass and potential/kinetic energy transfer to that section. Again when this closed system is left alone in the constant gravity field, the temperature would eventually equalize through convective transfer throughout the gas (at a higher temperature because of the gravity potential energy added) even though the pressure would be higher at the ‘bottom’ of the tube.
If this were not the case, all one would have to do for free energy is to install a heat engine between the top and bottom of the tube since there would be a constant temperature difference even in the closed system.

May 9, 2010 5:22 pm

However, if you changed the composition of Venus atmosphere to 95% nitrogen and 5% CO2, the temperature and height of the atmosphere would not be hugely different than it is at present. Why? Because the greenhouse effect is logarithmic. After the first few percent, additional CO2 makes much less difference to the temperature.

Jbar
May 9, 2010 5:26 pm

RealClimate [yeah, yeah, I know] provides some insight into why Venus’s surface temperature is so uniform even though there is very little surface wind to redistribute energy, and minimal light on the dark side.
The Venutian atmosphere is incredibly massive, roughly 40% of the weight of Earth’s oceans. Consequently it would take an incredibly long time for the entire atmosphere to heat up or cool down. (In contrast, much of Earth’s thin atmosphere easily heats and cools in a day.) So expecting the surface temperature of Venus to vary would be like expecting the temperature at the bottom of Earth’s ocean to vary. This massiveness means that the lower atmosphere of Venus is able to equilibrate in temperature all the way around the planet with very little convection (i.e. very low wind). A simple solution when you think about it.
Venus Express finds no significant “daily” variation in Venus’s atmospheric temperature below an altitude of 45km. That altitude is equivalent to a depth (or rather, pressure) of two Earth atmospheres. All the action takes place in the upper atmosphere. The high speed winds in the upper atmosphere transfer energy from the day side to the night side and by the time you get down to 45km altitude, the temperature there remains constant. (This is a few km below the lowest cloud layer.)

May 9, 2010 5:34 pm

Something for those inclined to do a bit of web search…months ago, I noticed how the NASA planetary atmospheric science pages sadly lacked any reference to the “greenhouse effect”. I wonder if that’s still the case?

Dave McK
May 9, 2010 5:48 pm

stevengoddard says:
May 9, 2010 at 12:36 pm
Venus has no oceans, so it has no limestone. No limestone means a thick atmosphere of CO2. A thick atmosphere means high temperatures.
Bless the clams for saving us from venereal discomfort, for while Venus was being repaved with lava, they were constructing the white cliffs of Dover and starting to crawl from the sea.
Did I get the physics of this right, finally, Steve? It’s all about the fizz in the beer?
I think Dr. Pangloss was right and it’s time to get back to the farm where they don’t believe the rooster actually makes the sun come up.

May 9, 2010 5:53 pm

Jbar
The Real Climate explanation makes perfect sense. It is yet another indication that the climate of Venus is controlled by the pressure of the atmosphere.
All arguments lead to the same conclusion – i.e. if the Earth’s atmosphere was 100% CO2, the Earth would not be hot like Venus.

May 9, 2010 5:54 pm

Jbar, another aspect of the “low wind” on Venus is that, because of density, it still transfers a huge amount of heat. 10 km/h at the surface has been mentioned, but the gas heat capacity is (very roughly) 90X greater than Earth, so its heat transfer capability is like a 900 km/hr blast here.

May 9, 2010 5:58 pm

Nick Stokes,
If there were no greenhouse gases or clouds (as Wikipedia implied) temperatures would be very cold.
But if Venus had the same relative composition atmosphere as Earth, it would still be very hot because the atmosphere on Venus is much more dense.

