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.
=============================
UPDATE: Lubos Motl has written an essay and analysis that broadly agrees with this post. See it here
Good article. Just one slip. “9000 kPa atmospheric pressure would occur on earth at an altitude many miles below sea level.”
In the oceans, pressure increases by one bar – the equivalent of sea-level atmospheric pressure – for approximately every 10 metres, or 30 feet, of depth. A simple calculation shows that the pressure will exceed 92 times atmospheric pressure at less than one kilometre depth, or just over half a mile.
Excellent post. Venus is for me the cpnvincing example that CO2 has no influence on the temperature in the atmosphere. In addition: when the atmosphere of Venus would consist mostly of a two atomic gas like nitrogen then the temperature would be 200 °C higher as it is now.
Steven; I hear what you are saying and I do not want to say that the pressure and depth of the atmosphere is irrelevant but not in the way you think. Green house gases absorb because they have a resonance in a molecular bond. When a photon with the same frequency as the bond resonance commes along it can be absorbed with the energy going into exciting the resonance. This energy is then dissipated to other moelcules through collisions. As the gas pressure increases there are more collisions between molecules. Some of these collisions momentarily upset the resonance somewhat changing its resonant frequency and thereby allowing it to absorb a photon of a slightly different frequency if one comes along at just the right time – this is pressure broadening. On top of that, the resonance lines plotted with respect to frequency (or wavelength) do not have infinitely steep sides. Rather they are somehwat like a gaussian curve. As the amount of gas in the path increases, wavelengths out in the wings where the absorption was very small start to show sigificant absorption and this again leads to line broadening (this is what gives rise to the logarithmic relationship). These are exceptionally well understood aspects of spectroscopy which are beyond dispute. Denying them does not advance the sceptical cause.
The impact of line broadening is very interesting. Lets take a very stylised example (one that is clearly much more simple than reality but it shows the point) Imagine the surface of the planet can emit to space at say 50 wavelengths and it emits equally at all wavelengths (yes I know very over simplified but it shows the point). It emits 50 watts so 1 watt at each wavelength. Now you place over it a green house gas which prevents it from emiting to space at say 5 of those wavelengths. For equilibrium the planet still has to emit 50 watts but now it can only emit at 45 wavelengths so it has to emit 1.11 watts at each wavelength. To emit more at each wavelength it has to get hotter. OK the GHG line broadens so that it now blocks 10 wavelengths. Now the planet can only emit at 40 wavelengths so it emits 1.25 watts/wavelength and gets yet hotter in a reasonably close to linear fashion. But what happens when 40 wavelengths are blocked and further broadening cuts that down to 45 wavelengths? For the same reduction of 5 wavelengths the energy at each of the remaining wavelengths has to double. That is one of the reasons why one cannot extrapolate from the situation on Earth to Venus.
So one may ask, what happens when all 50 wavelengths are blocked? Does the temperature go to infinity? No, because other mechanisms come into play. The heat travels up the atmospheric column via conduction and convection eventually heating the outer layer of the atmosphere which radiates the energy to space. The point is that the heat has to have a thermal gradient driving it up the atmospheric column and as a result, the thicker the atmosphere the longer the thermal gradient and the greater the temperature difference between surface and top of atmosphere. Since the top of the atmosphere is dictated by the energy radiated to space if this does not change neither does the top of the atmosphere temperature and all the increase is via heating of the surface. So in that sense the much thicker atmosphere does contribute very much to the surface temperature but only becuase the CO2 has blocked virtually all surface emission directly to space.
This is of course very much simplified, both radiation and convection processes occur on Earth. This is one of my objections to the Kiehl and Trenberth model. They claim something like 2/3 of the direct radiation is blocked and must travel via convection yet the data from the interferometer abord the Nimbus satellite clearly shows that the direct radiation from surface to space is much larger – more like 2/3 than 1/3.
If the atmosphere on Venus was all nitrogen with no GHG I think you would find the planet was not all that much warmer than earth despite the deep atmosphere and the closer proximity to the sun.
