Saturday, June 30, 2007

Lubos Runs a Three Card Monte Game

The greenhouse effect is a wicked combination of spectroscopy, radiation and collision dynamics superimposed on fluid flow. Gravity makes an appearance through the lapse rate, which among other things means that it is colder the higher you go and there are a few other things thrown in for the joy of it. Explaining it to your mom is not recommended for a family fun night. One of the associated issues is that increasing greenhouse gas concentrations in general, and CO2 in particular, does not increase the greenhouse warming in a simple linear way. Spencer Weart (popular version) and Ray Pierrehumbert (more detail) recently assayed an explanation on Real Climate.

Into the swamp wanders one Lubos Motl, a wanna be climate guru who is running for Bjorn Lomberg of the Czech Republic. Lubos then plays an elegant game of three card Monte with Richard Lindzen as the outside man on the short con. Watch the cards as you listen to the spiel. The trick here is to bury the switch into a morass of polemic and nuttiness. Rabett Labs has filmed the whole thing in slow motion, stripped out the flim to show you the flam. The rubber meets the road about a third of the way down

focus on the gases and frequencies where the absorption rate significantly differs from 0% as well as 100% - will effectively eliminate oxygen and ozone. You end up with the standard gases - water, carbon dioxide, methane, and a few others.

Moreover, you can use the approximation that the concentration of water in the atmosphere rapidly converges to values dictated by other quantities.

which are determined by the extra forcing from increased CO2 concentrations which raises the vapor pressure of water in the atmosphere. But Lubos goes on
The conventional quantity that usually measures the strength of the greenhouse effect is the climate sensitivity defined as the temperature increase from a doubling of CO2 from 0.028% of the volume of the atmosphere in the pre-industrial era to 0.056% of the volume expected before 2100. Currently we stand near 0.038% of the volume and the bare theoretical greenhouse effect, including the quantum-mechanical absorption rates for the relevant frequencies and the known concentration, predicts a 0.6 Celsius degrees increase of temperature between 0.028% and 0.038%,
This is a low estimate of the increase in global temperature due ONLY to the direct effect of adding CO2 without amplifying feedbacks direct from Richard Lindzen. Low, but in bounds. And here comes the switch and there goes the Queen into the grifter's pocket. . .
roughly in agreement with the net warming in the 20th century.
The measured net warming INCLUDES the feedback from increased water vapor in the atmosphere due to warming of the ocean surface. Lucky Lubos covers it back up again
This bare effect can be modified by feedback effects - it can either be amplified or reduced (secondary influence on temperature-driven cloud formation etc.) - but it is still rather legitimate to imagine that the original CO2 greenhouse effect is the driving force behind a more complex process
The direct influence of CO2 concentration increases from the feedbacks AMPLIFY period. So let's see. The direct effect of doubling CO2 would be an increase in global temperature of 0.6 to 1 K. The total effect, the climate sensitivity, will be 2-5 K, with a best estimate of 3K (see the AR4 WGI and all over). And now, the fellow behind the cardboard box asks you to pick the shell with the pea under it
In terms of numbers, we have already completed 40% of the task to double the CO2 concentration from 0.028% to 0.056% in the atmosphere. However, these 40% of the task have already realized about 2/3 of the warming effect attributable to the CO2 doubling. So regardless of the sign and magnitude of the feedback effects, you can see that physics predicts that the greenhouse warming between 2007 and 2100 is predicted to be one half (1/3 over 2/3) of the warming that we have seen between the beginning of industrialization and this year. For example, if the greenhouse warming has been 0.6 Celsius degrees, we will see 0.3 Celsius degrees of extra warming before the carbon dioxide concentration doubles around 2100.
In the reality based community, we have had about 0.7 K of warming in the last century. That is 0.7/3.0 or about 30% of the warming predicted for a doubling, but because the Earth appears not to have re-established radiative equilibrium it is generally considered that there is an additional 0.5K of warming built even if greenhouse gas concentrations cease to grow. 1.2/3.0 = 40%.

As Eli said, watch the switch. The observed warming must be compared to the 3K climate sensitivity which INCLUDES feedbacks. By comparing the observed warming to the much lower 0.6-1K estimate without feedbacks it appears that much more of the warming has already occurred, and that adding more CO2 will have little effect.

