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
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Zeke: Obviously you are NOT our skeptic friend Zeke the Sneak. Don’t you have any creativity as to invent another name but to copy one of ours?
Cam_S
The amount of solar energy entering Venus atmosphere is about the same as earth, because of the extra cloud cover. Venus reflects most of the sunshine it receives, which is why it sometimes appears so bright
I also bet the slow rotation speed would also contribitute to the high temps.
He didn’t say that. He said that the heat in the cylinder would be taken away by the air surrounding it. The cylinder model of Venus is one where the cylinder is already in a perfect insulator when it is filled with case.
What happens when you let the gas out of that cylinder at a high rate? Bet it gets pretty cold, yeah? Same effect in reverse.
“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.”
??????
Okay sure, point granted. Yes, if we allowed Venus to cool giving it a sink to dump it’s heat into it would not re-warm, absent some outside influence, by pressure alone.
But what would happen if you filled your cylinder inside of a perfectly insulated conatainer. Would it still cool off?
I don’t understand the physics but I do think this article is wrong, because Genus being warm because of a greenhouse effect is backed by physicists, not merely an urban legend.
So the question becomes, where is this article wrong? I don’t understand the physics to know how physicists propose the greenhouse effect works on Venus, but I can observe this:
-If Venus was that hot because of pressure, then surely Jupiter should be alight in comparison. Jupiter does generate heat, but far too little compared to how warmer Venus is and Jupiter generates it through contraction.
-Sunlight might not reach the surface, but if nevertheless passes through thick greenhouse gases before being absorbed in the atmosphere, there would still be a strong greenhouse effect.
-I am not aware that high pressure on the sea floor is proposed to generate heat.
Anyway those are my initial thoughts on where this article may be wrong.
The references to Boyle’s and Charles’ law are not correct here.
In both cases they describe changes that take place when one of the parameters change.
In the case of Boye’s law it shows the relationship between volume and pressure WHEN TEMPERATURE IS HELD CONSTANT.
Avogardro’s law is more appropriate, which is basically:
(P1.V1)/(T1.n1) = (P2.V2)/(T2.n2)
P = pressure
T = temp (K)
V = volume
n = amount of substance
This shows that as you increase the pressure of a fixed quantity of gas its temperature increases and its volume decreases.
You know this from blowing up tires = as the air compresses, it gets warm.
Does the air in your tires STAY hot? (Answer – no).
But that doesn’t mean that it STAYS warm. Just because a gas is compressed doesn’t mean its hot forever. That would equivalent to perpetual motion.
This is the principle of a heat pump and air conditioner.
Something with a thick atmosphere is not forcibly hot at the surface just because of pressure.
“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.”
Hmmm. I know that’s a popular view but I’m not so sure . . . .
Indeed, if one compresses or decompresses a quantity of a gas the temperature will rise or fall to reflect the “work” done on on that quantity (for compression) or the work that it does on its surroundings (for expansion).
But that’s not what’s happening here, is it? We’re not actually moving air from the top of Mt. Everest to the lower parts of Death Valley, doing the mechanical work to heat it up, are we?
Say I connect a SUBA diver’s air tank to a compressor and “fill” the tank with compressed air. I ask how come the tank is warm and you reply “because it has an extremely high pressure.” Okay, but I come back in an hour, the gauge still reads 3000psi but the tank is no longer warm. How come? The gas is still at an extremely high pressure.
Just guessing here but I think that the pressure differential, Earth vs Venus, is not a complete explanation.
Comment?
The why isn’t Jupiter that hot?
This argument seems quite wrong to me. Pressure and temperature are independent variables — both can be high, both can be low, one can be high and the other low, etc. The temperature of a planet is determined by its energy balance: in the long run, solar energy absorbed must equal long-wave radiation going out. (I am aware that this is a substantial simplification, but it captures the main truth about terrestrial planets.)
Sunlight is almost twice as intense at the orbit of Venus, but because Venus is more than twice as reflective as the Earth (due to the clouds), it actually absorbs slightly less radiation per square meter. Yet the surface of Venus is hot — we know this by direct spacecraft measurement — so that surface must be radiating long-wave radiation upward like crazy — about 40 times the amount that Earth’s surface radiates. Yet the radiation to space at the top of the atmosphere is only 2% of this. As far as I can see, the ONLY way to explain this is that the atmosphere of Venus strongly absorbs IR. That’s the greenhouse effect, isn’t it?
