http://wattsupwiththat.com/2009/02/25/a-short-primer-the-greenhouse-effectexplained/#more-5853
A short primer: The Greenhouse Effect Explained
25 02 2009
Guest post by Steve Goddard
There is a considerable amount of misinformation propagated about the greenhouse effect
by people from both sides of the debate. The basic concepts are straightforward, as
explained here.
The greenhouse effect is real. If there were no greenhouse gases in the atmosphere, earth
would be a cold place. Compare Mars versus Venus - Mars has minimal greenhouse gas
molecules in its’ atmosphere due to low atmospheric pressure, and is cold. By contrast,
Venus has a lot of greenhouse gas molecules in its’ atmosphere, and is very hot.
Temperature increases as greenhouse gas concentration increases. These are undisputed
facts.
Heat is not “trapped” by greenhouse gases. The earth’s heat balance is maintained, as
required by the laws of thermodynamics.
outgoing radiation = incoming radiation - changes in oceanic heat content
The image below from AER Research explains the radiative balance.
http://www.aer.com/scienceResearch/rc/rc.html
About 30% of the incoming shortwave radiation (SW) is reflected by clouds and from the
earth’s surface. 20% is absorbed by clouds and re-emitted back into space as longwave
(LW) radiation. The other 50% reaches the earth’s surface and warms us. All of that
50% eventually makes it back out into space as LW radiation, through
intermediate processes of convection, conduction or radiation. As greenhouse gas
concentration increases, the total number of collisions with GHG molecules increases.
This makes it more difficult for LW radiation to escape. In order to maintain
equilibrium, the temperature has to increase. Higher temperatures mean higher energies,
which in turn increase the frequency of emission events. Thus the incoming/outgoing
balance is maintained.
It has been known for a long time that even a short column of air contains enough CO2 to
saturate LW absorption. This has been misinterpreted by some skeptics to mean that
adding more CO2 will not increase the temperature. That is simply not true, as higher
GHG densities force the temperature up. There is no dispute about this in the scientific
community. See the graph below:
Click for larger image
As Dr. Hansen has correctly argued, increases in atmospheric temperature cause the
ocean to warm up. Thus changes the oceanic heat content become the short term
imbalance in the incoming/outgoing equilibrium equation, which is not shown in the
AER diagram.
The image below shows GHG absorption by altitude and wavenumber. As you can see,
there is a strong absorption band of CO2 at 600/cm. That is what makes CO2 an
important greenhouse gas.
http://www.aer.com/scienceResearch/rc/m-proj/lbl_clrt_mls.html
The important greenhouse gases are: H2O, CO2, O3, N2O, CO and CH4. The reason
why the desert can get very cold at night is because of a lack of water vapor. The same is
true for Antarctica. The extreme cold in Antarctica is due to high albedo and a lack of
water vapor and clouds in the atmosphere, which results in almost all of the incoming
radiation returning immediately to space.
An earth with no CO2 would be very cold. The first few tens of PPM produce a strong
warming effect, and increases after that are incremental. It is widely agreed that a
doubling of CO2 will increase atmospheric temperatures by about 1.2C, before
feedbacks. So the debate is not about the greenhouse effect, it is about the feedbacks.
Suppose that the amount of reflected SW from clouds increases from 20% to 21%? That
would cause a significant cooling effect. Thus the ability of GCM models to model
future temperatures is largely dependent on the ability to model future clouds. Cloud
modeling is acknowledged to be currently one of the weakest links in the GCMs. Given
the sensitivity to clouds, it is perhaps surprising that some high profile climate scientists
are willing to claim that 6C+ temperature rises are established science.
So the bottom line is that the greenhouse effect is real. Increasing CO2 will increase
temperatures. If you want to make a knowledgeable argument, learn about the feedbacks.
That is where the disagreement lies.
“Lisa, in this house we obey the laws of thermodynamics“
- Homer Simpson
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46 responses to “A short primer: The Greenhouse Effect Explained”
25 02 2009
Policyguy (23:04:07) :
Steve,
Here is an excerpt from your post on 2/21
“Consider the earth 14,000 years ago. CO2 levels were around 200 ppm and
temperatures, at 6C below present values, were rising fast. Now consider 30,000
years ago. CO2 levels were also around 200 ppm and temperatures were also
about 6C below current levels, yet at that time the earth was cooling. Exactly the
same CO2 and temperature levels as 14,000 years ago, but the opposite direction
of temperature change. CO2 was not the driver.
