Wednesday, December 17, 2014

A Nice Example of Scientific Ignorance

Someone in an online discussion posted a link to what was claimed to be an experimental demonstration of global warming by a young student. It was presented by the Cleveland Museum of Natural History and the Clean Air Conservancy.

The experiment consisted of filling one jar with CO2 and one with ordinary air, illuminating both with heat lamps, and observing the temperature. The temperature in the jar with CO2 went up more. The experimental design was imperfect, since the lamps might have differed a little in intensity or placement, but that's not a serious criticism given the age of the experimenter.

The real problem is that the experiment does not demonstrate the greenhouse effect. That effect depends on selective absorption, on the fact that CO2 is more transparent to the short wave length light coming down from the sun than to the long wave length light coming up from the Earth. The experiment showed that CO2 was less transparent than ordinary air to long wave length light but provided no evidence at all of its transparency to short wave length light, hence no evidence in support of the greenhouse effect. To do it right, it should have been repeated using a source of short wave length light such as sunlight. If that didn't heat the bottle with the CO2 more than the other bottle, that would have provided evidence of selective absorption, hence support for the claim that CO2 is a greenhouse gas.

My conclusion is that the people who webbed the video were ignorant of the science they claimed to be demonstrating. The student who did the experiment was equally ignorant, which suggests, but does not prove, that whoever taught him was as well. The case of the student or the Clean Air Conservancy isn't all that surprising, but it is a little disturbing that the Cleveland Museum of Natural History would post a video based on a complete misunderstanding of the science it purports to demonstrate.


Jon said...

I think it's a decent test because it's still demonstrating that more IR radiation is being absorbed with the CO2 filled flask. Think of the heat gun not as the sun but as the source on the surface of the earth emitting longer wave radiation. Ultimately that's what happens. The sun sends UV radiation and visible light through our atmosphere and it warms the surface of the earth. The surface of the earth in turn returns that radiation in the form of infrared. That's the radiation that is being stopped up by the CO2, warming our planet. Less of that IR escapes.

Also I would add that a heat gun is emitting higher frequency radiation. In fact heat guns typically show visible light, like oven coils. So this is shorter wave length radiation, along with radiation at the lower end of the spectrum. Not exactly the spectrum of the sun, but demonstrating the principle nonetheless.

Anonymous said...

What can be done to improve secondary education in science? I know of the voucher-system proposal, but as far as I know it's not been widely implemented (and if it was available to this young man's parents then either they didn't take good advantage of it or it's an insufficient proposal).

The basic problem with our society today is scientific ignorance on the part of the public. The gap between what scientists know, can prove, and claim they can prove on the one hand, and what ideologically motivated zealots, self-serving charlatans and an incompetent press can impress on the public as supported by science is horrifically dangerous in a society sustained more or less completely by the fruits of scientific inquiry.

ZombieHero said...

I see this on social media a lot. It's pop-Science. It's "doing science" to be cool. The kind of people who share those videos also share IFLS posts and Bill Nye memes.
They probably have no clue what is really going on, they share because its social signalling. They are showing their tribe that they are part of the in-group.

I've recently got into it on Facebook with Pro-GMO people who will do anything to defend Bill Nye against Bye blatant anti-GMO fabrications in his new book. To criticize a pop-science promoter like Nye is tribal treason and the mental hoops they will jump through to defend Nye is amazing to see.

Basically Haidt has is right. When science conflicts with ideology, the science goes out the window.

David Friedman said...


You have it backwards. The more short wave light in the source, the worse the evidence. The greenhouse effect depends on the difference in absorption with frequency. The experiment shows no evidence that there is a difference.

David Friedman said...


It's in someone's interest to have accurate beliefs about matters where his decision affects his welfare, such as what goods to buy, what job to take, what woman to marry. But one person's beliefs about issues such as evolution or global warming have essentially no effect on the world, so it's in someone's interest to have whatever beliefs make him most popular with the people who matter to him, his reference group.

That's one of the reasons why democracy works poorly, a special case of what economists refer to as rational ignorance.

Xerographica said...

1. Trees/epiphytes absorb CO2
2. Tropical forests are being destroyed
3. Less CO2 is being absorbed

Do you disagree with any of the above?

TCC_69 said...

