Titan is my new favourite moon/planet. It orbits Saturn, is a bit bigger than our Moon, and has an atmosphere that is strikingly similar to Earth's - it's mainly N2, with 5.65% CH4 to spice things up - with a surface pressure 1.48 times as much as Earth's surface pressure.
Harry Dale Huffman pointed out that comparing the surface temperatures of Venus with the surface temperature of Earth 288K is a diagonal comparison. Venus' surface temperature is ~737K, largely because atmospheric pressure is 92.1 times as much as on Earth. A direct comparison is the temperature of Venus' atmosphere at the altitude where atmospheric pressure happens to be equal to Earth's surface pressure versus Earth's surface temperature, so we compare 338K with 288K.
Then you just adjust Venus' temperature down to compensate for the fact it is nearer the Sun and the solar radiation it gets is more intense. The adjustment factor is the fourth root of (2,601 W/m2 ÷ 1,361 W/m2) = 1.91 ^ 0.25 = 1.176*. Divide 338K by 1.176 = 287.4K, that's as close to 288K as makes no difference, job's a good 'un.
HDH does not claim to be able to explain why this is so (see discussion here), but that's just how science works. First step is observe stuff, recognise clear patterns, and then you try and work out why. His guess appears to be that you can ignore a planet's albedo when looking at temperatures, because higher temperature causes clouds; clouds increase the albedo; thus reducing incoming solar radiation; which would reduce the temperature. So we would end up in a circular calculation. Or something like that.
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OK, let's strap on our space suits, fire up the rockets and head off to Titan. Temperature at the surface is measured/estimated to be 93.7K. It receives 14.8 W/m2 solar radiation (same as Saturn, but knock off 0.8% because it is in Saturn's shadow 0.8% of the time and add on 0.08 W/m2 which Titan receives from Saturn itself).
Let's adjust Earth's surface temp (288K) down using the same method as above: 288K x ((1,361 W/m2 ÷ 14.8 W/m2)^0.25) = 93K. That's pretty close to 93.7K!
However... HDH's direct comparison method is the temperature on Titan at the altitude where pressure = Earth's surface pressure versus Earth's surface temperature, which happens to be at ~8 km. With a lapse rate of ~0.5 K/km, the temperature there is ~89.7K, against our predicted 93K. So it's ~3 degrees cooler than predicted by HDH's approach, which is still close enough, I think.
Which all demonstrates that a planet's albedo and the precise composition of its atmosphere are probably irrelevant, and whether or not the constituent gases can 'trap' radiation is almost certainly less than irrelevant.
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* The short cut is divide distances from the Sun and take the square root = (149.6m km ÷ 108.2m km) ^ 0.25 = 1.176.
Saturday, 22 May 2021
Let's see if Harry Dale Huffman's approach works with Titan
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30 comments:
Is it made of cheese like our moon ?
MC, no, it's made of Titanium.
Titan is a cool place regardless, and I mean not only because it is literally cool at 90K. It has rivers and lakes of hydrocarbons, sadly almost no mountains and you can't see Saturn from the surface or its rings (wrong angle for rings and haze blocking any outer space views, including Saturn itself).
PW, indeed. It is quite unusual in many ways.
Actually comparing temperatures at different heights where the pressure is equal does not negate the composition of the Atmosphere.
A couple of reasons come to mind.
As a gas heats up it expands and so a warmer atmosphere is taller. Pressure decreases with height and so does temperature. And so a composition that warms the surface and atmosphere is also causing the equal pressure to be at the higher altitude where it is cooler.
Also greenhouse gases have higher molecular weight than nitrogen and so they also cause the equal pressure to be at a higher altitude where it is cooler.
If that is a bit hard to follow consider this.
Take experimental columns of gas A and gas B with lapse rates. Heat up A, the gas height A rises and then the height where the pressure of A is the same as B also, because of the lapse rate, coincides with equal temperatures because and that is a consequence of the Gas law/ lapse rate and atmospheric pressure.
Din, yes, but pressure at the surface is fixed by mass of atmosphere and acceleration due to gravity.
HDH takes as his fixed point Earth surface pressure/temp.
If, coincidentally, surface pressure on other planets were the same as on Earth (and Titan is pretty close) then it would be an even better comparison. Choosing the appropriate altitude is a good second best.
If the effects you mention made a big difference, then the HDH results would be miles out, not accurate to within a couple of degrees.
Din "Also greenhouse gases have higher molecular weight than nitrogen"
That's not even true is it?
CO2 = 44,
'air' = 29,
H2O = 18,
CH4 = 16.
https://myengineeringtools.com/Data_Diagrams/Tools_Molecular_weight.html
"If the effects you mention made a big difference, then the HDH results would be miles out, not accurate to within a couple of degrees."