Now consider 120,000 years ago. Temperatures were higher than today and CO2
levels were relatively high at 290 ppm. Atmospheric H20 was high, and albedo
was low. According to the theorists, earth should have been warming quickly. But
it wasn’t - quite the opposite with temperatures cooling very quickly at that time.
CO2 was not the driver.
If CO2 levels and the claimed lockstep feedbacks controlled the climate, the
climate would be unstable. We would either move to a permanent ice age or turn
into Venus.”
So, if not CO2, maybe its clouds? And what drives the clouds? Is there room for a
solar component too? Are the GCM’s even capable of considering these variables
or should we start from scratch?
25 02 2009
David Corcoran (23:08:26) :
The argument really isn’t about a slight AGW effect (few disagree over that), it’s
whether Catastrophic Anthropogenic Global Warming (CAGW) will engender a
runaway greenhouse effect that will turn our planet into a mirror of Venus in no
time at all, geologically speaking.
For instance: Dr. Hansen says the seas will rise 25M in 91 years, I don’t know
why low lying nations are stubbornly insisting on making him a liar.
25 02 2009
Mark N (23:15:03) :
Thanks, reads like a simple explanation that I could perhaps give it to ten year
olds (or is there a better source of information for them?). Was wondering about
H2O. I was under the impression that it is the major GHG. Thanks for your
patience.
25 02 2009
Bill Yarber (23:24:20) :
Your use of Mars, Earth and Venus to prove that CO2 putis a major green house
gas is totally flawed. You completely neglect their diameters and their distance
from the Sun. Venus is 2/3s the distance from the Sun than earth and less than 1/2
that of Mars. Ergo, since the watts/sqm of the Sun’s out decreased with the square
of the distance from the Sun, Venus gets over twice the energy that Earth gets and
four times the energy Mars gets. Venus is warmer because it has a denser
atmosphere and gets twice the energy Earth gets. This would be true if Venus had
no CO2 in its atmosphere. Each planet has a different diameter but the difference
is insignificant when compared to the impact of their individual orbit radii.
Bill
25 02 2009
kevindick (23:26:15) :
It seems like there are actually two things you need to know. You need to know
the 1st order sensitivity to a doubling of C02 and you need to know the total
feedback. So it’s pretty important to know whether the 1.2C number for 1st order
sensitivity is right.
What do you think of Miskolczi’s work reassessing this sensitivity? My partial
differential equation days are 20 years behind me, but I’ve read his paper and his
argument seems superficially coherent.
I don’t feel qualified to fully judge the results though. It would be easy to sneak a
specious mathematical argument by my given the current degraded state of my
skills. Do you know any serious mathematical physics types that have reviewed
his work and formed an opinion? Thanks.
25 02 2009
Molon Labe (23:30:41) :
“It has been known for a long time that even a short column of air contains
enough CO2 to saturate LW absorption. This has been misinterpreted by some
skeptics to mean that adding more CO2 will not increase the temperature. That is
simply not true, as higher GHG densities force the temperature up.”
Utterly ridiculuous and contradictory. If CO2 absorption is “saturated”, adding
more CO2 cannot have any effect. Period.
25 02 2009
Jim G (23:33:53) :
Can someone double check this?
It appears the maximum CO2 effect is centered at a wavenumber of 650.
wavenumber = 1/lambda (in cm)
=> @ 650cm-1, lambda = 15.38 um
lambda (in um) = 2897/T (in deg K)
=> T = 2897/lambda
= 188K, or -121F (-85C)
The graph also shows that the CO2 absorption is at high altitude. ~10mb.
At 50F (10C) lambda should be about 977 which would be in the H2O absorption
region.
Am I missing something? Obviously the heat radiated from the earth’s surface
isn’t going to be -85C.
Is this why there should be a CO2 hotspot in the troposphere above 100,000 ft?
25 02 2009
Steven Goddard (23:35:29) :
Mark N,
Temperatures are very sensitive to H2O levels, particularly at night. Which is why
deserts get cold at night. H2O is the most important greenhouse gas.