How Venus got to be in such a state is another (and very interesting) question. But surely there can’t be much doubt that the present high surface temperature is due to a present very strong greenhouse effect?
Postscript: I am a physicist, and though my specialty is not atmospheric physics, I do know a thing or two about thermodynamics. I believe that anyone who is cautious and skeptical about AGW is obliged to be equally cautious and skeptical about stuff on the other side. The present argument doesn’t just cut it, in my view.
Very interesting points, Steve. Your point about pressure sounds very plausible, so it will be interesting to see if someone can find a flaw in it.
It does seem to me that your point that there will be no GHG effect there because incoming radiation can’t reach the surface is weak — The incoming radiation that doesn’t get reflected must get absorbed somewhere, if only by the upper atmosphere. This layer then should act like the radiative “surface” of the planet, and should radiate long IR back into the outer atmosphere where it generates a GHG effect.
However, it would then seem that the equilibrium temperature of this layer would behave like the surface of an ordinary planet with this distance from the sun, albedo, and upper atmosphere. From that point down, then, temperatures would increase with pressure as you describe, leaving the actual surface temperatures much higher than the “radiative surface” temperatures. (I’m just musing here — an actual physicist should check in on this.)
It would take a lot more than one doubling of the exisiting level of CO2 to get earth’s CO2 surface partial pressures up to those of Venus!
We grew up to COSMOS on TV.
Sagan was good at flights of the imagination, even then, Post Normal was trying to lure us with its Siren song.
Apart from the measurable facts of Venus, its atmospheric properties and temperature, and the known Laws of Thermodynamics, what do we have?
We have a puzzle, missing a lot of pieces, periodically assembled into a shape, that the public never gets to see scientists label a theory as….”We Think…x,y,z…”
Thats the bit that drives me crazy, the sudden shift in discussions in private where words like….”we assume, we currently think, the data currently shows, it appears…” transitioning to the printed word as….”Venus is a perfect example of run away green house effect.”
I blame the French school of Management, which excludes the function of uncertatiny in managers, it filtered into everything in the late 60’s and 70’s, and permeated the mindset of the western man. Now we must all be experts, all the time, if we are uncertain, we keep it to ourselves, because confidence is a component of competence, and we must always have an answer ready. Uncertainty, promotes a lack of confidence, low confidence impacts the bottom line. Cha-Ching $$$.
Add to that the Human tendancy to seek group approval, and we have the perfect mess of nodding and smiling, and concensus, and approval for policies sake.
You want to know why Venus is as it is? First ask how Holy has our confidence in the KNOWNS become, is it assailable? Shouldn’t it be?
And what else about pressure broadening of molecular absorption lines is not understood?
OT but might be something for another post.
If you are using the Yahoo browser you’ll probably have seen the latest from the “we’re all going to die” MSM hysteria.
“Now the bad news: The ozone layer has also thinned over the North Pole. This thinning is predicted to continue for the next 15 years due to weather-related phenomena that scientists still cannot fully explain, according to the same UN report. And, repairing the ozone hole over the South Pole will take longer than previously expected, and won’t finish until between 2060 and 2075. Scientists now understand that the size of the ozone hole varies dramatically from year to year, which complicates attempts to accurately predict the hole’s future size.
Interestingly, recent studies have shown that the size of the ozone hole affects the global temperature. Closing the ozone hole actually speeds up the melting of the polar ice caps, according to a 2009 study from Scientific Committee on Antarctic Research.
So even though environmentally friendly laws have successfully reversed the trend of ozone depletion, the lingering effects of aerosol use, and the link between the ozone hole and global warming, virtually ensure that this problem will persist until the end of the century.”
Thus endith today’s reading according to ….. ah hell, there just so many!!!!
Funny thing about the Sagan Venus conundrum… that put me on the path to AGW skepticism. I had the pleasure of seeing him in person for a 2 hour lecture in 1992. He presented a lot of his “Cosmos” stuff, and then turn his presentation to global warming , Venus, and CO2. That was the weakest part of Sagan’s presentation. He didn’t cover the great differences between the two planets, atmosphere composition, distance from sun, etc, that make Venus and Earth a poor comparison. At the time, the press was using the Venus analogy to promote AGW, yet, no one would raise the same questions, since, well, it was Sagan after all, everyone was GaGa over him, and who would be so foolish to question Sagan.
