I was sitting here this morning and from memory just realized that I forgot the best part of Chris Colose’s post ‘Even Princeton Makes Mistakes”. I was going to add this at the end and just tired myself right out – or bored myself to death. Here’s the best quote I’ve read in a long time from the pseudoscience of climate (my bold):
Personally, I have little interest in the legality of making CO2 a “pollutant” or not. I’m quite sure different people here have their own perspective on this, but to me whether we call it a “pollutant” or a “banana” doesn’t change its physical properties: CO2 is a strong greenhouse gas, and it is important in impeding how efficiently our planet loses radiative heat to space. We don’t often think of CO2 as a “pollutant” on Venus, yet it still allows the planet to support temperatures well above the melting point of lead or tin.
Now, just what the HELL do they teach Atmospheric Science students in school? I’m just an Aeronautical Engineer so perhaps someone will have to help me figure this idiocy out. Venus does have a more reflective atmosphere but it is also closer to the sun than the Earth. For the thinking mind, it is difficult to ignore that the atmosphere is a ridiculous 90 times more dense. The Russians landed probes on Venus without using parachutes at the end of the decent because the atmosphere is so thick. The point is that if you replaced Venus’s atmosphere with one of Earth’s composition, you would still have plenty of heat at the surface -even if you took the CO2, Water and Methane out. In fact, if you just used Nitrogen alone at the same mass you would get a ton of heat just by the insulating properties of a gas. Is there a single gas in the known universe which wouldn’t cause a hot Venus surface? Better yet, one wonders if Chris would still blame any trace amounts of CO2?
Perhaps Chris shouldn’t be lecturing to Princeton Physicists.
the Air Vent 
Apparently CO2 trapping heat is physics but PV = nRT is not. At least, if you “believe” in the former you are applying physics, but if you so much as mention the latter you are ignoring physics.
That’s why learned folks actually refer to these people as climatologists.
Mark
The idea that CO2 is responsible for the current conditions on Venus has been thoroughly debunked. But the “Venus syndrome” is about the warming that originally caused these conditions. Wikipedia mentions only water vapor specifically. I don’t know how relevant this is to the Earth. http://en.wikipedia.org/wiki/Atmosphere_of_venus#Evolution
Is there a single gas in the known universe which wouldn’t cause a hot Venus surface?
Colosium?
It leaves me cold, but then again, you seem to be inflamed by it. /sarc
Jeff, don’t over analyze silly statements. I think sometimes you give too much credit to those with countervailing POVs by giving them space on your blog. If there is some scientific or factual based content in their comments that might make for an interesting discussion, I can see it being used as a springboard to an interesting thread. If you are merely pointing to the fact that people on all sides of the AGW issue can make silly statements, I think you are showing something that is rather obvious to most interested parties.
Kenneth,
Actually, if you read Chris’s page, you find that he considers himself somewhat of an expert in planetary atmospheres but I just forgot to add the goofy part in my last post.
A 90 times more dense atmosphere yet it is the evil CO2 which causes the heat. That doesn’t stop him from critiquing all kinds of noted scientists in the same post.
Also to expound on what Colose’s comment is intended to portray, it is obvious that he wants to make a point that one would not require an atmospheric material to be called a pollutant to make life unlivable on an entire planet. To emphasize his point he makes reference to Venus which has no relevance to AGW issue here on earth at this time – unless he can make a connection. Obviously the point in questions, as I recall, is the EPA calling CO2 a pollutant in order to regulate it and initiate government mitigation without passing specific legislation. It would appear like all too many AGW advocates he avoids the specifics of the case by generalizing and making a meaningful discussion impossible.
Sadly, Jeff, science and the scientific community seem to have been corrupted “from tit to tail” by government research funds.
Even the most prestigious research universities and government laboratories have apparently been compromised.
Why else would organizations hide or ignore experimental data [1] on the Sun’s a.) Origin, b.) Composition, c.) Source of energy, and d.) Influence on Earth’s changing climate ?
1. “Neutron Repulsion”, The APEIRON Journal, in press, 19 pages (2011) http://arxiv.org/pdf/1102.1499v1
Yesterday someone reminded me that our “peacetime” government greatly expanded after WWII. During the Cold War government funds for research and development were increased sharply under President Eisenhower to protect national security.
In his farewell address to the nation on 17 Jan 1961, Eisenhower specifically warned about two threats to our free society [2]
a.) An “industrial-military complex”, and
b.) A federal “scientific-technological elite.”
2. President Eisenhower’s farewell address (17 Jan 1961)
http://mcadams.posc.mu.edu/ike.htm
Since the corruption of government-funded science seems to have began soon after Eisenhower’s speech, my friend asked if fear of mutual destruction in nuclear warfare (e.g., the Cuban missile crisis) might have persuaded world leaders to stop the development of honest, competitive science to save their own lives?
I do not know the answer, but I am certain that government science and the scientific community have been seriously compromised.
With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
When I read Happer’s and Colose’s comments, I got the distinct feeling that neither of them hits the right note on estimating the uncertainties of the consequences of AGW. Happer’s intent was good in showing that not all of the consequences of AGW are detrimental as is so often portrayed by some climate scientists and that clinmate scientists can over-hype consequences without putting objective confidence limits on their projections. On the other hand, Happer appears to hand wave away feedback effects on temperatures and the explanations for temperature apparently leading CO2 concentration increases in the atmosphere.
I’ll also be honest enough to say that climate science is something that scientists in other fields do not always get and particularly the more nuanced parts of it, and that is the case many times no matter where the scientist’s opinion comes down. The consensus of so-called scientists on AGW, whether in the field of climate or not, suffers credibility from this very condition of being specialized and depending on opinions that can be tainted with advocacy from other scientists.
Jeff, you’re spot on with your critique of the substance.
However, I don’t think Colose’s first sentence should be let slide either. It is an attempt to brush aside all the (well-deserved) criticism of the ‘CO2 is a pollutant’ idea. By saying, well, different people have different views and let’s not talk about whether it is a pollutant or not, he is implicitly supporting the CO2 is a pollutant movement. Contrary to his approach, it needs to be clearly pointed out, and repeated, that CO2 is not a pollutant, that it is essential for life, and that by all accounts life does better with more CO2 (within the numbers we’re talking about). These are important facts about CO2 that shouldn’t simply be brushed aside as a techical “legality.”
Jeff,
I argued this out with Chris Colose on “Science of Doom”. If you replace the CO2 in the Venusian atmosphere with an equal mass of Helium the surface temperature would be slightly higher. In other words, the measured (near adiabatic) lapse rate in the convective part of the Venusian atmosphere is all you need to explain the surface temperature.
As you point out it makes little difference what gas you choose but the amount of gas makes a huge difference.
Chris is typical of academics. Arrogant in the extreme and lacking in common sense.
The same subject was also debated on “Brave New Climate”. Here is a link that includes the Jenkins et al. publication based on measurements in the Venusian atmosphere:
http://bravenewclimate.com/2010/05/09/clarons-despair/#comment-64131
Eric FYI: A pollutant is not defined by whether it is essential for life, but at what concentrations does it harm. An example is phosphates. They are great fertilizers, and in that lies the problem. The ban on phosphates in detergents, where there were used as a wetting agent, is because at high concentrations it was proven that they damaged the recieving waters which is legally considered a taking or tresspass of other’s property including the commons, an illegal act.
This episode is why it is so important as to whether the courts uphold EPA’s finding of harm for GHG’s here in the USA.
At this point in the USA, Chris is correct, not Happer. Even though I think the finding of harm is incorrect, the EPA doesn’t. Now it is up to the courts.
To be fair to these “opinion” statements it should be acknowledge that both Colose and Happer threw out these statements to make a point: Happer to make a statement about the beneficial effects of CO2 while at the same time minimizing the direct effects of low/no CO2 on humans and Colose to make a statement about what he thinks can be detrimental effects of something in the atmosphere whether it is properly labeled a pollutant or not. Happer was not quite correct based on what we learned about the body’s need for CO2 to breath reflexively. Colose was off the mark based on straight climate science.
Getting into food fights over these errors would appear to me to allow the subject to change to minor points from the more important points which in this case started out to be, I think, an argument against CO2 being deemed a pollutant in order to empower the EPA.
As a libertarian I would much rather debate and show evidence for the case of seemingly benign regulation being used (based on vague limits in the enabling legislation) to impose something very different. I think this is a topic of discussion currently in the Obama administration where even left wingers realize there is a price to pay for regulations and particularly those that are vague. Investors and job creators will tend to shy away from those areas where their investment success can depend on the whim of a regulator.
“The point is that if you replaced Venus’s atmosphere with one of Earth’s composition, you would still have plenty of heat at the surface -even if you took the CO2, Water and Methane out. In fact, if you just used Nitrogen alone at the same mass you would get a ton of heat just by the insulating properties of a gas. “
Not true – with N2 alone, it would be about 230K. N2 has no insulating effect. Chris is right.
The question with regard to Venus is “does an atmosphere require the presence of a ‘thermalising gas’ in order come close to obeying the ideal gas law”? In other words would the atmosphere virtually collapse to a cold liquid state if it contained no greenhouse gases? This is an argument I have seen advanced in the past. By the way it is worth noting that James Hansen got his start as a scentist theorising about the atmosphere of Venus. It’s possibly one of the reasons why his entire career seems to have been tainted by an AGW alarmist stance.
Nick,
N2 absorbs in the UV range and would heat from the top down in addition to its large “blanket” effect at 90X earth as Jeff points out.
Of course the main heat retention on Venus is known to be from the sulfur cloud layer, about where the earth pressures start, that only allows about 20% of the suns heat in and also REFLECTS a lot of IR back down (unlike CO2 which is omnidirectional). CO2 just can’t do the work being done by those REFLECTIVE clouds. Even they can’t explain how Venus got that hot as they are a result of the heat just like the increase in CO2 on earth is the result of ocean warming.
Nick, at the surface of Venus the temps are about 450c. At that temp the black body is close to the weaker CO2 absorption band. How broad do the “wings” get for this weak band at those temps and pressures??
KK,
Yes, there’s a lot to be said about clouds, bands etc. But it isn’t just mass of gas or ideal gas law. The CO2 is doing something. The threads of SoD and those that he links to go into it pretty thoroughly.
Jeff said:
“Venus does have a more reflective atmosphere but it is also closer to the sun than the Earth.”
While earth is 150M km from the sun, Venus is only 108M km away, a ratio of 0.72.
The “solar constant” at the earth is 1367 W/m², and, as energy intensity is proportional to the square of the distance away, or “r²”, the solar constant at Venus is 1367/(0.72²) = 2,636 W/m² – Venus is closer, so it receives more solar energy per m².
If Venus had the same albedo as the earth, the energy absorbed per m² of surface area would be, E = 2,636 * (1-0.3) / 4 = 461 W/m².
But Venus has a much higher albedo than the earth, with an albedo of 0.76 – meaning that 76% of the solar energy is reflected.
E = 2,636 * (1-0.76) / 4 = 158 W/m² – which equates to an “effective radiating temperature” of 230K (-43°C).
“For the thinking mind, it is difficult to ignore that the atmosphere is a ridiculous 90 times more dense.”
What exactly does a more dense atmosphere do to temperature?
PV=nRT as many people know but misunderstand. If you increase pressure does T increase or does V decrease? How is this determined? Those with thinking minds please explain.
Does high pressure cause high temperature?
The article Venusian Mysteries might be interest to some readers, along with the follow up article and the lengthy discussion, Convection, Venus, Thought Experiments and Tall Rooms Full of Gas – A Discussion.
Thought experiment no 1
Is a bike tire with 100psi at a higher temperature to a bike tire at 20psi?
Take a bike tire and pump it up quickly. It gets hot. This is because work is done on the air in the tire, heating the air which conducts through the rim. We can feel it.
Leave the tire for a week. Is it still hot?
Take a bike tire and pump it up very very slowly – over a week. Does it get hot?
Thought experiment no 2
Take a planet which is lost in space with a small atmosphere which has radiatively-active gases (“greenhouse” gases). It has no internal heating and no sun to warm it. Surface temperature = 3K (background temperature of the universe).
Now we pour in a massive atmosphere from “above”. Work done on the atmosphere in compressing it adds heat. Let’s suppose the temperature of the surface reaches 100K (it could be any number).
Now we wait 1 billion years – will the atmosphere still be at 100K? Or will it be almost back at 3K?
Does a high pressure cause a high temperature?
Does a high pressure cause a higher temperature than a low pressure?
What determines surface temperature?
Many many factors but three relevant ones for this topic:
1. The amount of energy absorbed by the climate system from the sun (probably everyone agrees with this one)
2. The opacity of the atmosphere
3. The height of the atmosphere and its lapse rate
Point 2 – Opacity of the atmosphere
The opacity of the atmosphere determines from what average height the climate system radiates to space. Let’s call this height Z.
If Z = 0, i.e., the surface because the atmosphere was transparent, then the surface emission of radiation must directly balance the absorbed solar radiation.
If Z = 5km, then the emission of radiation from 5km up must balance the absorbed solar radiation. (In fact it is a mixture of all different heights due to the wavelength dependent opacity of the atmosphere).
Point 3 – Lapse rate
The temperature drop from the surface to Z determines the surface temperature “increase”. This drop (lapse rate) is determined by the ideal gas laws (yes everyone knows these) and is around 10K/km for a dry atmosphere and less than 4K/km for a very moist atmosphere.
