(UPDATE: sadly, there may be problems with the first video - see the comments and this article. The article mostly deals with convection from open containers, but argues that closed containers have problems too. No problems identified yet with the second video.)
I doubt Heartland's anonymous donor would ever do anything sensible, at all, but this kid could provide sensible, accurate information and how-to guidance instead of the lies that Heartland wants to put in children's education.
My vision is to see him tooling around the country on a biodiesel bus with his entourage, all of them dressed up in Ray-Bans and Bill Nye Science Guy bowties, laying on the science and helping kids run their own experiments. Too bad it won't happen.
NASA, btw, agrees with his experimental proof. I thought he stole it from NASA but his video is four years old, so maybe the theft went the other way. The NASA link also describes how to do it cheaper, without seltzer siphons and heat lamps, so I might try that and put up my own video.
Also relevant, "Visual proof that CO2 absorbs infrared radiation," with this BBC video:
Bill Nye performed the visual proof experiment on his show back in the 90s.
ReplyDelete-The Wonderer
I believe that NASA is wrong in this case. And, by the way, it isn't "NASA" that puts up an experiment like that - it is probably some communications officer, maybe assisted by a contractor of some kind, and possibly checked by someone with a science degree.* I'll be contacting them on my opinion about the experiment.
ReplyDeletePeer-reviewed evidence for my opinion: Wagoner et al., "Climate change in a shoebox: Right result, wrong physics" - http://ajp.aapt.org/resource/1/ajpias/v78/i5/p536_s1?isAuthorized=no. Basically, Wagoner et al. do two things. First, they theoretically determine what the temperature change _should_ be from the amount of CO2 in a small volume. The answer is pretty small. Remember that an atmosphere worth of CO2 is a couple watts per meter squared: now, your bottle might have much higher concentrations than the atmosphere, but the radiative properties do not increase linearly (though possibly higher than logarithmically, as new weaker lines begin to dominate the saturating strong lines). Second, they do the right control experiment - not air, but rather argon.
The explanation for why the naive experiment gets a result that agrees with our intuition: CO2 is not only different from air in its radiative properties, but also in its density, and the latter is possibly key for this experiment. Also, remember the bottle is not a good model for the Earth - it mostly loses heat by convection and conduction, not radiation. You'd want to surround it by a vacuum for a good experiment of this kind. And a _really_ good experiment would somehow create a lapse rate in the model system...
-MMM
*Some website get more scrutiny than others, and there _are_ some government climate websites that I think are pretty good. This particular webpage is not.
http://rtobin.phy.tufts.edu/Wagoner%20AJP%202010.pdf may be a better link for the paper in question.
ReplyDeleteI'll point out that if Bill Nye performed the experiment, I'm claiming that he was wrong as well. Ditto for Al Gore (of course, Watts Up totally missed a chance to find an actual science mistake in the video in their post on the subject, instead spending all their time trying to argue about thermometers and videotaping issues).
-MMM
Well, that's depressing, MMM. The article's behind a paywall - is it the same experiment?
ReplyDeleteAbstract says "The greater density of carbon dioxide compared to air reduces heat transfer by suppressing convective mixing with the ambient air" but there's no mixing if it's in a jar.
Any relationship between the density of CO2 and quenching returning CO2 to ground state that Eli talked about some years back?
OK, the article's available at the second link. They used an open container and mostly talk about convection, which isn't relevant here. However, they claim that absorption still shouldn't show the result obtained in sealed container experiments.
ReplyDeleteI think they've made a good argument for open containers. It's less final on sealed containers but raises significant doubts. I'll update.
Yeah, I was a bit sad about the loss of what would have been a great teaching tool experiment. I contacted Wagoner back when I first read the paper to see if he had a suggestion for what tabletop experiment might work, but it sounds like it would be very difficult to do right.
ReplyDeleteI think a minimum step, given this paper, is that anyone claiming to have a tabletop experiment that shows that CO2 is a warming agent should do the argon control in addition to the air and CO2 experiments.