Don’t get me wrong, I love Carl Sagan. Will always be a great admirer of him and his work. I just though that he purposely over-emphasized the weak Venus / Earth correlation to increase the fears and concerns of AGW, a concept he strongly championed. I believe his convictions to save the planet over-rode his common sense.
Onion
The ocean is made of water, which is a liquid. Unlike gases, liquids are not very compressible, so they do not heat much under pressure.
To Onion: Jupiter actually emits more energy than it receives from the sun. To expand on my comment previous. The Pauli exclusion principal prevents fermions from being in the same state in the same place. Also leptons. Bosons are a different matter. As you increase pressure on any gas you are forcing more and more fermions into a smaller and smaller volume. The spectral line of absorption/emission of that gas will get wider and wider because the gas objects have to be in a different state than the others. At 60 bars of pressure, CO2 on Venus has a barn door absorption spectrum. At a pressure of a couple of millibars on Mars it’s a razor edge. The earth is approximately 1 bar (the standard atmosphere is 1013 millibars at sea level).
tommy
Temperatures on Venus are same on the day side and the night side, so at this point in Venus history the rotation speed is probably not a big factor.
I think you need to start our discovery of Venus way back in geologic time. Two points to consider, Venus has no magnetic field of significance and therefore no real magnetosphere. Second at the distance it is from the sun, with no magnetosphere to shield it’s atmosphere, all but the heaviest of molecules would have long since been blown away by the solar wind.
No one seems to know when Venus went magnetically dead, we may never know.
All that is left of Venus’ atmosphere is what we now see, with no way to determine the complete picture of how it arrived at what is left. Without understanding that, comparisons make little sense. We face similar problems on Earth, don’t we.
geronimo
Excellent point about Mars.
Denis Hopkins says: “…My understanding is that this [flat earth] was a myth put about by Washin(g)ton Irvine in the 19th century…”
As a descendant of the Irving clan, I should like to point out that the author you refer to was Washington Irving. There are, on the other hand, no fewer than 145 ways to spell “Irving,” so Irvine is close enough for jazz, hand grenades, astrophysics, and climatology.
Sagan said that marijuana helped him write some of his books.
The trouble of Marijuana (Pot) is that cannabinoid chemicals resemble almost exactly that of the female hormone (estrogen).
These results indicate that there are some metabolic interactions between cannabinoid and steroid metabolism and that the constituents showing estrogen-like activity exist in marijuana
http://www.ncbi.nlm.nih.gov/pubmed/15588936
So GWRs. sneak out from the closet!
stephen richards says:
May 6, 2010 at 12:51 pm
Or Boyles law PV=RT where P=pressure and R is a constant
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I do believe the greenhouse effect occurred Venus since pressure alone may not completely contribute the temperature increase.
The reason is:
On the Venus, temperature increases 400 C at 90 atmos of CO2, that is to say every atmos of CO2 contributes 400/90=4.4 C forcing.
Since on the Earth, the CO2 pressure is 0.004 atmos (398ppm), the CO2 caused greenhouse effect is about 4.4 X 0.004 = 0.018 C.
Here we completely recognize CO2 as a greenhouse gas, it indeed causes greenhouse effect on the Venus’ temperature but did insignificantly on the Earth’s because the difference between the concentrations of CO2 in both planetary atmospheres.
I was confused where the heat from pressure came from, this helped:
http://en.wikipedia.org/wiki/Adiabatic_process
I cant say I follow this idea that its the pressure that keeps Venus warm.
If you have
-A big cylinder with a piston at one end, filled with CO2 at one athmosphere, and it is very well insulated.
-Then compress the Co2 to a very high pressure.
Okay, now we all know about PV=RKT, so it becomes very hot.
Now leave it alone for, say, 100 000 years.
I think we can safely assume this heat would leak out? Sloooowly?
And that very little heat comes in, from the sun?
Finally it will reach ambient temperature? Yes?
The only explanation that sounds reasonable to me, is that someone put a very hot entity inside the cylinder, leaking heat. (Like, a vulcano-entity)
But then again, I dont know much about Venus. Just philosphying a bit.