Therefore, putting these together, if the average emission to space takes place from a higher altitude (Z increases), the surface temperature will increase (all other things being equal). If the lapse rate changes, of course, then the surface temperature change will be affected
I respect “Science of Doom”; he has been most helpful to this camel who flunked thermodynamics. I heartily recommend the links that he provides.
However, it is my contention that you do not need the clever stuff such as RTEs (Radiative Transfer Equations) and MODTRAN to get a feel for what the surface temperature of Venus should be. All you need is Stephan’s Law, the properties of sulphuric acid and adiabatic lapse rates. It turns out that the measured surface temperature falls between the temperatures calculated using the dry and wet lapse rates, whether you use CO2, Nitrogen or even Helium.
http://scienceofdoom.com/2010/06/12/venusian-mysteries/#comment-2953
Jeff,
Looking back at that exchange of views on “Science of Doom” I asked a question that nobody addressed. Shouldn’t the Earth’s atmosphere consist mainly of steam with a surface pressure of 320 bars and an average temperature of 1,000 Kelvin? That would be a pretty impressive Greenhouse Effect.
http://scienceofdoom.com/2010/06/12/venusian-mysteries/#comment-3240
What do you think? When did the water arrive on Earth?
Sod 19:
“But Venus has a much higher albedo than the earth, with an albedo of 0.76 – meaning that 76% of the solar energy is reflected.
E = 2,636 * (1-0.76) / 4 = 158 W/m² – which equates to an “effective radiating temperature” of 230K (-43°C)”
A venusian year lasts 224d, while a venusian day lasts 116d. So a year_v has nearly 2 (two!) days_v. Have you even remotly thought about the effect of a nighttime period of 58d? So why exactly do you divide it by 4 and not by 2?
Last time I checked, the Stefan-Boltzmann-equations were valid only for black bodies with absorbtance of 1, transmissivity of 0 and reflectivity of 0. Why would anyone want to compare venus whith a reflectivity of 0.76 to a black body? It’s pretty much the exact opposite of it.
sod 20:
“Take a bike tire and pump it up quickly. It gets hot. This is because work is done on the air in the tire, heating the air which conducts through the rim. We can feel it.
Leave the tire for a week. Is it still hot?”
Keep a heater (say, the sun) shining on it for the whole week. Is it still hot? Yes.
Joel Heinrich said on May 28, 2011 at 5:08 am:
“So a year_v has nearly 2 (two!) days_v. Have you even remotly thought about the effect of a nighttime period of 58d? So why exactly do you divide it by 4 and not by 2?”
The reason for dividing by 4 is explained in The Earth’s Energy Budget – Part One.
It’s just geometry and nothing to do with the period of rotation of the planet. If you want to compare a) radiation emitted from a sphere with b) radiation absorbed by a sphere from a point source a long way away, you have a radiating surface of 4.pi.r^2 compared with an absorbing area of pi.r^2.
If the planet is approximately in energy balance then energy absorbed = energy radiated.
If this is something that seems wrong, just calculate total energy in = total energy out. Do it over a year if you like.
Total energy in over 1 year = S.pi.r^2 (1-A) x 3600 x 24 x 365.25, where S = W/m^2 irradiated flux, A = albedo and r = radius.
Total energy out = 4.pi.r^2.E x 3600 x 24 x 365.25, where E = emitted flux in W/m^2 from the climate system.
We can cancel out pi.r^2 x 3600 x 24 x 365.25 to get:
S(1-A)/4 = E
“Last time I checked, the Stefan-Boltzmann-equations were valid only for black bodies with absorbtance of 1, transmissivity of 0 and reflectivity of 0. Why would anyone want to compare venus whith a reflectivity of 0.76 to a black body? It’s pretty much the exact opposite of it.”
The effective radiating temperature is just a useful shorthand (a convention) for emitted radiation.
Instead let’s just compare the Earth and Venus.
To be in energy balance with the sun, the Earth emits 239 W/m^2 (globally annually averaged).
To be in energy balance with the sun, Venus emits 158 W/m^2 (globally annually averaged).
You see – no “blackbody assumptions” and yet we can compare the two planets. The earth is further away and yet must emit more radiation from the climate system than Venus which is closer.
Joel Heinrich said on May 28, 2011 at 5:16 am:
“Keep a heater (say, the sun) shining on it for the whole week. Is it still hot? Yes.”
Fantastic.
Now think before posting your next comment.
Compare the high pressure and the low pressure tire with the sun shining on it for the whole week.
It is the comparison between pressures that we are interested in. If the sun is shining for the whole week and we have pumped up the tire to a high pressure will it be hotter at the end of the week than the tire at low pressure with the sun also shining on it the whole week.
This is not a difficult concept.
Two tires, side by side.
One kept at 20psi – with the sun shining on it.
One pumped up to 100psi – with the sun shining on it.
Does the high pressure tire stay at a higher temperature?
Or does it cool back to the same temperature as the 20psi tire?
sod 25:
“It’s just geometry and nothing to do with the period of rotation of the planet. If you want to compare a) radiation emitted from a sphere with b) radiation absorbed by a sphere from a point source a long way away, you have a radiating surface of 4.pi.r^2 compared with an absorbing area of pi.r^2.”
Ah, well, my point was more that if there was a (near) synchronous rotation, like the moon-earth-system, then you would have half a sphere radiating on average 316 W/m² while the other would be at 3K, thus reducing the average “effective radiation temperature” to 117K (-156°C) while still having an average energy flux density of 158 W/m². Sorry that I wasn’t so clear before.
Which means that you can not just use the stefan-boltzmann-law for the whole planet.
“The effective radiating temperature is just a useful shorthand (a convention) for emitted radiation.”
No. It is a highly specialized law with very strict confinements.
Ok. Let’s say we have two tires E and V. Both have absorptivity of 1 for short wave radiation and emissivity of 0.8 for long wave radiation. Now we pump tire V up fast while on the same time reducing it’s emissivity to 0.1 with the sun shining the whole time at 300 W/m².
Both tires would first be radiating 300 W/m² (equivalent to 270K) but would have a temperature of 285K (eq to 375 W/m²). That’s because of the emissivity of 0.8 (300/375 = 0.8). But still with energy in = energy out.
After pumping up (and changing emissivity) tire V would have a temperature of 480K (eq to 3000 W/m²). It’s still 300 W/m² in and 300 W/m² out, but the temperature would stay this high.
The problems lie mostly in all the underlining, never to be mentioned, but unfortunatly often wrong, assumptions.
“To be in energy balance with the sun, the Earth emits 239 W/m^2 (globally annually averaged).
To be in energy balance with the sun, Venus emits 158 W/m^2 (globally annually averaged).
You see – no “blackbody assumptions” and yet we can compare the two planets.”
Sure, but nobody is arguing about that. It’s exactly when you get to the “blackbody assumptions” that the problem start. The question being: “Why is the surface temperature of the Earth (and Venus) not the same as for a blackbody?” Well, they are no blackbodies. Simple as that.
Joel– The concept of an “effective radiating temperature” for a blackbody is really just a convenient reference system, it doesn’t need to correspond to a real, physical temperature (although emissivities very close to one is a common characteristic in the infrared– it doesn’t work so well, in say, the microwave)
In any case, as others have pointed out, this attempt to correct me is just a lack of understanding of what the equation of state can tell you. This weird meme that Steve Goddard (with a bit of helping from Lubos Motl) started really baffles me, and I’m all for scientific skepticism, but a little bit of physical insight and not jumping on the “every counter-argument to AGW that possibly exists” bandwagon is always appreciated.
The equation of state is PV=nRT/μ (where μ is the mean molecular weight). You cannot determine T from p alone (by all this reasoning, I could just as well argue that the high pressure on Venus is caused by the high temperature, but that doesn’t work either). You need additional information to construct profiles of all the relevant climate variables, and radiative heating and cooling rates is not a bad place to start. It’s certainly attractive to think that all of planetary climate is reducible to simple high school algebra manipulation, but alas, it isn’t so easy. There’s an odd distrust of experts in this blog, but because things aren’t so easy is why they exist. Maintaining a super-hot temperature on Venus adaibatically (i.e., where there are no energy inputs) just makes no sense in the equilibrium state the atmosphere must relax into.
Without a greenhouse effect, and once all flows decay, the atmosphere would become isothermal (so the tropopause approaches the surface); the high optical thickness on Venus explains the high tropopause, and because of the greenhouse effect one can extrapolate down the adiabat to reach a very hot surface temperature, since the atmosphere only becomes optically thin enough to let radiation out at a relatively thin part of the air near the top of the atmosphere. Ray Pierrehumbert’s recent Physics Today article explains this all very clearly, and with good illustrations as a guide.
I don’t see the relevance of “hot” bicycle tyres. Of course they will cool down to ambient. The air in the tyre is confined. The atmosphere is only confined by gravity. The air in contact with the surface, any surface, will rapidly aquire the temperature of that surface. That heat is transported up the atmosphere at a well defined rate, known as the adiabatic lapse rate. For the ideal “model” atmosphere the formula is dT/dh = -g/CpT = -9.8 K/km
CO2 and H2O, “greenhouse” gases, will not effect this rate UNTIL the water vapour starts condensing at dew point. The water vapour phase change from gas to liquid and consequent energy changes will reduce the lapse rate such that the average lapse rate is considered to be about -6.5 K/km. With a surface temperature of 15C the temperature at 5,000 metres will be -17.5C. The observed average temperature at that altitude, by satelite, is -18C, the required outgoing radiative temperature to balance the incoming energy from the sun. That 33C degree difference between the surface and the atmosphere at 5,000 metres is the “greenhouse” effect. CO2 does not effect the lapse rate.
Joel Heinrich said, #27:
“Ah, well, my point was more that if there was a (near) synchronous rotation, like the moon-earth-system, then you would have half a sphere radiating on average 316 W/m² while the other would be at 3K, thus reducing the average “effective radiation temperature” to 117K (-156°C) while still having an average energy flux density of 158 W/m². Sorry that I wasn’t so clear before.
Which means that you can not just use the stefan-boltzmann-law for the whole planet.”
I haven’t used the Stefan-Boltzmann law at all.
I have used the First Law of Thermodynamics and geometry to find how much the earth’s climate system must radiate (globally annually averaged) compared with Venus’ climate system.
Take a look back at #25. Geometry and the First Law of Thermodynamics is all you need.
Where is the Stefan-Boltzmann equation in #25? Can you find it?
Where is the flaw in the comparison in #25?
“The effective radiating temperature is just a useful shorthand (a convention) for emitted radiation.”
No. It is a highly specialized law with very strict confinements.
The Stefan-Boltzmann law which I think you are commenting on is first not a highly specialized law, it is an equation which describes the emission of radiation from all bodies, because the Stefan-Boltzmann law is E = emissivity x 5.67×10^-8 x T^4. Emissivity is a value from 0 – 1, where 1 is a black body.
Many people who have learnt their thermodynamics from blogs believe the Stefan-Boltzmann equation is a law of “black body radiation” but this is not correct. Open up a textbook on heat transfer and turn to the chapter on radiation.
There is no alternative equation for emission of radiation.
Secondly, “effective radiating temperature” is a convention. People who use this convention know that it is not the actual temperature.
And as you can see, I reverted to comparing the two planets by radiation emitted. This is because obviously people here aren’t familiar with the convention.
A convention is something different from a law.
Richard111, # 29:
“I don’t see the relevance of “hot” bicycle tyres. Of course they will cool down to ambient.
The author of the post, Jeff, appears to believe that pressure causes high temperature. Therefore, the comment is relevant to that belief.
Perhaps he doesn’t think that, so I hope he can clarify why he thinks pressure is so obviously a factor in the high surface temperatures of Venus.
I agree with the rest of your comment – it’s what I already wrote in #20 under “What determines surface temperature?”.
(Except for your implication that at condensation “greenhouse” gases do affect the lapse rate. Perhaps you didn’t mean that. Radiation has nothing to do with the lapse rate at all).
And amazingly many people think that climate science believes the lapse rate is affected by radiation. It just demonstrates that if you want to find out what people think you have to read their books or papers, not read what a totally random person heard down the pub.
For example, Things Climate Science has Totally Missed? – Convection.
Joel,
ScienceOfDoom is on-target for the Earth-like limiting case (and I highly recommend his multi-part series on radiative transfer and the Earth’s energy budget, it’s very good).
However, you do have a point for a more generalized situation, since there’s more assumptions built into the factor of “4” in the radiative balance equality than just geometry. In particular, while the concept of an “effective radiating temperature” may be a convention and not a law, it’s a pretty useless convention for bodies such as Mercury or the Moon (or perhaps with many newly discovered tide-locked planets orbiting M-dwarf stars) that have substantial diurnal temperature gradients. In these cases, a factor of “2” or 1/cos(Zenith Angle) or even a factor of “1” may be more appropriate, depending on whether your interest is the instantaneous radiative equilibrium temperature for a low thermal inertia point on the surface, the starlit side of a hemisphere, or whatever is most appropriate.
The uniform temperature approximation is not bad on Earth because we have oceans to smooth out diurnal gradients (obviously no point on Earth ever reaches 3 K). Even further, water vapor reduces the slope between the OLR and temperature, making a more linear approximation of the Stefan-Boltzmann law even more valid over a small range. On Venus, you do have slow rotation, but to lowest order the night-side doesn’t get much colder than the day-side because the dense 93 bar atmosphere is very good at transporting heat around. The key thing here is the thermal relaxation timescale compared to the timescale over which substantial diurnal, seasonal, or orbital (e.g, eccentricity) variations are important.
