2010-10-05 07:43:25Saturated absorption
Riccardo

riccardoreitano@tiscali...
93.147.82.168

Reading that incredible guy The Inconvenient Skeptic I thought that maybe a bit of physics would not hurt.

I wrote somenthing about it, the first things that came out of my mind. I'm not sure it's ok for the advanced version of  "The CO2 is saturated" argument, so I didn't claim it and didn't put anything on this site. You'll find it in my bogus website :)

2010-10-05 08:18:41looks good
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.249
Other than a few typos which can be easily cleaned up, I think this could make for a good advanced saturated CO2 rebuttal.
2010-10-05 08:21:35
nealjking

nealjking@gmail...
84.151.46.226

The presentation looks good.

However, what's missing is the explanation of the skeptical argument to be countered.

2010-10-05 16:22:36
Ari Jokimäki

arijmaki@yahoo...
192.100.112.202

I think it also might be good to mention that at different altitudes there are different levels of saturation. Higher up in the atmosphere there's more room at the wings to get more absorption. Some relevant references here (especially Strong & Plass, 1950, for the altitude point):

http://agwobserver.wordpress.com/2010/03/18/when-carbon-dioxide-didnt-affect-climate/

2010-10-05 21:21:57
Riccardo

riccardoreitano@tiscali...
192.84.150.209

Neal and Ari suggestions can be summarized in the missing of a first and a last part. That's what I did.

There's one more paragraph at the beginning a three more concluding paragraphs with a few more details, including the full quote from Plass stolen from Ari, i love quoting old articles too much to miss this opportunity :).. The central part is almost identical. I spotted a few typo but there are probably more and maybe also awkwardly worded sentences. Feel free to give me an F in written english.

The post is still here. I prefer to start the fight with  alignement, quotes, paragraph, images and the like when I'm done with the text.

 

2010-10-06 23:07:48Great rebuttal, should spark interesting discussion
John Cook

john@skepticalscience...
124.186.160.198
A few suggestions, minor textual stuff:

First line, perhaps mention year. Eg "After the famous Arrhenius paper in XXXX..."

'This is the birth of the "CO2 effect is saturated" argument' perhaps changed to 'This was the birth of the "CO2 effect is saturated" argument'

"It was not until the '50" => "It was not until the 1950s"

"In some way we may think" => "In some ways, we may think"

"The absorption coefficient of a gas specie depends"... Is specie meant to be specifically?

"Did this energy disappeared forever?" => "Did this energy disappear forever?"

"The intensity of the emerging light will be that appropriate" => "The intensity of the emerging light will be appropriate"

"the layer at which the absorption coefficient at each wavelength is low enough to let the IR light escape will be found upper in the atmosphere" => "the layer at which the absorption coefficient at each wavelength is low enough to let the IR light escape will be found higher in the atmosphere"

"It is from the '50" => "It is from the 1950s"

Btw, for the record, once I planned to do a blog post "history's first global warming skeptic", it being about Angstrom. Your post covers what I would've said, only much better

2010-10-07 05:37:15
Riccardo

riccardoreitano@tiscali...
93.147.82.79

John

I think it's a great idea to write a post on the first skeptic. I'll be happy to change the first part of my post if you still plan to write it. I think you should.

I made the corrections. As for the gas specie, it was really poorly worded. In the meanwhile I realized that it was also unnecessary. Now it simply reads "The absorption coefficient of a gas depends, among other things, on the concentration (pressure); [...]"

2010-10-08 11:05:55History's global warming skeptic
John Cook

john@skepticalscience...
124.186.160.198
Riccardo, I don't think it's necessary - I wouldn't say much more than what you've said here, you've covered it also nicely. If you like, you could always use that title for the blog post of this rebuttal, just as a hook to get people's interest (and if so, perhaps tweak the first paragraph wording to reference it). Up to you though. Let me know when you're happy for me to post this.
2010-10-08 19:24:40
Riccardo

riccardoreitano@tiscali...
93.147.82.144

Ok, I'll borrow your title and expand the first paragraph a little bit.

2010-10-09 05:24:54
Riccardo

riccardoreitano@tiscali...
93.147.82.188

Heavily modified version. I stole John's idea of the first skeptic (I love it too much) and emphasized the historic point of view much more. I also added a final note acknowledging the role of Spencer Weart book, which I love too. (Please don't tell my wife I'm in love with an idea and a book  :)). I left it where it was for the reasons I'll tell John below.

---

John,

i started my usual fight with the editing system, there must be something wrong with me (the age? :)).

As advanced version of an existing argument the title will obviously be the same as the argument. Is it possible to have it as rebuttal but with a different title? You can eventually delete the incomplete version I saved.

From the editing page of the rebuttal I cannot upload images.