Xyrus
May 9, 2010 6:11 pm

First let’s clear up some very basics physics.
The ideal gas law is appropriate when talking about gases in confined volumes. When talking about atmospheric pressure, you use the barometric formula.
http://en.wikipedia.org/wiki/Barometric_formula
There are several constants used that are specific to the atmosphere you are trying to use it on.
Atmospheric pressure is dependent on mass and gravity, among other things, and is derived from the ideal gas law.
To wit, as you approach zero kelvin your atmospheric pressure approaches infinity, not zero. (NOTE: Of course, under that scenario you can’t use basic formulas anyway.)
But back to the main discussion. Mr. Goddard is proposing that pressure is somehow driving the temperature on Venus. However, this makes no sense. Titan is a solid counter-example. It has a dense N2 based atmosphere and yet it is still bone chilling cold. There is simply nothing there that can hold onto the meager amounts of heat it receives from the sun (or Saturn).
Venus is another matter entirely. You don’t need a complex experiment to verify that the atmosphere is preventing almost all heat from escaping. We have a good idea of the surface temperature. We also can figure out how much combined IR radiation is escaping the planet (both reflected and emitted through day and night side IR measurements). If what is radiating from the planet is much less than what it should be given the other constraints, then SOMETHING between the surface and the TOA is preventing heat from escaping.
If it were merely density of the gas and NOT composition, then we can verify this quite simply. Take a few different gases (GHG and non-GHG) and place them in IR transparent containers at various pressure levels. Fire an IR laser through each sample at each level and measure. If pressure is indeed the key player, then we should see similar results across all the gas samples. However, if composition is the key player, then we should see disparate results across the gas samples. GHG gasses at higher pressures would absorb more IR while non-GHG gasses would show little to no differences regardless of pressure level.
Fortunately, these have already been done many times over in establishing thermal properties for various gases. It should come as no surprise that atmospheric composition is what matters. Density matters as well. After all, if you don’t have much of an atmosphere you’re not going to be absorbing much of anything no matter the composition. But you can have an N2 atmosphere at 1000 atmospheres and it still won’t create a greenhouse effect. Saying otherwise is the equivalent of saying you can can make salt taste like sugar by adding more salt.
Can what happened to Venus happen to Earth? Not very likely. We’d have to try really hard to do so, and it would take a long time of trying hard (centuries). I’d like to think that we would be smart enough to notice palm trees growing in Antarctica and know that something might be amiss.
At any rate, composition AND density determine the IR profile of an atmosphere. Basic high school/college level physics that has been validated many thousands of times in labs across the planet.
~X~

May 9, 2010 6:14 pm

Title: Radiative Transfer Within the Mesospheres of Venus and Mars
Authors: Ramanthan, V. & Cess, R. D.
Journal: Astrophysical Journal, Vol. 188, pp. 407-416 (1974)
Bibliographic Code: 1974ApJ…188..407R
Title: The Thermal Balance of the Venus Atmosphere
Authors: Crisp, D. & Titov, Dmitri
Issue Date: 1995
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/18365/1/99-1842.pdf
Interference of spectral lines in thermal radiation from the lower atmosphere of Venus
T. S. Afanasenk and A. V. Rodin, 2006

Abstract The absorption spectrum and thermal radiation fluxes in the lower atmosphere of Venus are calculated using the theory of molecular state interference in the strong collision approximation. Comparison is made with the absorption and radiative transfer calculations in terms of the statistical theory of collisional line broadening and based on an empirical form factor. The calculations show that the line broadening mechanism does not affect the thermal regime of the atmosphere at heights above 60 km, but affects significantly the behavior of the greenhouse effect below the cloud layer.

Venus as a more Earth-like planet
Håkan Svedhem, Dmitry V. Titov, Fredric W. Taylor & Olivier Witasse, 2007
http://www.nature.com/nature/journal/v450/n7170/full/nature06432.html
The structure of Venus’ middle atmosphere and ionosphere
M. Pätzold, B. Häusler, M. K. Bird, S. Tellmann, R. Mattei, S. W. Asmar, V. Dehant, W. Eidel, T. Imamura, R. A. Simpson & G. L. Tyler, 2007
http://www.nature.com/nature/journal/v450/n7170/full/nature06239.html

Jbar
May 9, 2010 6:16 pm

To Nick Stokes:
OK, let’s say the surface emits 12,000 W/m2. Yet Venus only radiates 300-400 W/m2 from the top of the atmosphere, and the net radiation from the surface must be on the order of 70 W/m2. (That is 16% of the radiation received by Earth’s surface, which is what my source says reaches the surface of Venus.)
Doesn’t this prove how dramatically large the greenhouse effect is on Venus??!! The surface radiates 12,000 W/m2, but 11,930 W/m2 gets reflected back down to it by the atmosphere!!! That is a SUPER-GREENHOUSE.

Leonard Weinstein
May 9, 2010 6:18 pm

Jbar,
The radiation between two surfaces (or a surface and a gas layer) at different temperatures will have both an outgoing radiation from the surface and an incoming absorbed radiation from the gas layer. The NET flux is the difference, but the fact of the outgoing radiation is valid. The surface of Venus does radiate about 12,000 W/msq (assuming near unity emissivity), but absorbed back radiation is also very close to the same level due to the absorbing greenhouse gasses back radiating. The process is actually much more complicated, both due to the specific active wavelengths in the gas and due to it being an extended thickness effect. The emissivity and absorptivity of the ground may not be real close to 1 but probably is not too far off at the ground temperature and long wave radiation wave lengths. I think your disagreement is more one of semantics, not truth vs false.