Your point that a vessel of oxygen would have to be close to absolute zero because it is not a GHG is not quite accurate. Oxygen does not have any absorption lines in the thermal infrared which means it is also not capable of emiting in the thermal infra red. As a result its temperature will not be determined by thermal infrared radiative processes (more by conduction and convection). I am not sure but from memory it does have some emission lines in the microwave region so it can both absorb and emit in that wavelength region.
This comment isn’t about Venus, but a there is a lot of misinformation, erroneous Physics, and random nonsense being presented in many of the comments on this thread. Perhaps Moonbat’s Trolls are out in force. In any case, it would take forever to sort out some of the errors or misdirections, but I was gratified to see George E. Smith setting a few things straight, and I will add one comment on a matter that I think is important to understand. To wit:
Re-distribution of energy in the atmosphere is largely carried out by convection processes, and an analysis of such processes, in and of themselves, leads to the conclusion that the top of the troposphere should be about 70°C cooler than the surface of the Earth, which is indeed the observed situation.
It isn’t that the pressure gradient warms the bottom. It is that the surface (initially warmed by the Sun) heats the lowest layer of air by contact. This layer then starts to rise. As it does so, it performs work on the cooler air through which it pushes its way while rising. The rising mass of air is itself cooled as it expands while rising, but will keep rising as long as it is a bit warmer than the air it encounters. Energy is thus transferred from the surface to the atmosphere above, and makes it warmer than it would be, while simultaneously cooling the surface. The overall effect, however, is a vertical temperature gradient (a lapse rate) with the top cooler than the bottom.
There are times and places where this process does not operate. In such cases, there can be Chinooks, Foehn winds, and various kinds of down-flowing air masses, but they are all short-lived events, and not the dominant effect.
The fact that we have an atmosphere in the first place, and the fact that the Earth spins on its axis, then allows redistribution of energy in a lateral sense. This minimizes the day/night variation, and we thus do not thave the boiling day and freezing night conditions that would otherwise be present.
The process mechanism itself sets a value for the lapse rate, which can be calculated from first principles. The simplest case is with dry air expanding adiabatically as it rises, giving a lapse rate of just under 10°C/km. The exact expression is (Mg/R)(γ-1)/γ, where γ is the adiabatic exponent, M is the molar mass of air, g is the acceleration of gravity, and R is the usual gas constant. If humidity is added to the air, the same process takes place, but leads to a smaller lapse rate, depending on the amount of water vapour present. The “global average” is generally taken to be 6.5°C/km, and at any given time and geographical location, the actual value will be somewhere in this range.
In summary then, on Earth, the pressure gradient does not warm the surface. The surface warms the atmosphere by a convective re-distribution of energy that is facilitated by the pressure gradient. Without this process, the surface would be much hotter than it is.
/dr.bill
Those statements are utter nonsense. The Earth and Venus have had radically different origins and development of compositions as evidenced by the existence of the Moon (Luna) in orbit with the Earth. /The Earth’s first atmosphere was overwhelmingly dominated by Hydrogen and Helium as was most likely true of Venus. As the Sun’s solar winds stripped the inner planets of this first atmosphere of of Hydrogen and Helium during its T-Tauri phase, Venus, Earth, and Mars were left their second atmospheres dominated by percentages of carbon dioxide greater than more than something around 96% Carbon dioxide with methane, ammonia, Nitrogen and other gases. The second atmosphere of Earth was massive enough to produce surface pressures of far more than 150 atmospheres, much like what is found on Venus at the present time. Unlike Venus, however, the Earth was most likely smaller than present until a collision with a Mars size planet sometimes dubbed as Theia. The collision increased the mass and size of the Earth, radically changed the mass and composition of the planetary core, mantle, crust, and atmosphere. Much of the massive second atmosphere was ejected into the solar wind and swept away to the outer solar system. Much of the lighter crustal mass of Theia and the Earth were incorporated into the Moon, while much of Theia’s iron core was incorporated into the Earth. The much lesser mass of the post-collision Earth was still many atmospheres greater than at present and overwhelmingly dominated by Carbon dioxide. The Moon’s atmosphere was lost to space, and the Earth’s massive atmosphere was also greatly reduced by further losses to space before the geomagnetic core became effective in producing a magnetosphere obstructing the solar wind. Yet, the much reduced atmosphere continued to be composed of Carbon dioxide by overwhelming percentages until the biosphere began to sequester Carbon dioxide in the the lithosphere by biological activity. Venus most certainly did not experience these dramatic events and consequent changes. The Earth most certainly was not comparable in size to Venus at its origin. The Earth’s atmosphere was nearly all Carbon dioxide and massive like that of Venus until the biosphere removed the Carbon dioxide from the Earth’s atmosphere.
