Model CO2 as Greenhouse Gas: Tips & Results

[Andre]

... gives you a greater value of about 1.7 or so.

How did you get 0.9?

From the default http://geosci.uchicago.edu/~archer/cgimodels/radiation.html settings ...

(CO2 (ppm> 375
CH4 (ppm) 1.7
Trop. Ozone (ppb) 28
Strat. Ozone scale 1

Ground T offset, C 0
hold water vapor pressure
Water Vapor Scale 1

Locality Tropical Atmosphere
No Clouds or Rain

Sensor Altitude km 70
Looking down

...We get an output of:

Iout, W / m2 = 287.844
Ground T, K = 299.70

Now we change only:

(CO2 (ppm> 750

and the output changes to

Iout, W / m2 = 284.672
Ground T, K = 299.70

So obviously less IR energy reaches the sensor and we have to increase the temperature to get the original / apparently equilibrium I-out back (287.844 w/m2)

So we put in Ground T offset, C the value +0.89 to see an output of

Iout, W / m2 = 287.844
Ground T, K = 300.59

hence we have to increase the surface temp with 0.89 degrees according to MODTRAN to regain radiation equilibrium.

Now we go back to the defaults and change hold water vapor Rel. Hum. which does not change the output from the basis, however if we double CO2 now, the output is

Iout, W / m2 = 284.672
Ground T, K = 299.70

And now we have to enter 1.48 degrees in ' Ground T offset, C' to regain the equilibrium value again.

For the 1976 standard atmosphere these values are 0.88 and 1.30 degrees respectively

Perhaps it's better to give Karner a dedicated thread as we explore the characteristix of feedback in general.

 

[chriscolose]

sylas, Michael Tobis had this to say a while back in a RC comment (to Andre actually) on Karner.

33.Re #3, specifically to the references to work by the Estonian statistician, O. Karner.

Karner has been taking single time series of diurnal temperature differences and showing that they act as if they are constrained to return to a fixed value. The statistical properties of this time series are “antipersistent” and may be associated with a feedback in a simple lumped parameter model. This is a purely statistical rather than physical model, and it shows there is a homeostatic process, with a number that can be considered “the feedback”.

Unfortunately, it appears to me that Karner confuses this mathematical property with the H2O amplification of radiative forcing, a physical quantity with which Karner’s feedback constant has only a distant relationship.

Indeed, there is an antipersistence in temperature anomalies on Earth, and the mechanism is well-known: radiative equilibration. In this phenomenon, water vapor plays an important role but it isn;t a soliloquy. Thus, when Karner says things like (see http://www.aai.ee/~olavi/2001JD002024u.pdf )

The revealed antipersistence in the lower tropospheric temperature increments does not support the science of global warming developed by IPCC [1996]. Negative long-range correlation of the increments during last 22 years means that negative feedback has been dominating in the Earth climate system during that period. The result is opposite to suggestion of Mitchell [1989] about domination of a positive cumulative feedback after a forced temperature change

to my reading he is confused. (I am surprised this text passed review at JGR-A.)

His subsequent paper ( http://www.aai.ee/~olavi/cejpokfin.pdf ) seems to show increased awareness on the matter:

Using the H estimates to ascertain the cumulative feedback sign dominating in the Earth climate system for the particular variable. In the present study the term feed-back is used in the sense of total reaction of the variable to customary forcing in the Earth climate system. Such an understanding is unavoidable in statistical analysis of meteorological time series because, as a rule, they are affected by many forcing types including the seasonal and daily cycles in solar radiation. In climatology the term feedback is usually connected to the corresponding feedback loop, e.g ice-albedo feedback [13]. For the whole climate system this means that one has to consider many feedbacks at the same time.

Karner’s methodology does not separate out specific physical mechanisms but is simply a way of characterizing a time series. It in some sense includes but (as I understand it) in no sense measures the impact of water vapor feedback on radiative equilibrium.

My own reading of the Karner paper is that it has little at all to do with attribution or long-term climate feedback, and thus claims as in the abstract are unsupportable. I don't quite understand the statistical end of things in the way Tobis does, but the relation to long term climate feedback is kind of evident.

 

[Andre]

Chris, the articles of Olavi Karner are peer reviewed and the physics of feedbacks are clear albeit complex.

