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.
http://www.globalwarmingart.com/images/7/7c/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.
http://en.wikipedia.org/wiki/File:Emagram.GIF
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.
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UPDATE: Lubos Motl has written an essay and analysis that broadly agrees with this post. See it here
Lon Hocker says:
May 6, 2010 at 9:23 pm
And then what happens? The heated gas convects upward to a region transparent enough to radiate in wavelengths that aren’t blocked.
Carl Sagan…….up until now, the most prolific science fiction writer ever to pass his work off as science. He had a great imagination. When the Martians or Saturnians come and get us, he’ll be proven correct. Like the rest of the cast of idiots, he said “I’ve got a degree from a meaningless institution that gives me license to say whatever comes off of the top of my head and people should believe me. After all, I’ve got a degree in…..lunacy.”
Sorry Steve, while I am very much a skeptic of AGW I have to disagree with your analysis. You make a mistake early on in the analysis. Doubling of CO2 relates to doubling the partial pressure or if you like the number of molecules per square meter of surface area. On earth the partial pressure is about 350e-6 of 1 atmosphere. On venus it is close to all of 92 atmospheres or about 250,000 times greater. At that sort of pressure there is absolutely massive pressure broadening so that CO2 absorbs almost everywhere. Thus it retains a very large amount of heat pushing the temperature up very considerably. But there is worse. CO2 also has very strong absorption bands at 2 and 4 microns which will also be massively pressure broadened. As the surface heats up, more and more of the emission moves to shorter wavelengths (look at planks distribution curve) where it is also intercepted by these other lines.
This is a totally different situation to that existant on Earth. The Earth is too cold to emit signifcantly at 2 and 4 microns. The logarithmic law is a good approximation at Earth conditions where CO2 absorbs only a small part of the surface emission but cannot be extrapolated to a change as large as a quarter of a million times increase. The broadening becomes so extreme it occupies the entire spectrum.
It is really nonsensical to try and draw parallels between 0.0003 atmospheres and 92 atmospheres.
One thing I would say however is that it is also ridiculous to talk about run away green house effect. The term runaway implies positive feeedback causing an unstable escalating effect often called a tipping point. The situation on Venus is nothing of the kind. You might as well say that plugging a radiator into the wall socket causes runaway heating causing it to glow red hot. Certainly it glows red hot but there is nothing runaway about it. Its simply the equilibrium point that results from the power input and cooling available. Its the same on Venus. If one were to decrease the amount of CO2 in the atmosphere the temperature would come down progressively, there would not be any tipping point.
“Earth’s atmosphere has 1,000 times the concentration of water as Venus. Venus has only 90 times as much atmosphere. That means that earth has 10 times as much water stored in the atmosphere as Venus, plus a massive buffer of excess water in the oceans.”
Steve, you mean “mixing ratio” not “concentration”. On Earth, H2O is ~0.5% or less of the column (though of course it can be much higher in the boundary layer). This is relatively similar to the amount thought to be present in the atmosphere of Venus. The high pressure of CO2, however, makes the water significantly more opaque due to pressure broadening of the IR transitions. I encourage you to do the radiative calculation — it isn’t so hard and there are some nice tools available (try modtran).
Your argument about the lapse rate is largely correct, but as others have commented, the question is at what altitude does the OLR = absorbed solar. In the venus atmosphere this is at high altitude; it is the very efficient greenhouse that allows the surface to be cooked. If the venus atmosphere was transparent to IR (e.g. made of N2 for example) the surface would be very cold, no matter how dense the atmosphere was.
Oh why do we think that there has been a lot of water on Venus in the past? Isotopes, the ratio between Deuterium and Hydrogen on Venus is much higher than it is on Earth.
So Dennis, how about a little quantitative information, how much wider, how much taller? If you integrate the curve, do you really get a lot of area, or maybe just a slight spreading, but these are the tails of the absorption bands, and so how much matters a lot.
The detailed information on this is from the textbook “The Quantum Theory of Light” by Loudon, page 84-91. I have the 1968 version of the textbook. The equations for line broadening of CO2 are both temperature and pressure dependent.
stevengoddard says:
May 6, 2010 at 9:52 pm
Well, according to the usual font of misinformation (Wikipedia),
I’d suspect that would be sufficient to come close to equalizing the temperature on the two sides, but what do I know? I was born yesterday …
Savant
If you dug the Grand Canyon down to a depth of 30 miles below sea level, what would be the temperature there?
michael hammer
If you dug the Grand Canyon down to a depth of 30 miles below sea level, what would be the temperature there?
I’m fascinated by some people here who are implying that a test tube full of oxygen would have to be close to absolute zero, because it is not a greenhouse gas.
James Sexton says:
May 6, 2010 at 9:56 pm
While there were a couple good things in Cosmos (the Samurai crabs of the coast of Japan, for one), his stupid dandelion starship (likely made of star-stuff) was one of billions and billions of shortcomings.