There, is, as there always is, much more. Anyhow, Lubos as part of his pitch tells us in detail that he is going to explain it all and starts by getting it wrong in strange ways. After a page or two of polemics, Motl starts out on the science ok, sort of, but quickly falls into two of the usual traps
The requirement that low-energy transitions must be allowed within the molecule is why the mono-atomic inert gases such as argon or even di-atomic molecules such as nitrogen are not greenhouse gases. Those absorbed infrared rays that are relevant for the greenhouse effect are quickly transformed to kinetic energy of the atmosphere and this energy is either re-emitted in the downward direction or it is not re-emitted at all.
Molecules and Motl's basically don't know which end is up, so the energy is re-emitted in all directions, not only downward and although the thermal energy can be moved considerable distances by convection, it eventually has to be re-emitted to space. How the energy gets there in the end is what the greenhouse effect is all about. Lubos continues by showing a figure

The meaning of the ordinate is not clear, but Lubos does provide a link to David Hodell's version at the University of Florida from a course on Global Change. Hodell, btw, does not agree with Motl's foolishness. We learn that Motl's unattributed graph (Eli thinks he has seen it elsewhere, but can't remember) really shows the percentage of incoming solar radiation at a particular wavelength that is absorbed by a molecule before hitting the surface (Hodell's abscissa is backwards from Motl's, Motl's spectra, wherever they came from are a bit higher resolution). The Wikipedia article on global warming provides the context that Lubos lacks

UPDATE:7/2/2007 Lubos has now added this figure to his post. It was not originally there.

The sun's spectrum is a 5000 K black body with a whole bunch of sharp atomic lines in it. Ozone (305-195 nm) and O2 (<0.2>4 um) absorb UV light The emission from the surface is a smooth black body.

From the Wikifigure you can see that in the range where the earth emits IR, water vapor is the most important absorber, but CO2 plays an important role and tropospheric O3 also has an effect. (Note to the interested: The total emission from the sun is much higher than shown in the figure, but only a small fraction of the sun's light intersects the earth's orb and the average amount of energy hitting the surface is further decreased because the sun don't shine anywhere half the time on average and the fact that most places it hits the surface obliquely. This all works out to a difference of a factor of 4 less than the solar intensity hitting a disk held at right angles to the sun in orbit. Thus the relative intensities of sunlight falling on the surface and IR emission from the earth are as shown). Eli could niggle a bit more, both CO2 and H2O have strong absorption spectra below 200 nm which Lubos does not show (they don't play any significant role in absorbing solar radiation), etc. but it is more fun to look at the next lubosaloser
You can see that water is by far the most important greenhouse gas. We will discuss carbon dioxide later but you may also see that we have included oxygen and ozone, for pedagogical reasons. They don't have too many spectral lines but there is a lot of oxygen in the air, a thousand times the concentration of carbon dioxide! So you might think that the precise concentration of oxygen or ozone will be very important for the magnitude of the greenhouse effect, possibly more important than the concentration of carbon dioxide.
Lubos has not quite figured out the difference between a vibrational band and a spectral line. Bands consist of lots of lines. The resolution of these figures is too poor resolve the lines. Ozone does contribute to the greenhouse effect, at least the ozone that we see in the troposphere and ozone has lots of lines in its vibrational spectrum. Oxygen (O2) has a lot of spectral lines, its just they are mostly below 300 nm (there are some very weak ones in the near IR and red, from forbidden triplet-singlet transitions which, as Lubos says, you can see because there is a lot of O2). Motl continues down the bunny trail
The reason why it's not true is that there is actually so much oxygen in the air that the radiation at the right frequencies is completely absorbed - 100% - while the radiation at wrong frequencies is of course not absorbed at all - 0%. At least ideally - when you neglect the collisional broadening and the Doppler width of the lines and other effects - it should be so. That's why the greenhouse effect of the oxygen doesn't depend on the concentration of oxygen in any significant way.
Cod's wallop. The reason why O2 does not contribute to the greenhouse effect is that just like N2, it is homonuclear diatomic. While the oxygen and nitrogen molecules can vibrate, because of their symmetry these vibrations do not create any transient charge separation. Without such a transient dipole moment, they can neither absorb nor emit infrared radiation.
***************
On top of this there are language problems which are not Lubos' alone. I/Io is the ratio of the intensity of light after passing through some distance L of anything. I and Io are functions of wavelength. (Io-I)/Io x 100 is the percent transmitted. Transmission is almost always given as a percentage. Transmission must be between 100% and 0%. Absorption can be found from the Beer-Lambert law
I/Io = exp (-SNL)
where S is the molecular absorption , N the concentration and L the path length. S can in principle take any value (negative values of S would correspond to situations in which there were emitters in the path, not absorbers in which case the transmission would be > 100 %). SNL is called the absorbance and is unitless.

