What would the average surface temperature of the earth be, if there was no atmosphere (how alarmists overstate the greenhouse effect, by making an incorrect assumption)
Climate Realist
was no atmosphere (how alarmists overstate the greenhouse effect, by
making an incorrect assumption).
There are many websites which claim that the average surface
temperature of the earth would be about -18 C, if there was no
atmosphere. They then state that since the actual average surface
temperature is about +15 C, the greenhouse effect must be responsible
for warming the atmosphere by about +33 C.
The above claim is incorrect. To see why, we need to look at how the
-18 C is calculated. The calculation is based on the Stefan–Boltzmann
Law
F=kT^4
where F = energy flux density
k = Stefan–Boltzmann constant = 5.67 * 10^-8
T = temperature
We also need to include:
S = the Solar Constant = 1360 W/m^2
A = the albedo of the earth
this is normally assumed to be 30%, meaning that 30% of the incoming
radiation is reflected back into space, and 70% of the incoming
radiation is absorbed by the earth.
d = ratio of the cross section of the planet, to the surface area of
the planet = Pi*r^2 / 4*Pi*r^2 = 1/4
this is the ratio of the area that the incoming radiation is absorbed
over, to the area that the outgoing radiation is emitted from.
Using all of the above, we get:
T=(S*(1-A)*d/k)^0.25
putting in the values for all variables, we get
T=(1360*(1-.3)*1/4/5.67*10^-8)^0.25 = 254.54 K
In celsius this is 254.54 - 273.15 = -18.61 C
-----------------------------------
What is the incorrect assumption?
Here is a quote about the albedo of the earth, from the website:
http://www.eoearth.org/article/Albedo
"On average the Earth and its atmosphere typically reflect about 4%
and 26%, respectively, of the sun’s incoming radiation back to space
over the course of one year. As a result, the earth-atmosphere system
has a combined albedo of about 30%, a number highly dependent on the
local surface makeup, cover, and cloud distribution."
So 26% (out of the 30% total) of the earths albedo, is due to the
atmosphere.
The calculation giving -18 C is meant to be the temperature of the
earth with no atmosphere, but it assumes that the albedo is 30%, the
value when the earth does have an atmosphere.
The calculation should be done with an albedo of 4%, if the earth has
no atmosphere.
Doing this gives a temperature of +2.30 C (instead of -18.61 C)
This is 20.91 C warmer than the incorrect calculation.
Using this value of +2.30 C, and the average surface temperature of
+15 C, the greenhouse effect only needs to be responsible for warming
the atmosphere by an additional +12.7 C (instead of +33 C).
In summary, the incorrect assumption means that the greenhouse effect
is overstated by a factor of about 2.6
Giga2
Surely some 'non-GHG' have some warming effect as well, just as an
insulator? Like maybe oxygen, I wonder what only an oxygen atmosphere
temperature would be? Then you could add in just WV. Probably get 33.
Climate Realist
>
> - Show quoted text -
A 'non-GHG' atmosphere would warm by conduction from the land and the
ocean (just like the present atmosphere does). This would lead to
convection in the 'non-GHG' atmosphere (just like the present
atmosphere).
The main difference between a 'non-GHG' atmosphere, and the present
atmosphere, would be the lack of water vapour and clouds. This would
expose the earth to more of the present solar radiation, because
without clouds, the albedo of the earth would be much lower. Water
(which covers about 70% of the earth), has an albedo of about 3%,
compared with the present total albedo (earth and atmosphere and
clouds etc) of about 30%.
We would go from absorbing about 70% of the solar radiation, to
absorbing about 96% of the solar radiation. This is an increase in
absorbed solar radiation, of about 37% over what we absorb now. This
would increase the temperature of the earth by about 21 C.
erschro...@gmail.com
The albedo isn't all there is to the GH effect. When the planet
absorbs heat, it re-radiates it. The atmosphere traps that heat, due
to GH gases in it; without an atmosphere, that heat would be lost to
space.
You really should learn some basic science.
erschro...@gmail.com
And the speed of light is 20 mph. Both are silly answers I'd expect
from simpletons.
Tom P
You are comparing apples and pears.
There are two independent variables - the albedo due to cloud cover and
the greenhouse effect. You are comparing a planet with cloud cover and a
greenhouse atmosphere with a planet with no cloud cover and no
greenhouse atmosphere, and reaching the wrong conclusion about the
greenhouse effect.
Basically, you are comparing planet earth with the moon. Even the most
dedicated climate scientist would agree that the greenhouse effect on
the moon is extremely weak - but it really says nothing about the
greenhouse effect on the earth.
BTW, if the earth's surface temperature really were 2.3°c, the planet
would be mostly covered in ice - which would raise the albedo.
Bill Ward
Another effect of a non-GHG atmosphere is that the incoming energy would
spread poleward, warming the poles and cooling the tropics. Because of
the T^4 dependence of power density, the surface as a whole would cool
less effectively.
That would require a warmer equivalent surface temperature to maintain
equilibrium between the incoming and outgoing energy.
There was a thread (in a.g-w) a year or so ago on this very subject.
Giga2
And at night would there be any insulating effect?
Bill Ward
The radiating surface would become colder than the air, forming an
inversion layer that would reduce convection. Lateral winds would likely
still warm the surface, but not as effectively as direct convection would
cool it during the daytime. At least that's my guess.
Climate Realist
This is a stupid comment, for a number of reasons:
1) I never claimed that the albedo is all there is to the GH effect.
(If you think that I claimed this, then point out where I said it)
2) In actual fact, albedo is quite separate from the greenhouse
effect. CO2 is a GHG, but is not important for albedo. Water vapour is
a GHG, and is very important for albedo (clouds etc). This shows that
albedo and the greenhouse effect are independent.
< When the planet absorbs heat, it re-radiates it.
Yes, my explanation included this. What do you think the Stefan–
Boltzmann Law was used for?
< The atmosphere traps that heat, due to GH gases in it;
< without an atmosphere, that heat would be lost to space.
Yes, this is the classical greenhouse effect. My analysis was based on
the fact that without an atmosphere, the heat would be lost to space.
Why do you think the temperature of +2.3 C is cooler than the present
average surface temperature of +15 C. It is because without the
greenhouse effect, more radiation is lost to space.
> You really should learn some basic science.
You seem to have a serious comprehension problem. You criticisms seems
to consist of copying what I said, as if you said it, and implying
that I don't understand it.
You really should learn some basic comprehension.
Climate Realist
What sort of moron are you?
Is this the best scientific argument that you can come up with.
First you say something stupid (this is your strong point), and then
you point out that only a simpleton would say what you just said.
You have convinced me. You are a simpleton.
Climate Realist
>
> - Show quoted text -
I am comparing a planet with an atmosphere, to a planet without an
atmosphere.
A planet with an atmosphere, has a high albedo due to clouds etc, and
has a greenhouse effect.
A planet without an atmosphere, has a low albedo due to no clouds, and
no greenhouse effect.