I bought my first color TV in 1974 to watch Jacob Bronowski’s The Ascent of Man, a vastly superior series, IMHO. Okay, not-so-humble-opinion.
The existence of crystals proves the existence of atoms. The mud at Auschwitz.
http://www.museum.tv/eotvsection.php?entrycode=ascentofman
I agree totaly that atmosphere density/pressure is the key driver for climate on planets.
As I hypothised earlier when we discussed(in the end of comments)
http://wattsupwiththat.com/2010/04/07/faint-sun-paradox-explained-by-stanford-greenhouse-effect-not-involved/
As such I really really have problems accepting that the Earths atmosphere is warmed up by an “greenhouse effect”?
When we can explane this better if we use the words “isolation/insulation effect” and the “thickness”(“air”pressure on the surface of the planet) .
And the composition of the atmosphere, water, metan, co2 etc. etc. can also have some effect?
A thicker atmosphere means that less energy is needed to warm it up and that the energy stays longer or use longer time to escape the atmosphere.
As it is with houses that are better isolated/insulated in cold weather.
Who made up this idea that Earths atmosphere has a “greenhouse effect”?
When it is totally wrong and misguiding?
Radical environmentalist? Again?
Steven G:
“some people here who are implying that a test tube full of oxygen would have to be close to absolute zero, because it is not a greenhouse gas.”
Where on Earth do you get that from? Oxygen neither emits nor absorbs IR, so that’s neutral on temperature. It is held at ambient temperature by thermal conduction and convection, which has nothing to do with GHG status.
A test tube full of oxygen, suspended in space so it isn’t getting any convective or conductive heat transfer, would be pretty darn cold.
(note you’d have to prevent ozone formation and there would be some energy absorption of very high energy photons even with a diatomic gas so it wouldn’t be quite absolute zero, but… darn cold, yes).
ps. “pressure broadened absorption lines” is not “lapse rate” so perhaps you want to try rereading Lon Hocker’s statement? And in an atmosphere with slow radiative heat loss and lots of atmospheric circulation, I don’t see why you are so hung up on a warm night-side.
Two questions for you, Steve Goddard: if the Sun were turned off, what would the temperature of Venus be? And, if you had a black planet with an atmosphere that was transparent to all radiation, how could the surface of the planet be any warmer than the blackbody temperature as defined by the incoming solar radiation, regardless of how much atmosphere the planet had?
-Dave
Ric Werme,
As I explained, I was throwing plain English into the mix. At the very least, what I wrote about turbos helps explain to those who are not familiar with the more technical aspects of gases. Judging by some of the comments on this thread there are quite a few people who want to understand but don’t have the background.
After all, one of the appeals of WUWT is that it is more accessible than CA to the average reader.
Brian says:
May 6, 2010 at 6:27 pm
Here is the part that still confuses me. Looking at the Radiation Transmitted by the Atmosphere chart. At the Wavelenghs that CO2 absorbs radiation, no radiation escapes the earth. How does adding more CO2 decrease the outgoing radiation more that it does.
That’s because it’s a cr*p graph that doesn’t represent what it purports to (it’s used all over the internet though). Here’s a detail of part of the CO2 absorption spectrum at both the conditions of Mars and Earth (under venusian conditions it would fill in and look more like that cartoon).
http://i302.photobucket.com/albums/nn107/Sprintstar400/Mars-Earth.gif
“A thicker atmosphere means that less energy is needed to warm it up and that the energy stays longer or use longer time to escape the atmosphere.”
Should be:
A thicker atmosphere means better isolation/insulation and that less star/Sun energy is needed to warm it up because this energy use longer time to escape the atmosphere again(Stays longer in the better isolated/insulated atmosphere).
Not that this explanation has no merit at all, but I’m appalled that the water cycle is constantly overlooked. The earth’s climate is dominated by a giant air conditioner, which constantly moves heat from the surface to higher altitude. I suspect the earth would be much, much hotter if there were no water.
As a chemist, it is interesting that soooo many people cite things like the ideal gas law. No gas is “ideal” – they all begin to fail under low temperatures and – wait for it – high pressures. Ever heard of the van der Waals equation?
One thing the trolls cite is that a compressed gas will lose its temperature over time. That is true on earth as heat always flows from hot to cold objects (the surrounding uncompressed air). However, one of the fundamental principle’s of a gas is that it’s collisions are ELASTIC. Energy In to a Collision = Energy Out of a Collision. Thus, a constantly compressed gas will ALWAYS remain warmer. This is why gas molecules do not continually slow down (like billiard balls on a frictionless table) until the liquefy.
I await the troll responses…
geronimo
……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…..
Professor Bryan Cox discussed Mars in his recent excellent TV series “The Solar System”.
He came to the conclusion that Mars had lost almost all of its geothermal activity.
This has led to the present climate.