PolicyGuy,
Good questions. It is clear from the ice core records that there are other cyclical
drivers of climate which can vary temperatures by 10C or more. CO2 is higher
now than it has been in recent centuries, and Dr. Hansen asserts that the recent
rises will overwhelm the natural variation.
Some climate models do consider TSI changes due to solar cycles. Cloud
formation is not well understood or modeled. Weather forecasting models often
mispredict clouds on the same day.
25 02 2009
Richard111 (23:39:44) :
I have lived many years in desert climates and well remember the temperature
drop after sunset. Part of my duties was to note the relative humidity. It drops
during the day and increases during the night, so much so that you could get
condensation, dew, at dawn. This is what most desert creatures seem to survive
on.
This is a personal observation. I would be interested to learn how heating the air
would reduce the water content. As I understand, you must cool the air to get the
moisture out. Just because deserts are hot and surface dry does not mean there is
less moisture in the atmosphere. The air that blows in from cooler climes to
replace the rising air over the desert does not lose its moisture. Deserts are dry.
Usually.
25 02 2009
Steven Goddard (23:39:50) :
Molon,
What you are not considering is that LW is absorbed and emitted many times on
it’s tortuous path out of the atmosphere. The more GHG, the more times it is
absorbed.
Your argument is analagous to saying that one stop light has the same effect on
your commute time as does 100 stop lights.
25 02 2009
John F. Hultquist (23:51:54) :
Holy Cow! Your first diagram doesn’t show any longwave radiation in the Solar
spectrum which is +/-50% depending on your choice of the wave length for the
boundary. Seems that might at least be mentioned.
“There is no dispute about this in the scientific community.”
“It is widely agreed that a doubling of CO2 will increase
atmospheric temperatures by about 1.2C before feedbacks.”
Neither of these is true.
David Archibald claims an increase to 620 ppm, projected by 2150, will raise the
temperature by only 0.2 degrees C. (May 2007) in “The Past and Future Climate.”
“An earth with no CO2 would be very cold.”
Proof? Why should this be as H2O and the other gases you mention don’t rely on
CO2 to work as GHGs.
Also, AGW is “widely” questioned and even if it is “widely agreed” that doesn’t
make it true. The references to Mars and Venus don’t help. The situations are so
different you set me thinking about other topics.
Is the phrase “before feedbacks” meant to imply positive feedbacks?
How do you explain the cooling after 1940 to 1977 while CO2 was increasing and
with no change in that trend a warming began in 1977?
Now for the past ten years temps have not continued there rise, even decreased
some, and CO2 has not stopped going up?
Most reading this will be aware of or can easily find on WUWT material
questioning the straightforward and undisputed facts you present so I haven’t
bothered to add sources here. If anyone needs these, say so.
Your short primer appears not just to be short in length but short in its explanatory
power. Give it another try. There are many of these short explanations on the
WEB so I think this one is a set-up of some kind. I can’t figure out, though, just
what the purpose is.
26 02 2009
manse42 (00:00:55) :
I feel lost…
Isn’t the enthalpy and specific heat capacity somehow missing?
The potential heat content of the entire atmosphere above 10mb is less than 1/100
(because of lack of water vapours high heat capacity) of the potential heat content
below 10 mb.
And it is above 10 mb the big CO2 effect comes is as I read the chart…
26 02 2009
Steven Goddard (00:01:08) :
Richard111,
Relative humidity means just that - relative to the temperature. You can change
the relative humidity without changing the absolute humidity, by heating or
cooling the air. The Utah desert can have swings of 60 degrees between day and
night with no changes in the very low absolute humidity. As soon as water starts
condensing due to cold, it releases heat and limits further temperature drops.
26 02 2009
Robert David Graham (00:04:48) :
Thanks for the post. I’ve long been frustrated by friends claiming “there is no
greenhouse effect” or “man is not responsible for the extra CO2″.
I would point at that the disagreement lies in three places. The first is that
computer climate “feeback” models are bogus.
The second is that the data are inadequate, such as the UHI, the “How Not To”
series posted here, fertilized tree rings, etc.
