Greenhouse Effect Experimental Designs

[BrianG]

... You are looking for something which makes no logical sense. You are looking for a correlation between,

1. The temp / concentration dependence in a small experiment
   
2. The temp / concentration dependence of the earth
   

Such a correlation (between 1 and 2) should not exist. No one would propose such an experimental result—it would be nonsensical. Unless you have another earth identical to this one except for CO₂ concentration as an experiment then the temperature / concentration dependence between the experiment and the earth that you are looking for simply does not exist.

 

You should either explain exactly how such an experiment would be performed and exactly what the results would mean or you should stop insisting that the results of the 'experiment' are needed...

 

I'm looking for a test of climate change mitigation.

 

The ideal climate mitigation experiment would release and capture a greenhouse gas into and from the atmosphere, and measure temperature changes. The experiment would be repeated many times, to capture a temperature signal out of random noise. Failing that, a physical model that simulates as many significant variables as possible would be constructed and different concentrations of greenhouse gas would be tested against temperature change.

 

A wind tunnel isn't a full description of an atmosphere, but it does help show how a wing will lift an aircraft. A wave tank isn’t an ocean, but it’s instructive. Millikan's oil drop experiment didn’t pluck an electron out of the oil drop and put it on a scale, but he did a fantastic job measuring the charge on a single electron. Experiments don’t have to be perfect, just good enough to be repeatable and demonstrate physical laws.

 

The few experiment’s I've found and imagined are described here: http://hypography.com/forums/environmental-studies/21736-greenhouse-effect-experimental-designs-4.html#post287475 , http://hypography.com/forums/environmental-studies/21736-greenhouse-effect-experimental-designs-4.html#post287465 , http://hypography.com/forums/environmental-studies/21736-greenhouse-effect-experimental-designs-4.html#post287400 , http://hypography.com/forums/environmental-studies/21736-greenhouse-effect-experimental-designs-4.html#post287399 , http://hypography.com/forums/environmental-studies/21736-greenhouse-effect-experimental-designs-3.html#post287773 , http://hypography.com/forums/environmental-studies/21736-greenhouse-effect-experimental-designs-3.html#post287546 and here http://hypography.com/forums/environmental-studies/21736-greenhouse-effect-experimental-designs-3.html#post287518 . The purpose of this entire thread is describing, criticizing and designing experimental tests of the greenhouse effect. I don’t have a perfect answer yet, but, I’m looking.

 

Please forgive me; I won’t tell anyone they need results from experimental tests. You have the right to believe whatever you want. For myself, I’ve found experimentation is the best way to test a hypothesis. Would you like to discuss methods of testing theories without experimental tests?

 

"Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning. A scientific method consists of the collection of data through observation and experimentation, and the formulation and testing of hypotheses."

 

From: http://en.wikipedia.org/wiki/Scientific_method

[CraigD]

Experiment - The Greenhouse Effect uses 100% [ce]CO_2[/ce].

...

 

Per the above, doubling the [ce]CO_2[/ce] in air 12 times ([imath]2^{12}= 4096[/imath] times) would result in a 24 to 55 C increase. This is an inappropriate use of the forcing equation, however, and an impossible condition, as increasing [ce]CO_2[/ce] concentration from its present day 0.037% by a factor of 4096 gives a concentration of 152% - that is, you’d have to have a pure [ce]CO_2[/ce] atmosphere with and/or greater density than the current one – in which case breathing would, I suspect, be of greater concern than temperature. ;)

 

:QuestionM What’s your source for doubling [ce]CO_2[/ce] concentration forcing a 0.5 C temperature increase, Brian? This is a much smaller constant than any I’ve seen.

Thanks for your help, I should have used the value 11, the amount of CO2 has been doubled more than eleven times and yields a temperature change of 6C, or 6/11C per doubling, about 0.545 C per doubling.

If you’re referring to the concentration of [ce]CO_2[/ce] in the Earth’s atmosphere, you shouldn’t be stating that it has doubled 12, 11, or a similar number of times.

 

[imath]2^{11}= 2048[/imath] is still an impossibly large increase in atmospheric [ce]CO_2[/ce] concentration, corresponding to 76% and a 12 to 28 C temperature increase.

