Wednesday, February 13, 2008

Why it pays to have clever anonymice

Previously, Eli had written about Gerhard Kramm in the field of rakes. it was a mystery why Kramm thought the emissivity of the surface was .612. In the comments to the Krammfest one of the mice found the answer

Looks like kramm may have copied right off the wikipedia page for Climate Model

The problem is, he apparently does not understand what "effective emissivity" is -- ie, that it already includes the influence of the greenhouse effect due to atmosphere.
From wikipedia: * ε is the effective emissivity of earth, about 0.612

The constant πr2 can be factored out, giving

(1 − a)S = 4εσT4

This yields an average earth temperature of 288 K [3]. This is because the above equation represents the effective radiative temperature of the Earth (including the clouds and atmosphere). The use of effective emissivity already accounts for the greenhouse effect. (along with clouds and other stuff)


So, in effect, Kramm is trying to "prove" that with no greenhouse effect, the earth would have the same temperature that it actually does by using an effective emissivity that already takes into account the greenhouse effect!

Also from wikipedia:

The average emissivity of the earth is readily estimated from available data. The emissivities of terrestrial surfaces are all in the range of 0.96 to 0.99 [4] [5] (except for some small desert areas which may be as low as 0.7). Clouds, however, which cover about half of the earth’s surface, have an average emissivity of about 0.5 [6] (which must be reduced by the fourth power of the ratio of cloud absolute temperature to average earth absolute temperature) and an average cloud temperature of about 258 K [7]. Taking all this properly into account results in an effective earth emissivity of about 0.64 (earth average temperature 285 K).
Have a nice piece of cheese.

18 comments:

Anonymous said...

That was me.
Notwithstanding claims to the contrary, we anonymice do contribute something useful every once in a while.

--T
PS Thanks, for the cheese, Eli.

Anonymous said...

"This yields an average earth temperature of 288 K"

Is this in the shade or in the sun?

A-non-mouse

Hank Roberts said...

Now they've retreated to claiming you can't use a global average, you need to wait til all the surface stations are checked and use albedos from each local spot. And I didn't even know they measured that at weather boxes.

Sure, albedo needs work, there are studies comparing many climate models with several satellite records (the studies comparing satellite with earthshine is cited by most of them, an easy way to find them in the science citation lists).

But the notion that we need lots more little local measurements, and whatever you do don't talk about putting Triana up, is appallingly dense.

Anonymous said...

Is that average you use the average temperature interval or specific temperature? If it is specific temperature then isn't Celsius much much more relevant to Earth's climate as the zero point(water freezing, ice caps melting, snow coverage, glaciers melting) than is absolute zero?

Annoy-mouse

Anonymous said...

It's very late here and I'm dog tired after ~5 h kip over 2 nights, so perhaps I'm missing some irony, sarcasm or witticism in your comment, Annoy-mouse. If so, then give me a Doh!

Of course, I may wake in the morning and all will become crystal like. But if there's none of those ironymouse things, then it's clear to me why kelvin is used.

Night night.

Cymraeg llygoden

Dano said...

I'm quite sure the denialists appreciate the auditing, Eli.

Right, denialists?

Right?

Best,

D

Anonymous said...

Thanks Eli, reading your entries here (and on DotEarth) has been fun - this would be a great spectator sport if it wasn't so one-sided...

-Ian

Anonymous said...

Again Rabett, this is all very clever and all, but Arctic ice, Rabett. Greater than 13.4m sq km, so Sam-hec is shot to pieces. Can it get to that 14m sq km

Old cym, without his pis, must be the lack of sleep. And dano, the one word hero with, Right, being word for the day.

bi said...

A similar bit of hilarity from another denialist:

"Wikipedia says that it [Greenland glaciers] is losing 260 or so cubic kilometers of water per year. If it's not replaced, which I'm betting against, then the oceans will rise 0.025 inches per year."

Emphasis mine.

Anonymous said...

The Gerlich and Tscheuschner paper pops up in interesting places. I found it on a Canadian Blog and posted a bit about it - including a bit from Atmoz.

The blog owner e-mailed G and/or T with the bit and G replied. The reply is somewhat interesting.

It can be found here for those interested.

Best,
John

Anonymous said...

Re my post above: Opps, just got around to reading the onEarth thread and I see that G&T posted there as well but in more detail.

John

Lazar said...

Thanks, John, for bringing that to light (it's my comment from the Atmoz thread which they respond to).

So... they accept radiative transfer from cold bodies to warmer bodies, which, as you point in the comments, blows their 'second law' argument if one considers the logical next step, whether heat transfer wrt the second law refers to the gross or net radiative energy transfer, and so instead they...
a) make a big show of being confused by my, admittedly appaling, grammer, and the fact that I should have written 'transfer' in place of 'flow', and that I didn't write "first law of thermodynamics", just "first law" when discussing, umm, thermodynamics.
... b)

"In thermodynamics the exchange of heat is described with a differential form, the heat form (for instance in a temperature,volume manifold). It is not a (net) flow of energy. It is not an exact (closed) differential form. Irreversible thermodynamics is a field theory, then you have to use a temperature field, entropy densities, densities of heat, densities of internal energy and so on"

... which one does not need to for relating the GHG effect to the second law.