Nope if it was a big effect than HDH results would be spot on. Obviously my description of a column was an extreme case to illustrate a possible contribution to the correlation. An atmosphere also has two other dimensions contributing to volume.
The HDH results are only an observation, not an alternative mechanism that negates an effect of composition.
Din: "Nope if it was a big effect than HDH results would be spot on. "
So you are saying, his approach gives highly accurate results, therefore the approach must be flawed? That is a bit arse about face.
The mechanism is quite simple and was first described by Maxwell, I believe. Surface temp depends on two things, and two things alone - surface pressure and distance from the Sun.
Distance from the Sun is fixed and surface pressure is fixed, regardless of constituent gases or surface pressure. Surface pressure is simply mass of atmosphere per m2 multiplied by acceleration due to gravity.
This used to be widely accepted, as it explains everything nicely. Then the Alarmists made up an alternative explanation that explains sweet fuck all and gives completely wrong results for any planet except Earth, and that only because they tweak every single variable to suit themselves, the whole thing is based on a diagonal comparison and ignores a lot of basic physics.
No I am not saying that , I am saying that the HDH results do not tell you much because they could be true for an atmosphere with compositional effects.
Din, they could be true... But three out of three ain't bad
The HDH approach works for
- C02/N2 atmosphere (with SO2 clouds) and 2,601 W/m2 sunshine,
- N2/O2 atmosphere (with H2O clouds) and 1,361 W/m2 sunshine, and
- N2/CH4 atmosphere (with CH4 clouds), with 14.8 W/m2 sunshine.
That's one heck of series of coincidences if all those things have effects which just happen to cancel out to zero. Is it not more likely that they have no effect, apart from W/m2, obvs?
Its the basic premise that is a false premise. The fact that pressures and temperatures for two planets tally does not rule out the overall temperature of the atmosphere of each planet being affected by composition.
You could have in the first case, two planets with no greenhouse effect, and in the second case one with and one without, the pressures and temperatures could tally at the same height in case one but tally at different heights in case 2.
Din, OK, let's assume the Alarmist theory is correct.
Let's go with Case 2.
You are presented with
1. Venus, 95% CO2, so strong greenhouse effect.
2. Titan, 95% N2 and 5% CH4, so some small greenhouse effect.
You are then asked to interpolate Earth with 0.04% CO2 so tiniest Greenhouse effect. How would you do it?
Remember - there is slightly more atmosphere above 1 bar on Venus than there is above 1 bar on Earth. So there should still be a lot of greenhouse effect on Venus at 1 bar.
If the greenhouse effect exists, then temp on Earth at 1 bar would be higher than temp on Earth without any CO2.
Therefore, the temp at Venus at 1 bar would also be higher than temp on Earth at 1 bar.
Din, I have checked using Barry and your assumption that it somehow cancels itself out is basically incorrect i.e. wildly exaggerated.
Start with fantasy Alarmist earth where surface temp is 255K.
At an arbitrary altitude, 4.9 km, pressure is 0.5 bar and temp is 223K.
Then re-set surface temp to 288K, at altitude 5.5 km pressure is 0.5 bar and temp there is 252.
So comparing 0.5 bar with 0.5 bar, the extra Warming is 29. This is a bit less than the 33 degrees at the surface, but still significant.
Given that the Greenhouse Effect on Venus is allegedly ~500 degrees, there'd still be a significant difference at the 1 bar altitude.
If the greenhouse effect exists, then temp on Earth at 1 bar would be higher than temp on Earth without any CO2.
Thats true
"Therefore, the temp at Venus at 1 bar would also be higher than temp on Earth at 1 bar"
That is not true
That premise is unfounded. That position high in the Venus atmosphere where it is 1 Bar does not have a special significance for comparing with Earth at 1 Bar. Its only a point where the pressure is the same.
I did not say anything cancels out.
Why do you keep comparing temperatures at points where the pressure are the same. I hope you do not think that temperature goes up with pressure. The gas law is
T=PV/nR
As P goes up n goes up and so T is constant.
The main evidence for GH theory is that the surface radiates 390 W/m2 but only ~240 W/m2 gets to space due to insulation.
Fascinating that such a small planet has so much atmosphere. Apparently a human flapping wings could fly! Other similar moons in orbit have not preserved their atmosphere. Astronomers still have so much to explain!
Din, either you believe in The Greenhouse Effect or you don't. And either you have bothered to set up a spreadsheet with the lapse rate adjusted formula to do test runs (like I have) or you haven't.
And you clearly haven't bothered. It appears to me that you don't understand simple addition either.
You aren't very good at logical and fair comparisons, so let me do a Case 1 for you.
Compare fantasy Earth A with 255K surface temp with
Real Earth B with 288K surface temp.
Surface pressure on both is the same = 1 bar.
Tempt at 1 bar on Planet B clearly 33 degrees warmer than on Planet A.
