Thursday, January 06, 2011

The Ångström Effect

As the attentive (hey stop with the Facebook stuff you in the back) know, Eli has been going a few friendly rounds with John Nielsen-Gammon, who is not very happy with the term greenhouse effect, and is proposing "Tyndall Gas Effect" as a replacement. Well, Eli is quite happy with greenhouse effect, as it captures the core idea, that limiting the flow of energy out of a system will result in warming, and besides, Tyndall already has a milky effect in his name, and besides which, while the old guy did the first IR spectroscopy on gases, he never had anything to say about emission, aka backradiation.

With some help from the friendly hares in the neighborhood, Eli has found the seminal paper, by Anders Ångström, and, in his honor, proposes that in the spirit of replacing the perfectly useful Centigrade with Celsius, that if you really gotta do it and lose the useful analogy, well, ok, how about the Ångström Effect?

It's really nice when you consider that Ångström was the grandson of the guy they named the wavelength unit after AND the son of the guy who originated the sensitive IR detector that he used to measure backradiation.

Even better, best from Eli's POV, Harry Ångström is Rabbit.


John Mashey said...

Rabett: what did you do to me?
I clicked on Harry Angstrom is Rabbit, and later went again to Amazon, the first 4 recommendations from Amazon are:

Rabbit Angstrom: A Tetrology:... and then 3 Upton books:
Rabbit Redux
Rabbit at Rest
Rabbit is Rich

Mark said...

Sorry, but "Tyndall gas effect" sounds too much like something Tyndall would do after, say, eating a bowl of black bean chili. It's too easily mocked.

EliRabett said...

John, you forgot Rabett Run. . .:) Eli does like his puns warmed over.

Anonymous said...

That would be Updike, not Upton. Is this reference to the American novelist news to you guys??

Supercilious Anonymous

Anonymous said...

And the Swedish pronunciation sounds kinda like Ohng-strum.

Linguistic Anonymous

John Mashey said...

Sorry, that was Updike of course, but I've been thinking of this Upton of late and my fingers had minds of their own.

However, FreedomWorks didn't want him, so he can't be all bad.

Jim Bouldin said...

"while the old guy did the first IR spectroscopy on gases, he never had anything to say about emission, aka backradiation."

Rabbit, have you been into the catnip this week or something? I'm going strictly from memory here, but I'm virtually certain that Tyndall said something to the effect of: "variations in trace gases could have produced all the various mutations of climate seen in the past". That means he implicitly recognized that at least some of the gases he investigated had the ability to back radiate thermal energy toward the earth, not just absorb it. No?

Horatio Algeranon said...

Eli has found the seminal paper, by Anders Ångström"

Good one, Eli.

"Nocturnal Radiation" (aka Emissions)

John Farley said...

At the Consumer Electronics Show in Las Vegas, the Mindscape company is marketing a robot rabbit named Karotz, which looks unbelievably cool. As if the Star Wars robots R2D2 or C3P0 were replaced by the cute stuffed bunnies on this website. For details, see the video on the Los Angeles Times website.

Yes, I know this is off topic, but I just couldn't resist.

Anonymous said...

John Farley, Please only buy one for Eli, if you were to buy two & they already know multiplication... well, we certainly do not want a repeat of Eli's 'Tribbles' experience, now do we?

Even Spock was touched, a very dangerous situation for the Enterprise, Kirk & crew. Forward; into the past.

Unknown said...

I understand that Anders Aangstroem is great. But unfortunately labelling with his name is confusing, because the role taken by his father, Knut Aangstroem, whose earnest (but incorrect in retrospect) scientific work caused resistance in apprehension of Arrhenius's idea of anthropogenic global warming. See in Spencer Weart's "The Discovery of Global Warming".
Weart also mentioned it in RealClimate as .

Knut did not deny what we call greenhouse effect, but he thought that absorption of infra-red by carbon dioxide was already saturated, and also he missed the idea that cascades of emission and absorption could enhance warming even though absorptivity at each step cannot increase beyond unity. (Disclaimer: I have not read Knut's paper myself, but just read Weart's historical essays.)