Jbar
May 9, 2010 6:25 pm

Marc77:
Another thing about supercritical fluids – the supercritical point is the point at which the transition between liquid and gas disappears. There is no longer liquid and gas – there is only this supercritical fluid thing.
Something weird must go on at the altitude in Venus’s atmosphere where the pressure makes the CO2 supercritical.

May 9, 2010 6:31 pm

I appear to have mis-linked a citation in the above post:
Deconflicting the conflation …
Tectonic Effects of Climate Change on Venus
F. S. Anderson and S. E. Smrekar, 1999
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/18365/1/99-1842.pdf
Title:The Thermal Balance of the Venus Atmosphere
Authors: Crisp, D. & Titov, Dmitri
Issue Date: 1995
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/32268/1/95-1621.pdf

Jbar
May 9, 2010 6:36 pm

Bjorn & others: You haven’t heard the story of the “runaway greenhouse”?
Supposedly a long time ago Venus may have been like Earth, but being so close to the sun the oceans got hotter until the ocean started to boil. Water is a good greenhouse gas, so once the water started to boil, it made the greenhouse effect stronger, boiling more water, which made the GH effect stronger still, etc. and the greenhouse “ran away” as the oceans completely boiled away.
After that, there might have been 100 atm of water vapor in the atmosphere for some time. With water vapor reaching all the way to the top of the atmosphere, solar radiation could knock the hydrogens loose from water. Venus’s gravity is strong enough to hold onto oxygen but not hydrogen, so the hydrogen gets kicked out into space. Eventually almost all the hydrogen from the water got stripped away from Venus.
Meanwhile all the free oxygen (created by the stripping away of hydrogen from water) reacted with anything it could near the hot surface, especially carbon. Eventually this turned all the carbon on Venus into CO2. 90 atmospheres of CO2 makes a strong enough greenhouse to heat the surface to 470deg C.
Some evidence – what little water vapor there is left in the upper atmosphere is rich in deuterium. Deuterium is twice as heavy as hydrogen and so it’s harder for solar radiation to knock into space, so it gets more concentrated as the hydrogen goes away faster.

Jbar
May 9, 2010 6:43 pm

OkieSkeptic:
Venus has about 3% nitrogen, equivalent to roughly 3 Earth atmospheres of partial pressure. Earth in contrast has 0.8 Earth atmospheres partial pressure of nitrogen.

Keith Minto
May 9, 2010 6:43 pm

Okie Skeptic May 9 2010 5:17.
Again when this closed system is left alone in the constant gravity field, the temperature would eventually equalize through convective transfer throughout the gas (at a higher temperature because of the gravity potential energy added) even though the pressure would be higher at the ‘bottom’ of the tube.
If this were not the case, all one would have to do for free energy is to install a heat engine between the top and bottom of the tube since there would be a constant temperature difference even in the closed system.

More like radiative transfer as you are assuming(I think) no convection in your column.
You are right on the last point, a point I feel is the Achilles Heel of Steves conjecture. If Steve is correct, then he has invented the Venusian equivalent of perpetual motion.

dr.bill
May 9, 2010 6:44 pm

stevengoddard: May 9, 2010 at 12:32 pm
dr.bill
How is Venus “warmed from the bottom” during it’s thousands of hours long nights?

Hi Again Steve,
As I said a little earlier, I don’t know the answer myself, but I would give serious thought to the suggestion made by:
Jbar: May 9, 2010 at 5:26 pm
It makes more sense than anything I have previously seen.
/dr.bill

May 9, 2010 7:14 pm

Xyrus
You wrote ” as you approach zero kelvin your atmospheric pressure approaches infinity, not zero. “
PV = nRT
Pressure is proportional to temperature, not inversely proportional as you claim. Now start over.

May 9, 2010 7:17 pm

Xyrus
If you think pressure is inversely proportional to temperature, try sticking an aerosol can in the oven. Actually, don’t try that. You will probably get hurt.

May 9, 2010 7:19 pm

Nick Stokes
Your heat transfer analogy doesn’t work, because the amount of required work also increases by 90X.
The key issue is wind velocity, because that limits how far the differentially heated air can move in a given amount of time.

Phil C
May 9, 2010 7:31 pm

MaxL-
The gas law applies to gases. As the temperature drops you get a change in phase and the law no longer applies. If Venus were moved out beyond Pluto, where there would be minimal heat from the sun or any other source, the temperature would start to drop. The volume of the atmosphere would decrease. When the temperature reached ~200 degK the CO2 would change to a liquid or solid, depending on the pressure, and eventually all turn into solid CO2 as the temperature fell. The other trace gases would condense out at their characteristic temperatures too, eventually turning almost all the atmosphere into solid.
The ESA work shows that Venus has a very strange atmosphere and climate compared to earth, primarily due to the lack of water. Venus lies just sunward of the habitable zone and apparently lost all of its water, probably even as it formed.