How about some remark of somebody, challenging that? Is this also peer reviewed? If there is a discussion about this in a formal scientifically recognized magazine then it would be nice to quote that, however there is a strong viewpoint here about the autority of blog discussions.

There are more papers by the way, for instance:

http://www.aai.ee/~olavi/E-Ac-Sci-07.pdf

..The analysis of the OLR time series indicates that a negative feedback should dominate in the Earth climate system...

 

[chriscolose]

One way to think about the no-feedback case is to assume that the emission temperature and surface temperature are linearly related, and so it follows that


\lambda (planck feedback only) =\left(\frac{\partial ( \sigma T^{4}_{eff})}{\partial T_{s}}\right)<br /> <br /> ^{-1}

Please note that the resultant (4 \sigma T^{3}_{eff})^{-1} requires the emission temperature (i.e., 255 K) as an input, not the surface temperature. This evaluates to roughly 0.27 K (W m^{-2})^{-1}

which says that you get about a quarter degree change in temperature for each Watt per square meter forcing. The forcing for a doubling of CO2 is nearly 4 watts per square meter. This would imply a very stable climate since it would take a 23 W/m2 change in solar constant just to produce a 1 C change in global temperature, about the same as a doubling of CO2. Thus you'd need the equivalent of several doublings of CO2 and/or unreasonable changes in solar irradiance to be consistent with the magnitude of deep-time paleo changes.

Those arguing for net neutral, and especially negative feedbacks are simply not correct.

 

[sylas]

OK... thanks. I now see what you are doing with MODTRAN. You are actually calculating something rather different to the Planck response; although the reason for this gets a bit subtle.

The forcing for a doubling of CO₂ is known to be 3.7 W/m². This number is well constrained; with about 10% accuracy or so. The major reference for this value is Myhre et al., (1998) http://www.agu.org/pubs/crossref/1998/98GL01908.shtml, Geophysical Research Letters, Vol 25, No. 14, pp 2715-2718; and similar values are obtained in other work as well. It is not something that should be in serious dispute.

Unfortunately, you can't read this off MODTRAN very well. There are two reasons for this. One is that it depends on the latitude. The second is that it depends on the altitude of the sensor.

Part of the problem is the appropriate definition of a forcing. I describe it, with references, in [post=2162699]msg #1[/post] of "Estimating the impact of CO2 on global mean temperature". It corresponds to a change in energy balance at the top of the tropopause. There's a reason for measuring there rather than at 70km; and it is because of the rapid response of the stratosphere to a forcing... a response that this MODTRAN calculator omits. In [post=2165483]msg #3[/post] of that thread I repeat pretty much the calculation you have given here, but with a detector at 20km. Here is a tabulation of some results:

\begin{array}{cc|cccc}<br /> \text{Atmosphere} &amp; \text{Altitude, km} &amp; 375 \text{ppm} &amp; 750 \text{ppm} &amp; \text{difference} &amp; \text{extra T reqd} \\<br /> \hline<br /> \text{Tropical} &amp; 20 &amp; 288.378 &amp; 283.856 &amp; 4.522 &amp; 1.385 \\<br /> \text{Tropical} &amp; 70 &amp; 287.844 &amp; 284.672 &amp; 3.172 &amp; 0.89 \\<br /> \text{Std 1976} &amp; 20 &amp; 258.893 &amp; 255.47 &amp; 3.423 &amp; 1.03 \\<br /> \text{Std 1976} &amp; 70 &amp; 258.862 &amp; 256.004 &amp; 2.858 &amp; 0.88<br /> \end{array}​

The reason you get a difference at higher altitude is that the atmospheric temperature profile in this calculator is held fixed, and so the calculator actually has stratospheric warming as a response to an increase temperature offset. What happens in reality is that the stratosphere cools; mainly because of the increased emissivity of carbon dioxide which makes it shed heat more rapidly. Furthermore, this cooling response is very rapid, since it is a purely radiative effect. That is why the formal definition of forcing includes settling of the stratosphere, but not of the troposphere. Informally, you can say that the stratosphere response (which has little impact back to ground level) is considered so fast that it is part of the forcing, and not a separate feedback process.

The upshot is that to get a sensible value for the forcing response to doubled CO2, you should really take the lower altitude sensor. Also, you can't have a tropical atmosphere over the whole planet. The value you get will be somewhere between the tropical atmosphere and the standard 1976 atmosphere; and you also need to consider clear sky and cloud as well.