The third is obvious scientific malfeasance, such as the “Hockey Stick” affair,
GISS “normalized” temperatures, and so on.
26 02 2009
Cassanders (00:09:47) :
Kudos
It is useful to have clarifications on this theme, and I will store this for later
revisits.
Just a minor quiggle in a hurry.
When stating your fundamental desciption of the earth as a thermodynamic unit,
you do (correctly) include heat content (or eventually changes in ocean heat
content).
But my old and battered brain vaguely remembers that borehole reconstructions
of temperature was fairly prominent a number of years ago.
I assume borhole reconstruction of temperature is based on models wehre rock
also have thermal heat content?
Bur regardless borehole reconstructions: Does not earth (rocks + soil) have heat
content (with thermal inertia ) as well?
I assume it should be closer to the properties of water than atosphere.
Cassanders
In Cod we trust
26 02 2009
Scott Gibson (00:15:10) :
@Richard111
Heating the air doesn’t reduce the water content, it just reduces the relative
humidity, which is a measure of moisture content compared to the dewpoint of the
air at that temperature. That also explains why rising air forms clouds; as air with
a certain moisture content rises, it cools to its dewpoint, and water condenses into
droplets. See an article in Wikipedia for a graph showing the relationship between
the dewpoint and temperature.
26 02 2009
Scott Gibson (00:19:07) :
Oops, clarification: relative humidity is a measure of actual moisture content
compared to the amount of moisture that can be contained at the dewpoint.
26 02 2009
Fredrik Malmqvist (00:30:11) :
Note that CO2 doesn’t heat but rather act as a ”radiation blanket” . Nils Bohr
showed that gas molecules that absorb light are exited to a energy level and can
only give off this energy with light at the same wavelength. This light can go in
any direction. Some will again hit earth and create heat. Before Bohr it was
believed that gas was heated by absorbed radiation.
This effect is called “greenhouse effect” in the debate. A greenhouse is however
heated because the glass stops air convection. A greenhouse build with glass
transparent to all wavelength would be as good as one built with window glass.
This was also shown early last century (by a physicists named Wood).
26 02 2009
Jerry (00:33:25) :
I very much doubt that increases in atmospheric temperature cause the oceans to
warm up to any significant extent, given the vastly greater thermal mass of water
compared to air. Since about 72% of the Earth’s surface is water, which shows as
black on IR photographs and is therefore absorbing everthing, it is fairly obvious
that the oceans warm the atmosphere. We in the UK know this very well, as the
North Atlantic Drift stops us having the climate of Newfoundland.
All the theorising is fine, but before going public with the results of models you
have to show that the undoubtedly correct theoretical basis for some individual
parts of an immensely complex real system extends to all parts of that system. In
particular, if you want me to believe your predictions you must be able to show,
reliably, that any model run will always reflect accurately the state of the climate
at any time over known history. You are a very long way from even approaching
that.
26 02 2009
Lindsay H (00:35:54) :
As Dr. Hansen has correctly argued, increases in atmospheric temperature cause
the ocean to warm up.
really!
I have seen no proof of this, the average ocean temperature is about 4-5 deg c
90 % of the ocean is below the thermocline with a temperature of about 3 deg c
hardly a heat sink more like a cold sink, the surface temperature varies from -5 to
+ 30 deg c but its effect on the average ocean temperature is small.
The climate sensativity to co2 doubling is the issue, no one disputes the
absorption effect at 650 wave no, but there is dispute about the effect in the upper
atmosphere.
If there was no co2 in the atmosphere what would be the temperature using the
IPCC models?
an ice age ? it wouldn’t happen : The models are flawed. The average temperature
might drop 2 degrees ?
Isn’t water vapor responsible for 95% of absorption, thus maintaining the planets
temperature in a +- 5degree range, from ice age to ice age !
26 02 2009
tmtisfree (00:37:28) :
“It has been known for a long time that even a short column of air contains
enough CO2 to saturate LW absorption. This has been misinterpreted by some
skeptics to mean that adding more CO2 will not increase the temperature. That is
simply not true, as higher GHG densities force the temperature up.”
The 2 last sentences contradict physical laws. Reasoning only with CO²:
1/ As you said, all LW radiations are exciting a small and finite number of CO²
molecules within the first meters (<10m) above the surface. That means adding
more CO² molecules will not increase this finite number of excited molecules.