Of course, we’re still talking about very simple energy balance models. More elaborate GCM’s use the full form of the Planck function over many grid points, and compute radiative transfer with the gaseous absorber distribution and vertical profile taken into account.
Joel Heinrich in #27:
You didn’t answer my simple question in #26. This compares two different pressures with all other conditions the same.
This helps to identify whether pressure causes higher temperature or not.
Instead you introduced an example where emissivity is reduced while pressure is increased (is it being painted with highly reflective paint while being pumped up?) to create an example which demonstrates that radiative balance and not pressure causes higher temperature.
If you want to find out whether high pressure causes high temperature all other conditions should be the same. And when we do this we can easily see that high pressure cannot cause high temperature in the long term.
In the short term increasing pressure does work on a system which usually increases its temperature. This, I think, is where many people’s confusion lies about the relationship between pressure and temperature.
Chris Colose,
“The uniform temperature approximation is not bad on Earth because we have oceans to smooth out diurnal gradients (obviously no point on Earth ever reaches 3 K).”
Well, actually the thermal mass of the atmosphere is quire large enough to buffer diurnal variation. Ignoring latent heat content (which is also substantial), the dry atmosphere alone has a heat capacity of about 10 million joules per square meter per degree. Since average solar flux is only 21 million per day per square meter, a couple of degree change in the average atmospheric temperature is enough to buffer the daily swing in solar energy. Of course we see more than that much temperature change at the surface, since much heating is localized at the surface (convective and evaporative heat transport away for the land surface and radiative cooling mainly govern the diurnal range). The continental diurnal range is pretty much independent of ocean buffering in any case. Over open ocean the diurnal range is very close to zero, since essentially all solar energy reaching the surface is absorbed by the top 100 meters or so (too thermally massive to allow any daily variation).
scienceofdoom,
I don’t think Jeff believes pressure causes high temperature. The equation of state is pretty clear for ideal (or nearly ideal) gases. The point is that a denser atmosphere *of the same composition*, with some concentration of infrared absorbing gases, will always cause more surface warming than a thinner atmosphere. Surely you agree that is the case, right? The surface of Venus is very hot for several rather obvious reasons, including the composition and density of it’s atmosphere…. I tire of hearing arguments about why Venus is hot. It is quite irrelevant to the substantive question of surface temperature sensitivity to a change in CO2 of a couple of hundred PPM in *Earth’s* atmosphere.
Steve,
Jeff can defend himself, but concerning the Venus quote, there’s absolutely nothing contained in the sentence I originally wrote that anyone should have objections to. It’s very standard stuff you can find in the “introduction” of a gazillion papers about Venus, in textbooks, or even in K-12 grade school lessons/wiki articles about Venus. Just google/google scholar “CO2 and Venus” or something similar to see. Apparently the low quality education me and fellow students are getting these days is the same junky education every planetary scientist has gotten, because there’s no credible resource anywhere that attributes the high temperature on Venus to anything other than its greenhouse effect. And most of that greenhouse effect is CO2, a bit of water vapor, and some SO2 and sulfur clouds. Venus has been studied for decades now and the only deviants from this view seem to be Steve Goddard and the WUWT crew, Lubos Motl, and I don’t see much other way to interpret Jeff’s objections to the bolded quote.
I agree Venus doesn’t tell us anything about climate sensitivity on Earth, and I didn’t ever imply it did. It does however show that the rules of radiative transfer apply just as well there, and serves as a counter-example to people who don’t think the greenhouse effect exists, or that it can’t be enhanced, or whatever the new flavor of the day happens to be.
But a lot of people are interested in “substantive questions” other than climate sensitivity or whether the greenhouse effect is real or whether CO2 can cause global warming. The last two only seem to be debated in blogs, and I for one don’t consider them a topic of particularly interesting curiosity. I also think the sensitivity question is getting pretty boring too, but that’s me.
Chris Colose,
You are still selling your complex nonsense. You don’t need super computers to recognise the fact that clouds on Venus or Earth set the temperature at the top of the troposphere and you can calculate the surface temperature by applying the adiabatic lapse rate down to wherever the surface happens to be.
It works every time so why not admit it?
Clouds determine the temperature now? I keep hearing new things all the time
Gallopingcamel #37:
Why do we need these “over-complicated” equations of radiative transfer?
1. Small persistent changes in outgoing longwave radiation (and/or absorbed solar radiation) have the potential to cause significant (to us) temperature changes. (This is in the absence of any positive or negative feedback – let’s leave that to one side for the moment).
2. Emission to space of longwave radiation takes place from many different levels in the atmosphere – therefore from many different temperatures – and small changes in absorption characteristics can change this level.
Let me put it to you like this – are the equations of radiative transfer wrong?
If yes, go ahead and demonstrate. If no, then can you calculate the same results using your simpler method?
The history of most fields of scientific endeavor are full of simplifications which are used whenever possible. You can find simpler models in most atmospheric physics textbooks (as teaching tools).
If “the temperature of the tropopause is all we need to know” argument held up that would be fantastic.
As a nice simple example of why the “simple model” is not practically useful, consider the halocarbons, e.g. CFC11 & CFC12. CFC11 has a concentration of 0.3 ppbv and CFC12 0.5 ppbv. However, their absorption bands are in the “atmospheric window” and the estimates of radiative forcing since the mid 20th century due to these halocarbons is around 0.34 W/m^2.
Add up the changes from “minor gases” like N2O, CH4 and the halocarbons and you have a significant effect. The simple model has no way to predict this.
It’s possible that the equations of radiative transfer are just wrong. But as explained in Theory and Experiment – Atmospheric Radiation, you have to explain how the exact measured spectral features of the top of atmosphere and surface “back radiation” are reproduced by solving these equations.
One quick note—I agree with Steve that this comment by Chris C is off the mark:
Actually i think the constancy of the atmospheric temperature day-to-night has very little to do with the oceans smoothing out diurnal gradients….As I understand it, the time constant for interchange of heat between ocean and (entire, not just surface boundary layer) atmosphere is very long…maybe months (look at the lag between global mean atmospheric temperature and ocean heat content if you don’t believe me).
Regarding Jeff’s comments, I think he hasn’t spelled out what he really thinks in enough detail to know exactly what he thinks is important wrt Venus and high pressure. I certainly didn’t see the relevance of its high pressure to the question of why the surface of Venus maintains its current high temperatures.
Also, Chris C:
Actually the majority of the difference in climate sensitivity between “classic” and “full GCM” comes from the assumed positive feedback of clouds. So yeah, it’s kind of important, at least if you want to discuss the Earth, rather than the Moon.
SOD:
Exactly right, though I would put it differently: In order for an alternative theory to have equal standing, it must be able to do at least as well in explaining the observed data. You don’t have to explain why a wrong theory “gets it right some time”, that should be unnecessary, since in the comparison of data with model, eventually the predictions of the wrong theory must diverge from the observations. That is how we sort out competing theories that start with different interpretations of the underlying principles, not by incessantly arguing back and forth over whose interpretation is correct, in the absence of comparison to measurement.
I’ve seen no examples of where “competing” theories can reproduce the spectral features mentioned by SOD even grossly, and until I do, “competing” theories need the scare quotes—they aren’t competing if they have zero predictive value.
Steve Fitzpatrick, #35:
“I don’t think Jeff believes pressure causes high temperature.”
Let the author speak. Many people do misunderstand the equation PV=nRT. Some of these already identified in #36. Commenter #1 seems to understand Jeff the same way as me (and, unlike me, agree with the flawed idea).
“The point is that a denser atmosphere *of the same composition*, with some concentration of infrared absorbing gases, will always cause more surface warming than a thinner atmosphere. Surely you agree that is the case, right? ”
I’ve outlined the simple explanation in #20.
– A more opaque atmosphere = a higher (colder) emission to space = less radiation to space = a long term heating effect.
– A higher lapse rate = reducing temperatures at each altitude = less radiation to space = a long term heating effect.
We can add
– A “taller” atmosphere = a higher (colder) emission to space = less radiation to space = a long term heating effect.
I think this is what you mean by “a denser atmosphere *of the same composition*“.
So if I have understood you correctly then of course I agree.
“..I tire of hearing arguments about why Venus is hot. It is quite irrelevant to the substantive question of surface temperature sensitivity to a change in CO2 of a couple of hundred PPM in *Earth’s* atmosphere.
We can’t draw any kind of direct comparison if that’s what you mean. But understanding other planetary atmospheres is very useful for testing our understanding of atmospheric physics. Physics is the same everywhere (allegedly). But level of relevance is generally a subjective opinion.
scienceofdoom #31: you state;
“(Except for your implication that at condensation “greenhouse” gases do affect the lapse rate. Perhaps you didn’t mean that. Radiation has nothing to do with the lapse rate at all).”
I did not say that: #28, I said “CO2 and H2O, “greenhouse” gases, will not effect this rate” I then went on to qualify “UNTIL the water vapour starts condensing at dew point.”
I made no mention of radiation at all.
I simply pointed out the 33C temperature differential is a result of the lapse rate. H2O has a marked effect on the lapse. CO2 has no effect.
I have just re-read post #20 and totally disagree. Consider three very different environments on the planet. First a desert with temperature in the order of +40C, next a temperate zone with a temperature of +15C and last a polar region with a temperature of -30C. A total temperature change of 70 degrees and the lapse rate up the atmosphere will be the same at all three locations. The surface temperature defines the starting point of the lapse rate. The end point will be the same for all three cases but the altitude will differ. Thus the tropopause is much higher at the equator than at the poles.
Richard111, #43:
“I have just re-read post #20 and totally disagree.”
Can you narrow it down a bit.
Point 1 ok?
Point 2?
Point 3?
Do you perhaps mean point 2?
“Consider three very different environments on the planet. First a desert with temperature in the order of +40C, next a temperate zone with a temperature of +15C and last a polar region with a temperature of -30C. A total temperature change of 70 degrees and the lapse rate up the atmosphere will be the same at all three locations. The surface temperature defines the starting point of the lapse rate. The end point will be the same for all three cases but the altitude will differ. Thus the tropopause is much higher at the equator than at the poles.”
Why are you picking the tropopause? Why is that relevant for this discussion?
Perhaps if you can explain what specifically you take issue with in #20 I will be able to see what needs further explaining.
Later, for interest, I will post up some graphs of temperature vs latitude and pressure and link to them. The tropopause is coldest over the tropics and occurs at a slightly lower pressure over the tropics compared with the poles. In height terms, there is a much more significant difference, as 200mbar is more than 1km higher at the equator compared with the poles.
Guys, I don’t know where this idea that the lapse rate needs to be independent of radiation comes from, but the existence of radiative temperature inversions or the stratosphere are simple proofs of its absurdity. The “Adiabatic lapse rate” is only independent of radiation (or any other forms of external heat transfer) by definiton. In the midlatitudes for example, heat released by baroclinic instability affects the lapse rate. You can’t set dQ=0, watch dT/dz= -g/cp fall out of the thermodynamics, and then say nothing else matters. That’s just circular. Convection does tend to relax our atmosphere near an adiabatic state, especially very close to moist adiabatic in the entire tropics. In the optically thin case, convection sets in until instability is eliminated via intersection between the adiabat and the radiative equilibrium profile.
Carrick– The atmosphere and ocean both matter; obviously the high thermal inertia of a body that covers ~70% of our planet is relevant to determine the temperature re-distribution. Compare this to the same planet, but in a snowball state, which is usually much more comparable to Mars in terms of its seasonal cycle. Steve didn’t say much I disagreed with in his comment, and atmospheric transport is very important as well. I also agree about cloud feedbacks, but that wasn’t what we were talking about
Following on from my comment on #44, some extracts from the excellent Atmosphere, Ocean and Climate Dynamics by Marshall & Plumb (2008), which I realize that Chris Colose recommended in Finding Stuff out and Book Reviews.
Annual average temperature vs Pressure vs Latitude – here you can see that the tropopause above the tropics is the coldest place in the atmosphere (annually averaged).
Temperature vs Latitude and Height at Summer Solstice
Geopotential Height vs Latitude – here you can see that for a given pressure the height at the equator is greater than the height at the poles.
SoD writes “A “taller” atmosphere = a higher (colder) emission to space = less radiation to space = a long term heating effect.”
In what sense are you suggesting the heating effect is long term?
Given that there is a massive amount of energy added to the atmosphere every day and the rate of increase of CO2 is very small, I’d have thought that the atmosphere itself would be in equilibrium at all times.
For the same reason, the SST ought to be in equilibrium too.
So that leaves the ocean depths which may warm slowly…but how slowly? and what effect will that have on the climate anyway?
Re: scienceofdoom (May 28 06:33), As I understand it, the gas giants (at least Jupiter anyway) radiate more heat than they absorb. Where does that heat come from? Certainly one would imagine they have had long enough to reach thermal equilibrium (4 billion years or so).
TimTheToolMan, #47:
The “long term” statement is included because the whole climate system has a large heat capacity.
I’m trying to get a balance between being understandable and being accurate. These two are often mutually exclusive, as too many caveats and long explanations make statements hard to understand.
Exactly what climate response occurs for a specific radiative imbalance depends on a lot of factors.
The atmosphere doesn’t respond as fast as you might think. If you look at the DLR in The Amazing Case of “Back Radiation” -Part One you can see that the atmosphere doesn’t cool down as much as the land surface overnight.
The SST depends on the mixing that occurs in the top layer of the ocean, which is governed by many factors. If we take a general approach and say that the top 10m of the ocean is well-mixed, then how will the SST respond to a radiative imbalance?