(note that even in the sealed container, I imagine that much of the temperature loss is due to conduction through the walls rather than radiation, which is where the non-radiative gas properties may play a role, and which makes perfect controls kind of difficult)
-MMM
"suppression of convective heat transport between CO2 and air due to the density difference between the two."
ReplyDeletebut that is literally the greenhouse effect.
the glass prevents mixing of cold outside air and warm inside air.
I'm always looking for this latter video. Very convincing when you're just trying to show (someone naive to all this) a good place to start. I've found it a couple of times. Only 12,000 views. I wish people would stumble upon it in their own searches more often.
ReplyDeleteSteve, it's very easy to find at youtube using "Iain Stewart CO2" as your search term.
ReplyDeleteI think an experiment like this can be done properly in at least two different ways. The simplest is using a CO2 absorbing (or non absorbing in the control) lid on a insulated, sealed, evacuated chamber. By evacuating the chamber you eliminate convection as a confounding effect. It is also important that the lid be insulated from the rest of the chamber to eliminate conduction as a confounding effect, and of course that the walls of the chamber not be transparent. Finally, it is important to place a an IR reflective panel between the heat source (lamps or sun) and the chambers so that the floor of the chamber with the glass lid does not receive less energy from the heat source.
ReplyDeleteThe second method would be to use a large inverted chamber with the "lid" on the bottom and the "floor" on the top. The chamber would be heated from underneath. Given a large enough chamber, convection would set up a heat gradient between "floor" and "lid" thereby allowing a proper greenhouse effect.
Anonymous (3/3/12 12:53 pm) appears to believe that rubber ducks belong to the class Aves, and that all people surnamed "Smith" make a living by forging horse shoes. At least, that is what is inability to understand that names are arrived at by the accident of history and need not be strictly descriptive would indicate.
ReplyDeleteOf course probably s/he knows better about rubber ducks and men named "Smith", in which case s/he also knows that they are making an empty rhetorical point.
Tom, your second method is basically the NASA method that works without heat lamps, relying on warmth from the sunlight hitting the ground to heat the sealed bottles.
ReplyDeleteI'm wondering if we couldn't try this with water vapor, comparing sealed bottles with low and high relative humidity. Water vapor is less dense than air, so that would remove the argument that the dense gas is the issue.
I'm wondering if we couldn't try this with water vapor...
ReplyDeleteRefining and improving the experiment won't matter a jot (apart from one gaining some self-satisfaction, of course).
Why?
Well, all the idiots/septics/deniers subscribe to the many "water-vapour-rather-than-CO2-is-the-cause"-type memes anyway and would still have this CO2 disconnect in the face of a successful benchtop (or otherwise) experiment.
The CO2 disconnect is hard-wired, whether the reason for that is ideological blindness, blind stupidity or a combination of both.
Cymraeg llygoden
Brian, I am sorry, but the first video is just a poor experiment that doesn't demonstrate anything. You already placed a disclaimer on your post, but let me discuss this point a little more.
ReplyDeleteIt is extremely difficult to set up this test: even minor differences in the distance of the jars and the lamp can cause one or the other thermometers to show higher temperatures. You can easily see that making "blank" measurements. I tried this experiment myself and it took me truly a lot of work and fiddling to get the blank tests to show no difference and then to evidence that the gas composition did have an effect. This problem is additional, and possibly more important, than the one raised by Wagoner et al.
For a particularly bad example of poor setup in this example, look at this one; again, no blank and the two heat sources are clearly at different distances from the gas containers.
http://www.youtube.com/watch?feature=player_embedded&v=Ge0jhYDcazY
So, it is sad to see how the boy of the clip, probably well intentioned and bright, was misled into believing that he was doing something good. Someone should have explained to him that you don't make measurements like these without first checking with a blank.
What the lady did in the clip I linked above, then, is really inexcusable. In short, atmospheric physics is a complex matter and it is difficult to approach it with glass jars and light bulbs. Incidentally, even if it were possible, deniers would simply not believe it!!!