Gravity is the source of the energy which keeps any substance hotter at greater atmospheric, hydrospheric, and lithospheric pressures. Sunlight certainly does not keep the Earth’s mantle and core in a molten condition, but gravity and radioactivity do so. Without the events which greatly reduced the Earth’s atmospheric mass and then stabilizing it against further losses, the Earth would have eithr remained to massive and hot to precipitate its Hydrogen monoxide (water) into a hydrosphere or it would have lost the water to space by heat, dissociation, and solar winds in much the way we see occuring in varied circumstances on Venus and Mars.
I want to know when the EPA is going to recognize the dangers of greenhouse warming posed by the unregulated emissions of the world’s far most effective greenhouse gas, Dihydrogen monoxide, from pollution sources such as Hydrogen fueled automotive vehicles, power plants, and so forth.
I’m wondering; doesn’t an equivalent volume (column) of water exert more pressure than the atmosphere and if it does why then are our oceans not 600 degrees C at one mile deep? I believe the thermocline for the deep oceans show increased cooling for increasing depth but the pressure is increasing proportionately too. If pressure is the driving factor for atmospheric heating shouldn’t the same be true for oceans and lakes?
Correction:
The much lesser mass of the [post-collision Earth] Earth’s post-collision atmosphere was still many atmospheres greater than at present and overwhelmingly dominated by Carbon dioxide.
I am sorry but the analysis is wrong. You are assuming that CO2 is an ideal gas, when no gas is in fact ideal. What happens to a gas under pressure is that it tends to get hot, but if it cannot stay hot (because the heat is being taken away elsewhere) then it stops being a gas altogether. In other words, it liquifies (or in the case of CO2 solidifies directly). This is not taken into account at all by the gas equations, because they assume ideal gasses in isolation from external factors.
So what would happen on Venus if there was a lot of pressure but no solar heating? The CO2 would not be hot enough to stay a gas and would solidify, just as it does on many small moons in the outer solar system. Clearly it would not then be an ideal gas at all.
Gasses exist purely because they already have some energy within them that causes the molecules in the gas to vibrate. If that energy is allowed to transfer to space, then the temperature of the gas would drop and the gas would in fact cease to be a gas.
So, there is a gaseous atmosphere around Venus purely because a lot of energy is being absorbed from an external source, mostly from the sun. The planet doesn’t rotate very fast so heating from gravitational tidal forces is minimal. Heating from internal fission would likely be the same as the earth, except that the lack of a magnetic field suggests that there isn’t a lot going on insider Venus. So it is most likely that the planets temperature is most likely to be due to its thick insulating blanket of CO2. It is not a “runaway” effect because the planet’s CO2 and temperature is quite stable and predicatable.
However, this has almost nothing to do with planet Earth where the density of CO2 is so low it is more or less negligible and where the planet’s surface is within a powerful cycle dominated by the evaporation and precipitation of H20 close to the planets surface, and where internal fission and gravitational tidal forces generate substantial internal heating.
Shrnfr,
Your comments on pressure broadening are naïve Yes, pressure broadening exists. But for one, the effect isn’t as large as you make it out to be and even if it were pressure broadening doesn’t effect the integrated oscillator strength of the molecule. For exampIe, if the unbroadened spectral featrue of interest were 100 kHz wide and the peak extinction coefficient were 1000 mol^-1 cm^-1 then if it were pressure broadened to 1000 MHz the peak extinction coefficient would be reduced to 100 mol^-1 cm^-1. Of course, you’d have to have a spectrometer with much higher resolution than 100 kHz to see this. The point is, the area under the curve, which is the actual measure of total light absorbed, is identical in the pressure broadened and unbroadened cases.