Taking a simplistic 1d model for illustration only.. If you have a 1W/m^2 imbalance applied to the top 10m of the ocean, it will heat up by 0.002’C on the first day. Yet the long term radiative balance requires a temperature increase of almost 0.2’C (for a surface temperature of 288K with an emissivity of 0.96)
SST can’t respond overnight.
Anonymous said, #48:
“As I understand it, the gas giants (at least Jupiter anyway) radiate more heat than they absorb. Where does that heat come from? Certainly one would imagine they have had long enough to reach thermal equilibrium (4 billion years or so).”
Do you have any evidence for this?
If you do – then either heat comes from some kind of geothermal interior, or the first law of thermodynamics is about to get a shakeup.
The first law of thermodynamics has withstood 150 years of testing. That doesn’t mean it is correct, but faced with the famous “as I understand it” line of argument I am going to go with the odds here..
SoD writes “If you look at the DLR in The Amazing Case of “Back Radiation” -Part One you can see that the atmosphere doesn’t cool down as much as the land surface overnight.”
If you look at say the Antarctic, then air temperature is much colder than surface temperature during winter so its reasonable to expect it to come to equilibrium quite quickly even if not “overnight” with this example.
Plus I daresay there will be examples of warmer surface temperatures and colder atmosphere temperatures overnight so I’d expect it to not be a case of “cant”, rather a case of “doesn’t” and the distinction is important in terms of discussions of time to reach equilibrium.
However you paint it, you’re going to be hard pressed to convince me that 2ppm CO2 over a year cant be in equilibrium.
SoD ends with “SST can’t respond overnight.”
We disagree on this. SST is set by the “hook temperature” which is the temperature at which the DSR energy input balances the ULR (+evaporation) output of ocean energy and is well above the temperature of the bulk. That temperature can not only respond “overnight”, it can respond within minutes to hours.
So increased DLR (ie CO2) has an immediate effect of increasing the equilibrium temperature of the SST and the increased SST will indeed diffuse energy downwards over time. But if the bulk warms over time, will that change the SST in return?
I say no. Well not to any significant extent beyond that which the CO2 forcing caused in the first place anyway. It was in balance before and will be the same temperature to be in balance after the heating. The difference will be that the loss of energy over the entire day (including night) will eventually also reach equilibrium and to do that the overnight temperature will be on average higher for longer. Not the daily peak temperature.
Hence you’d expect to see immediate SST increase (which we measure although its unclear whether its GHGs or clouds causing it) and overnight warming with increased GHGs which is indeed what we also see.
…so it seems to me we’ll see more overnight temperature increase. Milder overnight temperatures (as opposed to the prevailing belief that temperature will actually increase) aren’t necessarily going to be a disastrous thing.
SOD #30:
“I haven’t used the Stefan-Boltzmann law at all.”
So, how did you calculate this (in # 19)? “which equates to an “effective radiating temperature” of 230K (-43°C).”
Again, I didn’t dispute the fact that Venus has an equilibrium energy flux density of 158 W/m². I said that if Venus were a black body without an atmosphere then it woul have an average temperature of 117K (-156°C).
” ..the Stefan-Boltzmann law is E = emissivity x 5.67×10^-8 x T^4. Emissivity is a value from 0 – 1, where 1 is a black body. ..
Open up a textbook on heat transfer and turn to the chapter on radiation.”
Well, my textbook sates for the Stefan-Boltzmann law: ‘the integral of the spectral radiation energy density over all frequencies of the radiation from a surface area is sigma*A*T^4.’
With the spectral radiation energy density being that of a cavity radiator (aka black body) with an absoptivity of 1.
So it actualy only relates to black bodies.
“Secondly, “effective radiating temperature” is a convention. People who use this convention know that it is not the actual temperature.”
Well, then obviously it shouldn’t be used to describe the real world, where there are actual temperatures.
If you use a simplification or “convention” then you have to make sure that it is valid to do so.
#33:
I agree with you there, just one comment: “with all other conditions the same.”
That is the point. You can not compare a black body to a planet or even Earth to Venus. And you do this when you use the “convention”.
Joel Heinrich:
What do you believe is the equation for the emission of thermal radiation for a body of emissivity = 0.5?
If it is E = 0.5 x 5.67×10-8 x T^4 (in W/m^2) then we are in agreement.
I don’t have the interest in arguing whether the Stefan-Boltzmann law is for a blackbody or as generally written applies for a non-blackbody. Heat transfer textbooks usually describe the original blackbody formulation THEN apply it to non-blackbodies with an emissivity < 1.
If we agree that the physics is correctly described by the above equation then we are in agreement.
The sole purpose of what I originally wrote in #19 was to identify the radiative balance as applies to Venus compared with the Earth.
The author wrote "Venus does have a more reflective atmosphere but it is also closer to the sun than the Earth.” and left the rest to the imagination.
It is clear that Venus, while closer to the sun, absorbs LESS solar energy than the earth, per m^2. That’s all I am trying to convey.
Chris Colose #32:
“In particular.. the concept of an “effective radiating temperature”… is a pretty useless convention for bodies ..that have substantial diurnal temperature gradients.”
Right. But every MODEL of a black body-planet would have this kind of diurnal temperature gradient.
“On Venus, you do have slow rotation, but to lowest order the night-side doesn’t get much colder than the day-side because the dense 93 bar atmosphere is very good at transporting heat around.”
“E = 2,636 * (1-0.76) / 4 = 158 W/m² – which equates to an “effective radiating temperature” of 230K (-43°C).”
So one calculates the effective radiating temperature of a planet model without atmosphere with a factor of 4 because the atmosphere is good at transporting heat around. This does sound pretty dumb to me.
Joel Heinrich # 54:
Actually I disagree with Chris. Forget about “effective radiating temperature” which I included at the start without thinking, forgetting that this convention isn’t understood. I abandon the convention.
If you want to know the total average annual emission of thermal radiation from the climate system of a planet then the equations provided in #25 are correct. It doesn’t matter how slow the planet rotates.
Energy balance and geometry still provide the equations.
Energy in = energy out (unless the planet is warming or cooling – see Technical note).
The geometry and the first law of thermodynamics therefore relate energy in and energy out like this:
Total energy in over 1 year = S.pi.r^2 (1-A) x 3600 x 24 x 365.25, where S = W/m^2 irradiated flux, A = albedo and r = radius.
Total energy out over 1 year = 4.pi.r^2.E x 3600 x 24 x 365.25, where E = emitted flux in W/m^2 from the climate system.
We can cancel out pi.r^2 x 3600 x 24 x 365.25 to get:
S(1-A)/4 = E
And this is true regardless of the rotation speed of the planet. The factor of 4 is from geometry.
Technical note: A planet may never be in radiative equilibrium. That is, over any given time it may be warming or cooling. However, over any period, the energy in – energy out = energy retained. Positive energy retained will show itself as a temperature increase.
SOD #53:
“What do you believe is the equation for the emission of thermal radiation for a body of emissivity = 0.5?
If it is E = 0.5 x 5.67×10-8 x T^4 (in W/m^2) then we are in agreement.”
We don’t agree, because the body (or maybe the term emissivity) is not sufficiently defined. The problem is with the integral.
Just compare a body with an emission spectrum of 0.5 over all wavelenghts to a body with an emission spectrum of 1 over half of the (relevant) wavelengths and 0 over the other half. The integrals (and thus E) are the same but the temperatures are different. Do both bodies have an emissivity coefficient of 0.5 over all wavelenght? In my opinion they do.
Nick Stokes writes “there’s a lot to be said about clouds, bands etc. But it isn’t just mass of gas or ideal gas law. The CO2 is doing something.”
Yes, the CO2 is being a supercritical fluid at the surface at 9.2MPa and 740K where the efficiency of conduction is presumably very much higher than for CO2 as a gas. Can that effect still be ignored on Venus? It seems to be ignored in the calculations…
SOD # 55:
Maybe you missed it, but I wrote in #27:
“To be in energy balance with the sun, the Earth emits 239 W/m^2
To be in energy balance with the sun, Venus emits 158 W/m^2
You see – no “blackbody assumptions” and yet we can compare the two planets.”
-> Sure, but nobody is arguing about that.
I’m not arguing about the energy flux densities but about the therefrom supposed temperatures. You just cannot tell anything about the temperatures without many more details. You can have a planet with a near uniform temperature or a planet with a baking hot sunlit side and a freezing night side (and therefore lower average temp.). Or a planet emitting radiation over a broad band of wavelenghts with a relatively low temp, or a planet radiating over a very narrow band of wavelenghts with a relatively high temperature. But still all radiating with the same (average) energy flux density.
Chris Colose,
“I also think the sensitivity question is getting pretty boring too, but that’s me.”
I must admit to being astounded by this comment. Climate sensitivity is pretty much the whole tamale. Everything else is secondary. An accurate value for climate sensitivity matters a LOT, and for a lot of reasons. I don’t think trying to figure that out is ever going to be boring, at least for me.
Chris:
It’s a matter of timescales…ocean matters for long-term climate fluctuations (> 2 months) and is a major driver of atmospheric circulation over those periods, not so much for periods of less than 2 months, and much less so for the response of the atmosphere to diurnal forcing, for which ocean and entire atmosphere (not just ABL) are essentially decoupled.
“Science of Doom”,
I really appreciate your patience. I tried to figure things out using RTEs and MODTRAN but eventually gave up. I followed those lengthy discussions on your web site even though most of it went well over my head.
When it comes to Venus you can get the right answer using back of the envelope calculations. Given that Venus has 100% cloud cover, any outgoing radiation that has not been absorbed by the lower atmosphere is absorbed in the cloud layer. Unlike Earth there is no way for radiation from the surface to go directly into space.
Thus the outgoing radiation from Venus is determined by the temperature at the upper cloud layer and this also controls the incoming radiation owing to its high albedo. The energy balance can therefore be done on the back of an envelope. Likewise the surface temperature can be estimated by applying the adiabatic lapse rate from the upper troposphere to the ground.
Jeff is quite right when he says that the high surface temperature on Venus is inevitable given the thickness of the atmosphere (~90 bars at the surface). I can show that it would make little difference if the CO2 in the Venusian atmosphere was replaced with other gasses.
By the way, I was hoping you or Jeff Id would respond to my “Aunt Sally”. I want to know how the Earth’s steam atmosphere managed to condense into water. Or did the water arrive after our planet’s surface had cooled down?
SoD, Richard;
The factor of “4” is geometrical, but when determining an equilibrium temperature we have to be conscious of what we’re determining. If we write Te = [S(1-a)/fσ]^0.25 as the equation for our “equilibrium temperature” it only makes sense to make f=4 for a situation where the incident energy is uniformly distributed on the planetary sphere, or as I said, where dynamics spreads things out smoothly enough to allow us to define this temperature meaningfully. This is also the notation found in Selsis et al 2007 (Astronomy and Astrophysics) or in Ray Pierrehumbert’s Climate book. In the case where every part of the planet is, to a good approximation, thermally isolated from the rest and it takes very little time for each point to reach its equilibrium temperature, then it makes little sense to average the energy budget out over the whole planet’s surface.
Suppose an airless planet has very little thermal inertia and reaches 400 K at its dayside and 100 K on its nightside. In this case, we could take something like the “average temperature” of 250 K, which is only a bit colder than Earthlike and try to compute the outgoing flux from that. Another person might say, well, we know the dayside radiates at 1450 W/m2 and the night radiates at only ~6 W/m2, an average of 729 W/m2. Inverting this value would give an equilibrium T of 337 K. In neither of these cases do they tell you anything meaningful about what is going on.
Consider a few practical examples of why this is meaningful:
1) We’re looking at measurements of light from some planet’s moon, and we find that a point on the day-side under the substellar point has a maximum T of nearly 380 K, somewhat like our own moon. If we think this is somewhat representative of the whole globe, we can conclude that the Moon must have either a very strong greenhouse effect or an efficient supply of interior heating. This amount of solar heating to a body with an ocean is sufficient to trigger a runaway greenhouse for Lunar or even Earthlike gravity. Our single data point of observation might then lead us in the wrong direction.
2) Suppose we’re interested in whether some newly discovered exoplanet, about 5 times the size of Earth, is potentially habitable. We want to use the presence of liquid water on the surface as a proxy for potential habitability (as is commonly done within this community, ignoring subsurface life or development of life in other solvents). The planet is far enough away that we only know its distance from the sun and the stellar luminosity– we have no information about its atmosphere. The planet is orbiting a low mass- low temperature M-dwarf star, and has rather small eccentricity, so if it’s close enough to the star in order to have liquid water rather than be in a snowball state, it’s almost sure to be tide-locked (i.e., one side in perpetual daytime and the other in permanent darkness)
A good starting point here would be to calculate its equilibrium temperature, assuming reasonable albedo limitations. If the equilibrium temperature is, say, 200 K (even for a low albedo estimate) then we can conclude it may not be habitable or at least its habitability depends on the strength of the greenhouse effect. For sufficiently low stellar insolation, any prospective greenhouse effect from CO2 will condense out on the surface rather than accumulating in the atmosphere. For a pure N2 infrared-transparent atmosphere, the globally averaged equilibrium surface temperature cannot substantially exceed the calculated temperature. However, the temperature on the dayside, at the subsolar point may approach 273 K rather easy. If even a fraction of the planet along the tropics is in an open-water regime, this could be considered a potentially habitable state (especially if our planet is larger than Earth, a small fraction of an open water pool can actually correspond to a rather large area); recommendations for future extrasolar planetary studies to look at this planet in more detail will be that much convincing to the funding board.