People are throwing around the word saturation. Saturation has a specific meaning for optical transitions. For a simple two level system, when the population of the upper and lower states are equal, the probability of absorbing a photon which matches the energy difference between the states is the same as emitting a second photon (there are caveats) and the transition is said to be saturated.

51 comments:

bigcitylib said...

Ah yes, but do you know string theory? No? I thought not! Your arguments are therefore USELESS and you must BOW before Lubos vaster knowledge.

Anonymous said...

EliRabett-

I would ask you to please re-read the Lubos post and then make the appropriate corrects to your piece. I am sure that if you read the thread you would see that many of the errors that you are committing have been called out. Finally, why make this personal. Are you seeking a faith-based or fact-based answer?

EliRabett said...

Notice o anon, that Eli QUOTED EXTENSIVELY from what Lubos wrote. The Bunny didn't pass Motl's words through a filter, he put them out there for you to decide. Now as to what is in the 3xx comments, the only really interesting thing is Venus, where everyone is making a complete bollocks. Hopefully there will be time tonight to post on this.

Lubos says straight out in the post and in the comments that using a climate sensitivity much lower than found from observation and theory is his only justification and he then waves the majic wand.

Marion Delgado said...

Okay, I have been to Motl's site a few times. He's just lying about things. This is not complicated. He doesn't even really pretend to be doing science, there. He just lies - clumsily, often. Lying about something you can just scroll up and read. But he's still pushing the most extreme false claims out of the GGWS playbook. and so automatically - look at his scripted reply to Sweart!

When I studied math physics in grad school (just a few classes) it was an accepted idea that some kind of supersymmetry or supergravity or whatever (what Gogol Bordello calls the supertheory of supereverything) was the likeliest path to provide us with insights into high energy physics, the big bang and before, and unification of forces. But it's a dwindling paradigm now. To defend it vociferously takes more energy every year. That's a sea change that's happened in my lifetime, an amazing one. But it means to me he's just a dead-ender.

So this GGWS-ism is perfect. he can use his dead-ender nimble rhetoric and obfuscutory skills and his right-wing politics and combine them for fun and profit!

And yes, I'm offended. I want cranks to not know they're wrong.

Belette said...

Its codswallop. Or just possibly Codd's wallop. But definitely not Cod's wallop.

Marion Delgado said...

Also, Eli, I want this to introduce a new phrase, and I encourage everyone to use it (i couldn't find a single hit for it on google).

Motl calls people "crackpots" all the time both on climate blogs and physics blogs. In such cases, I want it know that that is an example of

THE POT CALLING THE KETTLE CRACKED.

And i won't mind if it gets associated with lubos at all.

Marion Delgado said...

Oh shoot, a better search found "... calls", "called", even "calling" on a separate line. Credit goes to The Hairy Reasoner and he already hung it on Pat Robertson. But it should be more widely used. :)

Anonymous said...

I think the only thing "saturated" in this case is the web, with Moltl's half-baked "debunkings" of global warming.

EliRabett said...

First the honest answer, Eli separated Cod and wallop for emphasis. However, that's no fun.

The crack Rabett labs dictionary team quickly hopped over to the OED (if it did not agree with us, you seriously think we would link to it?? Cod's wallop

"codswallop DRAFT REVISON Jan. 2006
slang.

Also cod's wallop. [Origin unknown.
It is often suggested that this word is < the genitive of the name of Hiram Codd (1838-87 ), British soft drinks manufacturer, who patented several designs for mineral water bottles in the 1870s + WALLOP n. (see sense 4c at that entry), and that it was originally used by beer drinkers as a derogatory term for soft drink. However, no evidence has been found for early use of the word in this sense, and derivation from the surname is not supported by early spellings.]

Nonsense, drivel. "

Eli is quite fond of the odd aspiring to be one hisself.

Anonymous said...