If you compare temperatures at an arbitrary other pressure - like 0.5 bar, you find that the temp on Earth B at 4.9 km (0.5 bar) is 29 degrees warmer than on Earth B at 5.5 km (0.5 bar).
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So if we can compare Earth A with Earth B at 1 bar or at 0.5 bar and get sensible answers, we can also compare Earth with Venus at any arbitrary pressure, like 1 bar, and get a sensible answer.
Or to put in another way, if there were a Greenhouse Effect on Venus, it would be warmer at 1 bar there than at 1 bar on Earth (adjusted for extra sunshine).
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OTOH, yes, it's my new favourite moon/planet.
Din: "The main evidence for GH theory is that the surface radiates 390 W/m2 but only ~240 W/m2 gets to space due to insulation"
That is what people believe but it is clearly nonsense as it is based on a diagonal comparison.
I covered that ages ago here.
Your comment is a repetition of previous comments. Your assumption , your premise from HDH, is that pressure and temperature somehow have an invariant relationship regardless of the size of the planet or the atmosphere composition or other variables . My comment is that proposed relationship between temperature and pressure is unsubstantiated and you have not addressed that comment with any physical explanation to what you have in mind.
I have made the same comment at 24 May 2021 at 11:46 25 May 2021 at 10:44 25 May 2021 at 16:42
I read your post " What Missing Radiation" again.
The mistake you are making there is you first acknowledge that the surface emits 390 W/m2 and that reaching space is 240 W/m2 but you then ,to make an average, make the surface to one third , as if that makes the missing bit "go away". In fact that radiation does not go away , it stays in the surface atmosphere system.
That is what in the greenhouse theory is the greenhouse theory effect of insulation due to atmospheric coverage of the surface.
Its almost like you describe the greenhouse effect and then say , - " this is not the Green house effect " !
Din, first comment.
Let's start with basic building blocks. I invite you to divide an atmosphere into ten or twenty horizontal slices and tell me the density in each slice.
I will then use your numbers to illustrate why temperature must go up.
Din, second comment, reality check is always good.
Fact 1. Radiation emitted to space is less than radiation emitted by surface. That is because clouds reflect more, are higher up, are cooler, have lower emissivity etc. Agreed.
Fact 2. It is overall cooler when it is cloudy. Looks up some weather stats.
Therefore, while the diagonal comparison says that "clouds cause a greenhouse effect i.e. warming" real life tells us that clouds cool things down, precisely the opposite. That's how fucked up Warmenist propaganda is. Warming is cooling. Freedom is ignorance.
Quote
"Fact 1. Radiation emitted to space is less than radiation emitted by surface. That is because clouds reflect more, are higher up, are cooler, have lower emissivity etc."
That is impossible, the radiation in question that needs to accounted for is coming from underneath the clouds.
Din, how do you mean 'impossible'??
I did some nice little infogaphics showing exactly what goes where in real life. It actually happens like there ergo it is very possible indeed.
If you can't understand them, that's not my problem.
No you did not account for why the ground and oceans radiate 390 W/m2 into the atmosphere while satellites measure 240 W/m2 emitted from the atmosphere into space.
Din, look at the picture.
Land and oceans radiate 390, two-thirds of that is blocked by clouds, one-third (cloud free areas) goes to space = 130
Clouds radiate 165 upwards, that goes to space. Two-thirds (two-thirds of surface is covered by clouds) of 165 = 110.
130 + 110 = 240 weighted average, the number that goes to space.
I'm an accountant. I account for stuff.
That what you have just written at 18.28 is the Green house gas Explanation. That actually is the Greenhouse gas explanation of the atmosphere. It is, as you say blocked by clouds and to some extent I am not sure of the proportion, reflected down again.
Din, no, it is not even on the same page.
Alarmists - "CO2 traps 150W out of 390W emitted by surface to leave net 240W going to space"
In real life - "All radiation emitted by 'surface' gets to space. The 'surface' might be clouds (in which case ignore the land or oceans underneath them or it's double-counting) or it might be land or oceans (with no cloud cover)"
Maybe it would add some clarity if you were to read your own comment yourself,
at 26 May 18.28 . What are the four words that you wrote after the word "is".
" Land and oceans radiate 390, two-thirds of that is *blank,blank,blank,* "
Din, it is clearly blocked/absorbed/reflected by clouds. That's just a fact. No point in arguing over facts. Don't imagine that you have somehow cleverly forced me to confess to a fact, one which I have never disputed and take as a given.
What the Alarmists want us to believe is that clouds somehow disappear when looking at outgoing radiation and that one-third of the surface radiation is 'trapped by CO2'.
Funnily enough, Alarmists are happy to take clouds into account when calculating incoming radiation when calculating effective temperature.
I know that fair comparisons are not your strong suit, but do you not realise that Alarmism is based on a diagonal comparison?
Radiation in - clouds exist
Radiation out - clouds don't exist
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