EliRabett said...

Yes, but the beauty of it all is that Anders used Knut's apparatus to show that there is a cascade of emission and absorption!:)

Flavius Collium said...

Ångström = Steamstream...

David B. Benson said...

A fine name except for making the little circle over the A to form Å.

Timothy Chase said...

Jim Bouldin wrote, " I'm going strictly from memory here, but I'm virtually certain that Tyndall said something to the effect of: 'variations in trace gases could have produced all the various mutations of climate seen in the past'That means he implicitly recognized that at least some of the gases he investigated had the ability to back radiate thermal energy toward the earth, not just absorb it. No?"

Good memory. Tyndall states, "... may have produced all the mutations of climate which the reseraches of geologists reveal." (pg. 277)

However, this in itself does not mean that he was aware of backradiation, only that greenhouse gases reduce the rate at which energy escapes the atmosphere, and given energy entering the system at the same rate and principle of conservation of energy this implies a warmer climate system.

But it would appear that he was aware of backradiation as well.

He states,

My next care was to examine whether different gases possessed different powers of radiation; and for this purpose the following arrangement was devised....

The results of the experiments are given in the following Table, the figure appended to the name of each gas marking the number of degrees through which the radiation from latter urged the needle of the galvanometer:

Carbonic oxide... 12
Carbonic acid...18
Nitrous oxyide...29

pp.278-9, Tyndall, John, 1861. On the Absorption and Radiation of Heat by Gases and Vapours, and on the Physical Connection of Radiation, Absorption, and Conduction. 'Philosophical Magazine ser. 4, vol. 22, 169-94, 273-85

see article link at

Timothy Chase said...


Note: air was at the top of the list given by Tyndall -- but I omitted it -- which I should have indicated with ellipses. However, I was focusing instead on the difference between non-greenhouse gases that do not emit radiation and greenhouse gases that do emit radiation. This demonstrates the fact that Tyndall investigated backradiation by greenhouse gases.

Anonymous said...

Mr. Timothy Chase, If I am reading a right here, there, you show that by Tyndall, John, 1861...& this is know laughing matter either...we are all sure to die if we don't stop "Nitrous oxyide...29", Now! Stop!... This is 'nothing' to smile at. We see the above & understand.

Anonymous said...

I suspect that David B. Benson has a similar concern to my own.

If you succeed in your push, Brere Rabbet, I will be punished inhumanly for my pedantry, as I struggle to decorate my every mention of the Effect with the little bits of punctuary shit.

I have, however, left an alternative suggestion on the Eli Luntz thread.

Bernard J. Hyphen-Anonymous XVII

Jim Bouldin said...

Many thanks for digging that up Timothy as I couldn't find my old Tyndall publications. Without the radiation figures and quotes you present, I wonder how Tyndall could have concluded only that GHGs would slow heat loss (without back radiation).

Timothy Chase said...

Jim Bouldin wrote, "Many thanks for digging that up Timothy as I couldn't find my old Tyndall publications. Without the radiation figures and quotes you present, I wonder how Tyndall could have concluded only that GHGs would slow heat loss (without back radiation)."

No problem. Obviously he did know about back radiation. However hypothetically you could have a greenhouse effect even if there were no backradiation.

The radiation would get absorbed by the greenhouse gases. The greenhouse gases would thermalize the energy. As the atmosphere warmed this would reduce the rate of heat loss from the surface due to moist air convection, etc. Entirely hypothetical given Kirchoff's law and Tyndall's investigations.

However, the point is that absorption is what reduces the rate at which radiation escapes the atmosphere. If radiation is absorbed and thermalized this warms the atmosphere. By warming the troposphere you reduce the rate at which heat escapes, e.g., due to moist air convection. This would warm successively lower layers and ultimately the surface. A warmer surface will radiate more thermal radiation and the system will tend towards a new equilibrium.

At the surface the atmosphere is already about as opaque as it is going to get to thermal radiation. It is only by increasing the optical thickness of the atmosphere in the upper layers where it is currently optically thin that greenhouse gases are able to warm the climate system.