GallopingCamel,
Your reasoning is rather circular. If you know the temperature and altitude at a point in the sky, and if you know the temperature profile is dry adiabatic, then you can extrapolate down and find the surface temperature? Sure, I agree, but what determines the height of the cloud layer or the temperature near that point.
It isn’t simple. Venus is very hard to model radiatively and I would challenge you to build a radiative-convective model from scratch that can reproduce its spectra and temperature structure. Clouds are only part of the story on Venus, and to a large degree (just like on Earth) the albedo vs. greenhouse effect cancel to first order. Therefore they can’t be the cause of the high surface temperature, but they help in some transparent gaps in the CO2 spectrum (along with water vapor and SO2). You also need to get the radiation within the clouds right. For that matter, there’s three primary cloud decks on Venus at different altitudes, and they form by different processes. The lower ones are more convective in nature and exhibit more convective-induced variability like Earth, while many in the upper deck are photochemically produced.
Google some work by David Crisp for some good radiation literature on Venus. Otherwise, people who think CO2 doesn’t matter much on Venus are just spewing wingnut views that have zero support in the literature.
Chris Colose,
Rubbish! Nothing circular about my reasoning. My answer gives me a warm feeling because it agrees with the Jenkins et al. (1995) measurements.
We have been through this before. Lest you forget here are a couple of links to remind you:
http://scienceofdoom.com/2010/06/12/venusian-mysteries/#comment-2953
http://scienceofdoom.com/2010/06/12/venusian-mysteries/#comment-2969
You seem to have a “Thing” for CO2. The so called “Greenhouse” effect works just fine without CO2 and its strong absorption around 15 microns. What matters most is the mass of the atmosphere.
Chris Colose,
No circularity here! First I calculated the effective temperature of the Venusian cloud tops.
Science of Doom uses slightly different numbers, so let’s adopt his figures:
QUOTE (Science of Doom, June 12, 2010)
In any case, it turns out that Venus has a much higher albedo than the earth, with an albedo of 0.76 – meaning that 76% of the solar energy is reflected. Redoing the calculation, E = 2,636 * (1-0.76) / 4 = 158 W/m² – which equates to an “effective radiating temperature” of 230K (-43°C).
UNQUOTE
According to Jenkins (1995) the cloud tops are ~58 km above the surface of Venus. The theoretical adiabatic lapse rate for CO2 on Venus is 10.5 Kelvin/km. Thus using the back of only one envelope we have:
Venus surface temperature = 230 + (58 x 10.5) = 839 Kelvin
This is 89 Kelvin higher than the ~750 K measured surface temperature. The likely reason for the error is that there are traces of water and sulphuric acid in the Venusian atmosphere. “Wet” lapse rates are lower than “Dry” lapse rates.
How much closer can you get using your more complex approach?
“How much closer can you get using your more complex approach?”
I think you might be able to remove several kms from the effective atmospheric height that is actually CO2 as a supercritical fluid and not “atmosphere”. It must be more like an ocean and I do wonder how optically opaque it would be. Does light get to the “surface” at all?
2 + 2 = 2 X 2 = 4
Therefore, 3 + 3 = 3 X 3
Why would you need ANYTHING more complex than addition? My method works!
Anonymous:
As I understand it, the gas giants (at least Jupiter anyway) radiate more heat than they absorb. Where does that heat come from? Certainly one would imagine they have had long enough to reach thermal equilibrium (4 billion years or so).
Your understanding is correct. The same applies to Saturn, and especially to Neptune. It happens to Uranus as well, but to a lesser extent (the emitted radiation is about 110% that of the absorbed radiation, the other planets have an infrared excess of almost a factor of two, or in Neptune’s case, about 2.5). The cause of this is so-called Kelvin-Helmholtz contraction ( http://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_mechanism ), a form of interior heat flow. Similar arguments would apply to Earth without a surface, except in this case it would be radioactive decay providing the energy deficit, rather than gravitational contraction. But for the rocky planets, this flux is negligible compared to the energy received from the sun. The energy balance is different in the outer part of the solar system though.
Chris Colose,
Jeff Id was ridiculing your CO2 fixation when he said:
“Is there a single gas in the known universe which wouldn’t cause a hot Venus surface? Better yet, one wonders if Chris would still blame any trace amounts of CO2?”
Thus far you have come up with absolutely nothing to justify your dumb statements that triggered Jeff’s BS detector and mine too.
In spite of your advanced degrees I feel great sympathy for your gullible students at UW Madison. You have a long way to grow before you are big enough to admit you are wrong.
TimTheToolMan said:
“Does light get to the “surface” at all?”
While this is “Off Topic”, it is an interesting question, closer to my area of expertise (quantum electro-optics). Owing to the great thickness of the Venusian atmosphere, Rayleigh scattering strongly attenuates the shorter visible wavelengths. Sufficient longer wavelength visible radiation reaches the surface to allow colour photographs to be made, so two Venera space vehicles were able to transmit colour photographs in 1982. The transmissions were brief as the electronics could only be protected from the 750 Kelvin surface temperatures for a short time.
Outgoing radiation from the surface peaks in the infra-red region and there are “Windows” for outgoing radiation at some of these wavelengths. These windows permit surface hot spots to be seen (e.g. volcanoes) but they are relatively weak so the energy directly radiated from the surface to space does not materially affect the radiative energy balance of the planet. That is why it is a waste of time to apply sophisticated RTE analysis to Venus when estimating surface temperature.
The situation is quite different on Earth owing to the much greater transparency of our atmosphere.
Camel,
I will make this my last comment to you, and let you rejoice in having the last word. I have also taken the liberty of supplementing this post (at the end) of several quotes from refereed documents and by researchers/teams who actually study Venus, just in case third parties are confused and happen to be deriving information from whoever here happens to be the most articulate. Most of these are saved to my favorites so hopefully they become a handy one-stop shop as well for people actually interested in Venus. I’m sure GallopingCamel can explain why they are all wrong of course, since his high school algebra skills apparently have more explanatory and predictive power in determining profiles of temperature, heating and cooling rates, condensation levels for various gases, tropopause height, measurements of radiant spectra, etc., and can outperform some of the most sophisticated models in the world used for determining these things. I find debating this point ridiculous, and it draws attention away from more substantive questions/comments others have raised (which I am sure is partially the intention). I do not personally feel the need to “justify” my defense of radiative transfer theory and elementary principles of energy balance or thermodynamics, much of which I have blogged about, and SoD has also done as well. The derivation and physical basis behind the adiabatic lapse rate and ideal gas law can be found in any elementary textbook on the subject, and in no case with the discussion defend your absurd theories which violate basic energy conservation principles. Nor does the graph from “Jenkins et al 1995,” which as far as I can tell is just a GIF image you found on the internet and is not surrounded by any context, so you cannot possibly tell what the author was trying to convey.
I will also say that I believe the reason GallopingCamel flunked thermodynamics is not because he is “dumb”, but because he is too lazy to do any real reading on what he is talking about, and finally met someone (a physics professor) who he was unable to apply lawyer skills with. There are several people here (myself, SoD, Nick Stokes) who at least know enough not to be fooled by an articulate voice, and that can only be obtained by taking out a few months of time and working through some standard textbooks or perhaps relevant review articles on climate, some good resources I have already frequently mentioned.
For my supplement, as promised:
On the global scale, Venus’s climate is strongly driven by the most powerful greenhouse effect found in the Solar System. The greenhouse agents sustaining it are water vapour, carbon dioxide and sulphuric acid aerosols.
http://www.esa.int/esaMI/Venus_Express/SEMFPY808BE_0.html
The high temperature of the Venus surface results from the powerful greenhouse effect maintained by the presence of certain gases (CO2, H2O, SO2) and sulphuric acid clouds in the atmosphere (Crisp and Titov, 1997; Bullock and Grinspoon, 2001). Less than 10% of the incoming solar radiation penetrates through the atmosphere and heats the surface. However, strong absorption by gases and clouds prevents thermal radiation, which cools the surface, from escaping to space. The result is a temperature difference of 500K between the surface and the cloud tops
http://adsabs.harvard.edu/abs/2007P%26SS…55.1636S
We find that the observed surface temperature and lapse rate structure of the lower atmosphere can be reproduced quite closely with a greenhouse model that contains the water vapor abundance reported by the Venera spectrophotometer experiment. Thus the greenhouse effect can account for essentially all of Venus’ high surface temperature. The prime sources of infrared opacity are, in order of importance, CO2, H2O, cloud particles, and SO2, with CO and HCl playing very minor roles.
Radiation plays an important role in various processes on the planets. It defines temperature structure, controls photochemistry, induces atmospheric motions…In the lower atmosphere the balance between solar heating and thermal cooling results in very str
http://www.agu.org/pubs/crossref/1980/JA085iA13p08223.shtml
http://www.ep.sci.hokudai.ac.jp/~mym/OLD/Venus/Rad_Venus_Wrkshp.doc
Venus Express brings into focus the evolutionary paths by which the climates of two similar planets diverged from common beginnings to such extremes. These include a CO2-driven greenhouse effect…The extreme climate at the surface of Venus, driven by this excess of CO2 in the atmosphere, reminds us of pressing problems caused by similar physics on Earth.
Click to access venus.pdf
The present climate of Venus is controlled by an efficient carbon dioxide–water greenhouse effect and by the radiative properties of its global cloud cover….An efficient greenhouse effect prevails, sustained by an atmosphere whose major constituent is a powerful infrared absorber.
http://linkinghub.elsevier.com/retrieve/pii/S0019103500965709
“…For example, both Venus and Earth have similar effective temperatures (220K and 255K, respectively), but vastly different surface temperatures (730K and ,290K, respectively), owing to the divergent greenhouse gas column abundances”
Click to access marais_astrobiology_extrasolar.pdf
Presently, the surface of Venus is about 735 K, with a 92 bar carbon dioxide-nitrogen atmosphere. An efficient greenhouse effect prevails, sustained by an atmosphere whose major constituent is a powerful (and on Earth, troublesome) infrared absorber…Higher carbon dioxide pressure means a broadening of absorption bands and in increase in infrared opacity and the greenhouse effect.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.75.6539&rep=rep1&type=pdf
…Venus, with its dense, highly absorbing carbon dioxide atmosphere, has a large mean radiating height and a very strong greenhouse effect
Click to access Mitchell%201989.pdf
…Indeed, the thick infra-red absorbing atmosphere of Venus explains why its surface temperature is an uninhabitable 447° C
http://books.google.com/books?hl=en&lr=&id=SWFSXRv21_4C&oi=fnd&pg=PA1&dq=greenhouse+effect+on+venus&ots=_GVfEVsaTE&sig=2GHLrk3kksva3l9nRqufI07pxmM
The climate on Venus today is controlled by two main processes: global warming, largely resulting from the greenhouse effect of CO2, and cooling, owing to the reflection of solar radiation by the thick clouds of sulphuric acid
The greenhouse effect, whereby short-wavelength solar radiation heats the lower atmosphere more easily than the longer thermal wavelengths can cool it, raises the surface temperature significantly above that which would apply on an airless planet. The effect is particularly extreme for Venus, where the surface temperature must rise to 730 K in order to force enough IR cooling to balance the incoming solar energy
http://www.sciencedirect.com/science/article/pii/S0032063306001553
A much stronger greenhouse effect is observed on Venus where the 96% concentration of carbon dioxide in the atmosphere results in a troposphere that is more than twice as warm as Earth’s and a thermosphere that is 4–5 times cooler
Click to access angeo-26-1255-2008.pdf
Camel,
I will make this my last comment to you, and let you rejoice in having the last word. I have also taken the liberty of supplementing this post (at the end) of several quotes from refereed documents and by researchers/teams who actually study Venus, just in case third parties are confused and happen to be deriving information from whoever here happens to be the most articulate. Most of these are saved to my favorites so hopefully they become a handy one-stop shop as well for people actually interested in Venus. I’m sure GallopingCamel can explain why they are all wrong of course, since his high school algebra skills apparently have more explanatory and predictive power in determining profiles of temperature, heating and cooling rates, condensation levels for various gases, tropopause height, measurements of radiant spectra, etc., and can outperform some of the most sophisticated models in the world used for determining these things. I find debating this point ridiculous, and it draws attention away from more substantive questions/comments others have raised (which I am sure is partially the intention). I do not personally feel the need to “justify” my defense of radiative transfer theory and elementary principles of energy balance or thermodynamics, much of which I have blogged about, and SoD has also done as well. The derivation and physical basis behind the adiabatic lapse rate and ideal gas law can be found in any elementary textbook on the subject, and in no case with the discussion defend your absurd theories which violate basic energy conservation principles. Nor does the graph from “Jenkins et al 1995,” which as far as I can tell is just a GIF image you found on the internet and is not surrounded by any context, so you cannot possibly tell what the author was trying to convey.
I will also say that I believe the reason GallopingCamel flunked thermodynamics is not because he is “dumb”, but because he is too lazy to do any real reading on what he is talking about, and finally met someone (a physics professor) who he was unable to apply lawyer skills with. There are several people here (myself, SoD, Nick Stokes) who at least know enough not to be fooled by an articulate voice, and that can only be obtained by taking out a few months of time and working through some standard textbooks or perhaps relevant review articles on climate, some good resources I have already frequently mentioned.