Do they think no one can follow?

Anonymous said...

Lazar: I confess that I could not recall who wrote it and I was too lazy to dig it up. I am glad you claimed credit - it nicely summed up an argument I had been having with a number of people of that and a related site.

I also liked the way G&T challenged your example by essentially saying that they never said anything about 2000 degrees and 1900 degrees.

I also found the comments by the blog owner interesting. An appeal to authority argument apparently has a new appeal.

If you have the time I would encourage you to leave a comment there just to clue it up.

Very interesting posting between you, Eli and someone else whose name escapes me (Adam Smith?) over on onEarth.

Best
John

Lazar said...

John, thanks.
I think overall the discussion has gone quite well at DotEarth.
I've left a few comments at "Celestial Junk".

Anonymous said...

Hark!

"Again Rabett, this is all very clever and all, but Arctic ice, Rabett. Greater than 13.4m sq km, so Sam-hec is shot to pieces. Can it get to that 14m sq km

Old cym, without his pis, must be the lack of sleep. And dano, the one word hero with, Right, being word for the day
."

Did anyone hear anything? Sounded like a Scandinavian troglodyte falling in a polyna. No! Oh well. Must be imagining things.

Cymraeg llygoden

Anonymous said...

"Why it pays to have clever anonymice"

Pays whom?

You making money off us anonymice again, Eli?

I think we the un(der)signed anonymice should start an "Anonymouse Union" and demand "better blogging conditions", "better pay" (or some, at least. This "bits of cheese thrown here and there" is getting old), "more vacation time" the whole nine yards.

Hank Roberts said...

You could open a tip jar to be divided among the helpful. I'd gladly chip in to say thanks.

Aside -- I noticed the history of Heartland -- Heartland was set up to support Reagan's super-laser system to shoot down incoming nuclear weapons.

Much work was done understanding how infrared propagates through the atmosphere.

Then after that failed, Heartland switched to other bright ideas.

Poking around, I came across old papers in STINET, which I can't link to, but will turn up if searched for. Lots and lots about infrared transmission in the atmosphere, all arcane.

Just curious, you know, what the government knew, and when they quit knowing it.

E.g.:--------
Accession Number: ADA013719

Title: Band Model Calculation of Atmospheric Transmittance for Hot Gas Line Emission Sources. Account of Doppler Broadening.

Corporate Author: AEROSPACE CORP EL SEGUNDO CALIF CHEMISTRY AND PHYSICS LAB

Personal Author: Young,Stephen J.
Report Date: 30 JUL 1975

--------

Abstract: The effective transmittances along a slant path from the source altitude to space at a zenith angle of 75 deg are computed and averaged over three wide bandpasses in the 2.7 micrometer spectral region. Statistical band model calculations are performed for the assumption that the emission-absorption lines have a Lorentz, Doppler, or Voigt profile. Inhomogeneities inherent in treating the line of sight through the and the hot gas source as a single, highly inhomogeneous optical path are accounted for by using either the Curtis-Godson, the Lindquist-Simmons, or the two-path derivative approximation. The latter is derived herein and is shown to be superior to the Lindquist-Simmons approximation in treating radiative transfer calculations for the Doppler or Voigt line shape. With line shape properly accounted for, the results still indicate a large difference between the effective atmospheric transmittance and the atmospheric transmittance appropriate for continuum emission. This large difference can result only from the high degree of line correlation that exists between the hot H2O/CO2 emission spectrum and the cool H2O/CO2 atmospheric absorption spectrum. ...
--------------------

Here's the search that stumbled and dropped me into this brier patch:

http://stinet.dtic.mil/stinet/jsp/docread.jsp?K2DocKey=http%3A%2F%2Fstinet.dtic.mil%2Fstinet%2FXSLTServlet%3Fad%3DADA013719%40trA-search&Format=1F&Custom=&querytext=co2+emissivities&AD=ADA013719&TI=Band+Model+Calculation+of+Atmospheric+Transmittance+for+Hot+Gas+Line+Emission+Sources.+Account+of+Doppler+Broadening.&RD=July+30%2C+1975&DC=%26nbsp%3B+%26nbsp%3B+%26nbsp%3B+%26nbsp%3B+%26nbsp%3B+01+-+APPROVED+FOR+PUBLIC+RELEASE&XPC=&PAG=62+Pages%28s%29&MC=&PE=

CobblyWorlds said...

Anon 1:19
"Again Rabett, this is all very clever and all, but Arctic ice, Rabett. Greater than 13.4m sq km,"

I have two words for you - "Quikscat" and "Perenial".

Someone's going to look really stupid, real soon. Best they remain anonymous then eh?


Great blog Eli.
If those fish are stupid enough to keep jumping into the barrel, they're fair game. :)

Regards

CobblyWorlds.