 

2010-10-09 09:18:48Published
John Cook

john@skepticalscience...
124.186.160.198

Great stuff, Riccardo, am very happy that you used the 'first skeptic' idea as your treatment of the subject was better than I could ever have done. Also like that you credit Spencer Weart - he's a regular at SkS so I'm sure he'll be tickled pink to see the credit.

Re the title, do you want to use "the first global warming skeptic" as the headline at the top of the advanced rebuttal instead of "is the co2 effect saturated?"

Note: will work on making the editing system easier to use, particularly uploading images. Priority task for next week!

2010-10-09 16:58:17
Riccardo

riccardoreitano@tiscali...
93.147.82.104

Nice awakening for me this morning. John did the dirty job for me and I got a "well done" from Spencer Weart himself as he first comment :). Thank you.

 

2010-10-09 20:23:17
MarkR
Mark Richardson
m.t.richardson2@gmail...
134.225.187.80

I quite like it, but a few comments:

 

"less CO2 molecules" should be "fewer...". " "last" layer layer." should be "last layer" I assume?

Where you model the absorption lineshape with a Gaussian is easily misunderstood. The way you have your explanation, it seems like you're arbitrarily increasing the absorption linewidth simply because the function you've decided to use says that?

You then go on to explain that this does happen because of real, physical broadening mechanisms but I think the order could do with being moved around so that people understand why you modify the lineshape before you actually do it.

(after all, I thought pressure broadening was greater than Doppler, and that's a Lorentzian rather than a Gaussian!)


 

 

2010-10-09 22:40:08
Riccardo

riccardoreitano@tiscali...
93.147.82.104

I did not change the linewidth in the model: "We can now look at what happens when we increase α.". That's the cause, the effect is a wider peak in the absorbed energy energy.

This is the first step after Hulburt, an increase in absorption coefficient increases the energy absorbed whatever the linewidth is. Next comes more details: "Needless to say that there's much more than what can be done with the very crude model presented here.". I'm putting aside my rather crude model and go to a more advanced level, brodening and splitting (Plass).

The lineshape is a convolution of the two effects, i.e. a Voight lineshape, but in the tails it resembles a lorentian. Using a gaussian I minimized the effect. But it's irrelevant to my point, you get a widening with a gaussian as well. I never claimed that the real lineshape is gaussian.

Now it's too late to make changes to the post to better clarify these points, I cannot modify whole paragraphs unless they're wrong.

2010-10-09 23:00:17Updating whole paragraphs
John Cook

john@skepticalscience...
124.186.160.198

There's no set in stone rule here but personally, I tended to leave blog posts as they are (like a snapshot in time) but I am constantly tweaking and refining the rebuttal text (which you can edit via the Rebuttal List). This is digital, not paper, it's never locked in. So Riccardo, feel free to improve the rebuttal text if you wish - the rebuttal is like the encyclopedic reference that will stand over time and eventually be used in the iPhone app (and Firefox plugin) so good to perfect it if you see something you'd like to improve.

BTW, it's nice waking up to see a new blog post on the website, isn't it? :-) That's why I'm encouraging authors to post more blog posts - hoping to see more pleasant surprises when I wake up (as opposed to previous morning surprises like "your site's been hacked" or "WUWT has posted a personal smear against you").

And yeah, I thought it was cool having the first-up comment from Spencer Weart too :-)

2010-10-10 03:42:52This is really a nice article, but there are some expressions that are confusing:
nealjking

nealjking@gmail...
84.151.40.134

"After the famous Arrhenius paper in 1896, where he did the first calculations of the CO2 greenhouse effect"

=> "After his famous paper in 1896, where Arrhenius did the first calculations of the CO2 greenhouse effect"

 

"he concluded that very few CO2 molecules are enough to completely absorb the IR beam"

=> "he concluded that even a small number of CO2 molecules is sufficient to completely absorb the IR beam"

 

"The conclusion was that a CO2 increase could not matter. This was the birth of the first skeptic of the then called "CO2 theory" and of the more recent "CO2 effect is saturated" skeptic argument."

=> "The conclusion was that an increase in CO2 could not matter. This was the beginning of the first skeptic of what was then called "CO2 theory", and of the more recent skeptic argument that "the CO2 effect is saturated"."

 

"added convection to the purely radiative equilibrium assumed by Arrhenius."

=> "considered convection in addition to the purely radiative dynamics assumed by Arrhenius."

 

" while radiative holds equilibrium above."

=> "while radiative equilibrium holds above."

 

"what govern the energy balance"

=> "what governs the energy balance"

 

"Hulburt was very prudent"

=> "Hulburt was very cautious"

 

"forcing Huburt"

=> "forcing Hulburt"

 

"concentration anyways."

=> "concentration in any case."

 

"find a decreasing pressure, i.e. less CO2 molecules."

=> "encounter fewer and fewer CO2 molecules."