All told, the MODTRAN calculator will get you into the right ball park; but it can't serve as a refutation of the forcing for doubled CO2, which is about 3.7 W/m² to 10% accuracy or better.

Perhaps it's better to give Karner a dedicated thread as we explore the characteristix of feedback in general.

That's a good idea. I'll let you start it. Furthermore, if I don't join in right away it will be because I am reading, rather than trying to jump in before I understand it more.

Cheers -- sylas

PS. Added in edit. I see I've missed Chris' input since writing this.

 

[BrianG]

The effect of doubling CO2 is for conditions on Earth, where CO2 is a small part of the atmosphere. It's a fairly well constrained result that doubling CO2 in Earth's atmosphere, and holding everything else fixed, will give an additional 3.7 W/m² of forcing.

You can get approximately the right result here by using a crude estimate of

Q = \epsilon \sigma T^4​

Q here is the energy out the top of the atmosphere, T is the absolute temperature at the surface, σ is the Stefan-Boltzmann constant, and ε is a constant, written here a bit like emissivity, although it is is not actually an emissivity term.

T at Earth's surface is about 298, and Q is about 239 W/m²...

This is tested by experiment? Please cite; I am interested in experimental tests on CO2's greenhouse effect.

 

[BrianG]

But these formulas aren't tested in the lab? Can you cite any experimental tests?

 

[Skyhunter]

They are not tested in a lab, they are based on the results of extensive observations of the atmosphere.

 

[mheslep]

...
While average Antarctic sea ice has increased slightly, this is a function of ozone depletion and it's effect on circulation patterns in the Antarctic, not some alleged global cooling. other areas of the Antarctic, especially the western peninsula, are experiencing a sharp decline in average sea ice extent.

Do you have sources for this, especially the implication that ozone depletion is responsible for Antarctic sea ice creation via currents? Currents and circulation also have a great deal to do with Arctic ice depletion.[1]

...Antarctic total ice mass is decreasing to the tune of about 84 gigatons of ice per year.

That statement would seem to conflict with this

The Antarctic ice sheet is likely to gain mass because of greater precipitation,

http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/008.htm

[1]http://www.nasa.gov/vision/earth/lookingatearth/quikscat-20071001.html

Nghiem said the rapid decline in winter perennial ice the past two years was caused by unusual winds. "Unusual atmospheric conditions set up wind patterns that compressed the sea ice, loaded it into the Transpolar Drift Stream and then sped its flow out of the Arctic," he said. When that sea ice reached lower latitudes, it rapidly melted in the warmer waters.

"The winds causing this trend in ice reduction were set up by an unusual pattern of atmospheric pressure that began at the beginning of this century," Nghiem said.

 

[chriscolose]

For those interested, spectroscopic databases have been compiled for all the gases in the Earth's atmosphere (e.g., HITRAN) These databases contain line centers and parameters describing line shape as a function of pressure and temperature and provide the amount of absorption to very high spectral resolution.

Before reading too much into much simpler stuff then the approach of modern line-by-line radiative transfer codes and climate models, it may be worth reading some online material on the downfalls of simple experiments, like measuring radiation decay through a tube. See http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument-part-ii/ (and part 1) and check out Spencer Weart's site as well.

 

[Skyhunter]

Do you have sources for this, especially the implication that ozone depletion is responsible for Antarctic sea ice creation via currents? Currents and circulation also have a great deal to do with Arctic ice depletion.[1]
That statement would seem to conflict with this

It is in the Antarctic section. (large PDF 15mb)
http://www.ncdc.noaa.gov/oa/climate/research/2008/ann/bams/full-report.pdf

The TAR is a bit outdated and it appears you are confusing Antarctic land ice with Antarctic sea ice, and the Arctic with the Antarctic.

The State of the climate report I cited has the most comprehensive up to date assessment since the 4AR. The sections on the Arctic and Antarctic should help clear up your confusion.

 

[mheslep]

It is in the Antarctic section. (large PDF 15mb)
http://www.ncdc.noaa.gov/oa/climate/research/2008/ann/bams/full-report.pdf

Thanks, I'll take a look.

The TAR is a bit outdated and it appears you are confusing Antarctic land ice with Antarctic sea ice, and the Arctic with the Antarctic.