For my supplement, as promised ( I have removed the html:// part at the beginning, or the first “w” in triple “www” to avoid getting caught in spam):
On the global scale, Venus’s climate is strongly driven by the most powerful greenhouse effect found in the Solar System. The greenhouse agents sustaining it are water vapour, carbon dioxide and sulphuric acid aerosols.
ww.esa.int/esaMI/Venus_Express/SEMFPY808BE_0.html
The high temperature of the Venus surface results from the powerful greenhouse effect maintained by the presence of certain gases (CO2, H2O, SO2) and sulphuric acid clouds in the atmosphere (Crisp and Titov, 1997; Bullock and Grinspoon, 2001). Less than 10% of the incoming solar radiation penetrates through the atmosphere and heats the surface. However, strong absorption by gases and clouds prevents thermal radiation, which cools the surface, from escaping to space. The result is a temperature difference of 500K between the surface and the cloud tops
adsabs.harvard.edu/abs/2007P%26SS…55.1636S
We find that the observed surface temperature and lapse rate structure of the lower atmosphere can be reproduced quite closely with a greenhouse model that contains the water vapor abundance reported by the Venera spectrophotometer experiment. Thus the greenhouse effect can account for essentially all of Venus’ high surface temperature. The prime sources of infrared opacity are, in order of importance, CO2, H2O, cloud particles, and SO2, with CO and HCl playing very minor roles.
ww.agu.org/pubs/crossref/1980/JA085iA13p08223.shtml
Radiation plays an important role in various processes on the planets. It defines temperature structure, controls photochemistry, induces atmospheric motions…In the lower atmosphere the balance between solar heating and thermal cooling results in very strong (~500K) greenhouse effect caused by the presence of CO2, H2O, H2SO4 (clouds) and other “greenhouse” species.
ww.ep.sci.hokudai.ac.jp/~mym/OLD/Venus/Rad_Venus_Wrkshp.doc
Venus Express brings into focus the evolutionary paths by which the climates of two similar planets diverged from common beginnings to such extremes. These include a CO2-driven greenhouse effect…The extreme climate at the surface of Venus, driven by this excess of CO2 in the atmosphere, reminds us of pressing problems caused by similar physics on Earth.
physics.gmu.edu/~mjordan/venus.pdf
The present climate of Venus is controlled by an efficient carbon dioxide–water greenhouse effect and by the radiative properties of its global cloud cover….An efficient greenhouse effect prevails, sustained by an atmosphere whose major constituent is a powerful infrared absorber.
linkinghub.elsevier.com/retrieve/pii/S0019103500965709
“…For example, both Venus and Earth have similar effective temperatures (220K and 255K, respectively), but vastly different surface temperatures (730K and ,290K, respectively), owing to the divergent greenhouse gas column abundances”
cips.berkeley.edu/events/discussion_group_2003_spring/marais_astrobiology_extrasolar.pdf
Presently, the surface of Venus is about 735 K, with a 92 bar carbon dioxide-nitrogen atmosphere. An efficient greenhouse effect prevails, sustained by an atmosphere whose major constituent is a powerful (and on Earth, troublesome) infrared absorber…Higher carbon dioxide pressure means a broadening of absorption bands and in increase in infrared opacity and the greenhouse effect.
ttp://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.75.6539&rep=rep1&type=pdf
…Venus, with its dense, highly absorbing carbon dioxide atmosphere, has a large mean radiating height and a very strong greenhouse effect
ww.webpages.uidaho.edu/envs501/downloads/Mitchell%201989.pdf
…Indeed, the thick infra-red absorbing atmosphere of Venus explains why its surface temperature is an uninhabitable 447° C
books.google.com/books?hl=en&lr=&id=SWFSXRv21_4C&oi=fnd&pg=PA1&dq=greenhouse+effect+on+venus&ots=_GVfEVsaTE&sig=2GHLrk3kksva3l9nRqufI07pxmM
The greenhouse effect, whereby short-wavelength solar radiation heats the lower atmosphere more easily than the longer thermal wavelengths can cool it, raises the surface temperature significantly above that which would apply on an airless planet. The effect is particularly extreme for Venus, where the surface temperature must rise to 730 K in order to force enough IR cooling to balance the incoming solar energy
ww.sciencedirect.com/science/article/pii/S0032063306001553
A much stronger greenhouse effect is observed on Venus where the 96% concentration of carbon dioxide in the atmosphere results in a troposphere that is more than twice as warm as Earth’s and a thermosphere that is 4–5 times cooler
ww.ann-geophys.net/26/1255/2008/angeo-26-1255-2008.pdf
* Jeff you can remove my in moderation comment if you want, I just modified the links and fixed a couple pasting issues
By the way, yes, some sunlight does get to the surface of Venus. It’s just a trickle (~10%). I leave it as an exercise to you two to figure out why it’s a pretty important trickle.
Oh, I thought I had just logged onto Climate Audit instead of The Air Vent on this newfangled Internet doohickey thingamajig. And initially I was going to congratulate him for finally showing some semblance of raw emotion, but I also felt let down by his sudden lack of tight game, his lack of princehood. Ah, it’s just he Air Vent. I see. What else is going on out here, I wonder?
Chris Colose,
I too have a physics degree. I have spent many years on cutting edge physics research and I still teach. Unlike you I recognize my limitations.
At the start of each class I provide my students with a few cans of air freshener labeled as “BULLSHIT REPELLANT”. The idea is to encourage the students to think for themselves and spot any mistakes that I may make.
In academia it is OK to make bone headed statements and then double down when someone calls you. At the end of the day the worst that can happen is that someone’s mighty ego may get bruised.
Jeff Id and I have both worked as engineers in fields where the stakes are a little higher. If we screw up, money will be lost, lives will be lost.
I must admit to having taken advantage of you when I realized you are full of arrogance and youthful certainty just as I was 50 years ago. In the spirit of fairness, here is a link that will allow you to aim your barbs with greater accuracy than you did in comment #71 above.
http://bravenewclimate.com/2011/05/15/solar-power-in-florida/
I hope to make this a “Teachable Moment” but that will depend on you.
“By the way, yes, some sunlight does get to the surface of Venus. It’s just a trickle (~10%).”
Let me ask you this Chris… How different do you think earth would be if instead of heating the top of our ocean, the heating happened at the bottom?
The differences here could perhaps be settled with a request for temperature profile data from the operators of the HVAC system at the TauTona Mine in South Africa (http://en.wikipedia.org/wiki/TauTona_Mine).
At 3.9km deep, THE AIR supply VENT down to the bottom could serve as a 1:25 scale model of sorts to Leonard Weinstein’s tall room at SOD’s (http://scienceofdoom.com/2010/08/16/convection-venus-thought-experiments-and-tall-rooms-full-of-gas/). The roof over the mine entrance would perhaps roughly approximate Weinstein’s optical barrier.
In the the data request, it should perhaps be specified the time period shortly after the supply fan is shut off is of particular interest. Presumably, during normal flow a temperature lapse rate would be maintained. In the time period after this large convection is stopped, and before the air inside the duct reaches the same temperature as the surrounding exterior (let’s hope they have good insulation) we might see evidence of the temperature profile either:
1. moving toward an isothermal condition, where the top should start to warm and the bottom start to cool (if I’m understanding this correctly, this would be the position of Scienceofdoom and Chris Colose)
2. or, the temperature profile should remain steady (the position of GallopingCamel, Motl, Goddard, Jeff Id.)
(My deepest apologies if I’ve inadvertently mischaracterized anyone’s position here.)
Alternatively, a thought experiment along these lines might suffice. Then it would be easier to change the mix of gasses pumped down the supply vent.
Just a thought.
Scienceofdoom,
First, I’m sorry I missed all the fun this weekend, I should have some time later today to read the rest of the comments.
I never claimed PV=mRT was the reason for the temperature, although I have read that argument, it is incorrect. I clearly claimed that it was due to the insulating effects of the gas. Perhaps the true thinkers can find me a gas that doesn’t cause a warmer surface at 90:1 times more dense and leave my stupid head out of it. 😀
“I clearly claimed that it was due to the insulating effects of the gas.”
Except that the best insulator for convection and conduction is a vacuum. The only thing a vacuum doesn’t insulate for is radiation… which is where greenhouse gases step in.
Re: Galloping Camel and circular logic: The circularity of your logic, GC, is that you take the height of the tropopause as a given. Yes, if one knows the height of the tropopause, and the lapse rate, one can easily calculate the temperature of the surface. HOWEVER, the height of the tropopause depends on the composition of the atmosphere. An atmosphere composed of a magic gas that has no interaction with radiation of any wavelength will have a tropopause at Z=0. See Post #20, Point #2. And at equilibrium, the density of the magic gas will have no effect on the surface temperature,which will be defined solely by the absorbed radiation from the sun.
Re: Anti-AGW arguments: There are plenty of legitimate uncertainties surrounding AGW. It frustrates me that there are so many arguments over basic facts, such as the contribution of high CO2 concentrations to the heat of the surface of Venus, the contribution of human emissions to increasing CO2 concentrations, or that the proper term for adding CO2 to a body of water is “acidification” regardless of whether that body of water is basic or acidic… Sometimes I wonder if people like Galloping Camel are actually serious, or if they are just pulling our chains…
-M
M,
So as I said, look up some spectral curves and show me the gas which wouldn’t cause high temps on the Venusian surface. I’m curious if there is a non-greenhouse gas for Venus that the CO2 mongers know of.
@Jeff Id
In the shotgun blast of links emanating from the keyboard of Chris Colose in the direction of GallopingCamel (comment 71), a good number of them appear to simply repeat Venus-is-hot-due-to-CO2 claim.
However, there is at least one BB which appears to head in the general direction of the heart of the issue. On page 74 of the Bullock dissertation (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.75.6539&rep=rep1&type=pdf) Tables 2.4 and 2.5 list changes in Venus surface temperature predicted from the replacement of various gasses with nitrogen. The 400K+ reduction in surface temperature listed for the removal of CO2 appears to be in direct conflict with your statement –
“if you replaced Venus’s atmosphere with one of Earth’s composition, you would still have plenty of heat at the surface -even if you took the CO2, Water and Methane out.”
In order for your statement to be true, it appears to me there would have to something very wrong with the analysis behind those tables.
Publius_lxxii, that reference also has a nice review of the theory as well as these calculations. I found it to be very approachable.
Here is the tables in question.
This is pretty unambiguous: If Bullock is right, Jeff is wrong.
publius_lxxii,
Actually, you need to read that paper more closely. You did a great job though finding one. I just skimmed briefly but it discusses the removal of CO2, not replacement as I have made the case above. Since CO2 is 95% of the atmosphere you won’t have much left – certainly not 90 atmospheres. The paper then makes the case for a 100 fold increase in H20 – which still doesn’t equal that of CO2 and gives a much hotter surface. It’s all silly guys, if you have 90 atmospheres of any gas, you get higher temperatures than a 1 atmosphere world. That’s because all the gasses I know have some absorption.
Check out table 2.1 for gas concentrations, ask yourself what removal of 96% of the atmosphere would do and then look at what a hundred fold increase in from 30 to 3000 parts per million water vapor does later in the paper.
Jeff, in my reading of Bullock, he replaces the gas in question with N2 so as to keep the pressure on the surface constant.
Simply removing a large portion of the gas from the atmosphere, as you suggest he and Pollack separately did, doesn’t seem like a rational exercise.
Carrick,
Can you find that in the methods. It reads to me like the absorption spectrum was completely removed. I didn’t see any replacement. Since that is 96ish percent of the atmosphere, I’m not surprised at the result.
I’m at work and still haven’t even read chris’s comments above.
Jeff,
On p 73 Bullock says that the calculations held pressure constant by increasing the mixing ratio of N2.
He shows how his calcs agree with Pollack (1980). Pollack’s paper isn’t online, but his abstract is clear:
“Thus the greenhouse effect can account for essentially all of Venus’ high surface temperature. The prime sources of infrared opacity are, in order of importance, CO2, H2O, cloud particles, and SO2, with CO and HCl playing very minor roles.”
Nick,
It looks like I was wrong then but I didn’t make the claim that CO2 wasn’t the primary source, just that any gas would also probably do it to some degree. H20 seems effective also.
Actually on second thought, I didn’t claim that other gasses wouldn’t make less warming either. I am surprised at so much difference but whatever, my point is that all gasses create warming – especially at 90 atmospheres and the Venus CO2 example is silly. If it were H20 or CH4 at those densities, it would also be hotter than heck.
Actually Jeff, I’m inclined to agree with you here. However, if I can be convinced that you (and by extension I) are in the wrong, I’d rather start wolfing down the crow pie sooner rather than later.
The nagging question in my mind is how Bullock handled convection. On page 65 he mentions dealing with the convection which arises in the process of reaching radiative equilibrium, but I’m not convinced that’s the whole story:
In Motl’s writeup on this issue last year he mentioned another rather large source of convection which, as far as I can tell, remains unaddressed by Bullock:
The end result of substantial convection, as <a href="http://scienceofdoom.com/2010/08/16/convection-venus-thought-experiments-and-tall-rooms-full-of-gas/#comment-621" Leonard Weinstein argues over at Science Of Doom, would inevitably lead to a temperature profile approximating the adiabatic:
I’ve got a sneaking suspicion that the Venusian world in Bullock’s model is far too pristine and static to provide any realistic insight to the real planet. It’s like everyday, everywhere is stuck in the stock-still doldrums.
If a radiative-convective transfer model were done the other way around – starting with a profile maintained by convective mixing, and superimposed the radiative transfers on top of that, I wonder if Tables 2.4 and 2.5 might have very different values.