May 9, 2010 7:42 pm

Bob_FJ and Steve, if pressure could create heat it would mean gravity is not a conservative force. Energy could be extracted from gravity and converted to heat via the “Goddard PV = nRT” relation.
If Steve was right you would have to take an oxygen tank with you to the Arctic because low temp would mean low pressure. Low pressure systems would have lower temperature than high ones. Etc.
If it’s not greenhouse I think the answer lies more along the lines of: 1) There’s a lot more internal planet heat than given credit for. 2) There’s heat generated somehow from the solar wind and Venus gets twice as much of that as Earth.

Editor
May 9, 2010 7:45 pm

Xyrus says:
May 9, 2010 at 6:11 pm

Atmospheric pressure is dependent on mass and gravity, among other things, and is derived from the ideal gas law.
To wit, as you approach zero kelvin your atmospheric pressure approaches infinity, not zero.

Only if the gov’t is trying to bail out the atmosphere (it’s too big to fail!) by adding more air. Otherwise, the pressure at ground level doesn’t change, as the weight of the air above doesn’t change. The height of the atmosphere shrinks until it turns to liquid or ice, then it still shrinks, but a lot less quickly.

May 9, 2010 7:49 pm

Jbar says: May 9, 2010 at 6:16 pm To Nick Stokes:
Did you mean to address that to me? What you say has been my argument from way back.

May 9, 2010 7:51 pm

Paul Clark
Try again. Low temperature means low volume in Antarctica. The atmosphere is thinner at the poles.
PV = nRT
I really suggest that everyone pass a high school chemistry class before trying to tackle this problem.

May 9, 2010 7:55 pm

Jbar
It is extremely unlikely (impossible) that Venus was ever like Earth, because there are no limestones on Venus. The atmosphere must have always been very thick and hot.

May 9, 2010 8:04 pm

Steve Goddard
“If there were no greenhouse gases or clouds (as Wikipedia implied) temperatures would be very cold.”

Well, what they said was that they would be Earth-like. Maybe that’s high-ball. But the estimate you put up against the Wiki statement was 400C. And you said, with emphasis:
“The high temperatures there can be almost completely explained by atmospheric pressure – not composition.”
And here
“Your heat transfer analogy doesn’t work”
I wasn’t making an analogy. I was just pointing out that at 90 atm, even a 10 km/h wind can transfer a lot of heat. Heat transfer goes as mass flux, not velocity.

May 9, 2010 8:07 pm

The ideal gas law and Avagadro’s Law have been around a lot longer than I have.
The ideal gas law has four degrees of freedom (pressure, volume, number of molecules, temperature.) You can’t infer what one variable will do in response to a change in another, without also knowing what the other two are doing. For the sake of these discussions we can assume that n is constant. So the three degrees of freedom are P, V and T which are related by P = T*c/V where c is a constant.
If we assume in a given atmosphere that vapour pressure P is fixed through a reasonable range of temperature – then as T increases V also has to increase, and as T decreases V also has to decrease.

Bob_FJ
May 9, 2010 8:27 pm

ALL: Concerning the assertions above of high emissions from the surface, per Stefan-Boltzmann, I suggest that the calculation is incorrect, as discussed below:
a} Imagine a block of dry ice. It will emit a low level of EMR as a consequence of its T. Now let surface melting occur; what happens? Does it emit from the newly constituted solid surface, straight through the liquid, or does the thin liquid become a new effective surface, or what?
(Incidentally, if the wet surface behaves like a body, and the solid beneath continues to emit in the same way, then a wet body would emit more than a dry one…. Without considering evaporative cooling, if any).
b} If a dry body is immersed in say an Earthly thin gas, having a lower temperature, there will not only be EMR emission resulting in net HEAT loss, but also HEAT loss via conduction and convection. Where does this “extra energy” come from without upsetting the balance of the EMR? Or, to put it another way, the surface molecules are busy losing energy as EMR, (photons), and as HEAT, (KE). Can they do that without affecting each other?
c} Perhaps b} can be ignored in a thin gas, but what if the gas is at high pressure, and approaching a liquid state? (either absorbent or transparent)
d} What if we substitute a liquid in c}? We are back to a}, except the liquid is thicker/deeper.
As an engineer, I’ve puzzled over this stuff for many years but have not found it described anywhere. (with modest looking, admittedly).
Here is one typical assertion from above:
“…it is still true that the surface emits (about) 12,000 W/m2. The S-B law applies at that level. Of course, many wavelengths are then quickly absorbed in the real atmosphere. But they were emitted.”
I suggest that this is incorrect. Also, I believe that conductive/ convective/ advective surface heat loss must be very high on Venus for Steve‘s hypothesis to work. Can anyone show that these suggestions are wrong? (without simply appealing to authority)