I discuss this matter in my blog (unfortunately in Italian)
http://ugobardi.blogspot.com/2011/02/co2-il-grande-imbroglio.html
Hi Ugo - the automatic translation works reasonably well for your blog post.
ReplyDeleteI'm not certain I know what you mean by blank measurements, I think you mean running the experiment with no CO2 in either bottle. That sounds fine to me. Alternatively, they could carefully mark the bottle positions, run the experiment and then switch the bottles while not moving the lamps.
The NASA site describes the issue with lamp positioning, so when I read that I thought it would work better to just do the experiment in sunlight with sealed containers on a uniform dark surface, like pavement. That would be pretty similar to the experiment you did.
Cymraeg - you're right about denialists. The point is to persuade the fence sitters and the people that haven't thought much about the issue. Those who have settled on non-science will need bulldozers to move them.
Yes, that's what I mean as blank measurement. Run the test without CO2 in either bottle. It is extremely difficult to obtain the same temperature in both bottles - try it to believe. A millimeter or so is sufficient to unbalance the system so that you read a few degrees (centigrade) of difference when the system heats up to 50-60 degrees. The difference in temperature with/without CO2 is 2-3 degrees at most; so it is a very delicate measurement.
ReplyDeleteAnd, of course, in terms of balance, it is easier to use the sunshine; but here denialists have been doing better than some well-intentioned but misguided people. If you put two bottles in the sun, one with CO2, the other with air, then you don't see anything! It is because you also need something black to function as absorber - just as the Earth's surface does for the atmosphere. No absorber, no CO2 effect. You can do that if you use Coke for generating CO2 inside the bottle; then the Coke is dark and it works as absorber.
Ah... the test using Coke as both absorber and CO2 generator is here:
ReplyDeletehttp://tpt.aapt.org/resource/1/phteah/v45/i6/p376_s1?isAuthorized=no
The full article for the last link is behind a paywall, sadly.
ReplyDeleteIn addition to Iain Stewart's video it's worth noting that NOVA/Frontline produced a similar demonstration with Pieter Trans, where a thermal image of his head was obscured as a container was filled with CO2.
ReplyDeletehttp://access.teachersdomain.org/resources/phy03/sci/ess/watcyc/co2/index.html
For those who might not have teacher access, Peter Sinclair had the segment in one of his crocks, although I don't recall which one.
Bernard J. Hyphen-Anonymous XVII, Esq.
You can easily proved in the lab that CO2 absorbs/emits infrared and that the opacity isn't saturated, but no experiment you can do in the jar will reproduce the radiative greenhouse effect in the form it occurs in real atmospheres, because the latter depends on the expansion-induced temperature decline with height, which requires a column several kilometers high to reproduce. Maybe you could do it by putting your jar in a centrifuge (details left as an exercise for the bunnies). The conventional glass-box experiment, which actually goes back to de Saussure as referenced by Fourier, is a correct analogy for the way the energy balance works, but the extra insulation from heat loss does not work the same way as in an atmosphere, and Fourier knew this.
ReplyDelete--raypierre
Hi Raypierre - sounds like stratospheric temperature declines, which I really need to wrap my mind around. OTOH, I've got your textbook. My wife gave it to me as a Christmas present after Eli recommended it, so I need to crack it open and get reading.
ReplyDelete> expansion-induced temperature
ReplyDelete> decline with height ... requires
> a column several kilometers high
> to reproduce. Maybe you could do
> it by putting your jar in a
> centrifuge ..."
Could you do a multiple-slab -- a column made from a stack of transparent plastic bags in a series of different pressures, in a long tube (you'd have to evacuate the whole tube around the inflatedbags).
(or a series of transparent membranes in a column, at successively lower air pressure)?
------
while talking about technical fantasies, how about this optical heat pump: http://physicsworld.com/cws/article/news/48882
So could that LED-size heat pump be imitated in some designer single molecule, well enough designed, that would wind itself up with heat vibration and then emit an infrared photon every now and then? Get enough of a 200 percent efficient infrared emitter up into the upper atmosphere as a persistent chemical (we do know how to make those) ....