 

Best data indicate that, in the current geological period, the Pleistocene, about the last 600,000 years, excluding the last 100 years, average [ce]CO_2[/ce] concentration have been between 180 and 300 ppmv. The present-day average concentration of about 287 ppmv is thus only a little over one doubling of its most recent minimum of about 180 ppmv during the last glacial maximum about 20,000 years ago.

 

Much further in the past, [ce]CO_2[/ce] concentrations have been much higher, about 6000 ppmv about 600,000,000 years ago, in the Cambrian period. Taking this as a maximum and the Pleistocene’s minimums of about 180 as minimums, then, [ce]CO_2[/ce] concentrations span a range of about 5 doublings.

 

In short, for Earth as it’s been for the last 600,000 years, and is likely to be for at least the next few thousand, [ce]CO_2[/ce] concentrations have varied by 1 or a few doublings, not 11 or 12.

Is this the best experimental test we can find to experimentally verify CO2's greenhouse effect?

In terms of precision, the best experimental data about the greenhouse effect of mediums in general are their absorption spectra. A few promising web pages and images I've found concerning this are Greenhouse Gases, http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif, and http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif.

 

With precise absorption and emission spectra, either empirical or based on molecular models (free atom absorption and emission spectra agree so nearly perfectly with theory that empirical vs. theoretical are effectively the same), it’s in principle possible to actually physically model the Sun and the Earth. Computationally, however, this is challenging. As a result, computationally easier but less direct methods, such as the concentration-to-irradiance and irradiance-to-temperature formulae discussed above, with their mixed empirically and theoretically derived constants, appear to my inexpert eyes to be foundations of the state of the current art in climate modeling.

2007 IPCC calculations place it between 2.9 and 6.6, for a 2 to 4.6 C increase.

That's a real range of possible values, why can't we pin it down? The Gravitational Constant is 6.67428 +/- 0.00067 X 10^11m^3 kg^-1 s^-2, that's far more precise. The IPCC's larger estimate is over 100% larger than there smaller estimate. Can we find a more precise value with experimental tests?

Have you ever seen an experimental test that shows a greater value for CO2's greenhouse effect on temperature?

Trusting the people who’ve worked on encyclopedia articles such as the wikipedia articles above, I’m fairly confident the combined constant for the above equations in the range I quoted above, 2 to 4.6 C / doubling of [ce]CO_2[/ce] concentration.

 

More important than the precise values of these constants, I think, is to understand that they are based on many assumptions about atmospheric and environmental conditions – they’re not, in the sense that constants such as the gravitation constant are, really constant, and that more than a single gas molecule, such as [ce]CO_2[/ce], are significant in the models that use them. In short, no matter how much we might wish it to be, you can’t make the relationship between [ce]CO_2[/ce] and other greenhouse gases to temperature simple, because the physics underlying it – despite components of it being precisely measurable with such techniques as spectroscopy – isn’t simple.

 

I fear that to a detailed understanding of the physics of climate requires a lot of education and work. Though increased computing power may in the future allow people with merely a sound grasp of physical model programming to understand and write simple, accurately predictive programs, I don’t believe we’re there yet.

[BrianG]

Maybe we should limit the lab greenhouse experiments to testing Arrhenius’ formula from your previous post:

[math]\Delta T_s = \lambda \Delta F [/math]

 

That might simplify the lab experiment issue.

 

 

 

If you’re referring to the concentration of [ce]CO_2[/ce] in the Earth’s atmosphere, you shouldn’t be stating that it has doubled 12, 11, or a similar number of times.

Craig, you’re an administrator here, and when you tell me I shouldn’t be stating something, I pay attention. I’m stating the physical model at: Experiment - The Greenhouse Effect has one vessel with 0.037% [ce]CO_2[/ce] and another with 100% [ce]CO_2[/ce]. May I say the second container has doubled the [ce]CO_2[/ce] in the first between 11 and 12 times?

 

 

[imath]2^{11}= 2048[/imath] is still an impossibly large increase in atmospheric [ce]CO_2[/ce] concentration, corresponding to 76% and a 12 to 28 C temperature increase.

Do you think the primordial atmosphere may have contained this much [ce]CO_2[/ce] before it was sequestered with calcium or other fossil carbons? Carbon and oxygen are abundant.

 

 

...