I love the ironic comments by "bee" on Motl's blog, by the way (which sound an awful lot like the comment by anon 8:08 AM above)

"In reading your blog I see that you revert to name calling rather than offer a material alternative model [false: the "material alternative model" that Eli offers is none other than the one that the vast majority of climate scientists subscribe to] The criticisms you bring to bear have been addressed in this thread and thus I must say they appear disingenuous and self serving. [talk about disingenuous and self-serving]

As one who aspires to better understand the world around me, I ask that you reflect more deeply on what is being presented by Lubos. You stand to learn not only more about the topic at hand but also problem structuring and reasoning.
bee"

...and all in defense of a guy who regularly uses the word "crackpot" as if it meant little more than "humorous fellow."

Oh, the irony.

Anonymous said...

As Harvard physicist, Motl should certainly know enough physics to appreciate that the oceans have absorbed a great deal of heat over the past century (and particularly over the past 30 years), a significant fraction of which has yet to show up as a surface air temperature increase*

*referred to by Eli with the statement that "it is generally considered that there is an additional 0.5K of warming built even if greenhouse gas concentrations cease to grow" and explained here .

It is completely untenable to presume that we have already seen all the surface air warming that we are going to see from the CO2 increase over the past century.

SCM said...

I don't think Lubos's maths is self consistent in the first 5 sections of his diatribe quoted above. I believe the obsfucation begins earlier in the piece than Eli indicated.

In the 2nd segment you quote from Lubos, he says that he predicts 0.6 degree warming for going from 280pm to 380ppm (NB I think Eli misread this as the heating Lubos was expecting for a doubling of CO2?).

As far as I can tell Lubos never explicitly reveals the value he is using for sensitivity (change per doubling).

When I did the math on 0.6 degrees for 280pm to 380ppm, this seems to indicate that Lubos was using a sensitivity of 1.36 degrees per CO2 doubling (or at least that his caclulation implies this sensitivity)

This is rather a large sensitivity value (already beyond bounds), but one that makes it easier for him to compare the current measured warming to his theoretical value.

He then claims that having only gone 40% of the way to a CO2 doubling we've done 2/3 of the predicted warming. But if he used a sensitivity of 1.36 then from his own calculation we've only gone 44% of the way to the predicted warming (for CO2 alone). Hardly surprising since from the Arrhenius eqn ln(380/280)/ln(2) = 0.44.

Is he really this wrong or did I mess up the maths somewhere?

(And then there's feedbacks, and time lags due to ocean thermal mass, etc etc....)

Marion Delgado said...

scm: he'll pick the interpretation of his words that makes him least wrong, so you might as well, also.

But your comment and Eli's post are great responses to his actual post.

I do think his COMMENTS there are indicative, though. It's ALL politics to these people. Even Trofim Lysenko abused the political system to push something he truly believed was correct. In that respect, the denialism over there is not even fairly called Lysenkoism. It's a profound cynicism - who knows what the truth is or if it can be found out, if it makes us feel better about our tribe, we'll just trash scientists and call em commie bastards - after all, most of us won't live long enough to know for sure we were wrong.

In fairness, I think he's duly achieved his goal of being the Bjorn Lomberg from the Czech Republic, assuming he's still in Cambridge. If he wants to be the US' Bjorn Lomberg, He has to beat Richard Lindzen two fallacies out of three.

Magnus said...

It must be quite embarrassing for Cambridge (?) to have (had?) a string theorist that doesn’t know basic physical chemistry or is using his “status” to distort the public.

Munin said...

That's Cambridge, MA (i.e. Harvard) - Lubos may have many sins, at least he's not a bloody Tab.

Arun said...

Eli,

Along with the often quoted number for climate sensitivity, why isn't there an equally quoted number for the characteristic time scale on which the climate responds to a greenhouse gas forcing?

Motl is able to pull off this three-card monte by assuming that this time scale is rather negligible.

-Arun

munin said...

SCM, Lubos replies to a comment:

"Dear someone who asked, sorry I am not able to reproduce the number 2/3 here, especially not in the short comments here. Roughly, the decisive bands of CO2 are pushed to bands which are already covered by water as the concentration reaches roughly present values. Ask Richard Lindzen."

Reminiscent of Fermat's last theorem (other than the appeal to Lindzen).

Anonymous said...

Trying to analyze Motl's actual numbers is a waste of time.