No, I was drawing attention to the the way in which you were singling out winds and currents only for the Antarctic explanation; they also factor greatly in explaining Arctic melts as explained by Nghiem.

 

[BrianG]

They are not tested in a lab, they are based on the results of extensive observations of the atmosphere.

How do you isolate the effect of CO2? Are you saying the greenhouse effect is too small for exprimental measurement?

 

[sylas]

How do you isolate the effect of CO2? Are you saying the greenhouse effect is too small for exprimental measurement?

It is isolated by the experiments we have been discussing already, starting with Tyndal in the 19th century.

What you can't measure in an experiment is the total effect on Earth's climate. You can, however, confirm the basic underlying physics which is involved.

We know that carbon dioxide absorbs infrared radiation. We know how it works now in considerable detail, thanks to quantum mechanics; and there is a massive body of experimental work confirming the relevant physics. You can now calculate the absorption spectrum for different gases in considerable detail. The warming effect of this on a planet is consequence of very basic physics indeed. We've not conducted experiments on a planet as such, but experiments on radiation and thermodynamics confirms well beyond any credible doubt that an atmosphere which absorbs infrared radiation will give a higher surface temperature.

This is called the "atmospheric greenhouse effect". You still get people who deny that a greenhouse effect exists at all, but that is pretty much the young Earth creationism of climate science.

On the other hand, there is the effect of changing concentrations of greenhouse gases. This means quantifying the effect, in terms of concentrations; and that is not something you can do directly in a lab either. What you can do in a lab confirms that increasing carbon dioxide will give more absorption of infrared; but you can't just do a simple scale from a gas cell to an atmosphere. To quantify the effect well enough to infer the effect of changing concentrations on a planet is more difficult.

This problem can be broken into two parts; one of which is solved and one of which is not.

We know very well how carbon dioxide and other gases interact with radiation. We measure the spectum of light in the atmosphere (backradiation, radiation out to space, flux at different levels, and so on) and there's a well developed and tested theory associated with that; so that you can calculate to quite good accuracy how much additional energy is available with a change in concentrations.

What is hard is to tell how much the temperature of the surface changes in response to additional energy. Again; the relevant physics is fine, but the problem is the sheer scale of the major cycles and processes interacting in the climate system. You can test various parts of it, but to actually measure the temperature changes due to changing atmospheric composition can't be done directly. You can't separate out the causes and effects as you can in a lab.

Upshot is.

We know, as well as we know anything at all in science, that there's a greenhouse effect. There are all kinds of experiments, some of which we have discussed here, which show that carbon dioxide, water, methane, flourocarbons, and various other gases will absorb thermal radiation and heat up as a result.

We know, to a very high level of confidence, that the effect of a gas like carbon dioxide is logarithmic, and we've got a good handle on the factor. A doubling of CO2 concentrations will give a certain amount of additional energy at the surface of the planet... about 3.7 W/m². That's the result of a pretty detailed calculation over the surface of the Earth and and though all lines of the spectrum, using well tested physics. You can't measure that number directly; it is a calculation for a whole planet. But there's no credible doubt on the number beyond comparatively small errors of no more than 10%.

We have a rough idea only of how much temperature change that leads to, in the long run. It's something from 2 to 4.5 degrees. That based on empirical and theoretical studies.

Cheers -- sylas

 

[Skyhunter]

No, I was drawing attention to the the way in which you were singling out winds and currents only for the Antarctic explanation; they also factor greatly in explaining Arctic melts as explained by Nghiem.

I was addressing a direct point about the Antarctic, not ignoring the conditions in the Arctic that led to the rapid decrease in Arctic sea ice. I was trying to keep it brief since it is off topic.

The conditions that led to the sharp decline in Arctic sea ice were not unprecedented. The difference in 2007 was the abundance of thin ice that was more suscpeptible to being blown into more temperate waters by the wind.

The development of a relatively younger, thinner ice cover coincided with a strong, persistent positive pattern in the AO from 1989 to 1995 (see Figure A1). These characteristics make the current ice cover intrinsically more susceptible to the effects of atmospheric and oceanic forcing. It is of crucial importance to observe whether the sea ice cover will continue its decline or recover under the recent more neutral AO conditions (Lindsay and Zhang, 2005). http://www.arctic.noaa.gov/report07/seaice.html"

http://nsidc.org/arcticseaicenews/" sea ice extent there has been no recovery of Arctic sea ice.

http://www.antarctica.ac.uk/press/press_releases/press_release.php?id=838"

 

[mheslep]

http://nsidc.org/arcticseaicenews/" sea ice extent there has been no recovery of Arctic sea ice.