Of course, as far as I know this could be orders of magnitude more difficult. Perhaps that’s why it wasn’t done.
In 19 SOD calculated a -43C temp for blackbody only at Venus. With no C02 (mostly nitrogen atmosphere) the surface temp in Carrick’s 82 link drops from about 480C (wiki) by 422.7C leaving a Nitrogen based surface temperature of 57C. This means we can estimate a 100C warming effect from a mostly nitrogen composition atmosphere.
So here are my quotes:
I knew Nitrogen would be one of the weakest which I why I said ‘just used Nitrogen’, but the atmosphere still has one heck of a lot of heating even in this example. I’m still surprised that there was so much difference but perhaps ‘wrong’ was too strong a self-critique.
It happens because the gas is incredibly dense and to my knowledge they all have some ‘greenhouse effect’ — and that is the point.
Still haven’t read the thread.
———-
UPDATE The 480C number seems a little high for the popular articles. It seems that they have settled closer to 460C on the surface of Venus so we have more accurately ~ 80C of warming from a weak greenhouse gas combination in a 90 atmosphere environment.
Jeff,
I think there would be less confusion if you’d not highlighted the following line of Chris to dispute:
We don’t often think of CO2 as a “pollutant” on Venus, yet it still allows the planet to support temperatures well above the melting point of lead or tin.
So, you now say that meant that a 90 atmosphere N2 atmosphere also produces a lot of heat, but its not even enough to boil water. I now don’t understand what exactly it was that you highlighted about what Chris wrote that you are disputing strongly.
“leaving a Nitrogen based surface temperature of 57C. This means we can estimate a 100C warming effect from a mostly nitrogen composition atmosphere.”
Except that this no-CO2 atmosphere still has H2O and Clouds, both of which contribute a decent amount to a Venus Greenhouse effect. (admittedly, pressure matters here, because 30 ppm of H2O on Venus is as much water as almost 3000 ppm of H2O on earth, and there is pressure broadening of spectral lines to boot)
Basically, homogeneous diatomics like N2, and single atom gases like Argon and Neon, have basically zero absorption in the infrared because they can never have much of a dipole moment. Heterogeneous diatomics have inherent dipole moments, and triatomics like CO2 without a dipole moment have asymmetric vibrational modes that generate temporary dipole moments (which is good enough for absorption). All of this can be derived from quantum mechanics, though it has been enough years since I took quantum that I can’t remember the details of how to do so.
Now, high-pressure N2 does apparently have some Rayleigh scattering: Bullock cites some works on this: “For the Earth’s atmosphere, Rayleigh scattering in the infrared is usually ignored. However, in the dense Venus atmosphere, Rayleigh scattering may account for optical depths in the near infrared of 1 or more [Crisp, 1986; Meadows and Crisp, 1996].” So maybe you should look at the Crisp studies, and see if they estimate a temperature increase from Rayleigh scattering alone.
But basically, to the best of my understanding, Venus would not be scalding hot without a large greenhouse gas contribution. And if that’s true, you probably owe Chris an apology.
RB,
I was pointing out that CO2 is not the only global warming gas in the universe and that it would be difficult to find one which didn’t cause a lot of warming. He was comparing it to Earth (indirectly) – which is silly because the density of the atmosphere allows the huge warming effect on Venus. Replace the CO2 with Water, Methane, whatever, and what do you get? A very hot planetary surface.
If Venus had the same gas concentrations as Earth but in Venusian mass it would be a very hot place. However, if the Earth or Venus were 96% CO2 at one atmosphere, neither planet be anywhere near today’s Venusian temps. It is a sophists argument Chris made to intentionally trick the uninformed readers and that is the kind of thing I’ve pointed out about alarmists since this blog began. The high density of the gasses is what causes the dramatic effect, it just happened to be CO2 in this case. The weak gas Nitrogen even created a ton of warming in the Venusian high density environment.
Were I an ‘expert’ in planetary atmospheres, I sure wouldn’t go around comparing the two planets with a narcissistic intent to scare people and that is exactly what Chris did. He’s learned his lessons in class well.
M,
As I pointed out nitrogen is a weak gas and I agreed with everything you wrote except -owe Chris an apology? For what? He was comparing CO2 on Venus to Earth in an AGW context for a single false purpose and he is the one who should apologize for the blatant fear mongering. His article implies that somehow the Earth could be so warm, rather than the much lower limits of a 1 atmosphere system. It is a common tactic in politics and in AGW climate science, and it is complete crap.
What a joke, he and those who would scare the public with that kind of sophistry based propaganda are the ones who should apologize to the public.
publius_lxxii,
That deep mine is not really a good way to look at the “tall room” thought experiment because the walls are not perfectly insulated as Leonard Weinstein stipulated.
The adiabatic effect (my approach) or the greenhouse gas effect (Chris Colose’s approach) are both overwhelmed by heat transfer from the walls.
M,
Here is the full quote rebolded for context:
See the point now?
M @79,
I must confess to taking the cloud top height from Jenkins 1995 and my understanding is that his graph was based on Russian measurements.
This is a nasty habit of mine; preferring measurements to theory.
However when measurements are unavailable as in the case of replacing the CO2 in the Venusian atmosphere with an equal mass of Helium I was able to estimate the cloud top height using the physical properties of the material that the clouds are believed to consist of, namely sulphuric acid. Note that with a Helium atmosphere the cloud top altitude is likely to be at ~150 km rather than 58 km:
http://scienceofdoom.com/2010/06/12/venusian-mysteries/#comment-2953
You might take a look at that “Counting cats” link
Gallopingcamel,
I wholeheartedly agree with your point on the walls of the mine. That’s why I mentioned measuring the (hopefully) well insulated supply duct, and then only for a short period of time, and during that time only hoping to see a movement toward one profile or the other.
In reality, I think the thought-experiment version might actually be more feasible.
publius_lxxii,
Ooops! There is a typo in my #98. The cloud tops should be at 550 km not 150 km.
He was comparing CO2 on Venus to Earth in an AGW context for a single false purpose and he is the one who should apologize for the blatant fear mongering
No I wasn’t, and any rational person who reads this article objectively would not get what you seemed to get out of it. My original purpose for the statement was merely to illustrate how labeling something a “pollutant” is not really relevant to whether CO2 can generate a greenhouse effect. But since the discussion evolved into why Venus is so hot, I thought it would be interesting to pursue people’s objections/questions because I find planetary climate very fascinating. Not everyone interested in the atmosphere is thinking of “AGW” whenever they talk. This is your blog of course, so you are welcome to use it as a place to just insult people based on odd interpretations of what they said. I don’t need any “apology” and my intent on the blogosphere is not to play “gotcha” games, but note neither your interpretation of my statements nor that of the current science (as my many links should illustrate) is correct.
Back to the science– In order to reproduce Venus’ surface temperature, you need to know what the radiation is doing, and understanding the line and continuum absorption and the spectra produced by the combination of various gases/clouds in the Venusian atmosphere. Even further, Venus generates a non-negligible IR scattering greenhouse effect too (unlike the absorption-emission greenhouse on Earth, and where we can typically neglect the IR albedo).
For a completely infrared transparent atmosphere, the equilibrium temperature will eventually relax to no more than the effective radiating temperature determined by the absorbed incoming sunlight. For Venus, water and sulfur compounds which together maintain the cloud deck on Venus also raise its albedo, so it’s very artificial to keep a truly IR-transparent atmosphere and its current effective temperature the same. As M noted, for dense enough atmospheres, the albedo gets pretty high (for Sun-like stars at least, this may not be the case for lower mass stars). A dense CO2 atmosphere like Venus has a ~40% albedo, so even without the clouds, the albedo is still higher than Earths.
Is it possible for a pure diatomic-molecule atmosphere to generate a greenhouse effect? The answer is yes, since collision-induced absorption can open up otherwise forbidden opacity from the simpler molecules; this happens on the gaseous planets, and a notable example is Saturn’s moon, Titan. These molecules also broaden the absorption features of CO2 and the more “classical” greenhouse gases, which is why N2/O2 are still important for the greenhouse effect on Earth, and also why Mars cannot generate much of a greenhouse effect even with a ~95% CO2 atmosphere.
Unfortunately, if you want to pick your atmospheric pressure/composition, stellar characteristics, and the size of your planet, you need radiative-convective models to sort through the various competitive roles of how the albedo and greenhouse effect will work out, how the absorption features of different gases overlap, where they absorb relative to where the planet emits radiation, etc. It isn’t a trivial problem, and there’s much more to it than simple algebra equations.
Chris,
You stuffed a bs reference to a planet which is a non-sequitur for Earth AGW, included the word ‘strong’ as an adjective for the greenhouse gas and pointed out that it was enough to melt lead. You are right, it is my blog, so I’ll write again that you were clearly intending to scare readers away from the possibility that Dr. Happer’s and many here have a lukewarm view of CO2 as a dominant greenhouse gas. It may very well have a weak effect rather than strong (as you assert) on Earths warming as the models are running high, the hotspot is missing and dozens of other predicted effects haven’t happened. This is because the Earth runs rather close to 1 atmosphere vs Venus’s 90.
None of your links or writing above demonstrate that my statements were incorrect regarding science, your example was a clear exaggeration of reality for anything Earth-like done specifically to make example of the ‘strong’ effect of CO2 gas. My point may have been poorly worded but it was correct in that the density of the atmosphere creates the extreme effects – not simply the 96% CO2. I am also correct that many many other gasses would do the same and more at similar mass.
I called bull and still do. Stop placing exaggerations in the middle of attacking a scientifically accurate article written by Happer and we’ll get along just fine.
The hottest places on the surface of the Earth are the lowest ones – those below sea level. How exactly does the back-radiation effect of greenhouse gases explain that.
Mount Everest (has an average mean temperature of -25C at 8,850 metres) and the Dead Sea (has an average mean temperature of 26C at -424 metres). Yet both are at the same latitude. 51C difference over only 9.2 kms difference in height. Interesting.
Jeff Id,
“Stop placing exaggerations in the middle of attacking a scientifically accurate article written by Happer and we’ll get along just fine.”
Hummm… I honestly do not think that is going to happen. Happer’s (perhaps a bit over the hill) POV of GHG warming reality is NEVER going to be compatible with Chris Colose’s and company’s view of GHG warming reality. The odd thing is this: Happer is old, and presumably inflexible (right or wrong), Colose and company are young and presumably flexible… but in reality…NOT AT ALL flexible! Nothing outside the mainstream catastrophic POV could EVER be entertained as true by Colose et al…. and that is their real weakness as scientists. And I do use the description ‘weakness’ without careful consideration.
Bill Illis, @103
That was the point of “Science of Doom’s” “Tall Room” thought experiment proposed by Leonard Weinstein. Imagine building a really deep hole with perfectly insulated walls.
I subscribe to the simple minded “Adiabatic” approach advocated by Steve Goddard, Lubos Motl, “Counting Cats in Zanzibar” and many others. We say that the temperature will increase by 6.5 Kelvin for every added kilometer of depth. Thus if you want to have a temperature that will melt lead (601 Kelvin) you dig a hole 50 km deep assuming we are talking about planet Earth at the equator. No need to go all the way to Venus.
The pressure at the bottom of that 50 km hole would be 47 bars (cf 92 bars at the surface of Venus) and temperature ~610 Kelvin, assuming that the relative humidity is low (dry adiabat).
If you dig a similar hole on Venus you can expect a larger temperature increase as the dry adiabatic lapse rate for CO2 on Venus is 10.5 Kelvin/km. At the bottom of that 50 km hole, look for 750 + 10.5 x 50 = 1,275 Kelvin.
I would like to hear what Chris Colose predicts and why.
Steve Fitzpatrick @104,
You have a great point. When it comes to physics us grey beards can be a real barrier to progress.
Remember the brilliant William Thompson (Lord Kelvin) who became a liability in his later life with statements like this:
“There is nothing new to be discovered in physics now, All that remains is more and more precise measurement.”
As one gets older it is more difficult to embrace new ideas. For example, I have eleven patents but not one in the last 35 years and I still have trouble with enthalpy, entropy, tensors and matrix algebra. That is why my advanced degree is in electrical engineering rather than physics.
My little spat with Chris Colose stems from the brash arrogance of youth versus the capabilities of someone who is past his prime. I suspect Chris and I could enjoy a beverage together. That said he is still WRONG!
Camel #105, here it is in electrical terms. The adiabat is like a chain of batteries in series. Temp gradient (g/cp=10 K/km) — voltage gradient. With GHG’s, the battery chain is earthed at TOA. That’s where IR is mostly emitted and you have a voltage-current fixing point – Stefan-Boltzmann related heat-flux to temp. The slope of that dependence is the impedance, so it’s a “resistive earth”.
It’s a bit more complicated, because there is another resistive relation at the bottom relating to the atmospheric window frequency band. Another S-B relation. But the window is small, specially on Venus, so the TOA earthing dominates, and the voltage gradient in the battery chain settles accordingly.
But with no GHG’s, TOA is insulated. Infinite impedance – there can be no heat flux within the gas. There is of course IR flux, but it doesn’t interact.
The bottom, however, has a low impedance earthing from S-B. In fact, with no GHG this is a true earth (no pun). The temp is fixed by the flux. And the voltages in the battery chain (adiabat) are set relative to it.
So you can’t just say that mass of gas determines temperature. It determines the number of batteries in the chain. But then it depends on the earthing.