As Eli pointed out, he is comparing apples to oranges (observed warming over the 21st century to climate sensitivity sans feedbacks) and the actual number of apples vs number of oranges therefore makes not one bit of difference.

--Horatio Algeranon

Anonymous said...

Eli,

Is the saturation you define really the one at issue here? The point is not creation of a population inversion in the atmosphere but the integrated opacity. If a spectral region is effectively opaque all the way to the tropopause you don't get much additional insulation from making it more opaque.

CIP

Anonymous said...

"you might think that the precise concentration of oxygen or ozone will be very important for the magnitude of the greenhouse effect

The reason why it's not true is that there is actually so much oxygen in the air that the radiation at the right frequencies is completely absorbed - 100%"

Perhaps Motl is under the impression that the atmosphere is made up of a solid "slab" of salami ...I mean oxygen and nitrogen... both of which do absorb IR (though you have to place them very high pressure combined with low temperature to observe the absorption).

Deli owners in Cambridge almost certainly heat their sandwiches in toaster ovens (IR), so Motl's confusion is completely understandable.

Munin said...

Lubos has provided a reference for the 2/3 claim: a Lindzen paper that actually says 3/4, and appears to justify the figure by reference to a paper by Hansen.

Intriguing, though unfortunately I don't have time to chase this up.

Anonymous said...

Reminiscent of Fermat's last theorem (other than the appeal to Lindzen)."

... and the fact that Motl is no Fermat.

...which, in turn, is reminiscent of this exchange:

Dan Quayle: "I have far more experience than many others that sought the office of vice president of this country. I have as much experience in the Congress as Jack Kennedy did when he sought the presidency. I will be prepared to deal with the people in the Bush administration, if that unfortunate event would ever occur.

Bentsen: "Senator, I served with Jack Kennedy: I knew Jack Kennedy; Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy."

http://en.wikipedia.org/wiki/Senator,_you're_no_Jack_Kennedy

Anonymous said...

Eli,
This may be where you saw the graph that Motl posted without attribution (or more precisely, the wrong attribution, which is even worse).

It can be traced to Cold Facts on Global Warming (by a neuroscientist!), which lists "Peixoto, J.P. and Oort, A.H., Physics of Climate Springer, 1992. p.118" as the source of the data.

You know the climate science "debate" has been excited to the "absurd" energy level when you have string theorists and neuro-scientists telling us how the climate works.

What do you call a system that works based on a logic inversion and subsequent transition between the "ridiculous" and "absurd" energy levels?

A lyser.

Anonymous said...

or perhaps it would be spelled "lieser"

EliRabett said...

CIP no it is not, and the problem is that the word is being thrown around so loosely that it means different thing to the same person in the next paragraph. I'm not sure the best way of expressing the idea tho.

Anonymous said...

Motl seems to be arguing on his blog that the oxygen absorption band near 760nm has a significant impact on the green-house effect!

Earth to Motl:

At what wavelength does the peak emission occur for a body at 288K? (that of earth, for example)

Hint. Use Wien's Displacement Law (which most people learn in freshman physics).

You will discover that the answer is nowhere near 760nm. Not even close.

In fact, you will find that 760nm lies far in on the left "wing" of the emission curve for a body at 288K (a left wing conspiracy if ever there was one)

On the other hand, the answer (for wavelength of peak emission of a body at 288K) is relatively close to a major absorption band of CO2 near 15 micron.

But don't take my word for it. Do the math yourself.

Anonymous said...

Correction to above: "Motl seems to be arguing on his blog that the oxygen absorption band near 760nm has a significant impact on the green-house effect!

should read "Motl seems to be arguing on his blog that the oxygen absorption band near 760nm would have a significant impact on the green-house effect were the absorption not saturated"

Dano said...

I never thought of the idea that Lubos might want to be the new Bjorn Lomborg and eat at all the banquets on the Heritage Victory Tour. After all, Lubos has had at least one course in the Natural Sciences, so that's 100% more education in the subject than Lomborg.

Hmmm...it just might work.

Best,

D

CapitalistImperialistPig said...

It seems to me that the crucial question for "saturation" is the height and consequently temperature of the effective radiating surface - what you see when you look down from, say, 70 km. with a certain MODTRAN toy that a kindly Wabbett showed me.