In terms of precision, the best experimental data about the greenhouse effect of mediums in general are their absorption spectra. A few promising web pages and images I've found concerning this are Greenhouse Gases, http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif, and http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif.

 

Did you note http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif lists [ce]O_2[/ce] as a major greenhouse gas? That’s the first time I’ve seen that, I’m aware ozone [ce]O_3[/ce] is a greenhouse gas. This is the first time I’ve ever thought of oxygen, nearly 30% of the atmosphere, as a greenhouse gas, thanks!

 

With precise absorption and emission spectra, either empirical or based on molecular models (free atom absorption and emission spectra agree so nearly perfectly with theory that empirical vs. theoretical are effectively the same), it’s in principle possible to actually physically model the Sun and the Earth. Computationally, however, this is challenging. As a result, computationally easier but less direct methods, such as the concentration-to-irradiance and irradiance-to-temperature formulae discussed above, with their mixed empirically and theoretically derived constants, appear to my inexpert eyes to be foundations of the state of the current art in climate modeling.

 

Yes, I’m concerned combining empirically and theoretically derived constants as the foundation, without experimental tests might introduce errors.

 

Trusting the people who’ve worked on encyclopedia articles such as the wikipedia articles above, I’m fairly confident the combined constant for the above equations in the range I quoted above, 2 to 4.6 C / doubling of [ce]CO_2[/ce] concentration.

 

More important than the precise values of these constants, I think, is to understand that they are based on many assumptions about atmospheric and environmental conditions...

 

I hate it when people tell me, trust them, I never do. I don’t think science should be a faith based operation. I like to see models and tests, show me. I’m very unhappy with the 2 to 4.6 C / doubling of [ce]CO_2[/ce] concentration “constant”. The upper value is 130% more than the lower value, that doesn’t seem like precise science to me. Is it possible to experimentally test those assumptions? Is there some way an experimental test might narrow this margin?

 

... In short, no matter how much we might wish it to be, you can’t make the relationship between [ce]CO_2[/ce] and other greenhouse gases to temperature simple, because the physics underlying it - despite components of it being precisely measurable with such techniques as spectroscopy - isn’t simple...

 

Things don’t have to be simple, to be tested. We test IQ and behavior, those aren’t simple phenomena. Would constructing pipes of different lengths filled with [ce]CO_2[/ce] help test the assumptions Modest describes here?:

Re: Greenhouse Effect Experimental Designs

Is climate change mitigation based on prudence, as Bill states here: http://hypography.com/forums/environmental-studies/21736-greenhouse-effect-experimental-designs.html#post288809 , instead of experimental science? Michaelangelica compares this to Natural Selection as a purely observational science, is that the state of the science? There are over five million pages referencing to experimental evolution here: experimental evolution - Google Search , climate science isn’t there yet?

[BrianG]

Please give us the benefit of your profound wisdom and design such a test/experiment for us.

 

Working on it, your help is appreciated.

 

Does it follow that you don't believe in Darwin and Natural Selection because it is based on "interpretation of observations"

 

I'm not a creationist or ID'er, if that's what you mean. We've tried policies based on Darwin and Natural Selection, eugenics is a loser. Did you know "Svante Arrhenius was one of several leading Swedish scientists actively engaged in the process leading to the creation in 1922 of The State Institute for Racial Biology in Uppsala, Sweden, which had originally been proposed as a Nobel Institute. Arrhenius was a member of the institute's board, as he had been in The Swedish Society for Racial Hygiene (Eugenics), founded in 1909. Swedish racial biology was world-leading at this time, and the results formed the scientific basis for the Compulsory sterilization program in Sweden."?

http://en.wikipedia.org/wiki/Svante_Arrhenius

 

This isn't an attack on Arrhenius' theory, that's ad hominem, this is an observation about eugenics and policies not based on experimental science. Please also note that consensus, even Nobel science isn't always true.

[Michaelangelica]

There are over five million pages referencing to experimental evolution here: experimental evolution - Google Search , climate science isn’t there yet?

Wrong yet again BrianG , if you base your assumptions on a Google search.

Try a Google search for climate science (30Mil) or global warming (36Mil)

[BrianG]

You're right, M. I withdraw any claim that there are over five million cited experimental evolution studies, there aren't five million experiments in the field.