At one time Mars had much more geothermal activity and liquids produced huge “Grand Canyon” like features on Mars.
One feature throughout the series was his emphasis on geothermal activity.
In the whole series of about 6 episodes his only reference to the “greenhouse effect” was given in one sentence .
“2. At present, the atmosphere of Venus contains very little nitrogen (~ 3.5%). What happened to all the early nitrogen?”
Venus has about 90 atm- or about 90 times earth’s atmosphere.
So if Venus has 3.5 % nitrogen, it has 2 times or more as much nitrogen as Earth’s atmosphere.
Same goes for the low percentage of water in Venus’ atmosphere- because it’s such a huge atmosphere, it’s quite a bit of water. Though not anywhere near the amount on Earth, but perhaps near the amount on Mars- a small ocean or very large lake worth.
You are correct that Venus does not have any Greenhouse Effect at the surface. However, you are wrong to use that drawing showing the spectra of IR absorption because, while it is useful at 1 atm, it is completely wrong at 92 atm. At that pressure, CO2 is totally opaque to longwave IR (due to bandwidth broadening) with 99.99% being absorbed within one foot of the surface at most important frequencies. (A few frequency bands require about 200 meters to absorb 99.99%.) Your discussion of logarithmic decrease with concentration only applies to a narrow band around a selected frequency. A different (and highly complex) set of equations applies to the analysis in a wide band of frequencies. And another set of equations is needed at high pressure.
Thus, your association of temperature with atmospheric pressure is wrong. The correct association is that the atmosphere becomes IR opaque at those pressures. If the atmosphere was Nitrogen, then it would remain transparent and the surface would be cold.
As for Sagan – he was correct to assume a runaway Greenhouse effect when it was believed that the atmospheric pressure on Venus was maybe two times the pressure on the Earth. However, once probes landed on the surface that theory was shown to not be necessary or correct.
Steve Goddard,
I thought that Velikovski’s prediction of the cooling of Venus and its confirmation was well known,
this is one ref. that confirms that it is emitting more heat than it receives,
http://www.agu.org/pubs/crossref/1992/91JA02444.shtml
Thank goodness you are doing something to refute the ‘ runaway greenhouse’ myth of Venus, and I would like to point out to others that the churning of the atmosphere restores the adiabatic lapse rate constantly both here and on Venus, a reliable guide to temperatures where I live at 1000mtrs at the same latitude as Sydney, 9°C below their forecast, absent strong winds.
A profile of temp. pressure of Venus is shown here, indicating that at a similar pressure, our temperatures are remarkably similar taking into account insolation and the different properties of CO2 at saturation and high pressure. http://nova.stanford.edu/projects/mgs/images/t3213.gif
Couple of points:
1. Venus is about half the distance of earth from the sun. It surely follows that it receives four times the radiative energy (inverse square law).
2. It may be a bombshell to state this, but the ‘radiation trap’ hypothesis to explain a glasshouse warming invented by Fouier, Tyndall and Arrhenius is wrong.
A. The Wood experiment of 1909 killed it completely. He showed that short wavelength radiation is not transformed into long wavelength by the ground nor does a glasshouse warm by feedback of radiation from the glass – it is purely due to conduction of heat from the ground to the air above, convection which recirculates the air which cannot escape through the glass roof. If the glass WERE really radiating IR to further warm either the air or the ground it would have to be itself warmer than the ground – basic laws of thermodynamics. Next time you park your car/automobile
in the sun, feel the dashboard then the windscreen/windshield. Which is warmer?
A recent experiment using a laser beam (0.7Wm) onto a thermometer showed no change in temperature. http://www.greenhouse.geologist-1101.net//
Similarly unless the air above the ground containing ‘greenhouse gases’ were always warmer than the ground, it cannot heat the ground. Reality is that the atmosphere is always cooler than the ground.
The earth’s atmosphere keeps us warm simply by the gases absorbing heat by conduction and convection – as Cp/Cv is more or less the same for all gases it does not matter what those gases are (except H2O which undergoes changes of state) – slowly losing that heat overnight.
B. NASA released a report recently of the temperature fluctuations of the surface of the moon. Just like the earth it too shows a ‘greenhouse’ temperature elevation of 40K about the theoretical surface temperature. In other words neither the earth nor the moon (nor Venus) is kept warmer by any greenhouse effect.
http://www.climaterealists.com/attachments/database/RadiativeNonEquilibrium_BHermalyn_Final.pdf
With Earth having water in a dynamic state as gas, liquid and ice, this must be part of the engine that creates the climate system here( I know this is simplified). The tropical part of this system starts out producing vertical convection at the equator, turning horizontal and distributing heat to the poles.
There is nothing that I can see that can produce any phase change on Venus that in any way resembles the water phase change on Earth, nothing to produce vertical convection and convective heat distribution. This lack of vertical convective energy may be responsible for the ‘layered’ wind pattern on Venus that seems to be maintaining the dark side heat content.