The reason that I am comparing these 2 states, is because that is what
the other websites claim to compare. But the other websites get it
wrong, because they assume a high albedo with no atmosphere. Where do
the clouds exist, if there is no atmosphere?
Yes, this is similar to the moon. Except the earth is rotating faster,
so that it doesn't get as hot in the direct sunlight. I understand
that the moon gets to 120 C in the direct sunlight, because it only
rotates once per month.
You make an interesting point about ice. Note that the 2.3 C is an
average in several respects.
It is an average over day and night. Warmer in the day and cooler at
night. (just like now)
It is also an average between the tropics and the poles. Warmer in the
tropics, cooler at the poles. (just like now)
Because the solar radiation intensity varies with the angle of
incidence to the surface, it is much stronger in the tropics (where
there is no ice), than it is near the poles (where there is ice). Most
of the energy is absorbed at the tropics anyway (even if there was no
ice). So the solar radiation lost to the albedo of the ice near the
poles, is not full strength solar radiation. Since we are only losing
the weak solar radiation, it does not have a very strong cooling
effect (but it will have some effect).
The classic calculation of -18 C with no atmosphere, makes you think
that the whole planet would be an ice cube. But +2.3 C is above the
melting point of ice. This is a MAJOR difference.
Climate Realist
I don't think that there would be any insulation effect against losing
energy by radiation.
But I agree with Bill that a 'non-GHG' atmosphere could slow heat loss
by forming an inversion layer.
It could also pass some heat back to the surface by conduction.
Warm winds can also provide energy, and cold winds can remove energy.
These are probably more local effects, rather than global effects.
erschro...@gmail.com
And the planet would be much colder.
> Why do you think the temperature of +2.3 C is cooler than the present
> average surface temperature of +15 C. It is because without the
> greenhouse effect, more radiation is lost to space.
>
> > You really should learn some basic science.
>
> You seem to have a serious comprehension problem. You criticisms seems
> to consist of copying what I said, as if you said it, and implying
> that I don't understand it.
>
> You really should learn some basic comprehension.
Your post only discussed the albedo. If you really believe other
things are important, you should have mentioned it. You didn't, which
left yourself open for (deserved) charges of stupidity.
You made some calculations assuming no atmosphere, but taking only the
albedo into account. That is stupid.
erschro...@gmail.com
Yes, because you didn't take into account 2 things affect the temp --
albedo and GH gases.
Giga2
> On Mon, 26 Apr 2010 23:21:23 -0700,Giga2wrote:
> > On 26 Apr, 13:46, Climate Realist <climate.real...@gmail.com> wrote:
So does a GHG work the same way as an insulator? Or more clearly an
insulator work by trapping and re-radiating photons of LWIR, the same
way a GHG is supposed to?
Giga2
> On Apr 27, 6:21 pm,Giga2<justho...@yahoo.com> wrote:
>
>
>
> > On 26 Apr, 13:46, Climate Realist <climate.real...@gmail.com> wrote:
>
Right.
Bill Ward
I'm not so sure. If the planet is rotating, convection plus the Coriolis
effect should set up global circulation bands of winds similar to the
present atmosphere.
The weather should get really interesting near the terminator, though,
with the day/night temperature differentials.
The GHG-free atmosphere should be a good candidate for modeling.
Tom P
2.3°c as an average temperature is quite cold enough to cover a large
area of the planet with ice. During the Last Ice Age, the planet was
only around 5°c colder on average than the present day.
Bill Ward
Sort of. If you think of an insulator as a substance with low thermal
conductivity, then the atmosphere could be thought of as a region of
variable thermal conductivity between the surface and space. Without
GHGs, the atmosphere would have no resistance to outgoing radiation, and
the surface would have an equivalent average temperature of ~255K.
If GHG's are added, they convert outgoing LWIR to heat, which must
convect up to a higher altitude, lower temperature to radiate. That
forces the surface to become warmer because of the lapse rate below the
radiating layer.
You could think of that as a decrease in thermal conductivity, or
insulating effect.
When you include water and its latent heat, it increases the thermal
conductivity, because the convective transfer of latent heat is more
effective than LWIR. The more WV, the higher the thermal conductivity
between the surface and the lapse rate.
That's essentially a variable insulator that maintains the 255K average
radiating layer at an altitude that maintains constant optical depth in
LWIR. If the surface increases in temperature, the additional
evaporation of latent heat WV increases the thermal conductivity to the
radiating layer, cooling the surface. If it gets too cold, less water
evaporates, and the thermal conductivity drops, reducing the heat loss.
The absorption and re-radiation of LWIR photons is a red herring. All the
GHGs do is reversibly convert LWIR into thermal heat in the air around
them. Within a few km of the surface, there's enough WV to absorb all
the LWIR to heat within a few meters. In LWIR, it would appear as a
black cloud.
Within that black cloud, the temperature quickly comes to a local
thermodynamic equilibrium(LTE), because heat always flows from hot to
cold. No net energy can be transported by radiation because everything
"within sight" is at the same temperature. Convection of the warmed
gases is the only way energy can get up to the radiating altitude.
Once the air convects close enough to the top of the WV layer to "see"
space, GHGs and cloud droplets radiate the energy to space.
There's also a "window" around 10u unaffected by GHGs, in which some LWIR
can radiate directly to space, but it doesn't really affect the above
explanation. Think of it as a parallel, unmodulated path to space.
The bottom line is that GHGs can't "trap" heat. It's always free to
convect.
Dawlish
>
> - Show quoted text -
No-one's arguing with that Bill. What happens if the depth of the re-
radiating layer of GHGs gets deeper? Is the same amount of heat lost?
Giga2
I'll have to let that sink in a bit, its quite a bit over my head.
Climate Realist
My post discussed far more than just the albedo. It included:
- the Stefan–Boltzmann Law
- the Solar Constant
- the albedo of the earth
- the ratio of the cross section of the planet, to the surface area of
the planet
- energy flux density
- the mistake that many websites make, when they claim that the
average surface temperature of the earth without an atmosphere would
be about -18 C
- the incorrect assumption that the albedo of the earth without an
atmosphere, would be the same as the present albedo
Your brain may only be able to handle one word per post ("albedo" in
this case), but everybody else got far more out of it. As I have said
before, your comprehension level appears to be that of a junior school
child.
< You made some calculations assuming no atmosphere, but taking only
the
< albedo into account. That is stupid.
The calculation took into account, what needed to be taken into
account. What else do you want me to take into account, when there is
no atmosphere.
- there is no greenhouse effect, because with no atmosphere there are
no greenhouse gases
- there is no high albedo, because with no atmosphere there are no
clouds
What is really stupid, is you expecting me to discuss more factors,
when there are no more relevant factors to discuss.
Climate Realist
Do you legally have to warn people that you are a moron, before you
communicate with them?
Tell me how greenhouse gases are relevant, when there is NO
atmosphere.
I DID take the albedo into account. The albedo is low, when there is
NO atmosphere (no atmosphere means no clouds).