 

Wiki says: "In evolutionary and experimental biology, the field of experimental evolution is concerned with testing hypotheses and theories of evolution by use of controlled experiments..." here: Experimental evolution , there are books on experimental evolution like this one here: Experimental Evolution : Edited by Theodore Garland, Jr., and Michael R. Rose and university courses and projects on experimental evolution, like here: E. coli Long-term Experimental Evolution Project Site .

 

I'm especially wrong to make a comparison between experimental evolution and climate science based on a google search, thank you for the correction, Michaelangelica.

[BrianG]

That's not an experiment. An Experiment is the way science tests hypotheses.

[modest]

Maybe we should limit the lab greenhouse experiments to testing Arrhenius’ formula from your previous post:

[math]\Delta T_s = \lambda \Delta F [/math]

 

That might simplify the lab experiment issue.

 

If you found the radiative forcing for the experiment you are talking about using the Beer-Lambert law, or through measurement—in fact, let's say it is 30 Watts per meter squared—we would know the change in temperature,

and we would know the radiative forcing, so we know,

[math]\Delta T_s = 6 \ \degree C[/math]

[math]\Delta F = 30 \ W/m^2[/math]

Now using the climate sensitivity equation we can find lambda in this lab experiment,

[math]\Delta T_s = \lambda \Delta F [/math]

[math]\lambda = \frac{\Delta T_s}{\Delta F}[/math]

[math]\lambda = \frac{6 \ \degree C}{30 \ W/m^2}[/math]

[math]\lambda = 0.2 \ \degree C / (W/m^2)[/math]

The point being, lambda can be determined empirically for our lab experiment in such a manner.

 

According to Craig,

Taking typical present results for [math]\alpha[/math] and [math]\lambda[/math], [imath]3.35 \,\mbox{W/m}^2[/imath] and [imath]0.8 \,\mbox{K}/\left(\mbox{W/m}^2\right)[/imath], a doubling of [ce]CO_2[/ce] concentration results in a 3 C rise in temperature.

[math]\lambda[/math] should be 0.8 C/W/m², not 0.2 C/W/m². In other words, the lab experiment should have a lesser effect for a given change in radiative forcing than does the earth. The lambda we found in the lab is not the same lambda we found for the earth. The reason, which you have not yet recognized that you understand, is explained by Craig,

More important than the precise values of these constants, I think, is to understand that they are based on many assumptions about atmospheric and environmental conditions

– they’re not, in the sense that constants such as the gravitation constant are, really

constant

, and that more than a single gas molecule, such as [ce]CO_2[/ce], are significant in the models that use them.

Lambda is not constant across different experimental or real-world setups. The relationship between CO², radiative forcing, and temperature in the small lab experiment is not the same relationship between CO², radiative forcing, and temperature for the earth. Measuring and determining the factor by which delta-F and lambda affect temp in the lab experiment cannot be generalized to a different experimental setup.

 

The things which are constant between the lab and the earth are more fundamental such as the absorbance and transmittance of carbon dioxide. Change in temperature is a derived quantity that depends on too many factors for this,

The lab experiments cited in the first post for this thread show a very weak greenhouse effect from doubling CO

₂

, about [math]0.5\celsius[/math], far lower than the IPCC's projection from the preindustrial ideal of 280ppmv, to our current approx 390ppmv.

to be true, or meaningful.

 

Did you note http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif lists [ce]O_2[/ce] as a major greenhouse gas? That’s the first time I’ve seen that, I’m aware ozone [ce]O_3[/ce] is a greenhouse gas. This is the first time I’ve ever thought of oxygen, nearly 30% of the atmosphere, as a greenhouse gas, thanks!

Test your interpretation. Gases which block incoming light do not contribute to the greenhouse effect. Gases which block outgoing light do contribute. The graph Craig posted does not mark a distinction between oxygen and ozone and it does not mark incoming and outgoing wavelengths. Let's find another,

-

source

Blocking the red hump (the left side) does not contribute to the greenhouse effect. Blocking the blue hump (the right side) does contribute. Notice once again that no distinction is made between oxygen and ozone. We still do not know if oxygen, ozone, or both contribute to the greenhouse effect. Investigating further and finding more information,

-source

It appears ozone alone blocks outgoing, infrared, light. It contributes to the greenhouse effect while oxygen does not. A closer look at the right hump (the outgoing spectrum) of a real-world measurement,

-

source

Indeed, your first inclination was correct: ozone is a greenhouse gas and oxygen is not. Oxygen absorbs wavelengths (especially very short wavelengths) of incoming light—not outgoing light. Oxygen is therefore important to consider when modeling the radiation budget of earth's surface, but it is not a greenhouse gas.

