Iain Stewart demonstrates infrared radiation absorption by CO2

Iain Stewart demonstrates a simple experiment that shows that carbon dioxide absorbs infrared radiation. Scene from BBC's 'Earth: The Climate Wars' documentary.

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  Science & Technology

[undeadpresident]

Why is it so hard for so many of you morons to see that what is happening is that the CO2 is absorbing the infrared wavelengths?

Now, does anyone know how to quantify infrared absorption?

[m1der1]

If, instead of a candle, you have a source of infrared radiation with known wavelength(s) and intensity of output (say an infrared LED), you can use an infrared camera to determine how much and what wavelengths of radiation have been absorbed by the CO2 between its output and reaching the camera.

[Randall Logan]

Nice demonstration!! I am trying to do the same experiment but with emphasis on viewing the CO2 flow patterns. If you could do the same experiment with a wide light source (as opposed to the candle point source) you may be able to see the CO2 motion and flow properties. Did you need to use any specialized bandpass filters on the camera? Maybe the Camera sensor has specific response in the CO2 absorption band(s)? Sure would like to chat about this more. Thanks again for the demo!

[m1der1]

Hi, your welcome, but unfortunately this isn't my own experiment - it's from a BBC documentary. Sorry! Good luck with your experiment.

[C2shiningC]

Interesting experimental set-up

The light absorbed from the candle is in the visible spectrum? I notice that the light blue halo is not attenuated as much by the introduction of CO2. Is that the long wave IR? Rather than a candle, try a long wave IR source or filter out-of-band radiation. Then use an appropriate detector to see if you get the same results?

[m1der1]

Hi, sorry for the delay in replying. I'm afraid this is not my own experiment so I don't know the details - it was demonstrated on a BBC documentary. I can tell you though that the light absorbed was definitely infrared, not visible. I'm not sure why the blue halo wasn't attenuated - perhaps the radiation from that part of the flame is outside the CO2 absorption spectrum? I'm not a physicist though, so not sure!

[y2knoproblem]

Wait a second. If the candle represents the sun and the tube represents our atmosphere and the ground represents the camera, the obvious conclusion is that CO2 is blocking the radiation thereby making the ground cooler, not hotter. If there was no CO2 in the atmosphere, all the water on the planet would boil off during the day. However, the water vapor from the boiling seas would trap and deflect heat radiation just like the CO2 does. WTF?

[MrApplewine]

Global Warming is coming, the non-believers will be cleansed ! Praise Gaia !

[g1geo1g]

I am now fluent and confident enough to argue that a radiative 'greenhouse effect' is pure fiction. If you comment here I will answer

[g1geo1g]

Also, isn't the intermediate state in a CO2 laser Nitrogen? Chosen for its ability to hold energy for a long period. Isn't Nitrogen classed as meta stable because of its 'heat holding' abilities, whereas CO2 spontaneously emits? Doesn't laser physics turn the cards on climate physics?

[g1geo1g]

Curtis, I don't think you have properly addressed the distinction between thermalised absorption and non thermal scattering. This is pivotal.

[g1geo1g]

This is not meant to be derogatory to your input sir. I i asking for your honest response.

[g1geo1g]

Picet, around 200 years ago tried to amplify the thermal emissions from ice, which has an emissivity of 0.95 and only managed to produce a reflection of 'cold'. Heat travelled according to the second law.

[g1geo1g]

Curtis, I am sitting in a room where many materials with many varied emissivities exist in thermal equilibrium. The middle of the room 'sees' a virtual flux from the facing walls, floor and ceiling that adds to 'nothing' at equilibrium. If I use a parabolic reflector, or IR condensing lens, I cannot focus or amplify this massive 'virtual' energy upon anything at that temperature or above. The fluxes concerned at ambient are around 300Wm-2.

[g1geo1g]

Curtis, thanks for the input. Are you completely sure that phase coherent laser light is fully representative of normal thermal emissions?

[undeadpresident]

Thank you for the clear explanation. I'm very happy I'm not deaf because I accidentally turned on the captions and it's kind of funny lol