I suggest that you think before you post.
Climate Realist
>
> - Show quoted text -
From the Vostok ice cores, it looks like the difference between a
glacial and an interglacial, is about 12 C. Where do you get the 5 C
figure from.
As long as the tropics are ice free, the earth acts as a giant heat
pump, transferring the excess heat from the tropics towards the poles.
Bill Ward
Sorry. Is there some part I can clarify?
erschro...@gmail.com
That's what the earth would be without its atmosphere, not without
some hypothetical atmosphere.
> Your brain may only be able to handle one word per post ("albedo" in
> this case), but everybody else got far more out of it. As I have said
> before, your comprehension level appears to be that of a junior school
> child.
I ask you again: Why did you not include GH gases in your calculation
of what the earth would be like without its atmosphere?
>
> < You made some calculations assuming no atmosphere, but taking only
> the
> < albedo into account. That is stupid.
>
> The calculation took into account, what needed to be taken into
> account.
No, you neglected what earth's atmosphere does besides its albedo.
>What else do you want me to take into account, when there is
> no atmosphere.
> - there is no greenhouse effect, because with no atmosphere there are
> no greenhouse gases
> - there is no high albedo, because with no atmosphere there are no
> clouds
>
> What is really stupid, is you expecting me to discuss more factors,
> when there are no more relevant factors to discuss.
The lowering of temp. without earth's atmosphere must take into
account both the change in albedo AND no GH gases. You neglected the
latter and claimed all the scientists have it wrong. That's idiocy.
But then, that's you.
erschro...@gmail.com
The decrease in temp. from the current value would be due to BOTH
effects; you just took one into account.
columbiaaccidentinvestigation
>
> - Show quoted text -
Yes, you can correct your use of LTE, and then you can correlate your
statement about Green house gasses acting like an insulating blanket
to the increase in co2 concentrations increasing the effectiveness of
that insulating blanket. Save your apology, just try to do better next
time.
Giga2
Yes, what is this IOW?: That
Bill Ward
OK. I was too terse. Because air expands and cools as it rises, there
is a difference in temperature between altitudes - outside clouds, the
temperature drops about 10K for every km of altitude . This is called
the dry adiabatic lapse rate:
<http://en.wikipedia.org/wiki/Lapse_rate>
Now the radiating layer has to emit the same amount of energy the Earth
is receiving from the Sun, or the temperature would change. That works
out to the same as a black body at 255K. Without an atmosphere, that
would be the average temperature of the surface, which would be the
radiating layer.
When you have an atmosphere and an ocean with water, energy from the Sun
evaporates water to WV, absorbing latent heat from the surface and
cooling it. The higher the surface temperature, the more WV is formed,
and the more latent heat is transferred.
Now since WV absorbs LWIR very strongly, energy can no longer radiate
very far from the surface before it's absorbed by WV and converted to
heat in the nearby air. The outward radiative heat transfer is blocked,
but the warmer air convects the energy upward in the form of latent heat.
As it rises, the air temperature falls by the 10K/km dry lapse rate until
it reaches the dewpoint temperature. At that point, it condenses to
cloud, releasing the latent heat it's carried from the surface, and
begins to radiate that heat as a graybody (broadband) to space.
Now the radiating layer is higher altitude, but still must average to
255K to maintain equilibrium. The layer is higher than the surface by
some distance, so the surface must be warmer than the 255K by the dry
lapse rate of 10K for each km.
Looking from the outside in, the Earth must appear to have a temperature
of 255K, because that's how much energy it receives from the Sun. But the
actual level it radiates from is higher because GHGs, mostly water, block
radiation from the surface. Because of the lapse rate, the surface is
warmer than the radiating layer.
Is that better?
Climate Realist
>
> - Show quoted text -
< I ask you again: Why did you not include GH gases
< in your calculation of what the earth would be like
< without its atmosphere?
If there is no atmosphere, then there are no greenhouse gases.
If there are no greenhouse gases, then they can not have an effect on
the temperature.
If you think that greenhouse gases should be included in the
calculation of the temperature for the earth with no atmosphere, then
please show us your calculation. We could all do with a good laugh.
Climate Realist
>
> - Show quoted text -
< The absorption and re-radiation of LWIR photons
< is a red herring. All the GHGs do is reversibly
< convert LWIR into thermal heat in the air around
< them. Within a few km of the surface, there's
< enough WV to absorb all the LWIR to heat within
< a few meters. In LWIR, it would appear as a
< black cloud.
Bill,
are you saying that there is not much LWIR returned to the ground?
Your description sounds like there should be very little temperature
increase for the land. But that there should be some temperature
increase in the atmosphere.
Is that what you are saying?
Bill Ward
Good question.
To understand my answer, you need to understand Local Thermodynamic
Equilibrium (LTE). The atmosphere near the surface has enough water
vapor (WV) to absorb all the surface emitted LWIR within a few meters.
On absorption, the LWIR energy is converted to heat, so the temperatures
of everything in LWIR "sight" quickly equalize by exchanging photons. In
LWIR, it would appear as a black cloud of gas from the surface up to an
altitude of a few kilometers.
At equilibrium, everything within "sight" is the same temperature, so
radiation can't carry any net energy. Photons are continually exchanged
in all directions, but they act only to equalize temperatures. That
equilibrium condition is LTE.
The statement that LWIR photons are "returning energy to the ground" is
true, but they are canceled by exactly the same amount of energy
"returned to the air" from the ground. In LTE, there is no net transfer
of energy by LWIR photons.
Most of the energy transferred away from the surface on its way to be
radiated to space is carried by convection, often including the latent
heat of WV. There is no energy carried by LWIR from the radiating layer
back to the surface.
First of all, that would be transferring energy from cold to warm, which
is a second law violation, and secondly, the surface is covered by that
black cloud of WV and other GHGs.
So no, I don't think there's much LWIR energy returning to the ground.
>
> Your description sounds like there should be very little temperature
> increase for the land. But that there should be some temperature
> increase in the atmosphere.
>
> Is that what you are saying?
I'm not sure why you think there would be any temperature increase.
columbiaaccidentinvestigation
>
> - Show quoted text -
Your description of LTE neglects bouyancy/gravity waves, and once
again you are attempting to define LTE conditions within in the
planetary boundary that ignore reality.
Giga2
> On Wed, 28 Apr 2010 12:58:06 -0700,Giga2wrote:
: ) now I understand 'lapse rate' a bit more. SO all this is why there
should be a hotspot just below the troposphere (when there isn't)
because AGW means heat should be trapped way up there, not near the
surface?
Dawlish
>
> - Show quoted text -
You do realise that the second law of thermodynamics applies to a
closed system. You cannot, therefore apply that to an arbitrarily
defined "local" system. Photons can be transferred in all directions
and that means outside of the particular LTE you are talking about.
They can also be transferred in. If more photons are heading in, than
out, what will happen to the temperature? The whole of the atmosphere
must be considered. There are no closed "local" systems in the earth's
atmosphere, I'm afraid.