In the case where the absorption itself is highly saturated (like on Venus) broadening will some impact, but since the absorption is saturated, and since the spacing between ro-vibrational lines in the CO2 absorption peak of interest are already more closely spaced than the other homogeous broadening contributors (like Doppler) the only real impact that pressure broadening can have is on the outer edges of the envelope where it probably can’t contribute more than a percent vs. unpressure broadened.
michael hammer
Thanks for the explanation. I didn’t make any attempt in the article to explain the reasons why gas temperature increases with pressure – the article simply points out the correlation. Earth’s atmosphere would also be very hot, if it (at current composition) was much thicker.
The question Steven Goddard should be asking is “Who squished the Venutian atmosphere?”
Therein lies the answer to your conundrum
Ryan
I most certainly am not assuming that the atmosphere is an ideal gas. If it were, it would follow an isotherm when the pressure increased, and the temperature would not rise.
Richard Briscoe
I’m not talking about ocean pressure. I’m talking about atmospheric pressure. Death Valley and the Dead Sea are below sea level. Both are very hot places. Mt. Everest is at the same latitude as Saudi Arabia, and averages about -40 degrees.
The thesis is not correct .
1)
T and P are linked by the equation of state but don’t give any information about the energy dynamics .
In thermal equilibrium high pressures don’t cause high temperatures and high temperatures don’t cause high pressures !
Temperature being an average energy , its value is only determined by energy in and energy out regardless of the pressure .
The pressure adapts then accordingly following the state equation .
As Venus has a high mass of the atmosphere , it would have a high pressure in ANY case , regardless of the temperature .
2)
Let’s debunk fast the geothermal heat hypothesis .
We know that Venus radiates around 10 000 W/m² .
Let’s suppose that this energy is provided by solidifying lava .
How much lava do we need to generate 10 000 W/m² ?
You write 10 000 x S (Venus surface) = m (mass of the solidified lava per second) . L (latent heat of solidification) .
You can use L = 4.10^5 J/kg and density = 3000 kg/m^3 .
You will find that if whole Venus was initially molten , it would solidify by emitting
10 000 W/m² in some 2.10^11 seconds what is 7600 years !
So clearly it is not the lava that makes Venus emit 10 000 W/m² during billions of years .
3)
Let’s also debunk for the umptieth time the absurdity that I keep reading over and over that CO2 traps/stores heat .
It does nothing such and never did !
In equilibrium and we always consider equilibriums in these matters , CO2 emits exactly the same amount of radiation as it absorbs . It traps nothing and stores nothing , it only transmits .
Another a bit more “sophisticated” absurdity is that CO2 heats the atmosphere by collisions .
It certainly does nothing such because it does 2 things – it heats the atmosphere by collisions and it also cools it by collisions . By definition of equilibrium both (cooling and heating) are exactly equal .
4)
So now we are still left with the question how can Venus surface emit 10 000 W/m² and be in equilibrium ?
The only physical answer is that something is giving it also 10 000 W/m² and we excluded lava .
This something is not the Sun either because it doesn’t give enough .
So that leaves only the atmosphere which acts by convection and radiation .
Clouds , gases , particles , sulphuric acid , winds it’s all that .
Convecting and radiating (little phase change here) .
Does the CO2 “backradiation” play a role ? Surely .
How much ? Nobody knows but the computers make believe that they do .
Philip Foster
Venus is 0.723 AU from the sun, not 0.5. 0.723^2 = 0.522729
http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html
Venus Earth Ratio (Venus/Earth)
Semimajor axis (106 km) 108.21 149.60 0.723
Interesting in the comments seeing claims that my explanations of the causes of the warming are incorrect. I didn’t make any attempt to explain causes, rather I simply pointed out the correlation between pressure and temperature.
Sort of like how rumours and their attributions spread.
Julian Braggins
I didn’t see anything in that AGU abstract implying that Venus is losing substantial heat from it’s interior. Please explain.
Willis,
Thanks. Much appreciated.
Scipio
May 2010 3.41 am
The density of water attenuates incoming solar energy to near zero well before it gets to the bottom. Furthermore convection within the water and evaporation at the top draw energy back upward. Thus oceans of water are not affected by pressure in the same way as the atmosphere.