Chris,
“Unfortunately, if you want to pick your atmospheric pressure/composition, stellar characteristics, and the size of your planet, you need radiative-convective models to sort through the various competitive roles of how the albedo and greenhouse effect will work out, how the absorption features of different gases overlap, where they absorb relative to where the planet emits radiation, etc. It isn’t a trivial problem, and there’s much more to it than simple algebra equations.”
Yet the modelers, and you, seem to think you know how to compute this even though new papers come out pointing out “features” of our physical world that have not been taken into account in previous guesstimates. Which “features” are you missing Chris???
Jeff $91,
I’d still go with SoD’s -43C figure that I quoted in #14. Bullock quotes a no CO2 figure, but as M said that is with the other GHG’s remaining. SoD’s figure is with no absorption, which I think is what you intended with N2. M #93 suggests an IR OD of about 1 for N2 – if so, that implies a GHE somewhat less than we have on Earth, so the temp would still be below freezing.
In fact, Bullock also does SoD’s calc on p 22, following Eq 2.2 (he gets -41C).
So how is it that radiation plays a part at “the surface” at all? I can see that the IR emitted from the true surface would be absorbed immediately by the CO2 above it but then the CO2 is essentially a liquid and so I would have expected the radiation cant really penetrate anywhere in the same way IR cant penetrate water.
So once the radiation is absorbed directly above the surface, the primary mechanism for moving the heat must surely be conduction and perhaps convection which I believe supercritical CO2 is very good at.
And thats going to be the case for several kilometers above the surface. Is it not largely that the CO2 nearer to the surface has sufficient heat capacity and is heated from below that causes the massive heating effect?
I guess I’m saying that the “atmosphere” of Venus has no bearing to the atmosphere of earth in any way and to suggest similarities is simply not useful.
Nick,
I can’t follow your reasoning in 109. I am guessing that N2 alone still contributes more GHE than earth’s entire atmosphere with the pressure of Venus. I was surprised that it didn’t contribute more but it doesn’t change my contentions with Chris’s characterization’s of the nature of CO2 on Earth.
Others,
The surface pressure is 93 times that of Earth on Venus. Venus’s gravity is 8.87 m/s^2 whereas earths is 9.78 or about 10% greater. Venus has a surface pressure of 93 Earth atmospheres so we can calculate 93*9.78/8.87 = 102 times the mass of Earth’s gaseous atmosphere. If we divide Venus’s gas atmosphere into 102 separate layers assuming each has the same conditions as the others, each layer has an equivalent (similar) capacity for global warming to Earth’s own due to upwelling infrared radiation. An interesting number might be an estimate of how much warming does each Earth mass layer of Venusian gas create?
My contention is that the density of Venus’s atmosphere creates a greenhouse effect ‘capacity’ equal to approximately 102 times anything achievable at Earth’s surface. Using SoD’s ‘venus has no atmosphere’ -43 C blackbody calculation from the thread above and the actual surface temperature on Venus of 460C we see that Venus has an approximate 500C greenhouse effect from its gasses which are mostly CO2.
If we divide 500/~100 we get a total greenhouse effect from an Earth thick layer of 96% C02 of only 5C, whereas Earth with its comparatively moist atmosphere runs at about 33C of GHE by some calcs which shows that some other strange and rare gas like dihydrogen monoxide is probably a lot stronger greenhouse gas than CO2. What is also interesting is that from the table Carrick linked in #82, the CO2 creates an estimated 422C of those Venusian degrees so the total CO2 contribution of an Earth atmosphere that was a massive 96 percent CO2 would be about 422/102 or 4.2C – according to this simplified Venus model.
In other words, the melting of lead on Venus is not simply related to the huge concentrations of CO2 but due to the huge density of the atmosphere and the CO2. Also, Venus should be glad that the gas in the atmosphere isn’t water.
Nick Stokes @107,
I don’t deny that there is more than one way to skin a cat. You use your method and I use mine.
I can’t improve on what I said a year ago on “Science of Doom” to Chris Colose:
Planck and Shreodinger had a “failure to agree” over the nature of light. Particles or Waves? It turned out that both were right. Professor Gilbert Stead summed it up in doggerel:
QUOTE
There would be a mighty clearance,
We should all be Planck’s adherents
Were it not that interference
Still defies h “nu”
UNQUOTE
Your “Greenhouse Effect” theory does not work without the adiabatic lapse rate which allows the radiative layers to be cooler than the surface of a planet. Make peace with Goddard and Lubos Motl.
gallopingcamel #105,
Assumming that the 50 Km deep hole was wide enough to allow solar energy to enter and for heat to escape via convection and IR radiation (through the atmospheric window, http://upload.wikimedia.org/wikipedia/commons/6/6a/Atmosfaerisk_spredning.gif ), and assuming that you insulated the hole from the heat of the Earth, then yes, it would be very hot 50 Km below Earth’s surface, as you can estimate from the lapse rate. You need only descend in an airplane or hike down into the Grand Canyon from the south rim to verify that warming with decreasing altitude is quite real. But the lapse rate is a consequence of upward heat flux, not a cause of heating. On a still night in the desert, the air near the ground becomes much cooler than the air 100 meters up, because radiational cooling (through the atmospheric window) cools the ground and the air close to it. Under those circumstances, there is an inverse temperature gradient… a positive lapse rate in the surface layer, because the temperature of the surface is lower than the air above (adiabatically stable; no convection). When the sun comes up the next morning, the surface warms and the air near the surface warms via convection, gradually re-establishing a the normal decline in temperature with altitude. It is the atmosphere’s resistance to the passage of heat, combined with adiabatic heating/cooling due to pressure change, that establishes the lapse rate. Your 50 KM deep hole would not get hot (save for the local heat of the Earth at that depth!) if all sunlight were blocked from entering.
Steve Fitzpatrick @113,
The error in your thinking is summed up in your final sentence:
“Your 50 KM deep hole would not get hot (save for the local heat of the Earth at that depth!) if all sunlight were blocked from entering.”
That is complete nonsense. If the hole were dug on Venus where the atmosphere is so thick that less than 10% of the sun’s radiation reaches the surface, the lapse rate would still apply all the way to the bottom of that 50 km hole.
Remember that the lapse rate can be correctly derived using only gas equations and a gravitational field. No need to invoke external heat sources or Radiative Transfer Equations.
The lapse rate defines the temperature gradient within a planet’s atmosphere but one needs to define some boundary condition in order to calculate the temperature at the surface (e.g the temperature at the cloud tops that can be estimated using Stephan’s equations for energy transfer).
For a better explanation I recommend this:
http://www.countingcats.com/?p=4745
Steve Fitzpatrick, 113,
The key word there is “still.” As you allude, when there’s no substantial convection, radiative transfer dominates the temperature profile.
However, when there is substantial convection (like that almost always seen on a planet with uneven solar heating ) the temperature profile tends to approximate the adiabatic.
When the otherwise-stable arrangement of parcels in an inversion is mixed up by the vertical components of eddies from horizontal winds, their potential temperatures get evened out from the mixing.
In the case of hypothesizing 93 earth-like atmospheres on Venus, the big question is whether the weather would disappear if the GHG concentration were reduced.
As I mentioned in comment 90 , I can’t see where they even addressed these additional sources of convection (and the resulting tendency toward the adiabatic) in the analysis which claimed a 400K+ reduction in surface temperature from replacement of CO2 with N2.
I suspect a definitive answer to this big question might lie outside current human analytical capabilities .
gallopingcamel #114,
“If the hole were dug on Venus where the atmosphere is so thick that less than 10% of the sun’s radiation reaches the surface, the lapse rate would still apply all the way to the bottom of that 50 km hole.”
I did not say anything about a hole on Venus. On Venus, the atmosphere is opaque (essentially 100%) to all infrared. On Earth, there is a substantial radiative window (as shown in the graphic I linked to). If the sun is not allowed to warm the bottom of the 50 KM hole, then radiative heat loss would cool the bottom of the hole. Now if the hole were so large that atmospheric turbulence allowed rapid turn-over of the air within the hole, that would be more complicated. But for the simple case, if solar heating is eliminated the hole would become adiabatically stable (no convection) and the bottom would cool relative to the surface.
Your analysis of the processes involved in establishing the lapse rate is incorrect.
Steve Fitzpatrick @116,
The hole is 50 km deep with perfectly insulated walls. Now a add a metal lid that is maintained at a constant temperature of 288 Kelvin (Earth’s average temperature at ground level). This serves the purpose of setting a boundary condition, defining the temperature at the top of the hole,just as the cloud tops do in the “Counting Cats” link I sent you.
Assume that there is a small hole in the metal lid so that pressure can equalise. This sets another boundary condition so that the pressure at the top of the hole is 1 bar.
The metal lid eliminates any influence due to direct solar radiation.
At equilibrium, the temperature at the bottom of the hole will be determined as shown in @105 above so it will be hot enough to melt lead.
Where is that heat coming from? If any heat needs to be added or removed it can only come from that metal plate at the top of the hole.
How is the heat being transported inside the hole? I would contend that convection is the major player but radiation and conduction will also have some part to play. On “Science of Doom” there was a discussion of the relative contributions of these processes. That may affect the time it takes to reach equilibrium but not what the equilibrium state will be.
TimTheToolMan, @110,
Carbon dioxide is strange stuff as it sublimes at around -78.5 Centigrade at 1 bar pressure.
The cloud tops on Venus appear to be quite cold @ -30 Centigrade not too different from Earth’s, so even there the CO2 is nowhere near a change of state. As one descends through the Venusian atmosphere temperatures rise so CO2 is even further removed from liquifying or freezing.
@Camel
“As one descends through the Venusian atmosphere temperatures rise so CO2 is even further removed from liquifying or freezing.”
Beyond 7.39MPa and about 300K CO2 becomes a supercritical fluid.
http://en.wikipedia.org/wiki/Supercritical_carbon_dioxide
At the surface of Venus its 9.2MPa and 740K…so well and truely a supercritical fluid. Not a “gas” and not capable of transmitting radiation.
TimTheToolMan @119,
If there is one thing that Chris Colose and I can agree on it is that some of the sun’s radiation reaches the Venusian surface so the bottom of the atmosphere is capable of transmitting radiation.
If you need proof of this two Russian space vehicles landed in Venus in 1982 and they sent back photographs using the visible spectrum (400-700 nm).
gallopingcamel #117,
My friend, you are simply mistaken about this. The temperature inside the hole would slowly but surely settle at a constant value, and that would be the same as the metal lid… 288K. There is no possibility of maintaining a higher temperature at the bottom than at the top unless heat is added to the bottom, because if the initial temperature anywhere inside were >288K, that heat would be gradually lost to the metal lid. The lapse rate does not cause heating, the lapse rate is the minimum temperature gradient that causes convective instability, and is always a consequence of heating from below (OK there are a few circumstances, like Chinook winds, where the situation is a bit more complex, but not inside the thought experiment you describe).
Add one thing to the thought experiment. Suppose I place at the bottom of the hole a cooling coil, and remove heat from the air at the bottom of the hole. As the temperature at the bottom falls a bit, the gas becomes a bit more dense and locally convectively stable, so heat from above can only now reach the bottom via radiation or molecular diffusion. Questions:
1) Do you think what I suggest is physically impossible?
2) If so, how do you account for the well known existence of thermal inversions?
3) If I stop cooling, do you think the temperature at the bottom will return to the temperature predicted by the adiabatic lapse rate starting from the metal lid?
4) If so, how does that heat arrive except by radiation or molecular diffusion (remember since I have created a temperature inversion there can be no convection… the temperature profile is convectivly stable).
5) Since the air above the bottom is cooler than the bottom temperature was before I started cooling the bottom, (according to your lapse rate calculation), how does heat then flow from a lower temperature (the gas above) to a higher one at the bottom via radiation or diffusion? (remember without convection, there is no possibility of adiabatic heating, only radiation or diffusion; it is not possible for heat to flow from lower temperature to higher)
6) Once I stop cooling, I have removed a certain quantity of heat from the system. How can the average temperature within the hole not now be lower than it was? (That is, without a source of heat to replace what I took out, how can the average temperature not be cooler? The energy has to come from somewhere.
gallopingcamel,
“On “Science of Doom” there was a discussion of the relative contributions of these processes.”
Yes. I read that very long thread; only Arthur Smith had it right. Even SoD and DeWitt seemed a bit confused…. and for DeWitt, that is very rare.
Camel writes : “If there is one thing that Chris Colose and I can agree on it is that some of the sun’s radiation reaches the Venusian surface so the bottom of the atmosphere is capable of transmitting radiation.”
Yes, but not in the IR. It makes Venus’ atmosphere quite different to earth’s. As far as I can tell it makes Venus’ “atmosphere” within several kilometers of the surface more like earth’s ocean except its heated from both below and above and is a much better thermal conductor with about a quarter of the heat capacity (still a lot).
We usually think of the earth’s surface as being the surface of the land and the surface of the ocean. Thats not the case for Venus.
The point of all this is that there are absolutely fundamental differences between Earth and Venus and so no comparison between the two can be sensibly made particularly with respect to CO2’s role in the atmosphere.
I suggest that the bloggers read the article of Joseph Postma:
Click to access Understanding_the_Atmosphere_Effect.pdf
gallopingcamel said
“some of the sun’s radiation reaches the Venusian surface
If you need proof of this two Russian space vehicles landed in Venus in 1982 and they sent back photographs using the visible spectrum (400-700 nm).”
There are several reports that electrical activity in the atmosphere causes this light, have you ruled this out?