Thus the number of excited molecules depends exclusively on the solar
irradiation.
2/ Calculation and comparison of the frequencies (which can be interpreted as
probabilities of occurrence) of
a) decay rate (natural broadening),
b) relative molecular movement (Doppler broadening) and of
c) molecular collision (collisionnal broadening)
show that the frequency of molecular collision is at least 4 orders of magnitude
higher than the frequency of decay rate. That means that through molecular
collisions and de-excitation as kinetic energy (heat measured with a
thermometer), system reaches rapidly to a pseudo thermal equilibrium.
3/ The calculation of the velocity distribution in such system shows that only a
very tiny part of the CO² molecules will keep enough energy to re-emit a photon
with an energy corresponding to a 2.10^13 Hz frequency (or a 15 µm wavelength)
to re-excite an other (CO²/H²O) molecule. The tiny part which re-radiates does so
50% upwards and 50% downwards, but as the number of non excited CO²
molecules is far more higher (ie molecular system is far from being saturated), the
downwards re-radiation is rapidly trapped again by CO² (or H²O) and rethermalized by molecular collision as kinetic energy. Thus re-radiation in this
frequency range plays only a very small part in the energy “trapping” process.
Adding more CO² molecules just increases the probability that radiations from the
surface excite CO² molecules at a lower height of the atmospheric column.
4/ Consequently, any radiation outside this frequency range will be (except for
macroscopic aerosols which will absorb and re-radiate as a blackbody)
transparently returned in part to earth (slightly warming it) and in part to the upper
atmosphere (and thus slightly cooling it). This is this tiny re-radiation that is
thought to be the GH effect accounted for the GW. Quantitatively, the total
number of these low frequency photons depends only on the total number of the
photons radiated by the surface, and thus only on the solar irradiation. Thus
adding more CO² molecules will not change the total number of low frequency reradiated photon towards surface, that is to say the slight warming which results of
will not be modified when doubling (or more) the number of CO² molecules. As
the atmosphere is transparent for these downwards photons, their number will also
be independent of the height at which CO² molecules have been excited.
5/ So, what do an increase of CO² level?
As the number of CO² molecules increases, the probability that a finite number of
CO² molecules is excited tends also to increase at the same height. But as almost
the totality of the radiation from the surface is “trapped” within the first meters
above the surface, it will not modify the total number of exited CO² molecules
and have thus no effect on the total number of low frequency re-radiations
towards the surface (GH effect). And because atmosphere is transparent to them,
the height at which this process occurs will have no effect on the total number of
this re-radiation returned to the surface.
The slight warming is therefore independent of
a) the number of CO² molecules (at the current level),
b) the height at which CO² molecules have been excited.
and is dependent only of
c) the solar irradiation.
I hope the above, which is not true for very low level of CO² (or any GH gases),
makes sense.
Bye,
TMTisFree
26 02 2009
tmtisfree (00:39:45) :
As an analogy, if you use a blind over a window on a sunny day, adding more
blinds will not make the room any darker.
Bye,
TMTisFree
26 02 2009
par5 (00:54:10) :
Is all of this CO2 at ground level? Thermodynamics aside, how does CO2 force
heat back to the surface of the earth? Include thermodynamics, how can there be
an energy budget or a heat budget for the earth? I am neither pro or con AGW,
more interested in the science…
26 02 2009
tmtisfree (01:01:12) :
I forgot the main conclusion.
As the slight warming is already accounted for when temperature is measured,
consequently, and given the above, the current temperature can not increase with
an increase of CO² level.
Bye,
TMTisFree
26 02 2009
Carl XVI Gustav (01:03:16) :
“Its’ amosphere” indeed. Your Nobel is cancelled!
26 02 2009
Flanagan (01:09:23) :
Hi Steven,
I also really appreciate your effort and honesty in the process. I simply hope now
that the scientific basis we’re sure of will not be endlessly disputed - continuously
re-inventing the wheel is such a stupid loss of time, energy and money.
So I suppose the “big” questions you are disputing is whether the warming we are
observing is due to the increase of CO2 or not, and if yes whether it is caused by
human activities, am I right?
