An elegant proof of global warming

An easy yet elegant experiment to prove the role of carbon dioxide in global warming and show its effect to children, that was the question my colleagues were working on. The experiment is in fact really elegant, so I am happy to share it with you.

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Experimental set-up, with from bottom to top: a glass of hot water, a tube with carbon dioxide and a thermal camera

What you need is in the first place a tube, connected to a carbon dioxide source (our imaginative atmosphere). At one end of the tube, there comes a warm object (a candle, a glass of hot water, the earth, or anything else you have at hand), the other side of the tube is guarded by the thermal camera (the exact reason why I got involved, as thermal camera specialist).

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The thermal camera

The thermal camera will pick up the temperature of the warm object through the recording of infrared radiation. However, if we pump the invisible gas carbon dioxide into the tube, the temperature shown on the monitor will go down!

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Interestingly, it is not really the temperature of our candle that is not really going down. The candle gives of infrared radiation, the camera records exactly that. However, carbon dioxide is highly effective in absorbing this infrared radiation (at least part of it), which is exactly why we call it a greenhouse gas. The heath will not be able to escape through the tube and get recorded by the camera, so the temperature appears lower.

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The same thing would appear on our screen if we would imagine the thermal camera looking from outer space towards our earth. Earth omits heath as infrared radiation, our imaginative camera records it. However, several particles in our atmosphere, of which carbon dioxide is the most famous one, absorb this radiation and keep it trapped. The temperature of the earth gets higher, as less heath can escape towards our ‘thermal camera’ and outer space. So: the temperature on the camera appears lower, exactly because our candle/earth is warmer (which is an important sentence to grasp the meaning of the experiment).

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Pressure gauge of the bottle with carbon dioxide

It took us some finetuning of the temperature range of the camera, but in the end we managed to show the pattern as nicely as the scientists in this video. Now, my colleagues will take this little experiment to the children’s university at the end of this week, to give a bunch of 8 till 14-year-olds an awesome day, a nice encounter with science and a reasonable idea of how global warming works.

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