Very interesting, thanks. This reminds me of an essay I read by a now-retired sociologist titled "Scholarly Conspiracies, Scholarly Corruption, and Global Warming." It's a bit abrasive in places (the guy used to be French) but well-worth the read.

This sociologist, by the way, taught at Santa Clara's business school for years and years so you might actually know him.

Jon said...

The experiment shows no evidence that there is a difference.

I replied based on your description but hadn't watched the video. Now that I've seen it I see that showing a difference is not the point of the test. He uses IR heat lamps and specifically says that the heat represents the heat coming from the surface of the earth (IR) not the sun (UV). He's not trying to show a greenhouse effect. He's showing that IR radiation coming from the earth's surface is getting absorbed in the jar that contains CO2. He's demonstrated the mechanism that is producing global warming. That's the point here.

Mike Brady said...

Seems like I saw somewhere that Bill Nye, the self-appointed science guy, did this same experiment to help promote his climate change politics.

Benjamin. said...

It should be clarified; Someone's views on Global Warming COULD eventually affect there life, given it's affect on elections, choices, etc.
But it is likely that most people's concerns aren't that far out, but it is likely that many more people care about popularity than what the economy or environment is like in 20 years.

Benjamin. said...

Well Bill Nye DOES have a bachelor's degree in Mechanical Engineering, and since so many people are afraid of advanced math I'm sure many people surrender to his opinion on any issue.

David Friedman said...


The point isn't long term vs short term concerns. My decisions of what car to buy determines what car I get. My decision of whether to believe in global warming changes by something less than one part in a million the chance that a politician who supports action against warming will get elected. His getting elected changes the chance of action against warming by only a small amount. Even for someone who cares about events twenty years out (the real concerns are a good deal further out than that, actually), one chance in a million of a very small effect on such events isn't very important.

David Friedman said...


The fact that CO2 absorbs long wave length light doesn't imply global warming. The argument for global warming requires that it is less transparent to long wave length than to short wave length light, which requires measuring both effects. There is nothing in the video suggesting that the student is aware of that.

To make my point a little differently, you are saying that he is verifying one of the facts that goes into understanding global warming, which is true. Another fact that goes into understanding global warming is that if you increase net energy absorbed, temperature goes up. He could have demonstrated that by holding a cigarette lighter to one of his thermometers. Would you count that as a demonstration of "the mechanism that produces global warming?"

What makes something a greenhouse gas isn't the fact that it absorbs long wave length light, it's the fact that it is less transparent to long wave length than to short.

Benjamin. said...

Well purely in the electing process that may be the case, but in terms of open discussion it would actually affect a considerable amount more. If someone has a moderately substantial influence on their friends when they talk about these things, and some of those friends are persuasive in arguing too, it has an outward growing effect. This is how some fads can be started by only a few people.
Of course, this may also be a fairly small amount of influence. The point stands, regardless.

Kind of reminds me of those commercials about "every vote counts," because if everyone decides their votes don't count, then they have a large effect. Perhaps a more realistic way of looking at it would be "This commercial telling you that every vote counts, counts," because the commercial may have an influence on a considerable portion of voters. Of course, if the commercial said that, the commercial would be less persuasive, which would counter out the very effect. But that's a whole different issue, sorry for rambling on.

Benjamin. said...

OH! I see what you're saying about the light, I think.
The thing to prove would be that the CO2 provides a one-way screen, in which light comes easily down in short wave lengths, but will not go easily out in long wavelengths.

Do you know any experiment that has shown this? It seems as if it would be easy to do.

David Friedman said...


I don't know of an experiment as simple as that that would do a good job of demonstrating the point, but one could improve his experiment by repeating it using sunlight instead of the heat lamp. If the CO2 didn't warm up more than the air, that would be quite good evidence.

But it's possible that it would warm, and you would then need some way of comparing how much it warmed with sunlight vs how much with the heat lamp. I don't see a good way of doing that.

Brian said...


While your point is well taken about showing increased long-wave absorption relative to visible light, it's worth noting that low absorption of visible light is easily observed via the transparency of the gas in the jar. The student could have, but didn't, point out that the CO2 jar looks just as transparent as the regular air jar.

Patrick said...