Bill Ward
<big snip>
>> Looking from the outside in, the Earth must appear to have a
>> temperature of 255K, because that's how much energy it receives from
>> the Sun. But the actual level it radiates from is higher because GHGs,
>> mostly water, block radiation from the surface. Because of the lapse
>> rate, the surface is warmer than the radiating layer.
>> Is that better?
> : ) now I understand 'lapse rate' a bit more. SO all this is why there
> should be a hotspot just below the troposphere (when there isn't)
> because AGW means heat should be trapped way up there, not near the
> surface?
The heat isn't trapped. It can always convect. Climate models assume WV
positive feedback, which would be increasing the temperature at that
altitude. In reality, to cool more efficiently, the heat must be
radiated from lower altitudes, where it's warmer.
I suspect it may be radiating from the clouds below, which increase in
size and drop in altitude, because a warmer surface evaporates more
water, causing a higher dewpoint temperature.
BTW, when you post from Google Groups rather than a Usenet news reader, I
may miss your posts, as Google sometimes uses a funky "Content-Transfer-
Encoding: quoted-printable" header line that pan (my newsreader) doesn't
recognize. I have to manually edit the post to respond. That's why I
snipped most of the above post - I'm lazy.
Giga2
I really should go back to a newsreader but I like the Google stats
and being able to rate posts!
Rob Dekker
"Giga2" <just...@yahoo.com> wrote in message
news:353fd0a1-7fa4-4efa...@l32g2000yqm.googlegroups.com...
The adiabatic lapse rate as Bill describes it is correct.
However, it is not correct to assume that any excess heat will simply
radiate away from the upper troposphere.
The simple fact is that the adiabatic lapse rate is enforced by convection
as Bill describes, but the altitude (and thus the temperature) at which
photons can escape to space (and thus cool the planet) is determined by how
many well-mixed GHGs (like CO2) there are in the atmosphere. If there is
more CO2 in the atmosphere, the altitude of radiation to space will
increase. Since the overall, effective radiating temperature of planet Earth
will have to be 255 K (as Bill also describes) this means that the altitude
at which 255 K occurs will increase with increased CO2 concentration. Since
that lapse rate is still the same (determined by adiabatic expansion of air
molecules) the surface temperature will increase. That's global warming..
Please re-read the above paragraph again, because it really shows very
clearly how global warming (or climate change, as it is called since a Bush
administration officer changed the wording to make it sound less dangerous)
works.
Besides this, it is also not correct to think that hear would somehow
accumulate in the upper troposphere.
Any heat that makes it to the top of the troposphere, but does not radiate
away, will simply come down back to Eath due to downward air flow in Hadley
cells. Again : Convection will let heat (and air) flow upward, but air has
to come down somewhere. When it comes down, it will warm adiabatically, and
thus the heat itself that did not radiate away is still there. This makes
the poles warm up a bit more than other parts of the planet, since heat
eventually (net) always flows from hot to cold.
But again : since air that goes up has to come down somewhere, there will be
very little of heat remaining in the upper troposphere, and thus there will
be very little (or no) 'heat spot' in the upper troposphere noticable.
Rob
Rob Dekker
"Climate Realist" <climate...@gmail.com> wrote in message
news:4eb1a157-7520-455b...@11g2000prw.googlegroups.com...
....
> >
> > The lowering of temp. without earth's atmosphere must take into
> > account both the change in albedo AND no GH gases. You neglected the
> > latter and claimed all the scientists have it wrong. That's idiocy.
> > But then, that's you.- Hide quoted text -
>
> > - Show quoted text -
>
> < I ask you again: Why did you not include GH gases
> < in your calculation of what the earth would be like
> < without its atmosphere?
>
> If there is no atmosphere, then there are no greenhouse gases.
>
In which case the average temperature at the surface would be ?.....
> If there are no greenhouse gases, then they can not have an effect on
> the temperature.
Not on the average temperature, which would be...
>
> If you think that greenhouse gases should be included in the
> calculation of the temperature for the earth with no atmosphere, then
> please show us your calculation. We could all do with a good laugh.
Compare the average temperature without GHGs (but with an atmosphere) to the
current average temperature of planet Earth, and you get.....
Do we really have to do these calculations for you or can you do them
yourself ?
Rob
Giga2
> "Giga2" <justho...@yahoo.com> wrote in message
atmosphere there should be an ongoing hotspot. It is not like the heat
goes in and then goes out before the satellites get a reading. When
heat goes out other heat should be replacing it.
Climate Realist
> "Climate Realist" <climate.real...@gmail.com> wrote in message
I did these calculations at the start of this thread.
"erschroedinger" doesn't seem to understand, that when you calculate
the average surface temperature for the earth with no atmosphere, you
don't have to adjust for the effect of greenhouse gases, because there
are none.
He makes silly comments like:
< < < I ask you again: Why did you not include GH gases
< < < in your calculation of what the earth would be like
< < < without its atmosphere?
For your information, I calculate the average surface temperature for
the earth with no atmosphere, to be +2.3 C.
Many websites, and alarmists, claim that it would be -18 C. But they
do not allow for the change in albedo when there is no atmosphere (no
water vapour and no clouds).
Introducing an atmosphere to the earth, with the normal greenhouse
gases, would raise the temperature to about +15 C, an increase of
about +12.7 C (not the +33 C increase that many websites and alarmists
claim).
Climate Realist
> "Giga2" <justho...@yahoo.com> wrote in message
Hadley cells are driven by the temperature differences between
different air masses. Warm air tends to rise, and cool air tends to
sink. But air will not tend to rise unless it is warmer than the air
above it, and air will not tend to sink unless it is cooler than the
air below it.
If warm air makes it to the top of the troposphere, but does not
radiate away enough heat, it will NOT simply come back down to Eath
due to the downward air flow in Hadley cells. It will inhibit the
convection cycle in the Hadley cell, until it has lost enough heat
(become cool enough) to participate in the convection cycle again.
Therefore, heat would accumulate in the upper troposphere, under these
circumstances.
You claim that air that goes up has to come down somewhere. But it
only comes down when it is cooler than the air below it. And if it can
not come down, then no more air can go up. The convection cycle is
inhibited. Heat would build up throughout the system.
Bill Ward
> "Giga2" <just...@yahoo.com> wrote in message
> news:353fd0a1-7fa4-4efa-
b632-788...@l32g2000yqm.googlegroups.com...
Can you explain that a bit more specifically? The CO2 can only absorb or
radiate in the 15u band, while WV radiates from 3 to 8u and 11 to 70u,
while clouds radiate as a gray body over the entire LWIR spectrum. There
is much more energy in the shorter wavelengths associated with water,
while the CO2 is limited to a narrower, lower energy band.
Higher surface temperatures evaporate more water. More water means a
higher dewpoint. A higher dewpoint means a lower condensation altitude,
which means lower, warmer clouds and more energetic radiation.