26 02 2009
coaldust (01:12:56) :
David Corcoran (23:08:26) :
The argument [is] whether Catastrophic Anthropogenic Global Warming
(CAGW) will engender a runaway greenhouse effect that will turn our planet into
a mirror of Venus in no time at all, geologically speaking.
This is incorrect. The argument is about feedbacks, but not runaway feedback.
There will clearly be no runaway feedback since CO2 has been much higher in
the past, and runaway feedback that would “turn our planet into a mirror of
Venus” did not occur.
26 02 2009
John F. Hultquist (01:30:24) :
Scott,
That should be “relative humidity is a measure of actual H2O(gas) content
compared to the maximum of H2O(gas) that can be “contained” at the
temperature. The “contained” makes the atmosphere sound like a sponge, which it
is not. That’s bad science, as shown in these pages:
http://fraser.cc/ follow prompts teaching, sci., met.,
and: http://www.ems.psu.edu/~fraser/Bad/BadGreenhouse.html
26 02 2009
Kaboom (01:37:17) :
[snip- this comment is pointless and off color]
26 02 2009
fred (01:37:48) :
It is frequently argued that AGW is ‘just 200 year old physics’, and this helpfully
makes clear why this is not true and is in fact willfully misleading.
It is simple physics that CO2 absorbs heat, and that a gas with more CO2 warms
up more than the same one with less CO2. However, what happens next is a
different, independent, and more complicated question, and is about feedbacks.
The atmosphere is a system, not a gas. So it is perfectly possible that the figure of
1.2C for a doubling of CO2 could be right, but that the net effect of that doubling
could be zero, 1.2C or much greater. It depends how the rest of the system reacts
over time to the initial rise.
It is a bit like the argument that a given car will travel 40 miles on a gallon of gas
is simple physics, and comes from the energy content of the gas, which is not
subject to dispute. It is true that the energy content is not subject to dispute, but
how far it takes a car of this particular design may be physics, but it is not simple
physics, and is not primarily determined by the energy content of the gas. The key
question about the climate is whether clouds are negative or positive feedbacks.
Do clouds and rain and other atmospheric phenomena amplify smallish warmings
from whatever cause, or do they lessen them?
This is connected to the argument about the MWP and RWP. If we can point to
previous warmings followed by coolings which were not caused by CO2, it must
be more plausible that there is something which can produce cooling in response
to warming. So it must be plausible there is some form of negative feedback in the
climate system.
The hard thing for AGW to explain, given the hypothesis it is obliged to make
about climate sensitivity and feedback, is why cooling followed the MWP and
RWP. This on the face of it is inexplicable if they are right about climate
sensitivity and the direction of feedback.
26 02 2009
Stephen Wilde (01:41:49) :
I have a problem with the suggestion that a slightly warmer air could warm the
oceans on a timescale that need cause any concern.
A warmer air increases the temperature differential between air and space and so
could well accelerate energy loss to space before any significant effect on the
oceans could occur.
I also see difficulties with the proposed ocean skin effect which has been put
forward by AGW supporters to overcome the ocean warming problem but which
has not yet been proved to be effective in the real world.
26 02 2009
Stephen Wilde (01:51:46) :
The saturation issue and the density issue should be treated seperately in relation
to a single GHG.
It is quite true that a level of approximate saturation can be reached for any single
GHG but for a planetary atmosphere as a whole the total density arising from all
it’s constituents is the paramount factor.
In the case of CO2 on Earth such saturation is reached well before any increase in
the quantity of CO2 could have a significant effect on total density because the
proportion of CO2 is so small.
26 02 2009
Malcolm (01:57:06) :
I’m sorry Steve but as TMTisFree has shown the GH effect IS still poorly
understood. There are a finite number of radiant particles involved in the GH
effect on this planet, simply adding more GH gasses into the atmosphere does not
neccessarily equate to higher temperatures. That is what the temperature record is
telling us.
26 02 2009
John Finn (02:03:57) :
As Dr. Hansen has correctly argued, increases in atmospheric temperature cause
the ocean to warm up.
