Quote:
Originally Posted by clive milne
Renato, I would advise caution wrt to the greenhouse efficacy value statements pertaining to CO2 implicit in your sentence above. Whilst it is true that there are gases with far higher opacity to infra red radiation than CO2 (Methane is 20x more effective for example) It does not logically follow that atmospheric CO2 has zero effect on a planet's heat holding capacity. It can actually have a disastrous impact if you intend to live there ... Venus is an example.
As a slight tangent to validate CO2's ability to absorb infra red light, consider this; Once upon a time I was employed as a process analyser technician, one of the process analysers I was responsible for was used to measure the concentration of CO2. The opto-mechanical device used to measure CO2 basically employed an infra red light source and complimentary detector referenced against a sealed chamber (purged of CO2)
Implicit in this is that CO2 has a capacity to absorb infra red radiation that is so well understood that the petrochemical industry trusts it to the extent that they rely upon it as a calibration reference standard.
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CO2 absorbs a tiny part of the infra red spectrum, other gases absorb in different and more energetic parts of the spectrum. I don't think I'm saying anything unknown about relative efficiency of greenhouse gasses.
Mars has ridiculously more CO2 on it than earth does. But when illuminated by what is effectively earth twilight light on it - if you want earth like conditions there - you need a much better greenhouse gas there.
Cheers,
Renato