Why would more CO2 cause the average radiation altitude to increase? WV
and clouds clearly radiate most of the energy, while CO2 plays only a
small part. If the surface temperature were to increase, the additional
WV would lower the average radiating altitude, not raise it.
> Since the overall, effective
> radiating temperature of planet Earth will have to be 255 K (as Bill
> also describes) this means that the altitude at which 255 K occurs will
> increase with increased CO2 concentration.
You need to explain how that can happen, because a warmer surface will
cause the average radiating altitude to decrease.
> Since that lapse rate is
> still the same (determined by adiabatic expansion of air molecules) the
> surface temperature will increase. That's global warming.
See above. If the surface temperature increases, the WV content
increases, the radiating altitude decreases, and cooling is increased.
That's negative feedback.
> Please re-read the above paragraph again, because it really shows very
> clearly how global warming (or climate change, as it is called since a
> Bush administration officer changed the wording to make it sound less
> dangerous) works.
>
> Besides this, it is also not correct to think that heat would somehow
> accumulate in the upper troposphere.
Correct.
> Any heat that makes it to the top of the troposphere, but does not
> radiate away, will simply come down back to Eath due to downward air
> flow in Hadley cells.
> Again : Convection will let heat (and air) flow
> upward, but air has to come down somewhere. When it comes down, it will
> warm adiabatically, and thus the heat itself that did not radiate away
> is still there. This makes the poles warm up a bit more than other parts
> of the planet, since heat eventually (net) always flows from hot to
> cold.
>
> But again : since air that goes up has to come down somewhere, there
> will be very little of heat remaining in the upper troposphere, and thus
> there will be very little (or no) 'heat spot' in the upper troposphere
> noticable.
But if the WV feedback assumptions were correct, there would be a"hot
spot". The models which assume positive WV feedback all predict the hot
spot, but measurement shows it's not there.
So you have just debunked the WV positive feedback assumption and
confirmed Lindzen's findings, Congratulations.
Dawlish
> On Sat, 01 May 2010 01:07:05 -0700, Rob Dekker wrote:
> > news:353fd0a1-7fa4-4efa-
>
> b632-788ec694f...@l32g2000yqm.googlegroups.com...
The data, being only from the tropics (a major criticism of Lindzen's
work and not the only one), shows this feature only in the area where
data is weakest. That's why he "found" what he did. The careful
selection of time periods from within the data compounded this
(another major criticism of Lindzen and Choi). From Skeptical Science
(as it is clearer than I could put this) "The place where the the two
mechanisms (greenhouse gases vs solar) are distinguishable is in the
stratosphere where solar should cause warming and greenhouse gases
should cause cooling. There, the satellite and radiosonde data
unambiguously show cooling.
If Lindzen was correct, we should not see this outcome - and the
stratosphere has shown cooling, not warming.
This "debunks" Lindzen's findings far better than your interpretaion
above confirms them!
Rob Dekker
> On May 1, 8:48 pm, "Rob Dekker" <r...@verific.com> wrote:
> I did these calculations at the start of this thread.
> For your information, I calculate the average surface temperature for
> the earth with no atmosphere, to be +2.3 C.
>
> Many websites, and alarmists, claim that it would be -18 C. But they
> do not allow for the change in albedo when there is no atmosphere (no
> water vapour and no clouds).
You did, but your calculations are wrong, and this is why :
If there is no atmosphere, and no water either, then of course their will be
no clouds and the Earth resemble the moon (both in terms of albedo and
absence of atmosphere, and of course same distance from the sun).
For the moon, the mean surface temperature (day), 107 C. Mean surface
temperature (night), -153 C.
Now that is an 'average' temperature of -23 C. Even colder than the -18 C
often quoted.
Why is that different from your +2.3 C ?
Well, I did not check all your calculations, but even if you did not make a
calculation mistake, you sure forgot that radiation from the 'hot' side of
Earth-without-atmosphere will be much more than the radiation from the
'cold' side, since radiated energy goes with T^4.
In essence, an Earth without atmosphere (and without water) will radiate
mostly from only half of it's surface. That reduced radiation causes the
average temperature to drop. Just like the moon.
That's how it works.
Rob
Rob Dekker
.....
That does not make sense. In a Hadley cell, as long as the air is still
warm, it will rise further up.
With increased CO2, the altitude where radiation is effective enough to cool
the air will simply be a bit higher. So the Hadley cell will still run, as
before, but the top of the Hadley cell will be a bit higher than before.
>
> You claim that air that goes up has to come down somewhere. But it
> only comes down when it is cooler than the air below it. And if it can
> not come down, then no more air can go up. The convection cycle is
> inhibited. Heat would build up throughout the system.
Once again, the convection cycle will not be inhibited.
If it would, Earth's surface would warm up very quickly (and thus convection
would start again).
Rob
Rob Dekker
"Giga2" <just...@yahoo.com> wrote in message news:a65f9d4c-37e2-4b4f-91b2-
...
> > But again : since air that goes up has to come down somewhere, there
> > will be
> > very little of heat remaining in the upper troposphere, and thus there
> > will
> > be very little (or no) 'heat spot' in the upper troposphere noticable.
> >
> Ah, but if more heat is being cycled through this area of the
> atmosphere there should be an ongoing hotspot. It is not like the heat
> goes in and then goes out before the satellites get a reading. When
> heat goes out other heat should be replacing it.
Giga.
Climate Realist gave a similar response as you did, so please see my
response to you there.
Thanks
Rob
Climate Realist
> "Climate Realist" <climate.real...@gmail.com> wrote in message
In this context, warm is a relative term. Warm relative to what?
< With increased CO2, the altitude where radiation is effective enough
to cool
< the air will simply be a bit higher. So the Hadley cell will still
run, as
< before, but the top of the Hadley cell will be a bit higher than
before.
Don't Hadley cells go to the top of the troposphere? Can the
troposphere get a bit higher?
> > You claim that air that goes up has to come down somewhere. But it
> > only comes down when it is cooler than the air below it. And if it can
> > not come down, then no more air can go up. The convection cycle is
> > inhibited. Heat would build up throughout the system.
< Once again, the convection cycle will not be inhibited.
< If it would, Earth's surface would warm up very quickly (and thus
convection
< would start again).
The Earth's surface would warm up very quickly (and thus convection
would start again), and the entire system would run at a higher
temperature, with more heat present throughout the system. Therefore
there would be a "hot" spot in the upper troposphere. All of the
greenhouse climate models predict it (but it has NOT been found -
looks like reality is wrong again).
Dawlish
>
> - Show quoted text -
I think to really examine the existence of a hot spot, you've got to
go to the original recent papers; many are linked here:
http://agwobserver.wordpress.com/2009/09/06/papers-on-tropical-troposphere-hotspot/
The McIntyre and McKitrick paper was published in Feb 2009 and Mann et
al's rebuttal, in the same journal is easily found on the Internet.