 

~modest

[BrianG]

If you found the radiative forcing for the experiment you are talking about using the Beer-Lambert law, or through measurement—in fact, let's say it is 30 Watts per meter squared...

That's just an assumption, couldn't it be measured and manipulated?

 

The lambda we found in the lab is not the same lambda we found for the earth. The reason, which you have not yet recognized that you understand, is explained by Craig,

 

True, I'll explain below.

 

...

Lambda is not constant across different experimental or real-world setups. The relationship between CO², radiative forcing, and temperature in the small lab experiment is not the same relationship between CO², radiative forcing, and temperature for the earth. Measuring and determining the factor by which delta-F and lambda affect temp in the lab experiment cannot be generalized to a different experimental setup.

 

The things which are constant between the lab and the earth are more fundamental such as the absorbance and transmittance of carbon dioxide. Change in temperature is a derived quantity that depends on too many factors for this,

to be true, or meaningful.

 

...

How many factors? Can they be experimentally manipulated? Can we list the many factors?

 

This gets vague for me, the "too many factors" argument. Can we pin this down a little, and see how they change lambda?

[modest]

If you found the radiative forcing for the experiment you are talking about using the Beer-Lambert law, or through measurement—in fact, let's say it is 30 Watts per meter squared...

That's just an assumption, couldn't it be measured and manipulated?

The answer to your question, "can it be measured", is in the quote above your question.

 

...

Lambda is not constant across different experimental or real-world setups. The relationship between CO₂, radiative forcing, and temperature in the small lab experiment is not the same relationship between CO₂, radiative forcing, and temperature for the earth. Measuring and determining the factor by which delta-F and lambda affect temp in the lab experiment cannot be generalized to a different experimental setup.

 

The things which are constant between the lab and the earth are more fundamental such as the absorbance and transmittance of carbon dioxide. Change in temperature is a derived quantity that depends on too many factors for this,

to be true, or meaningful.

 

...

How many factors?

I'd imagine quite a few.

 

The equation you asked to focus on has change in surface temperature (ΔT_S) and change in radiative forcing (ΔF). The lambda term represents factors that relate the one to the other. A simple model which takes some of those factors into account is given in the 1979 paper by M.S. Lian, Increased Atmospheric CO₂: Zonal and Seasonal Estimates of the Effect on the Radiation Balance and Surface Temperature equation 1:

[math]r(\theta) \Big\{ \frac{\delta T_s(\theta,t)}{\delta t} + \omega [T_s(\theta,t) - T_s(\theta)] \Big\} = S(\theta,t)[1-\alpha(\theta,t)][/math]

[math]-v[T_s(\theta,t) - \langle T_s \rangle] - I(\theta,t) - \Delta F(\theta,t)[/math]

where

• [math]R(\theta)[/math] is effective thermal inertia of the earth-atmosphere system (in J m
  ^-2
  K
  ^-1
  );
  
  
• [math]T_s(\theta,t)[/math] is surface air temperature;
  
  
• [math]T_s(\theta)[/math] is annually averaged zonal surface air temperature;
  
  
• [math]\langle T_s \rangle[/math] is hemispherically averaged surface air temperature;
  
  
• [math]\omega[/math] is 2[math]\pi[/math]/[math]\tau[/math], with [math]\tau[/math] equal to length of year (12 months);
  
  
• [math]S(\theta,t)[/math] is incoming solar radiation (in W m
  ^-2
  );
  
  
• [math]\alpha (\theta,t)[/math] is zonal albedo;
  
  
• [math]v[/math] is dynamical transport coefficient, equal to 3.4 W m
  ^-2
  K
  ^-1
  ;
  
  
• [math]I(\theta,t)[/math] is outgoing longwave flux;
  
  
• [math]- \Delta F(\theta,t)[/math] is radiative heating due to increased CO
  ₂
  
  

If you then calculated [math]\Delta F[/math] (the change in radiative forcing) due to a doubling of CO₂ you could then solve for the expected change in temperature. It looks like the paper does that and finds [math]\Delta F = 4.12 \ W/m^2[/math] and [math]\Delta T_s = 3.29 \ \degree C[/math]. (i.e. doubling the concentration of CO₂ in the atmosphere will cause an average surface temperature increase of 3.29 degrees.)