May 9, 2010 8:53 pm

Nick Stokes
If you have 90X as much thermal flux and 90X as much mass, they cancel each other out. Wind can move heat no faster than it’s velocity.
As far as atmospheric composition goes, it makes little difference on Venus if it has 5% CO2 or 95% CO2. It is only the first few tenths of a percent that are really important to the greenhouse effect (relative to the importance of pressure.).

May 9, 2010 8:55 pm

Steve Goddard
“The atmosphere is thinner at the poles.”
This is getting surreal. The air pressure at the N pole surface is basically the same as elsewhere, and the density is higher (colder air). The S Pole has lower pressure, but nothing to do with the ideal gas law – just altitude.
You’re getting tied in knots by talking about volumes in a continuum situation. You’d do better to use the ideal gas law in the form:
P=(R/M) ρT
where ρ = density and M=molecular weight. (R/M) is constant.

Keith Minto
May 9, 2010 8:57 pm

stevengoddard says:
May 9, 2010 at 7:51 pm
Paul Clark
Try again. Low temperature means low volume in Antarctica. The atmosphere is thinner at the poles.

Wouldn’t be because of the rotation of the earth would it?

May 9, 2010 8:58 pm

I’m surprised that people are still arguing about this. You can see very clearly that temperature increases steadily downwards through the Venusian atmosphere.
http://www.astro.wisc.edu/~townsend/resource/teaching/diploma/venus-t.gif
If the atmosphere were thinner (like earth) the temperature would be much lower. Does anyone actually doubt this? This isn’t theory. It is observational data.

May 9, 2010 9:02 pm

Nick Stokes,
I said “can be almost completely explained by atmospheric pressure – not composition.”
Given the presence of a minimal amount of greenhouse gas, the pressure becomes dominant. The whole point of these articles is to demonstrate that Earth could not become like Venus, unless all the limestones dissociated. That would require a catastrophic event which would kill all life on earth anyway.

May 9, 2010 9:15 pm

Nick Stokes
Again PV = nRT
The North Pole has equal pressure (as you said.) n is fixed and the temperature is lower, so the volume also has to be lower. Lower volume means with fixed n means higher density (as you said.)
What is confusing to you about this? The ideal gas law works just fine, like it always has.

May 9, 2010 9:19 pm

Nick Stokes
Perhaps you are being confused by my use of the word “thinner?” I am using “thinner” to mean exactly that – the height of the atmosphere is smaller at the poles, because the atmosphere is more dense at the lower temperatures.

May 9, 2010 9:24 pm

The whole point of these articles is to demonstrate that Earth could not become like Venus, unless all the limestones dissociated.
Ummmm? Whats Up With That?
I think you have taken a fairly common statement “the atmosphere of both Earth and Venus demonstrate Greenhouse heating” and constructed a straw man “AGW will cause a runaway Venusian Greenhouse.” There may be some idjits bouncing around claiming that – but it ain’t mainstream AGW. Step away from the straw man, Steve.

May 9, 2010 9:50 pm

Steve Goddard:

“You can see very clearly that temperature increases steadily downwards through the Venusian atmosphere.”

Yes, and there’s a fundamental problem this observation presents to conventional physics. There’s no reason that the lower layers shouldn’t reach thermal equilibrium with the upper layers and warm them to the same temperature regardless of this pressure difference.
Take geothermal heat. About 200km down all rock is molten at at least 1000C. That heat can not ultimately go inward; it must all come outward. There should be an inverse square relation to the heat dissipation. The surface only being a fraction of an Earth radius higher than 200km down should be:
1/(Earth radius)^2 divided by 1/(Earth radius – 200km)^2 times 1000C = 938C.
The Earth’s surface should be 938C. It appears heat is disappearing. Meanwhile, the ocean below the thermocline is refrigerated at 2 to 4C when it should be boiling from the geothermal heat. The mid/low ocean can’t be cooling from evaporation on the surface because the upper ocean layer is warmer than the mid to lower levels. Heat can’t be extracted from a colder place through a hotter place. It appears to be a case where energy is either created or destroyed.
My own belief is that cooling might be caused by a thermoelectric effect related to the vertical voltage gradient.
Steve, there is apparently some sort of relation between temp and pressure in the air but it’s not one of cause and effect. We just don’t know what it is yet.