If you turn off the ozone (another tip from k.w.) and play around with the CO2, you can see that radiating temperature quickly decreases (with increasing CO2) to the temperature of the tropopause (TT) at band center. Cranking up the CO2 broadens the "saturated" part of the band at TT but ultimately line center temperature begins to increase again, because the effective radiating surface has moved up into the stratosphere where temperature increases.

Not precisely relevant, but I really like the toy, and think it can explain a lot.

CapitalistImperialistPig said...

Which brings to mind a question: if Venus had a stratosphere (which it doesn't) would the surface still be so friggin hot?

EliRabett said...

The 1 Sigma<-- 3 Sigma - transition at 760 nm is definitely NOT saturated as you can see by looking at the figure titled "Radiation Transmitted by the Atmosphere" above. The transition is incredibly weak and all the O2 in the atmosphere is not enough to block these bands which are at the far red side of what most people can see.

EliRabett said...

Lomborg got appointed something or other by a rather right wing government in Denmark. I suspect the same fate awaits Lubos.

Anonymous said...

"transition at 760 nm is definitely NOT saturated as you can see by looking at the figure titled "Radiation Transmitted by the Atmosphere" above."

yes, I can see that, but it does nevertheless appear that Motl is arguing that it is saturated with his statement that

"The reason why it's not true [that the precise concentration of oxygen or ozone will be very important for the magnitude of the greenhouse effect] is that there is actually so much oxygen in the air that the radiation at the right frequencies is completely absorbed - 100%"

Arun said...

Eli,
FYI - the Bee on Motls' thread is not our friendly Bee from backreaction.
See
http://backreaction.blogspot.com/2007/04/global-warming.html#c12728365418033805

Arun said...

http://backreaction.blogspot.com/2007/04/global-warming.html#c12728365418033805

Munin said...

RE: O2/O3 saturation, Lubos explains. It could be clearer, but he's actually talking only about O2 in the para under the pretty graph.

"O3 is not saturated in the IR but it doesn't matter too much because the amount of O3 is tiny."

IMO it's unfair to mention the ozone and then neglect it. A bit like that song about the holly and the ivy, where the ivy gets a mention, but then it just bangs on about how great the holly is. Personally, I feel sorry for the ivy.

Arun said...

Munin, its the Ivy League, not the Holly League; maybe Motl would make more sense if he belonged to the latter instead of the former.

:)

Anonymous said...

Here's a comment that Motl made on his blog:

"Dear CIP, great. So call the last line of O2 at 770 nm "deeply crimson" or "near-infrared". It doesn't really matter how you call it and whether we see it. What matters is that it contributes to the energy budget."

The narrow band near 770nm may contribute a little to the energy budget --in that it affects incoming solar radiation -- but since it is relatively far out on the limb of the sun's emission curve, it does not make much difference. It represents a very small fraction of the solar insolation). And, as Eli points out above, the absorption near 770nm is not anywhere near 100%, as Motl claims.

Motl continues:
"Once we accept that oxygen has some lines at frequencies where Earth radiates, could you please refine your argument why you neglect the concentration of oxygen even though it is 1000 times higher than CO2 and may also be changing? Is the Boltzmann suppression at the high-frequency end of the Planck curve enough to make this factor of 1000 irrelevant?"

[end Motl]


In a word: "Yes". In fact, it's far more than "enough".

At 770nm or thereabouts, the emission of a body at 288K has dropped to nearly zero -- for all practical purposes.

In particular, the emission intensity at 770nm is vanishingly small in comparison to the emission intensity near the peak of the (288K) curve at about 10 micron. The direct consequence is that the O2 absorption near 770nm makes virtually no contribution to the greenhouse effect. Diddly. Nada.

Had Motl done the calculation himself he would have known this.

SCM said...

Indeed you are right anonymous.

Perhaps someone should point Motl to the handy "black body" applet at spectracalc.com, where he will be able to work out that at 288K the 770nm radiation intensity is smaller than that at 10micron by about 20 orders of magnitude!

Anonymous said...

On the contrary, if it were up to me, I would not give him the link to that calculator.

Let him struggle with the math himself.

He might actually learn something.

I hate to admit it, but I actually read through a lot of the comments on Motl's Gardenhose ...I mean "Greenhouse" post (where I found the one above about the 770nm O2 absorption).