<shrug>So far in 2009 the Arctic extent is certainly lower than the long term mean, yet 2009 has been an improvement over 2007, and April 2009 almost rejoined the mean.

 

[Skyhunter]

<shrug>So far in 2009 the Arctic extent is certainly lower than the long term mean, yet 2009 has been an improvement over 2007, and April 2009 almost rejoined the mean.

April 2009 sea ice extent may have nearly rejoined the mean, but sea ice mass (extent x thickness) is steadily declining. 2009 is much less than 2008, and it is declining more rapidly than during the same period in 2007.

August 1, 2008

This rapid late season melt is indicative of the thinner ice that is well documented.

http://www.thedailygreen.com/environmental-news/latest/arctic-sea-ice-47011108?src=rss
http://www.nasa.gov/topics/earth/features/arctic_thinice.html
http://www.arctic.noaa.gov/reportcard/seaice.html

 

[sylas]

<shrug>So far in 2009 the Arctic extent is certainly lower than the long term mean, yet 2009 has been an improvement over 2007, and April 2009 almost rejoined the mean.

When you look at individual years, like 2007, or 2009, you have to consider that there's variation from season to season.

The trend, however, is very strong. Even though 2007 was a major outlier, well below what would be expected from the trend; the trend is still sufficiently high that it is a good bet that there will be a new record low within the next few years; and that the Arctic will have a summer essentially free of sea ice sometime within the lifetime of many of the people reading this thread. Probably within my lifetime, if I make it to the age of my parents.

Picking one month (April) is odd.. unless you have some prior reason for singling out April then it looks a bit like cherry picking; it doesn't mean much. One could as well say that as of now, the ice cover is lower than any year on record except the exceptional 2007 season. But that's no assurance at all that 2009 is going to get to second place for the summer minimum of cover. It might, it might not.

And how can you define a "mean"? The mean over what period? Of the last decade? Sure... but since ice cover as been falling steadily for some time now the idea of a "mean" is rather suspect.

Its worth noting that the Arctic is a region that is not representative of the whole planet. The warming in the Arctic is well above global warming, and is substantially a local effect on top the global warming phenomenon. We had a good thread on this recently: [thread=306202]"Only dirty coal can save the Earth"[/thread] (the title is not a good indication of the implications of the study discussed, but the discussion was interesting).

Cheers -- sylas

 

[mheslep]

Certainly the Arctic ice reductions are significant. I was replying only in context to Skyhunter's 'no recovery' comment about '2008, 2009' where April stands out. By 'mean' I was referring to 79-2000 mean depicted in the graphs he posted. I wasn't using April to make any broader comment than that.

 

[Skyhunter]

Certainly the Arctic ice reductions are significant. I was replying only in context to Skyhunter's 'no recovery' comment about '2008, 2009' where April stands out. By 'mean' I was referring to 79-2000 mean depicted in the graphs he posted. I wasn't using April to make any broader comment than that.

My no recovery comment is quite valid and not refuted by your comments or examples. Citing the sea ice maximum extent without the context of sea ice thickness is misleading. The surface is expected to refreeze during NH winter. The large open areas actually increases Arctic temperature because of the release of latent heat during the rapid refreeze. Also the rapid refreeze can have a negative impact on sea ice thickness due to the insulating properties of the snow that accumulates on it's surface.

 

[mheslep]

My no recovery comment is quite valid and not refuted by your comments or examples.

Then don't do it any more. You have several posts up above on extent only.

 

[Skyhunter]

Then don't do it any more. You have several posts up above on extent only.

I don't understand your criticism.

The links I provided dealt with both extent and thickness. If you have a point please state it clearly. Otherwise let's not drag this thread further off topic.

 

[BrianG]

... you can't measure in an experiment is the total effect on Earth's climate. ...
We've not conducted experiments on a planet as such,...