Is that what Dr Hansen has argued? His main point seems to be that ‘missing
heat’, i.e. heat not yet evident in the atmosphere is atually accumulating in the
oceans. I’d like to see the argument behind this since thermal emission from the
atmosphere can only penetrate a few micron into the ocean ’skin’.
26 02 2009
lgl (02:08:56) :
And what happened to the LW backradiation to the surface?
26 02 2009
Ceolfrith (02:19:15) :
http://www.telegraph.co.uk/earth/environment/climatechange/4808122/Scientistsfind-bigger-than-expected-polar-ice-melt.html
What next?
26 02 2009
Nylo (02:19:48) :
With “saturated”, I have always understood that all of the energy at a given
wavelength that is emitted is absorbed.
The Earth is a microwave oven and CO2 is food in it. If the effect is saturated, it
means all the energy provided by the microwave (i.e. Earth emissions at the right
wave length) will be absorbed by the food (CO2). When we have little food, the
food will get very hot. However, as it is little food (low concentration of CO2 in
the atmosphere), its total heat content or the total heat content inside the
microwave will not be very big. When we have a lot of food (high concentration
of CO2 in the atmosphere), it won’t get very hot but, as the concentration is
greater, it will have a similar effect in the overall atmospheric temperature (heat
content inside the microwave). Similar? I would rather say “exactly the same”.
If a higher concentration of molecules capable of absorbing the energy had any
effect in an already saturated effect, we all would put huge plates full of food in
the microwave. But this is not true. We know that if we put twice as much food,
we need twice as much energy to make it reach the same temperature.
26 02 2009
Julian Flood (02:21:35) :
Learn about feedbacks indeed. 30% of the ocean is covered by strato-cumulus
cloud, albedo about 60, while the open ocean is albedo effectively zero. How
anthropic changes alter that thin cloud layer will have massive changes on the
average albedo of the Earth, more than enough to change the temps.
If you look at Tinsdale’s graphs of maritime air temps you will observe an abrupt
rise in temperature from 1939 to about 1943 (this effect is smeared out in the
Hadley SST graphs as they’ve added a ‘correction’ which looks dubious to me)
and I have postulated that the oil-spills from the Battle for the Atlantic reduced
CCN numbers, lowered reflectivity during day and emmisivity by night, hence
warming the upper levels of the sea. The Kriegesmarine effect is about oil, but
you get the same result from surfactant. We cover the entire ocean surface every
two weeks with a thin layer of pollution — you can even see it when an ice-floe
melts, an oily smoothness all around the ice. That’s probably caused by
phytoplankton, but I’d not be too surprised if it turns out to be caused by stuff
entrained in the ice from the atmosphere over a few years.
Nozieres is researching bacterial surfactant effects on clouds. VOCALs is looking
at strato-cu off the coast of Chile. I hope they’re checking the cloud particles for
oil and surfactant pollution. If they find it them you read it here first: if not, please
forget I said anything!
The science of feedbacks is extremely poor — this is where I draw the line when I
hear the chant ‘the science is settled’. Until cloud feedbacks are intensively
researched, all the hooha is just hand-waving.
JF
26 02 2009
Ed Zuiderwijk (02:28:08) :
The figure shown is for summer at mid lattitudes. But it’s the winters that have
become warmer between 1970 and 2000, not the summers. So I’d like to see the
same diagram for winter conditions to see what the difference is.
26 02 2009
warm puddle (02:32:55) :
Thanks for the post, it is certainly an issue that needs clearing up. I am wandering
what literature the explanation of the greenhouse effect is based on. Is this
essentially still based on the work of Arrhenius that was never validated?
(Arrhenius, 1896).
I think your explanation can be best explained using hydraulics. co2 acts like
rocks piled across a river, the temperature grade acts like the hydraulic grade. As
the water slows to flow through the rock, water heads up behind due to the
restriction, however adding more rocks past a certain point wouldnt increase the
heading up of flow once it had reached equilibrium, only the first section of rock
would really determine the depth (equivelent to trapped heat at the surface) and
no flow would be sent backwards due to the net energy flow being downhill.
Would this be a fair explanation?
I have read several papers that claim a chamber filled with co2 becomes no
warmer in the sun than one with normal air, the same applies for tests using glass
and polished rock saltcrystals . Doesnt the hypothesis then fail testing?