May 9, 2010 10:01 pm

Steve Goddard
Well, Paul Clark said:
“If Steve was right you would have to take an oxygen tank with you to the Arctic because low temp would mean low pressure. Low pressure systems would have lower temperature than high ones.”
to which you responded:
“Try again. Low temperature means low volume in Antarctica. The atmosphere is thinner at the poles.
PV = nRT
I really suggest that everyone pass a high school chemistry class before trying to tackle this problem.”

Nothing Paul said related to the height of the atmosphere.

May 9, 2010 10:08 pm

Ron Broberg
The idea that Earth could become like Venus was a central point of Sagan’s TV show – Cosmos. A whole generation was corrupted by this idea.

Carrick
May 9, 2010 10:10 pm

Nick Stokes:

This is getting surreal. The air pressure at the N pole surface is basically the same as elsewhere, and the density is higher (colder air). The S Pole has lower pressure, but nothing to do with the ideal gas law – just altitude.

“Thinner” I believe refers here to height not density. See this.
The reasons for this are a lot more complex that just e.g. the ideal gas law, though. (Ref.

May 9, 2010 10:12 pm

Straw Man? LMAO – This is just one of thousands of similar articles:
http://www.is.wayne.edu/mnissani/a&s/GREENHOU.htm

If the process continues unchecked, it could reach a point of no return, as it apparently had on Venus. As the Earth heats up, water would convert into steam, which is a greenhouse gas. The Earth would get hotter and hotter. As the atmosphere heats up, more CO2 might escape from its present location in ocean rocks and shells. Beyond a certain point, the process may be self-sustaining. Venus tells us how far such a process can go—hellish temperatures, a cloud cover that lets less sunlight reach the earth but helps trap the heat, enormous pressures at ground levels weighing heavily upon everything and distorting the landscape. Venus provides us a timely warning. If we pay no attention, in some 800 years life on Earth might perish.

May 9, 2010 10:39 pm

Just to clarify my last comment: there is a PV = nRT relation for temps and pressure for changing situations in such as low pressure systems, Hadley cells, etc. But, it does not apply to the correlation between temp and pressure vertically as found on Earth and Venus.

Keith Minto
May 9, 2010 11:46 pm

stevengoddard says:
May 9, 2010 at 9:19 pm
Nick Stokes
Perhaps you are being confused by my use of the word “thinner?” I am using “thinner” to mean exactly that – the height of the atmosphere is smaller at the poles, because the atmosphere is more dense at the lower temperatures.

And because of the rotation of the earth/atmosphere system, troposphere goes to 7km at the poles and to 17km at the equator.

Spector
May 9, 2010 11:57 pm

In general, I believe that an adiabatic lapse rate in a planetary atmosphere is evidence of an active convection process. Without convection, such as in the stratosphere, higher parcels of air may be warmer than those below. Perhaps there must always be a greenhouse effect to force the tropopause above the ground level.
If Venus had an atmosphere as thick as it is now, but with a composition similar to the Earth, I suspect an active convection system would also exist and produce a lapse rate similar to that of the current Venusian atmosphere. Perhaps this is why Hungarian scientist Ferenc Miskolzi has said the magnitude of the greenhouse effect is limited by the thickness of the atmosphere.

Ralph
May 9, 2010 11:59 pm

>>>Ben Schumacher says: May 9, 2010 at 2:06 pm
>>>pressure and temperature varying at the adiabatic lapse rate —
>>>provided the conditions are suitable for convection.
You don’t need convection for an adiabatic lapse rate – it is purely gas density/pressure that makes the gas hot. I have adiabatic warming in my bicycle pump, but no convection.
http://en.wikipedia.org/wiki/Lapse_rate
But adiabatic temperatures can reduce, as the heat is conducted or radiated away, as in my bicycle pump getting cooler – and the result on Venus would be a cooler but denser atmosphere (but roughly the same pressure, I presume, because of the same weight of gas above the surface).
So the current high temperatures on Venus must be augmented by solar input (or geothermic processes) to keep this high temperature. I would suggest that the atmosphere is thick enough and opaque enough to absorb a large amount of solar radiation.
.
.

Ralph
May 10, 2010 12:08 am

>>>Paul Clark says: May 9, 2010 at 9:50 pm
>>> There’s no reason that the lower layers shouldn’t reach thermal
>>>equilibrium with the upper layers and warm them to the same
>>>temperature regardless of this pressure difference.
They may well do, in terms of molecular velocities (temperature), but the lower atmosphere has many more molecules/cm2 – so that same ‘temperature’ per molecule equals much more heat. That’s the whole point about compressing gasses and an adiabatic lapse rate.
But again that higher pressure does not preclude the lower atmosphere radiating and convecting away its heat, and becoming denser and cooler.
A HIGH PRESSURE GAS DOES NOT HAVE TO BE WARM. Touch the sides of a diver’s gas cylinder, and tell me if it is warm. Thus Venus must have a thermal input, to maintain its high temperature – otherwise it would end up like the diver’s very dense, very high pressure, but very cold gas cylinder.
.

Ralph
May 10, 2010 12:16 am

Just one question about the Venera pics – why did they never ‘normalise’ the colours? They have a colour chart there for comparison, but I have never seen an image of the surface as it would look under Earth-like light conditions.
.

Ian H
May 10, 2010 12:17 am

@Paul Clarke and others: The Pressure-Temperature link exists only in gasses that are vertically mixed. Water (being essentially incompressible) doesn’t do this even with vertical mixing. The earth’s crust doesn’t do this either. Not only is it almost incompressible, but it is also essentially static. So comments about a relationship between pressure and the temperatures of the sea and earth’s crust are way off topic.
A column of gas without vertical mixing would also be all the same temperature. Wherever there is some amount of vertical mixing however, the high pressure regions low down will be heated by this, and the upper low pressure regions will be cooled. A temperature gradient will then form.
Overall temperatures will be set by the part of the atmosphere which is in radiative equilibrium with space. On earth most radiation reaches the ground, and the surface itself is directly heated. Therefore the temperature at the surface mostly sets the overall temperature of the atmosphere. Since the rest of the atmosphere is at much lower pressure it will be much cooler than the radiative equilibrium temperature. On venus it is not the surface but the the upper cloud layers that are directly heated by the sun. The upper clouds therefore reach the temperature of radiative equilibrium with space, and the surface, which is at much higher pressure will end up being much hotter.
All this is approximate and ignores other effects, including the greenhouse effect which deals with radiative transfer within the atmosphere. But to first order this serves as an adequate explanation of why Venus is so much hotter than the Earth.

Ralph
May 10, 2010 12:29 am

Steve.
If you are implying from this post that Venus should have a much higher laps rate, due to its 99% CO2 atmosphere being a so-called ‘greenhouse gas’, that is not immediately obvious in your post.
You need a graph of lapse rate with 0.1% CO2 (Earth) and a lapse rate with 99% CO2 (Venus) being much steeper (because the latter should, according to green logic, capture more solar energy, which is distributed through the Venusian atmosphere by convection).
But this is something that Venus does not display, with both Earth and Venus having the same lapse rate.
Ergo – CO2 is not the big driver of temperature on Venus, and nor on Earth.
.

dr.bill
May 10, 2010 1:46 am

OK, I’ll try this once more.
When using the Ideal Gas Law, or any other equation of state for a gas, it is important to consider ALL of the quantities involved. It is also important to consider the circumstances. A sealed rigid volume such as a SCUBA tank isn’t the same as an inflated rubber balloon, and neither of those is the same as an open column of air “standing up” in a gravitational field. Details matter, and people have been conflating many issues incorrectly, or forgetting certain constraints and complications.
The Gas Law can be written as P = (N/V)kT, and the quantity N/V is called the particle density. There is no fixed volume for our atmosphere. Its volume can increase or decrease as it expands and contracts. In this context, it is the product of particle density and temperature that must remain fixed if the pressure is not to change.
This happens all the time, all around the planet. The surface temperature changes RADICALLY with time and location. Nevertheless, the pressure at sea level NEVER changes in any SIGNIFICANT way from 1000mb, no matter where you are on Earth, or what time of the day or time of the year it happens to be. Yes, it does change, and that is why we use barometers, but the AMOUNT of change is MINISCULE in comparison with the corresponding changes in temperature. Sea level pressure in the Arctic is essentially the same as sea level pressure in the Caribbean, despite the large differences in temperatures.
When you start climbing above sea level, however, you can’t just use the Gas Law by itself. You have to consider the effects of gravity. One of the consequences is the fact that pressure and particle density do not change in the same way as we go to higher altitudes. Both temperature and particle density decrease as we move upward in the troposphere, and because pressure depends on the product of these things, the pressure decreases more quickly than either temperature or particle density. At the tropopause, the particle density is typically down to about 30% of its sea level value, but the air pressure has gone down faster, and will only be about 20% of its sea level value.
The devil is in the details, and many people on this thread, and particularly Steve, are ignoring them. Actually, I think the tide has reversed on this. Many other posters appear to “get it”, but Steve doesn’t seem to be doing so. Another case of “right answer, wrong logic”, I guess.
/dr.bill