The lack of a "hot spot" in the upper troposphere is probably a myth,
but this really is an area where more research is needed, to confirm,
or deny it's existence.
(McIntyre S, McKitrick R(2009) Proxy inconsistency and other problems
in millennial paleoclimate reconstructions. Proc Natl Acad Sci USA
106:E10).
Bill Ward
> On May 3, 9:24 pm, "Rob Dekker" <r...@verific.com> wrote:
>> "Climate Realist" <climate.real...@gmail.com> wrote in message
>>
>> news:be3a270a-d9d0-4c45-90b1-
c1fc1f...@23g2000pre.googlegroups.com...
Relax. Most outgoing energy is radiated lower in the troposphere, from
clouds and the top of the WV layer. CO2 cools from the stratosphere, but
the radiation is limited to the 15u band, corresponding to a temperature
of only ~200K.
Here's Miskolczi's paper:
<http://www.met.hu/doc/idojaras/vol111001_01.pdf>
see page 19:
<quote>
"Since the Earth-atmosphere system must have a way to reduce the
clear sky OLRe to the observed OLRa we assume the existence of an
effective cloud layer at about 2.05 km altitude. The corresponding
optical depth is τCa = 1.47 . Fig. 6 shows the dependences of the OLR
and Ed on the cloud top altitude and Eu on the cloud bottom altitude. At
this cloud level the source function is Sc = 332.8 W m-2. We also assume
that the cloud layer is in thermal equilibrium with the surrounding air
and radiates as a perfect black-body. Clear sky simulations show that at
this level the OLR ≈ OLRa ≈ Ed and the layer is close to the radiative
equilibrium. Cloudy computations also show that Eu – and consequently K –
has a maximum around this level, which is favorable for cloud formation.
"In cloudy areas the system loses the thermal energy to space at a
rate of OLRa which is now covered by the absorbed SW flux in the cloudy
atmosphere. According to the Kirchhoff law, the downward radiation to the
cloud top is also balanced.
"Below the cloud layer, the net LW flux is close to zero. Clouds at
around 2 km altitude have minimal effect on the LW energy balance, and
they seem to regulate the SW absorption of the system by adjusting the
effective cloud cover β."
<\quote>
[caution - some of the equations suffer from font errors. Check the
originals if you step through any.]
The basic idea is that negative feedback from the layer of clouds at
about 2km regulates the surface temperature.
Before I hear howls of complaints from AGWers about this being just
another climate model, remember two things:
1) it's non recursive - errors are not compounded.
2) It matches actual observations better than the IPCC models because it
handles clouds and convection without assuming positive WV feedback.
Rob and I are discussing it in another thread, if anyone is interested.
Dawlish
> On Mon, 03 May 2010 04:31:51 -0700, Climate Realist wrote:
> > On May 3, 9:24 pm, "Rob Dekker" <r...@verific.com> wrote:
> >> "Climate Realist" <climate.real...@gmail.com> wrote in message
>
> >> news:be3a270a-d9d0-4c45-90b1-
>
Rob is actually doing an excellent job of debunking Miscokzi's paper
and criticising your support for it, as others have also ably done.
There are thousands of scientists working in climate science apart
from just Miscolkzi and Lindzen but you seldom refer to anyone else's
work. Why aren't those scintists not citing these two authors
regularly, if their work is so seminal? They are not citing them
because they can see the flaws that you ignore - or, of course, as
you've recently said, they are all part of a global science conspiracy
that only a cabal of top AGW scientists have been a party to (I know,
it's logically ridiculous, but that's what you've said).
Rob Dekker
> What would the average surface temperature of the earth be, if there
> was no atmosphere (how alarmists overstate the greenhouse effect, by
> making an incorrect assumption).
> Using all of the above, we get:
>
> T=(S*(1-A)*d/k)^0.25
>
> putting in the values for all variables, we get
>
> T=(1360*(1-.3)*1/4/5.67*10^-8)^0.25 = 254.54 K
>
> In celsius this is 254.54 - 273.15 = -18.61 C
>
> -----------------------------------
>
> What is the incorrect assumption?
>
> Here is a quote about the albedo of the earth, from the website:
> http://www.eoearth.org/article/Albedo
>
> "On average the Earth and its atmosphere typically reflect about 4%
> and 26%, respectively, of the sun�s incoming radiation back to space
> over the course of one year. As a result, the earth-atmosphere system
> has a combined albedo of about 30%, a number highly dependent on the
> local surface makeup, cover, and cloud distribution."
>
> So 26% (out of the 30% total) of the earths albedo, is due to the
> atmosphere.
>
> earth with no atmosphere, but it assumes that the albedo is 30%, the
> value when the earth does have an atmosphere.
>
> The calculation should be done with an albedo of 4%, if the earth has
> no atmosphere.
>
> Doing this gives a temperature of +2.30 C (instead of -18.61 C)
>
> This is 20.91 C warmer than the incorrect calculation.
Nice claim, but your number (or +2.3 C) is wrong, and this is why :
Bill Ward
> "Climate Realist" <climate...@gmail.com> wrote in message
> news:42dde1be-c0fd-4bd2-9870-
d1d1aa...@g34g2000pro.googlegroups.com...
How do you stop it from radiating on the day side? It should actually
radiate more, since it's hotter there.
Climate Realist
> "Climate Realist" <climate.real...@gmail.com> wrote in message
>
> - Show quoted text -
The method that I have used to calculate the average surface
temperature of the earth with no atmosphere, is the standard method
used by many websites. The only change that I have made, is to use a
more realistic value for the albedo. The result of +2.3 C is correct
(for an albedo of 4%).
I do have a number of complaints about the standard method. They
average the total energy flux over the entire radiating surface,
before calculating the average temperature. To be accurate, they
should calculate the temperature from the energy flux at each location
(it varies, compare the equator to the poles), and then average the
temperatures. This makes a difference, because the temperature is
raised to the power of 4 in the Stefan–Boltzmann Law. The more
accurate method is obviously far more complicated and difficult. So I
accept the standard method as a simple and hopefully not too
inaccurate method.
I agree with your comment about the earth with no atmosphere being
like the moon, in terms of albedo, absence of atmosphere, and distance
from the sun.
However, there is an important difference. The earth rotates with
respect to the sun, once every day (24 hours). But the moon rotates
with respect to the sun, about once every month. So a location on
earth is in sunlight for about 12 hours continuously, but a location
on the moon is in sunlight for about 14 days continuously. This allows
a location on the moon to get much hotter than the corresponding
location on earth.
A similar argument applies to a location on earth being out of the
sunlight for about 12 hours continuously, but a location on the moon
is out of the sunlight for about 14 days continuously. This allows a
location on the moon to get much colder than the corresponding
location on earth.
I looked up the average surface temperature for the moon, on a number
of websites. They all gave exactly the same values that you quoted.
The mean surface temperature (day) is given as 107 C, and the mean
surface temperature (night) is given as -153 C. As you pointed out,
averaging these two numbers gives -23 C (even colder than the -18 C
often quoted). Why is that different from +2.3 C ?