The experiment does actually provide weak evidence regarding CO2's transparency to short wavelength light. Short wavelength light, in this context, is visible light. In the video, the jar filled with CO2 gas is clearly transparent, and looks no darker than the air-filled jar. If CO2 absorbed visible light, the gas would appear colored and/or darkened.

The fact that the jar is transparent places an upper limit on the amount of visible light the CO2 could be absorbing. Ironically, given how poorly conceived and implemented the actual experiment was, CO2's transparency to visible light is much more convincingly proven here than CO2's absorption of long-wavelength light is.

David Friedman said...

I agree that the student could have strengthened the argument by observing that both jars appeared transparent, but that still doesn't cover the case of ultraviolet, which is also outside the visible part of the spectrum.

And, of course, there is no estimate of what fraction of the IR has to be absorbed to produce his result, air having a pretty low heat capacity. For all he knows, it's low enough so that the jars would still appear transparent in IR to casual inspection.

Mark Bahner said...

"The fact that CO2 absorbs long wave length light doesn't imply global warming. The argument for global warming requires that it is less transparent to long wave length than to short wave length light, which requires measuring both effects. There is nothing in the video suggesting that the student is aware of that."

Presumably, the kid watched his own video after he filmed it. When the two jars didn't look visibly different in the video, after he'd injected CO2 into one jar, he could tell that the CO2 wasn't absorbing visible light. (He probably didn't know enough to think about it, but if he had, he would have concluded that CO2 obviously does not absorb visible light. If it did, the jar with CO2would look visibly different.)

And in fact, his entire experience as a human would tell him that CO2 doesn't absorb visible light. Automobile exhausts, natural gas flames, and exhaled breath of animals all contain CO2, but there is obviously no visible light being absorbed.

David Friedman said...

Mark: As I already pointed out, the transparency to visible light doesn't tell us whether it is transparent to u-v, which is shorter wavelength than visible rather than longer. And nothing in his experiment as reported told him what fraction of the long wave length light was being absorbed—whether enough so the effect would be noticeable for the case of light in the visible spectrum.

Anonymous said...

My understanding is that CO2 does not in fact absorb LW heat net, but scatters it. That is to say it absorbs and re-emits, because the energy from the incident radiation excites the CO2 molecule making it unstable so it instantaneously emits radiation with energy of the same magnitude but not necessarily in the same direction of travel of the incident photon.

The CO2 molecule therefore does not itself get warmer.

The increase in temperature results from it slowing down the rate heat energy leaves the system compared to its rate of arrival.

In the atmosphere additionally this means outgoing LW radiation is scattered through 360° by CO2 preventing escape of some of it to Space and that retained in the atmosphere can react with water vapour molecules which do absorb in part or whole LW radiation and thus they warm up.

This warming induces more water to evaporate from the surface and increase global warming at a higher rate than CO2 alone... this is known as radiative forcing.

It is thus water vapour increase caused by CO2 increase which is the culprit as it acts as a multiplier... the Warmists leave this detail out... and nobody knows the actual factor of forcing. Estimates have ranged from 3 to 6; 2 to 4; more recently just 2. Others say it is lower, 1 or 0,5. But all agree that the estimates used to predict catastrophic global warming were far too high given evidence from observation.

Thus in the experiment the temperature being measured in the CO2 bottle is LW radiation being scattered about inside the bottle, so heat is entering the bottle faster than it is leaving and heating the container walls too.

The air in the other bottle contains only a trace amount of CO2, and 99% oxygen and nitrogen neither of which attenuate LW radiation so heat leaves that bottle almost as fast as it enters.

The experiment is flawed also because it omits to ensure the water vapour content in the bottle is representative of the atmosphere, which if it were would show a greater warming than the CO2.

It is also flawed because the greenhouse effect of CO2 is logarithmic so each additional molecule attenuates less radiation than the previous one until adding more has no more effect.

A doubling of CO2 concentration results in a maximum of 1,1C rise in temperature.

The experiment should have been repeated with increasing CO2 concentrations so the claim that adding more CO2 willy nilly just boosts the temperature up and up for ever is misleading.

The role of CO2 as a greenhouse gas is clear; it is the radiative forcing that is unknown.

The experiment would have been better designed to show that uncertainty.