You still get people who deny that a greenhouse effect exists at all, but that is pretty much the young Earth creationism of climate science...
the effect of changing concentrations of greenhouse gases. This means quantifying the effect, in terms of concentrations; and that is not something you can do directly in a lab either... To quantify the effect well enough to infer the effect of changing concentrations on a planet is more difficult...
to actually measure the temperature changes due to changing atmospheric composition can't be done directly. You can't separate out the causes and effects as you can in a lab.
...
A doubling of CO2 concentrations will give a certain amount of additional energy at the surface of the planet... about 3.7 W/m²... You can't measure that number directly...

No matter how large the container, no matter which greenhouse gas, how strong the light source, how long the trial run, you can't experimentally find a temperature change from CO2's greenhouse effect. Is that because it's too small to measure or is climate mitigation inherently untestable, unfalsifiable?

And you think skeptics are like creationists?

 

[Skyhunter]

No matter how large the container, no matter which greenhouse gas, how strong the light source, how long the trial run, you can't experimentally find a temperature change from CO2's greenhouse effect. Is that because it's too small to measure or is climate mitigation inherently untestable, unfalsifiable?

And you think skeptics are like creationists?

The experiments linked in this thread most definitely produce a measurable change in temperature from the radiative properties of CO₂. http://www.espere.de/Unitedkingdom/water/uk_watexpgreenhouse.htm"

If by skeptics you mean climate change deniers... yes, I do think they are like creationists. They ignore the overwhelming evidence because it does not fit their bias.

 

[BrianG]

No, by skeptics I mean folks who question the efficacy of climate change mitigation. Climate change is undeniable, the climate isn't static. If it was, it wouldn't be impossible to isolate a variable like CO2.

Do you really think that experiment is very good? How come it lasts only twenty minutes, there are only five data points for each sample, it tests CO2 at 370ppm and 1,000,000ppm but no other concentrations or other greenhouse gasses and neither the principle researcher or laboratory was identified? Has any other lab reproduced these results?

 

[Skyhunter]

No, by skeptics I mean folks who question the efficacy of climate change mitigation. Climate change is undeniable, the climate isn't static. If it was, it wouldn't be impossible to isolate a variable like CO2.

Do you really think that experiment is very good? How come it lasts only twenty minutes, there are only five data points for each sample, it tests CO2 at 370ppm and 1,000,000ppm but no other concentrations or other greenhouse gasses and neither the principle researcher or laboratory was identified? Has any other lab reproduced these results?

It is not impossible to isolate the radiative effect of CO₂. This experiment does just that.

If you want to deny and reject the evidence that is your perogative. Just remember... the truth does not require your belief, physics doesn't dither, and gravity always wins.

 

[Evo]

Let's refrain from calling names. There are nuts on both sides of the AGW debate, So called "Deniers" are no better or worse than "Alarmists", both cherry pick their data. Stick to discussing facts without getting emotionally involved.

 

[BrianG]

I can experimentally test gravity, how come this unknown researcher at an unknown lab wants this test to remain anonymous? What other labs are doing this work? What does the effect look like with CO2 concentrations at historic levels?

 

[sylas]

I can experimentally test gravity, how come this unknown researcher at an unknown lab wants this test to remain anonymous? What other labs are doing this work? What does the effect look like with CO2 concentrations at historic levels?

I'm assuming good faith here as best I can, but honestly, I have no idea at all what you are talking about.

Of COURSE you can test a basic greenhouse effect. You can't test on a whole planet at once, because it's too big to fit in a lab, but you can test the basic physics of the matter in labs just fine. That's what I tried to explain for you before. It sounds like you are making objections to experiments on a rather curious basis that I am finding hard to follow.

Have you looked at the rest of this thread?

We've been describing a number of experiments that reveal aspects of the problem, including experiments where you get increasing temperature due to the greenhouse effect in a lab setting. The results don't scale linearly to a whole planet; but the physics of the matter is quite straightforward.

A simple test at the level of looking for temperature change is not really all that useful for physics now; it is the kind of experiment used in a school to help children learn more about how science works and get practice doing experiments themselves. It's an experiment where you have to be careful controlling for what you are measuring, but it is entirely doable.

The experiment where you are making speculations about the "researcher" is not actually a "researcher", so much as a simple school level experiment. It's using really basic physics and confirming a result that that is elementary thermodynamics, in no doubt whatsoever for scientists.

The page is actually German, but has been translated for use in schools in the UK. The main topic of the site is water, in fact. Water is also a very important greenhouse gas. The site has a series of simple high school level pages going through some of the properties of water, and includes five pages of "experiments and homework"; the lab test of a CO2 greenhouse effect is one of these.

