| Topic: |
Science > Physics |
| User: |
"Bob Cain" |
| Date: |
13 Mar 2007 02:19:46 PM |
| Object: |
How Thick is CO2? |
If all the CO2 in the atmosphere were to be concentrated into a
spherical shell near sea level containing nothing but CO2 and that
shell were at, say 21 Celsius, how thick would it be?
Thanks,
Bob
--
"Things should be described as simply as possible, but no simpler."
A. Einstein
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| User: "OG" |
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| Title: Re: How Thick is CO2? |
13 Mar 2007 08:12:12 PM |
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"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:54-dnSJfpc7EZGvYnZ2dneKdnZydnZ2d@giganews.com...
If all the CO2 in the atmosphere were to be concentrated into a
spherical shell near sea level containing nothing but CO2 and that
shell were at, say 21 Celsius, how thick would it be?
This is what's known as the 'scale height' of a component of the atmosphere
The scale height of the entire atmosphere is reckoned to be about 8km, so if
the CO2 composition is 370 ppm (0.037%) this suggests a scale height of 2 -
3 metres (depending on whether the % given is by volume or by mass).
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| User: "Nomen Lapetos" |
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| Title: Re: How Thick is CO2? |
13 Mar 2007 10:17:37 PM |
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"OG" <owen@gwynnefamily.org.uk> wrote in message
news:55p0ffF25u14gU1@mid.individual.net...
"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:54-dnSJfpc7EZGvYnZ2dneKdnZydnZ2d@giganews.com...
If all the CO2 in the atmosphere were to be concentrated into a
spherical shell near sea level containing nothing but CO2 and that
shell were at, say 21 Celsius, how thick would it be?
This is what's known as the 'scale height' of a component of the
atmosphere
The scale height of the entire atmosphere is reckoned to be about 8km, so
if the CO2 composition is 370 ppm (0.037%) this suggests a scale height of
2 - 3 metres (depending on whether the % given is by volume or by mass).
that is linear, but pressure is different with height. So you could rescale
it.
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| User: "Uncle Al" |
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| Title: Re: How Thick is CO2? |
13 Mar 2007 03:57:07 PM |
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Bob Cain wrote:
If all the CO2 in the atmosphere were to be concentrated into a
spherical shell near sea level containing nothing but CO2 and that
shell were at, say 21 Celsius, how thick would it be?
Thanks,
CO2 is 370 ppm by volume of air. Air averages MW=29 daltons.
Atmosphere masses 5.136x10^18 kg. Look up the Earth's radius and run
the numbers yourself.
The Fermi answer is around 6 meters thick.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
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| User: "Bob Cain" |
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| Title: Re: How Thick is CO2? |
14 Mar 2007 01:22:27 AM |
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Uncle Al wrote:
Bob Cain wrote:
If all the CO2 in the atmosphere were to be concentrated into a
spherical shell near sea level containing nothing but CO2 and that
shell were at, say 21 Celsius, how thick would it be?
Thanks,
CO2 is 370 ppm by volume of air. Air averages MW=29 daltons.
Thanks, Al. So CO2 at MW=28 is about average for an air molecule. I
would expect it to be mo' bigger than average but just who the hell am
I anyway.
Atmosphere masses 5.136x10^18 kg.
Then CO2 masses approximately
28/29 * 370x10^-6 * 5.136x10^18 = 1.83x10^15 kg.
Look up the Earth's radius and run the numbers yourself.
The volumetric radius is 6371 km giving an area of 5.1x10^14 m^2. If
I've figured right there is about 3.6 kg of CO2 per m^2 of surface.
3.6 kg of CO2 is about 129 moles. So using PV=nRT in SI units at one
atmosphere and 21 °C
10^5 * t = 129 * 8.3145 * 294.15
giving
t = 3.15 m
Which is pretty close to what Robert S and OG said and in the ballpark
with Fermi. Any glaring errors?
Thanks,
Bob
--
"Things should be described as simply as possible, but no simpler."
A. Einstein
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| User: "John Park" |
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| Title: Re: How Thick is CO2? |
14 Mar 2007 01:06:45 PM |
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Bob Cain (arcane@arcanemethods.com) writes:
Uncle Al wrote:
Bob Cain wrote:
If all the CO2 in the atmosphere were to be concentrated into a
spherical shell near sea level containing nothing but CO2 and that
shell were at, say 21 Celsius, how thick would it be?
Thanks,
CO2 is 370 ppm by volume of air. Air averages MW=29 daltons.
Thanks, Al. So CO2 at MW=28 is about average for an air molecule. I
would expect it to be mo' bigger than average but just who the hell am
I anyway.
[...]
Which is pretty close to what Robert S and OG said and in the ballpark
with Fermi. Any glaring errors?
Yes. MW(CO) = 28; MW(CO2) = 44.
--John Park
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| User: "Bob Cain" |
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| Title: Re: How Thick is CO2? |
15 Mar 2007 02:32:34 PM |
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John Park wrote:
Yes. MW(CO) = 28; MW(CO2) = 44.
Thanks. Plugging that in the calculation chain I used gives the same
result showing that the scale height of a fraction is independent of
its MW. Combining the steps of that chain shows that it appears in
both the numerator and the denominator. D'oh.
Bob
--
"Things should be described as simply as possible, but no simpler."
A. Einstein
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| User: "Uncle Al" |
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| Title: Re: How Thick is CO2? |
15 Mar 2007 03:16:00 PM |
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Bob Cain wrote:
John Park wrote:
Yes. MW(CO) = 28; MW(CO2) = 44.
Thanks. Plugging that in the calculation chain I used gives the same
result showing that the scale height of a fraction is independent of
its MW. Combining the steps of that chain shows that it appears in
both the numerator and the denominator. D'oh.
We call that a "robust" calculation!
Calculate the thickness of pure humidity, say 70% RH in air overall.
If you want to stop Global Warming you must put plastic film over all
open water. Oh yeah... no respiration, no sweating, no peeing... and
no H*Y*D*R*O*G*E*N cars.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
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| User: "Robert S" |
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| Title: Re: How Thick is CO2? |
13 Mar 2007 03:54:45 PM |
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On Mar 13, 7:19 pm, Bob Cain <arc...@arcanemethods.com> wrote:
If all the CO2 in the atmosphere were to be concentrated into a
spherical shell near sea level containing nothing but CO2 and that
shell were at, say 21 Celsius, how thick would it be?
Thanks,
Bob
Back of the envelope calculation, it would be about 2.5 meters thick.
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