 

But, this is a quite old and rather simplistic model. There are factors, even pointed out explicitly in this paper, which are not accounted for. For example,

The procedure we adopt to compute the change in [math]T_s[/math] (due to increased CO

₂

) neglects the following two stratosphere-troposphere radiative interactions: (1) possible changes in stratospheric radiation due to changes in tropospehric and surface temperatures and (2) the coupling between tropospheric temperature increase and CO

₂

radiative effects within the troposphere. In order to examine the magnitude of the above two processes, we recomputed the [math]\Delta F[/math] values by incorporating the change in [math]T_s[/math] computed from (1).

You should also recognize that there are some factors standing between temperature and CO₂ which do not lend themselves to exact reproduction in a lab. For example, feedback effects from clouds. The experiment you're looking at in the opening post doesn't have any clouds. It doesn't have a troposphere or a stratosphere nor oceans nor rain forests. The relationship between carbon dioxide and temperature of a desktop experiment does not and should not be the same as for earth. There are factors besides CO₂ concentration which determine the equilibrium temperature. Even the radiative forcing is different because,

1. The tabletop experiment is smaller, with a smaller path length
   
2. The light sources have different flux
   
3. The tabletop experiment is affected by the temp of the room through convection
   
4. The tabletop medium has a different albedo
   

Can they be experimentally manipulated?

Yes. Through experiment and through our understanding of the laws of physics it is possible to know (with a certain amount of uncertainty) how the different factors affecting temperature work. This is exactly what a climate model does. It answers the question of how climate will change if the factors affecting climate change. The factors affecting climate can be, and are, experimentally and observationally investigated.

 

Can we list the many factors?

You can, if you are so inclined, investigate the newest climate models to see how (through what physical processes) the different radiative forcings affect temperature. But, this is not what you should do. Your questions show a very fundamental lack of understanding as to what the greenhouse effect is—in its most conceptual form. Trying to investigate something so particular and intricate before understanding the overall concept would not be helpful in my opinion.

 

This gets vague for me, the "too many factors" argument. Can we pin this down a little, and see how they change lambda?

The point is not that there are too many factors. The point is that th comparison that you have made time and again,

Two vessels, one with 100% [CE]CO2[/CE] and the other with 0.037% [CE]CO2[/CE] are exposed to IR and it looks like a [math]5\celsius[/math] is caused by the greenhouse effect. If you were to double the concentration by volume of the 0.037% [CE]CO2[/CE] a little more than 12 times, you would get 100% [CE]CO2[/CE]. Twelve doubling’s of [CE]CO2[/CE] produces [math]5\celsius[/math] warming, or each doubling of atmospheric [CE]CO2[/CE] produces about [math]0.42\celsius[/math] atmospheric warming. This greenhouse effect is significantly less than the IPCC’s forecasts for doubling the preindustrial atmosphere at 280ppmv CO2 to 560ppmv, yet it’s the best experimental test I’ve ever seen. Why is there such a large discrepancy?

disregards any such factors. The answer to your question "Why is there such a large discrepancy?" is that the two cannot sensibly be compared the way you have tried to compare them. I still don't think you have explicitly recognized this.

 

It is, like I've said, very much like assuming that a 100% lead bullet will damage a wall an equal amount as a 100% lead cannonball. You are ignoring other factors like velocity and mass—maybe because you don't understand why the wall is damaged in the first place. I don't think you understand why the container in the experiment heats up when CO₂ is added. In my opinion, that is what you first should focus on.

 

~modest

[BrianG]

The answer to your question, "can it be measured", is in the quote above your question.

 

Yet the experimenters don't provide the wattage, is that a serious omission?

 

...You should also recognize that there are some factors standing between temperature and CO₂ which do not lend themselves to exact reproduction in a lab. For example, feedback effects from clouds.