Was that ever an experience. I'd say about 3/4 of them (at least) are from what I would term "Motl Groupies", a group of barely literate folk who try to mimic Motl's pompous, insulting comments.

Problem is, it's clear from their comments that the vast majority of them haven't the slightest idea what they are talking about when it comes to physics.

It reminded me a lot of the output of the computers back in the early days of AI when the first Turing tests were run and the computer merely parroted back what the tester was saying, changing a word or two here and there.

Sometimes, the computer would get all messed up and trail off into total gibberish -- just Like most of the comments on Motl's blog.

Fancy Rat said...

On "saturation" CIP said "If a spectral region is effectively opaque all the way to the tropopause you don't get much additional insulation from making it more opaque."
This is an explanation of an anti-CO2 effect argument I have often heard from denialists, and I hadn't thought much about it. Today I realized that the insulation effect is a function of how far the radiation gets before it is absorbed. If, at a certain frequency, only 50% is absorbed when emitted vertically, then 50% will get all the way to space without absorption. If 50% is absorbed in getting through half the troposphere (which is equivalent to 75% absorption over the full column), then it will often have to scatter and bounce a few times to get out.
If 50% is absorbed in getting through 10% of the troposphere (equivalent to 99.9% absorption over the full column) then it will have to scatter and bounce many times to get out.

The denialist argument is that 99.9% is only one third greater than 75%, so it will only give one third more warming despite having five times more absorbing material. This apparent diminishing return (often described as such) is the mythical "saturation".

My physics didn't study this stuff enough, and it's too long (26 years) since I touched it. A post about it would be useful ("Why CO2's greenhouse impact won't saturate"). My personal analog is that one tight woven sheet stops 95% of convective and radiative heat loss, yet I still find several blankets keeps me much warmer than a single sheet.

Fancy Rat said...

O.K. so that's more or less what Spencer Weart did in "A Saturated Gassy Argument" on Real Climate. Thanks for the link :-)

Anonymous said...

SCM said above"I don't think Lubos's maths is self consistent in the first 5 sections of his diatribe quoted above....
this seems to indicate that Lubos was using a sensitivity of 1.36 degrees per CO2 doubling (or at least that his caclulation implies this sensitivity)"


To be honest, I don't think Motl figured anything out himself. I think he is just taking numbers directly from Lindzen. See this article.

Near as I can tell, Motl is using Lindzen's 0.64C sensitivity number (as shown in the graph that Motl has on his blog), and assuming, as Lindzen does that "the concentration of other greenhouse gases such as methane and freons is not likely to increase significantly in the future".

The key thing is that the 0.6C that Motl (Lindzen) gave for warming so far is not just due to CO2.

If one uses Lindzen's value 0.64C as the sensitivity, the Arrhenius equation gives a warming due to CO2 alone for the 20th century (for the CO2 increase from 280-380ppm) of about 0.3C (0.28C, to be precise).

0.28/0.64 = .44, (This is the fraction strictly for CO2 and is the same fraction SCM got above, as it should be, since the fraction is independent of the sensitivity)

Not all the warming over the 20th century was due to CO2 however. Assuming roughly half the warming over the 20th century was due to greenhouse gases other than CO2 (but excluding water), that gives a total theoretical warming (due to CO2 plus the other greenhouse gases EXCEPT water) of about twice that o f CO2 alone, or 0.6C, which is the number Motl (Lindzen) gave.

But, if one assumes -- as Lindzen does -- that "methane and freon no longer contribute to the warming", the warming for the remainder of the CO2 increase until doubling (560ppm) is basically that due to CO2 alone, or about 56% of 0.64 = 0.36C.

When added to 0.6C, this yields 0.96C for total theoretical warming.

So, continuing with these assumptions, one finds that the fraction so far of the total warming at (but not just due to) CO2 doubling (0.96C) is

0.6/0.96 = .63 = 63%

These numbers are not precisely the same as the ones Motl gave (63% is not precisely 2/3, and 0.3 vs 0.36 for example -- and Lindzen actually says we have seen "3/4" of the warming already [see reference below]) but they are close enough to make me think that Motl's numbers are indeed coming directly form Lindzen's values.

(The fact that Motl did not reproduce the calculations on his blog and simply said "Ask Richard Lindzen" when pressed on where the 2/3 fraction came from makes me wonder if he even knows how to do the calculations.)