Note also: maximum moon surface temperature 123°C - minimum moon
surface temperature -233°C
The fact that all websites give exactly the same temperatures for the
moon, suggests to me that they are all repeating the results of one
study. I have not managed to find that study, so I do not know what
assumptions were made in calculating the temperatures. My suspicion is
that the mean surface temperatures given are NOT the means for the
entire day hemisphere and night hemisphere. They may apply to smaller
regions. If this is true, then averaging the 2 temperatures to get an
average for the moon, is not valid.
My justification for my suspicion, is that 120 C is about the maximum
temperature you can get from the solar constant (1360 Wm^-2) (sunlight
shining permanently at right angles to the surface). This is close to
the maximum moon surface temperature. As you move away from hottest
spot on the moon (the spot nearest the sun), the sunlight strength
decreases with the cosine of the angle of incidence. By the time you
get to the edge of the day hemisphere, the strength is zero.
I have just calculated that by the time you are 30 degrees away from
the spot on the moon nearest the sun, the temperature would be 107 C.
It seems amazing that that is exactly the value given for the mean day
surface temperature. I wonder if that is how they worked it out. The
temperature drops off quickly as you move further than 30 degrees from
the hottest spot. So I find it hard to believe that 107 C is the day
hemisphere average.
----------------------------------------------------------
Finally, I found some evidence to support my calculation on wikipedia:
http://en.wikipedia.org/wiki/Black_body#Temperature_of_Earth
Temperature of Earth
If we substitute in the measured values for the Sun and Earth:
Ts=5778 K
Rs=6.96x10^8 m
D=1.496x10^11 m
alpha=0.306
If we set the average emissivity to unity, we calculate the "effective
temperature" of the Earth to be:
TE = 254.356 K or -18.8 °C.
This is the temperature that the Earth would be at if it radiated as a
perfect black body in the infrared, ignoring greenhouse effects, and
assuming an unchanging albedo. The Earth in fact radiates almost as a
perfect black body in the infrared which will raise the estimated
temperature a few degrees above the effective temperature. If we wish
to estimate what the temperature of the Earth would be if it had no
atmosphere, then we could take the albedo and emissivity of the moon
as a good estimate. The albedo and emissivity of the moon are about
0.1054[20] and 0.95[21] respectively, yielding an estimated
temperature of about 1.36 °C.
(Note: In all of my calculations I assumed an emissivity of 1.0)
---------------------------------------------------------
By the way, I sure did NOT forget that radiation from the 'hot' side
of Earth-without-atmosphere will be much more than the radiation from
the 'cold' side, since radiated energy goes with T^4.
As I explained above, the simple easy method is an approximation, and
averages the hot and cold sides together to give an average
temperature.
Rob Dekker
> On May 4, 8:17 am, "Rob Dekker" <r...@verific.com> wrote:
> > "Climate Realist" <climate.real...@gmail.com> wrote in message
> >
> > news:42dde1be-c0fd-4bd2...@g34g2000pro.googlegroups.com...
> >
> >
> >
> >
> >
> > > What would the average surface temperature of the earth be, if there
> > > was no atmosphere (how alarmists overstate the greenhouse effect, by
> > > making an incorrect assumption).
> > ...
> > > Using all of the above, we get:
> >
> > > T=(S*(1-A)*d/k)^0.25
> >
> > > putting in the values for all variables, we get
> >
> > > T=(1360*(1-.3)*1/4/5.67*10^-8)^0.25 = 254.54 K
> >
> > > In celsius this is 254.54 - 273.15 = -18.61 C
> >
> > > -----------------------------------
> >
> > > What is the incorrect assumption?
> >
> > > Here is a quote about the albedo of the earth, from the website:
> > >http://www.eoearth.org/article/Albedo
> >
> > > "On average the Earth and its atmosphere typically reflect about 4%
> accurate method is obviously far more complicated and difficult. So I
> accept the standard method as a simple and hopefully not too
> inaccurate method.
>
> I agree with your comment about the earth with no atmosphere being
> like the moon, in terms of albedo, absence of atmosphere, and distance
> from the sun.
>
> However, there is an important difference. The earth rotates with
> respect to the sun, once every day (24 hours). But the moon rotates
> with respect to the sun, about once every month. So a location on
> earth is in sunlight for about 12 hours continuously, but a location
> on the moon is in sunlight for about 14 days continuously. This allows
> a location on the moon to get much hotter than the corresponding
> location on earth.
>
> A similar argument applies to a location on earth being out of the
> sunlight for about 12 hours continuously, but a location on the moon
> is out of the sunlight for about 14 days continuously. This allows a
> location on the moon to get much colder than the corresponding
> location on earth.
>
> I looked up the average surface temperature for the moon, on a number
> of websites. They all gave exactly the same values that you quoted.
> The mean surface temperature (day) is given as 107 C, and the mean
> surface temperature (night) is given as -153 C. As you pointed out,
> averaging these two numbers gives -23 C (even colder than the -18 C
> often quoted). Why is that different from +2.3 C ?
>
> surface temperature -233�ｿｽC
> This is the temperature that the Earth would be at if it radiated as a
> perfect black body in the infrared, ignoring greenhouse effects, and
> assuming an unchanging albedo. The Earth in fact radiates almost as a
> perfect black body in the infrared which will raise the estimated
> temperature a few degrees above the effective temperature. If we wish
> to estimate what the temperature of the Earth would be if it had no
> atmosphere, then we could take the albedo and emissivity of the moon
> as a good estimate. The albedo and emissivity of the moon are about
> 0.1054[20] and 0.95[21] respectively, yielding an estimated
>
> (Note: In all of my calculations I assumed an emissivity of 1.0)
>
> ---------------------------------------------------------
>
> By the way, I sure did NOT forget that radiation from the 'hot' side
> of Earth-without-atmosphere will be much more than the radiation from
> the 'cold' side, since radiated energy goes with T^4.
>
> As I explained above, the simple easy method is an approximation, and
> averages the hot and cold sides together to give an average
> temperature.
You are on the right track distinguishing between the EFFECTIVE temperature Teff and the AVERAGE temperature Tave of a planet.
But to be accurate, you need to consider radiation absorption and emission at different latitudes, consider day/night, consider
rotation and both SW and IR albedo effects and (with atmosphere) also surface heat flows.
In short, you need to refine your planet model beyond the single T Stephan Bolzman Equation that you have been using so far.
It means that you need to get deep into integrals.
I would be happy to do that with you, but expressing formulas in text form is kind of difficult, and besides that, the various
'cases' (such as Earth with or without an atmosphere, Moon, rotation, albedo effects etc) really beg for a decent paper.
Now there happens to be paper that did much of this 'simple planet modeling' work already, with the relation between Teff and Tave
nicely derived in comprehensible integrals. It also works out influence on Teff of GHG in the atmosphere using a simple,
comprehensive but still pretty accurate model, without getting too deep into radiative transfer theory.