Do clouds lend themselves to exact reproduction in climate models? If not, aren't models no better?

 

...The factors affecting climate can be, and are, experimentally and observationally investigated.

Where can I find experimental investigations of other climate factors? I don't see how factors that can't be experimentally tested can be accurately tested in climate models.

 

.... Your questions show a very fundamental lack of understanding as to what the greenhouse effect is—in its most conceptual form... I don't think you understand why the container in the experiment heats up when CO₂ is added. In my opinion, that is what you first should focus on...

 

Isn’t it clear that CO₂ is opaque to some frequencies of IR? When exposed to that light, it heats up, warms nearby air molecules or glows away the heat in all directions?

[Essay]

How many factors? Can they be experimentally manipulated? Can we list the many factors?

 

This gets vague for me, the "too many factors" argument. Can we pin this down a little, and see how they change lambda?

:hyper:

 

Too Vague.... Must be certain, or if not....

:lol: ...Must rely on fundamental values!

===

 

Brian, I'd suggest not focusing on the accuracy of the models, or on what the models say will happen when; but instead, focus on what the models do NOT say.

 

None of the models say there is any chance of stability remaining in our climatically driven, over-amped, heat-dissipation system. There is some certainty you can rely upon.

 

~ :)

[modest]

Yet the experimenters don't provide the wattage, is that a serious omission?

 

Do clouds lend themselves to exact reproduction in climate models?

Nothing lends itself to exact reproduction in a model. Hence, "model".

 

If not, aren't models no better?

No better than...?

 

Where can I find experimental investigations of other climate factors?

Allen's Astrophysical Quantities is an excellent reference for that sort of thing. I've used it in the past in global warming discussions. If you need to know, for example, how thermally conductive the ground is (or even something specific like basalt or granite)—things a climate model might need to consider—then you're likely to find it there.

 

I don't see how factors that can't be experimentally tested can be accurately tested in climate models.

I made no mention of things being tested in climate models, so you've misunderstood something.

 

Isn’t it clear that CO₂ is opaque to some frequencies of IR? When exposed to that light, it heats up, warms nearby air molecules or glows away the heat in all directions?

That's very good. Carbon dioxide absorbs IR, so, we might sensibly ask next: how much infrared radiation does the sun produce?

 

I'll help. CO₂ absorbs at about 14.5 microns (according, at least, to the image I posted a couple posts ago). How much light does the sun produce at 14.5 microns?

 

The sun is 5700 K, so according to Wien's Displacement law it's peak radiation is about 500 nanometers (0.5 microns), which is, not incoincidentally, the center of a human's visual spectrum—green light. Using Plank's Law we can say how much more green light the sun makes as opposed to the .5 micron IR light that CO₂ absorbs,

[math]\left( \frac{2 hc^2}{(\lambda(P))^5}\frac{1}{ e^{\frac{hc}{(\lambda(P)) kT}}-1} \right) \div \left( \frac{2 hc^2}{(\lambda(CO_2))^5}\frac{1}{ e^{\frac{hc}{(\lambda (CO_2)) kT}}-1} \right)[/math]

where T is 5700 K, lambda(P) is the peak wavelength of 5x10^-7 meters and lambda(CO₂) is the IR wavelength of CO₂ at 1.45x10^-5 meters, and the rest of the variables are given here.

 

The answer is 25,200, about twenty five thousand. The sun makes 25 thousand times less light that carbon dioxide can absorb than it does visible green light that we can see. It, essentially, doesn't make any of it at all. The sun (essentially) does not make light that CO₂ can absorb. The light that the sun makes has a smaller wavelength... smaller than infrared.

 

 

 

So, let me ask, what if the lamp in the experiment in the opening post didn't make infrared light that carbon dioxide could absorb? Would the experiment still warm up with the addition of CO₂? Yes? Why is that?

 

~modest

[Moontanman]

Oo oo oo I know I know! The earth radiates in the infrared! The earth absorbs the suns light and re-emits it in the infrared!

[modest]

Yup

 

That's the key to the greenhouse effect, Brian.

 

This,

...

Can you explain, in your own words, what the greenhouse effect is?