• The index page is here: http://www.espere.de/Unitedkingdom/ukschoolweluk.html .
• The main page for the "water" unit is here: http://www.espere.de/Unitedkingdom/water/uk_overview.htm . Note that there is a list of contributors given here.
• The experiment proposed is number 5 on the list of experiments and homework. The experiment is described here: http://www.espere.de/Unitedkingdom/water/uk_watexpgreenhouse.htm .

This project was initially carried out in 2001/2002 in Germany, with students aged about 14; though I can't be sure what revisions have taken place since then.

Another greenhouse experiment and worksheet from ESPERE for schools is described here: http://www.atmosphere.mpg.de/enid/4...ion___greenhouse_gases/__Worksheet_2_1gb.html as worksheet 2 in a lower atmosphere unit.

The original of this kind of experiment, in which the effect was first discovered, was conducted in the 1850s by John Tyndall. Those experiments are described in [post=2187943]msg #10[/post] of this thread.

I repeat: this style of experiment is no longer of any great relevance for working scientists. The phenomenon being measured is very elementary physics.

In another thread, I showed an experiment I found with a quick google that is more along the lines of real research: V.G. Arakcheev et al., (2008) Broadening of vibrational spectra of carbon dioxide upon absorption and condensation in nanopores, in Moscow University Physics Bulletin, Vol 63, No 6, Dec 2008. This is not about "greenhouse effect" directly, so much as studying the interactions of radiation and carbon dioxide at genuine research level of experiment. But that is where science is at: the research questions have on.

I am at a complete loss to understand what you meant in this comment in reply to me in another post:

No matter how large the container, no matter which greenhouse gas, how strong the light source, how long the trial run, you can't experimentally find a temperature change from CO2's greenhouse effect. Is that because it's too small to measure or is climate mitigation inherently untestable, unfalsifiable?

And you think skeptics are like creationists?

Um... sure, we do find temperature changes experimentally from CO2 greenhouse effect. Several examples have been given in this thread and I describe some in the post to which you are replying.

As for the creationist remark; I take Evo's point that we want to keep things polite. I was not speaking of individuals here, and I was not speaking of "skeptics" in general.

I was describing three levels of confidence in the details of the greenhouse effect. They are:

• Is there a greenhouse effect at all? That is, does an atmosphere containing greenhouse gases help maintain a warmer surface temperature than otherwise?
• What is the consequence of a CHANGE in greenhouse gas concentrations, and specifically carbon dioxide, in terms of the additional energy available to the surface?
• What is the consequence of the additional energy at the surface in terms of a temperature response?

It was the denial of greenhouse effect at all that I compared with creationism -- point "A" above. I stand by that without hesitation; but it's not meant to be a put down of individuals here; just a clarification of what parts of the question are really really basic... and that IS a relevant point for the physicsforums rules, consistently applied.

As far as physics forums is concerned, I think a consistent application of the rules would mean that this forum is not a place for that level of denial of basic physics. There are some people who will think this is unreasonable or unfair or ignoring scientific criticism; and there's not much point in debating them, frankly. For various reasons this topic is one where public debate does include a lot of really nonsensical physics, but I would hope that the physicsforum mentors are not at that level. I think physics confirmed from over 150 years ago is not what we should be debating here.

The next level of "skepticism" is about quantifying changes in greenhouse gas concentrations. This is at a rather different level; although still actually quite basic and not in credible doubt. On the other hand, the physics now becomes much more subtle, and certainly something that could be usefully explained and discussed in these forums.

The final level is about quantifying a temperature impact, and this is wide open cutting edge science. There are some papers proposing rather extreme outlier values for the effect, but that's the game in science, and I don't have a problem with it.

My main interest here, by the way, is education. I'm not a physicist myself; nor a physics teacher; though I do a bit of tutoring on physics and maths as a sideline. I engage here in topics like cosmology, relativity, climate, because these are topics in which people are genuinely interested and on which there is a lot of public confusion sorting out some matters which are not really matter of confusion in the mainstream of science. That's where I get interested; in topics where there is a disconnect between working science, and public perceptions or policy.

Cheers -- sylas

 

[BrianG]

Sorry, I thought this forum was about experimental tests of CO2's effect on temperature when exposed to IR.

Bye.