It then tests the results with observations for various planets and the moon.
Here is the paper :
http://arxiv.org/PS_cache/arxiv/pdf/0802/0802.4324v1.pdf
It may not address all of your questions, but I think it will be of help to refine your calculations.
Rob
Climate Realist
> > "Climate Realist" <climate.real...@gmail.com> wrote in message
> >news:cc23e1d8-bea3-47b5...@g1g2000pro.googlegroups.com...
> > On May 4, 8:17 am, "Rob Dekker" <r...@verific.com> wrote:
> > > "Climate Realist" <climate.real...@gmail.com> wrote in message
>
> > temperature of the earth with no atmosphere, is the standard method
> > used by many websites. The only change that I have made, is to use a
> > more realistic value for the albedo. The result of +2.3 C is correct
> > (for an albedo of 4%).
>
> > I do have a number of complaints about the standard method. They
> > average the total energy flux over the entire radiating surface,
> > before calculating the average temperature. To be accurate, they
> > should calculate the temperature from the energy flux at each location
> > (it varies, compare the equator to the poles), and then average the
> > temperatures. This makes a difference, because the temperature is
> > accurate method is obviously far more complicated and difficult. So I
> > accept the standard method as a simple and hopefully not too
> > inaccurate method.
>
> > I agree with your comment about the earth with no atmosphere being
> > like the moon, in terms of albedo, absence of atmosphere, and distance
> > from the sun.
>
> > However, there is an important difference. The earth rotates with
> > respect to the sun, once every day (24 hours). But the moon rotates
> > with respect to the sun, about once every month. So a location on
> > earth is in sunlight for about 12 hours continuously, but a location
> > on the moon is in sunlight for about 14 days continuously. This allows
> > a location on the moon to get much hotter than the corresponding
> > location on earth.
>
> > A similar argument applies to a location on earth being out of the
> > sunlight for about 12 hours continuously, but a location on the moon
> > is out of the sunlight for about 14 days continuously. This allows a
> > location on the moon to get much colder than the corresponding
> > location on earth.
>
> > I looked up the average surface temperature for the moon, on a number
> > of websites. They all gave exactly the same values that you quoted.
> > The mean surface temperature (day) is given as 107 C, and the mean
> > surface temperature (night) is given as -153 C. As you pointed out,
> > averaging these two numbers gives -23 C (even colder than the -18 C
> > often quoted). Why is that different from +2.3 C ?
>
> > surface temperature -233°C
> > This is the temperature that the Earth would be at if it radiated as a
> > perfect black body in the infrared, ignoring greenhouse effects, and
> > assuming an unchanging albedo. The Earth in fact radiates almost as a
> > perfect black body in the infrared which will raise the estimated
> > temperature a few degrees above the effective temperature. If we wish
> > to estimate what the temperature of the Earth would be if it had no
> > atmosphere, then we could take the albedo and emissivity of the moon
> > as a good estimate. The albedo and emissivity of the moon are about
> > 0.1054[20] and 0.95[21] respectively, yielding an estimated
>
> > (Note: In all of my calculations I assumed an emissivity of 1.0)
>
> > ---------------------------------------------------------
>
> > By the way, I sure did NOT forget that radiation from the 'hot' side
> > of Earth-without-atmosphere will be much more than the radiation from
> > the 'cold' side, since radiated energy goes with T^4.
>
> > As I explained above, the simple easy method is an approximation, and
> > averages the hot and cold sides together to give an average
> > temperature.
>
> You are on the right track distinguishing between the EFFECTIVE temperature Teff and the AVERAGE temperature Tave of a planet.
> But to be accurate, you need to consider radiation absorption and emission at different latitudes, consider day/night, consider
> rotation and both SW and IR albedo effects and (with atmosphere) also surface heat flows.
> In short, you need to refine your planet model beyond the single T Stephan Bolzman Equation that you have been using so far.
>
> It means that you need to get deep into integrals.
>
> I would be happy to do that with you, but expressing formulas in text form is kind of difficult, and besides that, the various
> 'cases' (such as Earth with or without an atmosphere, Moon, rotation, albedo effects etc) really beg for a decent paper.
>
> Now there happens to be paper that did much of this 'simple planet modeling' work already, with the relation between Teff and Tave
> nicely derived in comprehensible integrals. It also works out influence on Teff of GHG in the atmosphere using a simple,
> comprehensive but still pretty accurate model, without getting too deep into radiative transfer theory.
> It then tests the results with observations for various planets and the moon.
>
> Here is the paper :
>
> http://arxiv.org/PS_cache/arxiv/pdf/0802/0802.4324v1.pdf
>
> It may not address all of your questions, but I think it will be of help to refine your calculations.
>
> Rob
I have read the paper that you suggested. It is better than most of
the articles that I have read on the subject, but they are still stuck
in the mindset of using the earth's current albedo (0.306 from nasa),
for all situations.
This means that in some situations (like no atmosphere), they are
wrong. Just like the other incorrect articles.
I agree that a proper analysis would require getting deep into
integrals.
I have developed a spreadsheet model of the energy flows, and
temperature changes for a planet. It calculates the energy in and out,
and the temperature of the surface, for each second of the day. It
uses the Stefan–Boltzmann Law, the solar constant, the specific heat
of the earth, the angle of rotation of the planet during the day, the
albedo, etc. It even lets me specify the strength of the greenhouse
effect (the proportion of outgoing radiation returned to the surface).
The model shows me the temperature variation over the day (the diurnal
cycle). I was impressed that this model generates a realistic diurnal
cycle, with the coolest time of the day being about 6:00 am, and the
warmest time of the day being about 4:00 pm. This is close to the
actual situation on earth. This happens, even though the maximum
incoming radiation occurs at noon (sun directly overhead).
The biggest problem with the model is getting an absolute result. To
be realistic you need to know the specific heat of each substance
(land, water, air), and how much of each substance gets heated. It is
hard to model things like how much the atmosphere or ocean spreads
heat by convection or currents, etc.
It shows relative effects quite well. Like the effect on the diurnal
cycle of increasing the greenhouse effect.
It is a work in progress, and doesn't get much attention most of the
time. It is good at making me think about how things work, and is one
of the reasons why I realised that an earth with no atmosphere has a
different albedo. In my spreadsheet model, albedo is just a value in a
cell, and I can change it to be anything I want. I think that many
people (including scientists), get stuck on the idea that the albedo
of the earth is a fixed number (equal to the present albedo). That is
why they keep getting the temperature calculation, for the earth with
no atmosphere, wrong.
Bill Ward
> On May 5, 12:14 pm, "Rob Dekker" <r...@verific.com> wrote:
>> > "Climate Realist" <climate.real...@gmail.com> wrote in message
>> >news:cc23e1d8-bea3-47b5-909a-
c307e2...@g1g2000pro.googlegroups.com...
Try making the albedo a function of surface temperature. The higher the
temperature, the more WV and clouds, which increase the albedo.