 

When you face the sun when it's high overhead, you can feel the heat, when you face the sun when it's lower on the horizon, you feel less heat. The greenhouse effect helps explain what happens to some of the heat in the air.

is not right. Greenhouse Gases do not absorb the sun's heat (in any significant way). If they did, it wouldn't be a greenhouse effect, it would just be a warming effect, and Earth would be an average of about 30 ºC colder.

 

The idea is that the sun's radiation can easily make it to the surface, but the re-radiated heat from the surface has a much harder time getting back out. Imagine turning on the faucet of a tub and opening the drain wide open. The tub will fill to a certain equilibrium height with water. It's known as a steady-state system, or a system in dynamic equilibrium. If you close the drain a bit so that it's harder for the water to get out then the water level will rise to reach a new equilibrium.

 

That is analogous to the earth. The more CO₂ you put in the atmosphere, the harder it is for heat to leave the atmosphere causing the temperature to rise. If CO₂ blocked the sun's radiation and earth's radiation equally then it would be like lowering the flow of the faucet and lowering the flow of the drain—the equilibrium level would remain unchanged. The key to greenhouse gases is that radiation is unhampered on its way to the surface, but radiation is hampered on its way back out to space.

 

~modest

[BrianG]

I stand corrected. I assume dynamic equilibrium of the greenhouse gas effect must be a very fast process, since IR travels at the speed of light.

[modest]

I assume dynamic equilibrium of the greenhouse gas effect must be a very fast process, since IR travels at the speed of light.

 

It takes different amounts of time for different parts of the atmosphere to 1) respond to a radiative forcing, and 2) reach an equilibrium with the rest of the atmosphere and the surface. Because of this, there are two types of radiative forcing that climate models must consider; instantaneous forcing, and adjusted forcing. The first is rather instantaneous as you suspect, the second takes a bit of time (and this is before considering feedback effects0. These links probably explain better than I could,

 

(D) When a perturbation is applied (such as increases in well-mixed greenhouse gases), there is an instantaneous change in irradiances that is manifest in general as a radiative imbalance (forcing) at the surface, tropopause and the top of the atmosphere. The rapid thermal re-equilibration of the stratosphere leads to an alteration of the radiative imbalance imposed on the surface-troposphere system (WMO, 1992), thereby yielding an adjusted forcing (SAR). The surface and troposphere, operating in a slow response mode, are still in a process of adjustment while the stratosphere has already reached its new equilibrium state. The SAR points out the clear distinction existing between the instantaneous and adjusted forcings.

 

For the arbitrary space and time mean stratosphere, there arises the need to evaluate the radiative flux changes with the stratosphere in a radiative-dynamical equilibrium. A classical method to determine this is the "Fixed Dynamical Heating" (FDH; WMO, 1995) in which it is assumed that the dynamical heating rate in the stratosphere is unchanged and that the stratosphere comes to a new thermal equilibrium in response to the perturbation through adjustments in the temperature profile, such that a new radiative-dynamical equilibrium is attained (radiative response; see Ramanathan and Dickinson (1979) and Fels et al. (1980)). The resulting adjustment process in the stratosphere makes an additional contribution to the forcing of the surface-troposphere system. When the stratosphere has adjusted to a new radiative-dynamical equilibrium with resultant changes to its thermal state, the change in flux at the tropopause and at the top of the atmosphere become identical. It is important that the stratosphere be in radiative-dynamical equilibrium and, as shown by Hansen et al. (1997a), it is the adjusted rather than the instantaneous forcing that is a more relevant indicator of the surface temperature response.

 

http://www.ipcc.ch/ipccreports/tar/wg1/258.htm

 

We calculate both the instantaneous and adjusted forcings for most of the climate change mechanisms that we consider. The instantaneous forcing, [math]F_i[/math], is the flux change at the tropopause that occurs when the radiative constituent is changed, but the temperature is kept fixed throughout the atmosphere. The adjusted forcing, [math]F_a[/math], is the flux change after the stratospheric temperature has been allowed to adjust to a new radiative equilibrium profile. It has been shown that the adjusted forcing in general provides a better measure to judge the expected climate response [RF-CR], so we usually illustrate the adjusted forcing.

 

http://pubs.giss.nasa.gov/docs/2002/2002_Hansen_etal_2.pdf

 

~modest