What are your thoughts on the following papers i.e. that convection is the main
factor in the GE or that atmospheric mass determines the GE?
http://www.ingentaconnect.com/content/mscp/ene/2003/00000014/F0020002/art0
0011 or
http://www.springerlink.com/content/t341350850360302/?p=eaccc84960854cb0b
aba8d1d3860ac53&pi=2 (also see their response to the rebuttal) also
http://xxx.lanl.gov/abs/0707.1161 claims to falsify the GE.
I think the practical testing issue needs to be resolved as does the contradiction of
the second law of thermo dynamics beforfe I take the GE as rock solid theory.
26 02 2009
Mark N (02:36:58) :
@John F. Hultquist
Thanks for interesting links
26 02 2009
Allan M (03:10:40) :
“Steven Goddard (23:39:50) :
Molon,
What you are not considering is that LW is absorbed and emitted many times on
it’s tortuous path out of the atmosphere. The more GHG, the more times it is
absorbed.
Your argument is analagous to saying that one stop light has the same effect on
your commute time as does 100 stop lights.”
This is all the SAME heat, it doesn’t matter how many times it is absorbed and reemitted. If absorption heats, then emission cools.
You cannot have your perpetual motion machine!
And, IMHO, the analogy stinks! (As most analogies do; stick to explanation.)
AM
26 02 2009
Sandy (03:14:16) :
If we are heat balancing the Earth we need to know the rate of transfer of the heat
from the magma through the crust. It would be a brave man who estimates the
total nuclear fission power of the earth’s core and braver still to claim that it may
be considered as being released uniformly over the globe.
26 02 2009
par5 (03:24:09) :
I have a problem with the first graph- it implies a ‘budget’. If watt/in equals
watt/out, then hotter days equal colder nights. Then, the mean temp would not
change but remain a constant? I understand the chemistry because it’s so easy and
provable (never met a theoretical chemist), but I’m still having trouble with the
physics. This is just one of the reasons that I am still a ‘fence sitter’ on this
subject. I will admit to being slightly skeptical, but that is just a personal trait.
There are just so many different opinions from well respected scientists on both
sides, and it isn’t nice or fair to beat up on them. Anthony- great site! Sending you
a donation immediately. Enjoy your day…
26 02 2009
Johnny Honda (03:27:08) :
Steve,
this is the first articel und WUWT that is disappointing for me. It is not a correct
description of the situation.
Most important fact: Until now, there is NO physical correct description or
definition of the greenhouse effect.
“outgoing radiation = incoming radiation - changes in oceanic heat content”
Wrong, you forget the latent heat of the water dampening out from the land (land
ist mostly not total dry).
You forget the heat loss by convection (wind is blowing along the earth surface
and is heated up).
The latter is important! Wind is heated up at the surface of the earth, is warmed
by this, is rising, and is emitting (by GHG!) heat to the space and so is cooling.
With this mechanism we have cooling by Greenhouse-Gases!
“If there were no greenhouse gases in the atmosphere, earth would be a cold
place”
“The other 50% reaches the earth’s surface and warms us”
OK, if we have no greenhouse gases (no water, no CO2), almost 100% of the
radiation reaches the surface (no clouds! amost no absorption!)), so it will be
colder on the planet??
Why is the day temperature on the moon ca. 160 °C ? No Greenhouse gases!
Another mechanism: Water vapor is rising, it condenses, and the heat is emitted
(to a large extent) to space! When the water is evaporating at the sea or
landsurface, heat is taken away from the surface. Result of the process: The
surface is cooled by the GHG water!
Please read the work of Prof. Gerhard Gerlich! It is essential for the
understanding of the situation. Why you don’t ask him for a guest article? His EMail: [email protected]
26 02 2009
tmtisfree (03:30:11) :
lgl (02:08:56) :
And what happened to the LW backradiation to the surface?
It simply warms slightly the surface. It is not sure if it is possible to
experimentally discriminate this ‘indirect’ heat. But it is possible (and
complicated) to calculate the probability of occurrence of this LW re-radiation
and thus estimate the small theoretical heat added to the surface. Anyway,
because atmosphere is transparent for this LW re-radiation, this slight warm is
already accounted for when measuring temperature.
Bye,
TMTisFree