 

"The intensity of the emerging light will be appropriate for the temperature of this "last" layer layer."

=> "The intensity of the emerging light will be appropriate to the temperature of this "last" layer."

 

"Plank law"

=> "Planck law"

 

"the emissivity of this outer layer is modulated between 0 and 1"

=> "the emissivity of this outer layer is modulated between the lower curve and upper curve"

 

"In the calculations I used an absorption wavenumber of 650 cm-1"

=> "In the calculations, I focused on absorption near the wavenumber of 650 cm-1"

 

 "correspond to the Plank law"

=> "correspond to the Planck law"

 

"This dip represents the energy prevented to reach the outer space, i.e. the greenhouse effect."

=> "This bite taken out of the 300-K curve represents the energy prevented from reaching outer space: the greenhouse effect."

 

This critique gets through about the first half of the article; I will continue with further suggestions later.

I think MarkR has a few good points, and will try to address them in my later commentary.

 

2010-10-10 09:30:07
Riccardo

riccardoreitano@tiscali...
93.147.82.104

Done with the corrections part I, ready for part II. :)

 Thanks Neal

2010-10-10 14:00:33Part II
nealjking

nealjking@gmail...
84.151.40.134

continuing on from the 300-K/220-K Planck curves:

"We can now look at what happens when we increase α. Following Angstrom (and many others in his times) the energy absorbed should not change. On the contrary, if we recall that the absorption coefficient is gaussian we would expect an increase in the energy retained by our layer along the wings. The effect is shown in the figure below."

=> "We can now look at what happens when we increase α. If we follow the reasoning of Angstrom (and of many of his colleagues), we would conclude that the total power absorbed should be unchanged. However, if instead we recall that the absorption coefficient is does not drop abruptly to zero, but can be modeled as a gaussian in frequency, we would expect an increase in the power blocked by the edges of the "bite", the so-called "wings". The effect is shown in the figure below: Although the emissivity does not dip below the 220-K curve, the bite becomes wider and more power is blocked.

[FIGURE]

What is happening is that the overall absorption that reduces the emission level depends exponentially on the absorption coefficient. If we consider frequencies moving away from the absorption peak, the coefficient gets smaller, thus the overall absorption is reduced; at some frequency displacement from the peak, we could consider the overall absorption negligible. Now when we add more CO2 to the atmosphere, the absorption coefficient increases at every frequency, so the frequency displacement for the point of negligible absorption gets moved out. Thus the wings broaden."

 

"We can see that although the absorption dip cannot fall below the 220 K curve, it becomes wider and the absorbed energy increases accordingly. This is as far as we can get with this simple model. Needless to say that there's much more than what can be done with the very crude model presented here. We know, for example, that the line shape of the absorption coefficient changes with both pressure and temperature due to what are called pressure and Doppler broadening. In the upper layers of the atmosphere the band initially gets narrower and then splits into several narrow bands (the roto-vibrational spectrum) leaving more room for the increase in CO2 concentration being more effective. We also know that there are weaker absorption peaks other than the stronger one quoted above which are not saturated."

=> "This simple model assumes that the line shape of the absorption coefficient is the same throughout the atmosphere; but in fact it is affected by pressure and temperature (pressure and Doppler broadening). At the upper layers of the atmosphere, the 15-micron band is actually split into several narrower bands (the roto-vibrational spectrum), providing even more scope for growing wings when more CO2 is added."

 

"There's one more subtle effect related to increased absorption. Upon increasing CO2 concentration, the layer at which the absorption coefficient at each wavelength is low enough to let the IR light escape will be found higher in the atmosphere. The emitting layer will then have a lower temperature, at least until the tropopause is reached, and hence a lower emitting power."

=> "There's another major influence on increased absorption. Upon increasing CO2 concentration, the layer at which the absorption coefficient at each wavelength is low enough to let the IR light escape will be found higher in the atmosphere. Because temperature decreases with increasing altitude (adiabatic lapse rate), until the tropopause, the emitting layer will then have a lower temperature than 220 K, and hence a lower emitting power."

 

"But you know, this is how science works."

=>

"But this is how science works."

 

2010-11-10 10:04:53
Riccardo

riccardoreitano@tiscali...
93.147.82.75
Was Peter Sinclair inspired by this post?  :)
2010-11-14 17:41:54
Glenn Tamblyn

glenn@thefoodgallery.com...
124.180.10.239

Gilbert Plass is someone that the pro-AGW side need to promote more. It was his work that first disproved the previously held views about CO2 saturation and paved the way for the modern understanding of Radiative Transfer. Also, at around the same time, Roger Revelle's discoveries on buffering of CO2 uptake by the oceans overturned the previous idea that the oceans would absorb most of what humanity pumped out.

Its spooky and humbling that in the year I was being born the core of modern climate science was being born. And now, over 1/2 a century later, how far have we progressed?