Friday, March 30, 2012

First try doesn't quite imitate a 13 year old's science experiment

Previous post refers to a kid's video about proving "global warming in a jar".  I'm not sure I'm proving anything given the comments, but I thought I'd try it out anyway.  Today was a dry run, so no video of my misadventures.

I wanted to do it cheaper, first of all, so no heat lamps or seltzer sources.  My thought was carbonated water versus regular water, and my heat source is the sauna at the gym.  I followed the NASA recipe where I hit my first snag, with trouble finding thermometers that I could stick through bottle caps.  No luck at the hardware store, and then thought I had the genius solution of using perfect-sized digital thermometers from the drug store.  Failing to read the fine print, I missed that these medical thermometers only register temps between 90 and 110F.

I thought it might still work though by placing them on the floor of the sauna.  Filled the bottom quarter of two bottles with water in one, cabonated water in the other, both waters starting at the same temp (kept the source bottles together in the backpack before pouring into receiver bottles), stuck them on the sauna floor and sweatily waited five minutes.  First reading was 107 for carbonated, 108 for regular.  Both increased temperature while I watched - within seconds, carbonated was warmer than regular, then within a minute it hit 110 and became useless.  The other took about three minutes to do the same.

I remove the bottles and me from the sauna.  The water at the bottom of both still seemed cool to touch, all the warmth was at the top of the bottles.  I was chagrined to realize I had put just slightly more water in the control than soda water in the experimental bottle, so even my very limited data has a problem.

So obviously the next step is get the right thermometers.  I'd also like to try it outside on dark pavement on a sunny day, but the sunny days lately have been pretty windy.  I think if I could leave the bottles in the sauna long enough, I might also be able to get enough water vapor to have an effect/feedback.  Maybe one bottle with baking soda and vinegar, one with water, one with carbonated water, and a control.


Anonymous said...

This way lies madness, witness this riff:

Thomas said...

I think this page may have some useful data for your experiment:

Anonymous said...

I guess the experiment proves that CO2 absorbs IR radiation. This is hard to dispute, even by climate skeptics, but in any case falls short of a proof of the greenhouse effect.

To do that would require a demonstration that energy flows more slowly in air with CO2 than otherwise.

I had thought of an experiment or 2, but these require some way to control for differences in thermal conductivity, probably by mixing in argon as the CO2 substitute.

I find it somewhat ironic about climate skeptics that they can't seem to bring themselves to do the experiments. Maybe the notion of mother nature saying no to their crazy ideas is a suspicious niggle they are not willing to face.

Climate Ferret

Anonymous said...

What you need are the temperature data logging versions of ibuttons:

I use them for my fieldwork, and to profile energy use in houses and temperature on my land, and I love the buggers. If you want to definitively waterproof them, parafilm or even a plain plastic bag (or both) are effective.

Every geek should have a pocketful of ibuttons.

Bernard J. Hyphen-Anonymous XVII, Esq.

Anonymous said...

Dr. Jay Cadbury, phd.

Unfortunately, the experiment does not prove the existence of the massively powerful 400% positive feedback, which you continue to avoid because you likely know that it's wrong.

Anonymous said...

The definitive experiment is to fill identical bell jars containing identical Cadbury chocolate Easter bunnies with various gases, and place them in the sun to see which melt first.

Experimenters may also seal live Cadburys in CO2 filled bell jars in order to enjoy their discourse on the harmless nature of the gas.

Anonymous said...

Dr. Jay Cadbury, phd.

Unfortunately, the experiment does not prove the existence of the massively powerful 400% positive feedback, which you continue to avoid because you likely know that it's wrong.
Reading comprehension probably failed you there Jay. Seems Eli did mention having liquid water in the jar as well as CO2, so I am pretty sure Eli or any other sensible person is not afraid of this at all.

After all none of us here are afraid of the truth.

Climate Ferret

raypierre said...

You're chewing up the wrong carrot. An experiment like this could just conceivably prove that CO2 absorbs IR (but that's easier to prove with an IR thermometer) but it won't get at the greenhouse effect as it happens in
a planetary atmosphere. That relies on the reduction of temperature with height, and given the large depth of column needed to see the compressibility effect, you can't do that in the lab. And why should you need to? The ocular proof of the greenhouse effect is abundant by looking at the spectrum of infrared from Mars, Earth or Venus, and that ought to be enough. Have a look at my 2011 Physics Today article.

Hank Roberts said...


Brian said...

Well, showing CO2 absorbs IR seems like a useful high school/junior high experiment. I'm still curious if we get more IR absorption by combining CO2 and water vapor in a hot environment like a sauna.

Mitch said...

As Raypierre said, you can't really show the greenhouse effect in a lab.

The simplest way to see what is going on is this: the atmosphere gets colder and thinner as it goes up, because in the troposphere the profile is more or less that of an adiabat. That is, if you take a parcel of air from sea level and allow the wind to transport it up, it will get larger and cooler because the pressure decrease with height, and it goes up too fast to exchange heat with its surroundings, so the expansion is adiabatic. When it arrives aloft, it will have the same temperature as the air that is already there. This yields a decreasing temperature profile and a number density profile that falls off close to exponentially.

The air is opaque to IR at sea level, but at some point it is thin enough to emit to space. It is that cooler point that radiates. The point that radiates to space more or less has to be at a temperature of 0F, because the watts per sq meter radiated has to match the energy the earth absorbs from the sun.

When you increase the density of CO2, you increase the IR opacity of the atmosphere and raise the height at which the earth's radiation to space takes place. It therefore increases the difference in temperature between the surface and the point of radiation, which has to stay at 0F.

You can see some slides that explain all of this here: or you can watch the video version of it here: