Hyperventilating on Venus

By Steve Goddard

The classic cure for hyperventilation is to put a paper bag over your head, which increases your CO2 levels and reduces the amount of Oxygen in your bloodstream. Global warmers have been hyperventilating over CO2 on Venus, ever since Carl Sagan made popular the idea of a runaway greenhouse effect. That was when he wasn’t warning about nuclear winter.

Sagan said that marijuana helped him write some of his books.

I bought off on the “runaway greenhouse” idea on Venus for several decades (without smoking pot) and only very recently have come to understand that the theory is beyond absurd.  I explain below.

The first problem is that the surface of Venus receives no direct sunshine. The Venusian atmosphere is full of dense, high clouds “30–40 km thick with bases at 30–35 km altitude.”  The way a greenhouse effect works is by shortwave radiation warming the ground, and greenhouse gases impeding the return of long wave radiation to space. Since there is very little sunshine reaching below 30km on Venus, it does not warm the surface much.  This is further evidenced by the fact that there is almost no difference in temperature on Venus between day and night.  It is just as hot during their very long (1400 hours) nights, so the 485C  temperatures can not be due to solar heating and a resultant greenhouse effect.  The days on Venus are dim and the nights are pitch black.

The next problem is that the albedo of Venus is very high, due to the 100% cloud cover.  At least 65% of the sunshine received by Venus is immediately reflected back into space.  Even the upper atmosphere doesn’t receive a lot of sunshine. The top of Venus’ atmosphere receives 1.9 times as much solar radiation as earth, but the albedo is more than double earth’s – so the net effect is that Venus’ upper atmosphere receives a lower TSI than earth.

The third problem is that Venus has almost no water vapor in the atmosphere.  The concentration of water vapor is about one thousand times greater on earth.

Composition of Venus Atmosphere

0.965 CO2

0.035 N2

0.00015 SO2

0.00007 AR

0.00002 H2O

Water vapor is a much more important greenhouse gas than CO2, because it absorbs a wider spectrum of infrared light – as can be seen in the image below.

File:Atmospheric Transmission.png


The effects of increasing CO2 decay logarithmically.  Each doubling of CO2 increases temperatures by 2-3C.  So if earth went  from .04% CO2 to 100% CO2, it would raise temperatures by less than 25-36C.

Even worse, if earth’s atmosphere had almost no water (like Venus) temperatures would be much colder – like the Arctic.  The excess CO2 does not begin to compensate for the lack of H2O. Water vapour accounts for 70-95% of the greenhouse effect on earth. The whole basis of the CAGW argument is that H2O feedback will overwhelm the system, yet Venus has essentially no H2O to feed back. CAGW proponents are talking out of both sides of their mouth.

So why is Venus hot?  Because it has an extremely high atmospheric pressure.  The atmospheric pressure on Venus is 92X greater than earth.  Temperatures in Earth’s atmosphere warm over 80C going from 20 kPa (altitude 15km) to 100 kPa (sea level.)  That is why mountains are much colder than the deserts which lie at their base.

The atmospheric pressure on Venus is greater than 9,000 kPa.  At those pressures, we would expect Venus to be very hot. Much, much hotter than Death Valley.


Wikipedia typifies the illogical “runaway greenhouse” argument with this statement.

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.

No it wouldn’t. 9000 kPa atmospheric pressure would occur on earth at an altitude many miles below sea level.  No such place exists, but if it did – it would be extremely hot, like Venus. A back of the envelope estimate – temperatures on earth increase by about 80C going from 20 to 100 kPa, so at 9,000 kPa we would expect temperatures to be in the ballpark  of :

20C + ln(9000/(100-20)) *80C = 400C

This is very close to what we see on Venus.  The high temperatures there can be almost completely explained by atmospheric pressure – not composition. If 90% of the CO2 in Venus atmosphere was replaced by Nitrogen, it would change temperatures there by only a few tens of degrees.

How did such bad science become “common knowledge?” The greenhouse effect can not be the cause of the high temperatures on Venus. “Group Think” at it’s worst, and I am embarrassed to admit that I blindly accepted it for decades.

Blame CO2 first – ask questions later.


UPDATE: Lubos Motl has written an essay and analysis that broadly agrees with this post. See it here


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Great column, and somewhat of a relief. As a teenager I read Sagan’s book where he made this claim, and it scared the hell out of me.
I feel much better now.

hippie longstocking

Which of course begs the question: Has anyone looked at the overall atmospheric pressure change during this supposed unprecedented warming? No? Oh, well, that data is probably as incomplete as the temperature data anyway, so why let the climate scientologists manipulate that to fit their agenda. I’m sure one of them will model it soon enough and cry out “It’s worse than we thought!” Dolts.
Disclaimer: The above statement was not meant to offend any real scientologists out there. I’ll get around to offending them some other time and some other place.


Sorry, I must be missing something. I’ve dealt with high pressure gases for many years, and while a cylinder will heat as it is filled to say 3000 psi, it quickly cools. It does not stay hot. So there must be something else on Venus – volcanic activity perhaps is part of it – that is at work there.

jack mosevich

Steve: I did a search and the 1st 20 to 30 sites, including NASA, stated that Venus’s temperature is due to the runaway greenhouse effect. Your analysis is very convincing. Then I found the following which comes to the same conclusion as you with a bit more analysis. I am convinced that you are correct and that the ‘consensus’ is wrong.


Well thats it. I am not going to venus!

Thanks Steve, interesting post! And if correct and reasonalble, it baffles me that noone else has noted this before …
This simply cannot be! Other people must have hade similar thoughts and estimates.

The Ghost Of Big Jim Cooley

Here in the UK, our Channel 4 news has been following the Catlin Jokesters in the Arctic. A journalist (I use the term loosely) has just given an appalling piece of television reporting. You can read his dire piece here: http://www.channel4.com/news/articles/science_technology/concern+over+impact+of+rising+ocean+acidity/3638487

Gail Combs

Quick send this information to Lord Monckton

Jason Lewis

What about the fact that the sunlight at Venus’ orbit is almost twice as intense as at Earth’s orbit?

As far as i understood it would take two things to turn Earth into a seccond Venus, and that is enough time, and about twice the amount of energy from the Sun.
And this all to start building up the atmospheric pressure which needs a lot of time, more energy means more watervapour, more watervapour means higher pressure wich in result in an atmosphere wich is beter suited to hold an higher temperature. Once all the water in the ocean has been transformed into atmosphere the temperatures will be high enough to start the outgassing of rocks wich raises the temperature and pressure even further. Eventually Earth would look like Venus with a high pressure and CO2 rich atmosphere.
And that will eventually happen, in a few hundred million to a billion years from now when the sun is (a bit) brighter than it is now.
So a runaway greenhouse? Yes, but not caused by us puny humans and not tomorrow.


Once again the Flintstones’ Universe Cosmology fails!. Anyone of us can recreate a small Venus in a microwave oven.


There is a terrestrial example of higher air temperatures resulting from greater depth / greater pressure – that of the occasional isolation and evaporation of the Mediterranean Sea:
It would be interesting to know what the atmospheric temperature on Venus is at the height equivalent to one Earth atmospheric pressure.

Henry chance

That explains why women are from Venus and men come from Marrs.

Denis Hopkins

That is one of the most interesting articles I have read on here in the 3 years I have been visiting….. Thanks… Just goes to show how we accept things if they are repeated enough. The trouble is that young people will only hear one argument and it, in time, becomes accepted wisdom. There is always the need to be sceptical.
By the way, on that point “climate deniers” have often been called “flat-eathers”. Most people believe that Columbus was thought to be mad to attempt the voyage west to India because he would “fall off the Earth”. My understanding is that this was a myth put about by Washinton Irvine in the 19th century. Columbus could not get funding because everyone knew the Earth was round. They knew its diameter. They knew you could not carry enough provisions for such a journey to India. Anyone who lives near the coast will see the hulls of ships disappear before the masts. Yet still we think that they thought the Earth was flat in 1490. Despite Erastothenes measuring the diameter in 200 BC to within 1% of today’s accepted value.

CRS, Dr.P.H.

I believe that the presence of sulfuric acid in the clouds of Venus also contributes to its greenhouse effect. Dr. Richard Lindzen touched upon this during his colloquium presentation at Fermilab National Laboratories.
It’s in one of the 9 parts on Youtube: http://www.youtube.com/watch?v=gMkyjyk-VEk


Talking of atmospheric pressure, co2 and temperature look at mars:
Carbon Dioxide (CO2): 95.32%
Temperature: + 1° F, ( -17.2° C) to -178° F (-107° C)
Atmospheric pressure: 6 to 10 millibars


If you consider a column of the atmosphere in a stable state, with thermodynamics, at the top you have 3K temperature, and you will see that the gradient of pressure implies a gradient of temperature.


Funny. My brother-in-law brought up Venus the other day. “Why is it so hot there if not because of all the CO2?” My response was, “Are you kidding me with this?”
“Group Think” just doesn’t adequately decribe it. I really simply cannot figure out how they get this stuff in their brain.


“Sorry, I must be missing something. I’ve dealt with high pressure gases for many years, and while a cylinder will heat as it is filled to say 3000 psi, it quickly cools. It does not stay hot. So there must be something else on Venus – volcanic activity perhaps is part of it – that is at work there.”
But what is the temp of the ambient air around the cylinder. Your filled bottle has somewhere to transefer the heat too. Where is Venus’ heat sink to spill all that heat into?

What keeps the earth warm? The sun. Without the sun, the Earth and Venus would be close to absolute zero.
Now, why is it -40 degrees on top of Mt. Everest? They get lots of sunshine up there and it is the same latitude as Saudi Arabia.

D. King

Thanks Steve.
92 atmospheres @ 14.7 psi per, is 1352.4psi (Earth)
@33 ft. per atmosphere that’s about 3036ft (ocean).
Ballpark SCUBA numbers!


If you really want to feel confused check out Nasif Nahle’s site: http://biocab.org/Induced_Emission.html. Professor Nahle seems to say that there is no “green house effect,” partly because none of the common models take thermodynamics into account properly. He argues, provided I follow his logic and mathematics correctly, that the thermal capacity of the atmosphere, being orders of magnitude less than the land and more importantly the oceans, cannot add any significant amount of heat to the climate. Instead, the land and ocean during the night damp atmospheric cooling by warming the air immediately above these important thermal masses. According to Nahle, the atmosphere’s primary climatic effect, mainly through convection, carries warmed air away from thermal masses warming it outward and upward to where it radiates away from the planet. This matches discussions on real greenhouse (transparent windows with plants inside) effects, which point out that a true green maintains a warmer environment than the surroundings by limiting convection. Energy loss through longwave radiation is not significant. Consequently the primary heat loss in a greenhouse is through conduction, and glass is a poor conductor.
Reading Nahle one might get the idea that any explanation of climate that admits to a “greenhouse effect” might be making assumptions that are contrary to the laws of thermodynamics. Not being a climatologist, physicist or engineer, I would really like to see this discussed.

This whole Venus thing goes back the E. Velekofski (sp?) in the 1950’s. Segan, like many others had some rather strange ideas. This one he picked up from Velekofski from one of his books. He wrote several (can’t be sure of the titles). I did try to read them and found his understanding of geology completely screwed up. So I judged his astronomy was little better. Like many strange people he was not completely, wrong just mostly so. Segan is much the same. Some of his stuff is okay and some not so good. When you get down to the facts we know so little about Venus that making any kind of comparison to Earth is rather foolish. Then if we did not have foolish people we would not need the term. Appeals to authority will never go away, let us hope the choice of that authority is a wise one in the future. (It won’t be.)

CRS, Dr.P.H.
No doubt the Venusian clouds create a barrier to IR. But they are 30 km above the ground surface. Most wavelengths of IR have almost nothing blocking them in the lower 30 km of the atmosphere.


I attended a talk by Andrew Weaver, and this was one of his big selling points of CO2 causing the Earth to get warmer. Venus is hotter than the Earth, because it’s atmosphere is mostly CO2. Not because it is closer to the sun.
If I remember my basic physics: energy absorbed is an inverse square to the distance from the source. Mercury has no atmosphere, and I’ll bet it’s sunny side is a lot hotter than Venus.


The critical pressure of CO2 is 7,380 kPa. The critical temperature is 30 C. In those supercritical fluid conditions it’s hard to say whether Venus has an atmosphere or an ocean. Pointing to Venus as a model demonstating something about earth is an exercise in lulling the mind into a belief that it understands something that it has a hard time even imagining.


PV=nRT. Venus is hot because of the pressure. I also maintain that some of the supposed 33 C temperature increase due to GHG is really caused by the pressure of our atmosphere. All the gases in our atmosphere would still be gases at the -18 C used as the temperature based on black body radiation. I maintain that the atmospheric pressure should bring us up to 0 C leaving only 15 C for greenhouse effect. Besides Wien Law says the absorbtion line at 15 mirco for CO2 is a temperature of 200K and that will not heat up anything.


What the hell happened at 12.5 kilometers? Each probe went haywire as it passed through a height of about 12 kilometers, or 7.5 miles, above the surface. The temperature and pressure sensors sent back crazy numbers, power surged throughout the probes, and some instruments stopped functioning entirely.” The NASA report found that “the sensors that failed at almost the same time were made of different materials and their electronics were isolated from each other.” Furthermore, some of the strange readings “can best be explained if the probe became covered with a plasma of charged particles.”


this is an interesting take, but what maintains the temperature?


Just because you don’t understand something doesn’t make it wrong… There is a wealth of literature on Venus’ atmospheric dynamics. A good starting point is here: http://www.nature.com/nature/journal/v226/n5250/abs/2261037a0.html
Also, Carl Sagan smoking pot is a bit of a cheap shot 😛

Dr T G Watkins

Excellent post and some interesting links.
Looking forward to the EPA hearings; not one prominent UK politician has expressed any doubts re. AGW.
Nearly 44,000,000 hits ! The message must be getting through and a tipping point will come.

Zeke says:
May 6, 2010 at 12:36 pm:
“…Carl Sagan smoking pot is a bit of a cheap shot :P”
And what is your opinion of all the ad-hom comments about Viscount Monckton? Are they cheap shots too?

There is a wealth of literature about catastrophic global warming. The weight of the literature is no more interesting than the weight of the duck in the Holy Grail.
And no, scientists should not be taking drugs.

The Ghost Of Big Jim Cooley

Anthony – have you seen this?!? http://www.telegraph.co.uk/earth/earthnews/7686079/Climate-change-deniers-accused-of-McCarthyism.html
REPLY: I can’t respond to every crazy journalist out there, and Louise Gray is certainly a victim of retarded thinking. -A

Troels Halken

Why does Venus have a much more dense atmosphere than Earth?


This article, more than most, is and example of how blind belief can distort physics almost beyond recognition. Perhaps something stronger that “pot” is at work!

The Russians have landed spacecraft on Venus and there is no ocean. Just rock.


@ SidViscous says:
May 6, 2010 at 12:14 pm
…………………But what is the temp of the ambient air around the cylinder. Your filled bottle has somewhere to transefer the heat too. Where is Venus’ heat sink to spill all that heat into?
That doesn’t compute. Let the cylinder stabilize at ambient. Then put it in a perfectly insulated container. It will not reheat due simply to pressure. It will stay at whatever temp it was when placed in the container.


There is a bigger issues with Venus many wont be aware off, not that long ago scientists thought venus would be a similar temperature to earth. Then a young upstart geologist came along and suggested that Venus would actually be around 450 degrees due to geothermal venting. He was laughed away of course, daring to question concensus, but later on when they actually measured the temperature they found he was almost spot on! This caused a problem for the “experts” so they came up with a compromise, it was called the “green house effect”, rather than accept the geothermal heating scenario they invented a new one so no-one had to be wrong. They all accepted it and shut their mouths. Of course it never actually fitted, as Steve points out, plus the temperature day and night are constant and the poles and the equator the same. This does support geothermal heat, and the atmospheric mass also explains the high air temps better. I am sure no-one really understands Venus, we dont understand earth yet!
It merely demonstrates that the greenhouse effect when applied to other plants doesnt work, NASA recently found it didnt quite work for Mars either when they tried modelling its climate. Atmospheric pressure is the key and it determines global temperature, its very reliable for predicting weather and temperature change over height changes, we should be looking at changes in atmospheric pressure as well as the atmospheric composition of the atmosphere. Venus merely highlihts the frailty of the “greenhouse” holy cow. It was invented to explain an observation and fortunetly came within a few degrees of observation, but fails any kind of testing when applied to alternative atmospheres!

stephen richards

Or Boyles law PV=RT where P=pressure and R is a constant
Therefore, p increases T increases proportionally;
p=9000 times more T = 9000 times more. voilà.
P= 1 atmos @ 15.9°C (the earth) P = 92 atmos @ 92*15.9=1462°c
obviously pressure is not the only factor in creating venus’ temperature but you can see where the difference in T comes from.

Bob H.

A lot of years (about 30) ago I took a thermodynamics class. In it we learned that when you increase temperature without increasing the volume, pressure increases. When you increase pressure without increasing the volume, temperature increases.
This is basic thermodynamics. If we want to make Venus more like Earth, we need to export to Venus some sun-loving, CO2 munching bacteria to turn CO2 into some solid carbon compound. This would eventually decrease the atmospheric pressure and thus reduce the temperature. In fact, if we really want to do geoengineering, Venus would be a good place to practice (until we get it right).


Do you know Steve I’d already figured that out, but in the opposite direction, I was trying to figure out why Mars with almost the same atmosphere in terms of CO2 as Venus was cold compared to Venus, and indeed the Earth. I figured it was because the atmospheric pressure was very low, I never connected it to Venus where it’s the opposite.


“What keeps the earth warm? The sun. Without the sun, the Earth and Venus would be close to absolute zero.”
Assume you mean surface temps here (both would remain internally hot for a long time without the sun). In the case of Venus it is quite likely that the surface temperature would be hot too, at least some of the time.
Venus’ atmosphere comes from volcanic outgassing, and Venus is a very different geological animal to Earth. It has no water so there are no tectonic plates. Instead of releasing heat gradually as does Earth, Venus is thought to occasionally “boil over”, where the whole surface completely melts. With the thick atmosphere, a high surface temperature would remain in the absence of solar heat.
In the outer solar system where the sun’s heat is minimal, the massively thick atmospheres of the giant planets are heated primarily from within and would remain almost intact if the sun was switched off.

Troels Halken
Venus does not have any limestone, so they have much less CO2 sequestered in rock. Because of this, their atmosphere is much more dense than earth.
My point is that it is the partial pressure of CO2 (much more than the IR absorption of CO2) which keeps Venus so hot. The implications for earth are completely different, because we have oceans which form limestone, particularly at warmer temperatures.


Venus is extremely volcanic.

stephen richards
The ideal gas law isn’t quite so simple as you are thinking. As the pressure increases, the volume decreases. In an ideal gas they would exactly balance each other out. But no gases are ideal, so they warm under pressure.

Heat flow from inside the earth is much smaller than the energy received from the sun.


What Steve Goddard is trying to tell us is that greenhouse effect will never explain Venus temperature. Would you cook your meals using it?


Dumb question: Given that it is hotter on the surface of Venus than the surface of Earth because of the mass of the atmosphere of Venus and the fact that it is closer to the sun and receives more energy than Earth on a daily basis, how did all that mass get into the atmosphere?
I am familiar with the suggestion written earlier in this thread that Venus started off with liquid oceans that were eventually evaporated, disassociated into hydrogen and oxygen and the hydrogen driven off; and then the carbon dioxide in the rocks baked out to form the atmosphere.
Given that both planets were formed in the same general region of the solar system accretion disk, does this mean that Earth also has about that same amount of carbon dioxide locked up in the rocks (not to jack up temperatures due to greenhouse, but to increase the total mass of the atmosphere)?