I am not justifying Motl's use of Lindzen's numbers here, only pointing out that if one uses Lindzen's assumptions about sensitivity and "no more increase in methane and freon", it removes at least some of the apparent internal inconsistency from Motl's results.

At the very least, Motl was very sloppy in not making his (ie. Lindzen's) assumptions about the 0.64C sensitivity and the "no more methane and freon increase in the future" perfectly clear.


-- Horatio Algeranon

/////////////////
Motl:

"Currently we stand near 0.038% of the volume and the bare theoretical greenhouse effect, including the quantum-mechanical absorption rates for the relevant frequencies and the known concentration, predicts a 0.6 Celsius degrees increase of temperature between 0.028% and 0.038%"

"these 40% of the task have already realized about 2/3 of the warming effect attributable to the CO2 doubling."

"For example, if the greenhouse warming has been 0.6 Celsius degrees, we will see 0.3 Celsius degrees of extra warming before the carbon dioxide concentration doubles around 2100."

And Motl answers a question in the comments
"Dear someone who asked, sorry I am not able to reproduce the number 2/3 here, especially not in the short comments here. Roughly, the decisive bands of CO2 are pushed to bands which are already covered by water as the concentration reaches roughly present values. Ask Richard Lindzen."

Later on in the comments, Motl said the actual number provided by Lindzen was 3/4, but he (Motl) reduced it (so he would not make people go so crazy).

This piece provides a clue as to where Motl got his numbers (40% and 2/3 [3/4], 0.6C, 0.3C ) from.

From "A climate of alarm"
Physicsweb
News & Analysis: February 2007
"How sensitive is the climate?

"The benchmark figure usually used to illustrate the climate's sensitivity is the temperature change caused by a doubling of carbon dioxide (CO2) in the atmosphere. In 2001 the IPCC's best estimate for this was 2.5 °C. But Lindzen believes this is a huge overestimate. He maintains that although levels of CO2 have only risen by around a third since the industrial revolution, some three-quarters of the heating associated with a doubling of the concentration of the gas has already taken place. He says that this is because the warming effect of each additional carbon-dioxide molecule decreases as more and more carbon is added to the atmosphere, and because the concentration of other greenhouse gases such as methane and freons is not likely to increase significantly in the future. He believes that even if man were responsible for the entire 0.6 °C rise seen in the last century, we can expect only another 0.3-0.4 °C when carbon-dioxide levels reach 560 ppm"

Marion Delgado said...

8:35pm anonymous (i wish you mice werent so anon)

EXACTLY. WONDERFUL description. That indeed is why I am so apoplectic and incoherent about that place. Unreason is contagious, we're emotional beings. On a related note, when someone tells me I have "faith in science" I reply, no, I have confidence in science. Now. If and when the angels come heralding the simpler but provable real explanation for everything, I will abandon those parts of science that are falsified and adopt the One True Faith, whatever it is.

Unfortunately, it's possible I'll die before that blessed event, and in that case, my confidence in science will stay with me all my life.

Anonymous said...

"(i wish you mice werent so anon)"

Ah, but I did identify myself (anonymously, of course, about midway down)

--Horatio Algeranon, at your service

EliRabett said...

Having written in the post that Lubos then plays an elegant game of three card Monte with Richard Lindzen as the outside man on the short con how can Eli help but agree with the further proof Anon 5:02 provides.

Essentially Lindzen is the guy who supports the con by winning a few games (not hard, since he is the confederate of the con man)

aaron said...

Thanks Eli, I needed a good laugh.

Silly rabbit.

Anonymous said...

Rabbit.

did you ed up with a dose of mixo? Show us where the guy is wrong instead of rabitting on like the fool you are and try to present a coherent explanation as to why he's wrong.

Lay off the abuse as it gets you nowhere, you dingbat. Proof please or shut the fuckup.

Hans Erren said...

Eli, it's Bjørn Lomborg.
I forgive you the ø, as most americans have difficulties with non-ascii characters, but at least you make an effort to spell his last name properly.

BTW Where do you get the 20th century cooling needed for a "best estimate" sensitivity of 3K/2xCO2?
http://www.sciencebits.com/OnClimateSensitivity

Hans Erren said...

oops
... but at least you could make an effort to spell his last name properly

Oly said...

It is completely untenable to presume that we have already seen all the surface air warming that we are going to see from the CO2 increase over the past century.