Gail Combs
May 10, 2010 3:28 am

Jacob says:
May 8, 2010 at 4:14 pm
Why is the atmosphere on Venus 92 times more dense than on Earth? That is the big question, that I don’t understand.
Now, if the atmosphere is denser – it means there are 92 times more molecules of gas in the same volume (or layer) of the atmosphere, therefore they would absorb 92 time more outgoing radiation (much more anyway). So, the heat on Venus’ surface is caused by the greenhouse effect after all, by the fact that the greenhouse effect is much stronger there, due to the density of the atmosphere, and not necessarily due to it’s composition (Co2).
If pressure alone could cause heating – why isn’t the bottom of the oceans very hot?
_________________________________________________________________________
J.Hansford says:
You are confusing gasses and liquids Jacob… Seems a few others are doing the same. Gasses are compressible, liquids are not…..
_________________________________________________________________________
PV=nRT is the ideal GAS law. How it applies to Venus and Earth is the topic under discussion.
“A law relating the pressure, temperature, and volume of an ideal gas. Many common gases exhibit behavior very close to that of an ideal gas at ambient temperature and pressure. The ideal gas law was originally derived from the experimentally measured Charles’ law and Boyle’s law. Let P be the pressure of a gas, V the volume it occupies, and T its temperature (which must be in absolute temperature units, i.e., in Kelvin). Then the ideal gas law states
PV=nRT
where n is the number of moles of gas present and R is the universal gas constant,….”

Source: http://scienceworld.wolfram.com/physics/IdealGasLaw.html

May 10, 2010 5:35 am

dr.bill
Remarkable that I have to explain this again. Please read my posts carefully before posting.
At temperatures where the atmosphere is a gas, the pressure is fixed by the weight of the column of air. The temperature controls the volume (i.e height of the atmosphere.) That is why the cold poles have a thinner atmosphere than the tropics.
P = T *c/V
This is the most fundamental physics. When the temperature decreases, the volume has to decrease. The volume is area * height. Area is fixed, so the only thing which can change at the cold poles is the height of the atmosphere.

DavidB
May 10, 2010 6:10 am

Consider a cylinder containing a quantity of gas. The cylinder is closed at one end and has a piston at the other. Suppose now we force in the piston, compressing the gas. What happens to the temperature of the gas?
Applying the ideal gas law, using the equation pV = nRT, the volume V is reduced by the compression, and nR is unchanged, so, other things being equal, T must be reduced. Thus we reach the remarkable conclusion that compressing a gas reduces its temperature!
Of course this is quite fallacious. In reality, compressing the gas increases its temperature because the kinetic energy of the moving piston is transferred to the molecules of the gas. To balance the equation, the pressure p is also increased. If the cylinder is perfectly insulated the increased T will be maintained indefinitely, so long as the piston is held in position. In practice, perfect insulation is impossible, and T will fall by conduction and radiation until it returns to equilibrium with the environment. As T falls, assuming the piston is held in position, pressure will also fall, though not back to its original level before the gas was compressed.
In this example the fallacy in the original argument was obvious, because we knew the conclusion was false, and it was easy to see the loophole in ‘other things being equal’. But in other cases the fallacies may not be obvious. The moral is that the equation of the ideal gas law cannot be applied blindly without considering the physical processes involved.

the fritz
May 10, 2010 6:34 am

experiment #5 Imagine the venusian atmosphere would be still heavier and no sunlight would reach the surface; the temperature would still be greater and would you still speak about greenhouse effect to explain the great temperature at the venusian surface?

Dave
May 10, 2010 7:02 am

“Why? Because the greenhouse effect is logarithmic. After the first few percent, additional CO2 makes much less difference to the temperature.
Consider earth, where a doubling of CO2 only increases temperatures by <1 (Lindzen) to 3 (IPCC) degrees C."
Again, NOT TRUE. The forcing from CO2 is logarithmic only within certain a certain range about the current concentration. At very high concentrations it approaches linearity again as the 15 um band saturates and the weak bands become predominant. This has been pointed out to you multiple times, and yet you keep repeating it.
If you want a reference, see Figure 1 in:
http://journals.ametsoc.org/doi/pdf/10.1175/1520-0469%281977%29034%3C0448%3AARCMSO%3E2.0.CO%3B2
(I might also recommend http://www.agu.org/journals/ja/v085/iA13/JA085iA13p08223/, one of the earlier calculations of the full temperature profile of Venus' atmosphere)

May 10, 2010 7:05 am

DavidB
If you push a piston down into a cylinder, you are exerting a force which directly increases the pressure. That is why the temperature increases. Your claim that “everything else is held equal” is incorrect.

Mike M