As regards the main point of this article I said this back in July 2008:
“The atmosphere of Venus is very dense so the surface is much hotter than it otherwise would be. That of Mars is very thin so the surface is only a little hotter than it otherwise would be. The Earth is a special case because I would argue that the oceans should be regarded as a form of atmosphere in much the same way as the air because both air and oceans have heat storing properties. In effect Earth’s ‘atmosphere’ is in two parts for heat storing purposes and water is the primary player in both components.”
and this :
“CO2 and other trace gases are too small a proportion of the atmosphere to make a significant difference to overall atmospheric density even if their volumes were to be multiplied many times over. This problem for warmists is greatly enhanced if one considers the much more dense oceans as part of the planetary atmosphere for heat storage purposes.”
from this article:
http://climaterealists.com/index.php?id=1562&linkbox=true&position=4
I always thought it was common knowledge that Venus was hot because of atmospheric density and not any so called greenhouse effect. Somewhere during the last 50 years that basic knowledge seems to have been overlain by nonsense.
stevengoddard says:May 7, 2010 at 4:36 am
“I most certainly am not assuming that the atmosphere is an ideal gas. If it were, it would follow an isotherm when the pressure increased, and the temperature would not rise.
Quite wrong. Some of what you’ve said about the adiabatic lapse rate is right, but it’s ideal gas theory.
An ideal gas under adiabatic compression follows the relation T~P^q, where q=1-1/gamma, gamma=1.4 for bimolecular. Definitely not isothermal.
Scipio says:
May 7, 2010 at 3:41 am
Scipio, isnt this related to the fact that water is “incompressible”. It doesnt compress (much) under pressure. While a gas is compressible. So when you compress a gas, the distance between mocelules becomes smaller.
Merrick
Thanks for the explanation about spectral broadening. Much appreciated.
Regarding Venus’ distance : I stand corrected – sorry for that error.
I stand by the rest of my posting.
CodeTech says:
May 6, 2010 at 11:41 pm
Ric Werme,
In these respects we fully agree. I’m getting the sense that the overall quality of comments here has declined in the last few months. That’s not necessarily a bad thing, as it means more people are finding WUWT and are here learning the skeptics’ understanding of “real” climate. While WUWT certainly should not strive to become a big version of ClimateAudit, it certainly should present interesting and relevant information.
Your notes about the temperature increase in turbochargers is something people here should understand (along with compression in diesel engines becoming hot enough to ignite fuel), even if I come along and question your description of increased energy density or if someone calls my added work as the source of the energy as goofy wrong.
In comments to this post, it’s unfortunate that Steve didn’t mention lapse rates, that could have deflected a whole bunch of comments that temperature is related just to pressure. (It is in ye olde perfect insulation and lack of conduction, radiation, etc. that is important in physics class but rarely exists outside of mental experiments.) The lapse rate concept is critical to understanding what’s going on and that convection is an important part of moving heat upward.
The recent post referring to 95°F wet bulb temperatures makes it clear that people don’t understand the concepts behind wet bulb and dew point temperatures. That’s one reason why I began to challenge all the claims that people regularly experience that environment.
I’m not sure how WUWT, you, or I should respond. Blogs are fine for issues of the day, but I prefer freestanding web pages for describing facts. I’m not real fond of Wikis that are open to anyone, so I’m tempted to write new web pages for describing my understanding of various phenomena. I already have several but not so many on climate issues. I’m not sure how they’d work into the discussion here and I certainly don’t have time to keep up with all of posts and comments here. BTW, in http://wermenh.com/2016.html about the movie The Day after Tomorrow I note how downdrafts brought stratospheric air down to the surface so quickly it didn’t have time to heat up. Compared to that movie, we’re doing pretty well.
Or I could go in a completely different direction and decide to “graduate” to ClimateAudit and Chiefio. I’ll be at http://www.heartland.org/events/2010Chicago/index.html and I want to talk about such stuff, time permitting.
@Smokey – I have never understood the point of that http://i224.photobucket.com/albums/dd137/gorebot/WaterAirvolume.jpg graphic. I get that they want to show water volume is tiny relative to the planet, but the relative volume of the air depends on the pressure. If they compared mass it would make more sense.
@Pamela Gray – Real GUYS don’t fish — they hunt 😉