This causes the atmosphere to warm in the upper layers. This reduces the rate of heat transfer from lower levels, causing them to warm, reestablishing roughly the same lapse rate but at a higher temperature at all layers. As such, the atmosphere warms from the outside in -- like baking a pot roast or boiling a frog.

The upper troposphere drags the rest of troposphere along and thus the surface with it. Sure, backradiation increases at the surface -- but only because the atmosphere near the surface is warmer -- not because of increased absorption by a near-surface atmosphere that has become optically thicker.

But when people focus on the backradiation they often have things reversed. They view higher levels of greenhouse gases at the surface as being responsible for the warmer temperatures at the surface, then the atmosphere as warming from the inside out. But it can't work that way since at the surface the atmosphere is already about as optically thick as it is going to get.

Jim Bouldin said...

Thanks Timothy! Bunch of ideas to chew on there. Damn radiation physics!

Hank Roberts said...

Well, the AÅngström Effect then?

David B. Benson said...

Oh fooey, there is also an umlaut on the o.

Timothy Chase said...


Actually this was something that Arch Stanton and I were still piecing together back at Tamino's in September, particularly the warming from the top down in relation to lapse rate, the transition from an optically thin to an optically thick atmosphere and the warming of the new, higher boundary where emitted infrared radiation escapes without further absorption so that radiation balance reachieved. Then I performed a search and found that Ray had said something similar:

"The way the greenhouse effect really works is that adding CO2 reduces the infrared out the top of the atmosphere, which means the planet receives more solar energy than it is getting rid of as infrared out the top. The only way to bring the system back into balance is for the whole troposphere to warm up. It is the corresponding warming of the low level air that drags the surface temperature along with it — an effect left entirely out of Plass' calculation."

Plass and the Surface Budget Fallacy
Ray Pierrehumbert, 13 January 2010

So it would seem that none other than Gilbert Plass was thinking in terms of forcing at the surface rather than at the top of the atmosphere. In essence he was thinking of the warming of the atmosphere being driven by increased backradiation at the surface. And that was one of the great minds in climatology circa 1956. I guess those of us thinking in terms of backradiation driving the greenhouse effect (and I was thinking along those lines a while back) are in pretty good company.

Anyway, my apologies for not looking this earlier stuff up sooner -- I was in a hurry. New job. Don't really have time for anything else at the moment.

Kevin McKinney said...

Old thread, obviously--but I was looking for another post involving A. Angstrom, and happened on this one, and I have this link that's so apropos, I'm just waving my (metaphorical) hand in the air like an excited third-grader.

See, I'm quite sure that Tyndall did know quite a bit about back radiation. The interesting thing is that measurements of that radiation go back *before* Fourier, to Dr. William Charles Wells's Rumford-medal winning paper "An Essay on Dew," published in 1814.

(At that point Fourier was trying to figure out how if there was any way he could still collect on the pension Napoleon had promised him. (Yes, really!--well, the Corsican really did award him one, at least.))

Anyway, Wells made all sorts of measurements of temperature at night--under clear skies, under cloud, under fog, varying heights, insulating thermometer bulbs, all sorts of experimental conditions. Just the thing for showing that the earth radiated to the sky--and vice versa.

As stated, Wells got the Rumford medal for this work--he was the fifth or sixth winner. And Tyndall was aware of his work; he writes about it in his book on radiant heat. Besides, solidarity forever! Tyndall was a Rumford winner himself. It behooved him to know the history of the jewelry the Royal Society was handing him.

I think one reason that many folks keyed on the idea of backradiation was that, while measuring it adequately is not easy, it was still a heck of a lot easier than TOA measurements. They went with data that they actually had, not the data they might have wished to have, pre-space Age.

kevin McKinney said...

Couldn't forbear to look up the Tyndall reference. It's in "Heat as a mode of motion," p. 426 et. seq.

Tyndall's beautifully written (and distinctly Victorian) praise of Wells is worth the look, and his review of subsequent research on the topic worthwhile.

Oh, and the book is available digitally, for free, from Google books.