Is carbon dioxide a weak green house gass?

Question

Ok adam c ken and others this isn't some convert believers into skeptics question i really don't know! So is co2 a weak green house gass? is it the strongest? are theres ones stronger then it?

Answer 1

     yes -  it absorbs a few wavelengths in the near infrared, other gases (water vapor) absorb a wide spectrum.  The amount of CO2 in the air, although very small (380 ppm) is already enough to block those few wavelenghts thouroughly.

Increased CO2 will add little, if any increase in greenhouse effect.  Here's a link - this chemist did some spectrographic experiments. apparently he's not in on the climate scare research grant funding party .

http://www.john-daly.com/artifact.htm

Answer 2

There are three main factors that go into calculating the strength of a greenhouse gas.  (1)  The absorption cross section, which is related to the transition dipole moment, is a measure of the probability that a photon will be absorbed by a molecule.  This is frequency dependent.(2) The degree of overlap between the absorption frequencies of a molecule and the frequency distribution of black body radiation from the earth.  This is approximated by the Planck formula, but a more detailed analysis takes into account the frequency dependence of the earth's emissivity.  The effectiveness of a greenhouse gas thus depends upon the temperature.  (3) The lifetime of the molecule in the atmosphere.  The radiative forcing from a molecule must be integrated over its lifetime in the atmosphere.  A weak absorber with a very long residence time may have a larger cumulative effect than a stronger absorber with a short residence time.  

(1) CO2 has a huge absorption cross section.  

http://cfa-www.harvard.edu/hitran//

(2) Although the absorption in the 2300 cm-1 region is very strong, the weaker absorption near 700 cm-1 is more significant due to overlap with the peak in the earth's thermal radiation.  Note that the wag and rock vibrations from methane also have significant overlap with the earth's thermal radiation and hence are significant.

(3) The residence time of CO2 in the atmosphere is on the order of 72 years.  

The three factors combined make CO2 a significant greenhouse gas.

The study by Hug referenced above makes the unremarkable observation that a globar at 1200 K emits more radiation than a gas at 300 K.  Hug overlooks the fact that molecules emit at the same frequencies that they absorb at.  The basics of molecular spectroscopy were worked out by Nobel Prize winner Gerhard Herzberg in the 1940's.  http://nobelprize.org/nobel_prizes/chemi...

Hug would be well-advised to learn the basics before attempting to write a serious paper.    

Answer 3

CO2 is a weak greenhouse gas when compared to water vapour, CFCs, etc.

However, "weak" is a simple, one-word description for a complex issue.

CO2 is weak in the sense that it doesn't trap as much heat on a ppm basis as the others.

On the other hand, there is a lot of it (compared to CFCs for example) and it has a long half life in the atmosphere (compared to water vapour for example).

To complicate things further, each greenhouse gas traps energy at a unique mix or "signature" of wavelengths. Thus one of the important things about CO2 is it captures energy at wavelengths that the more abundant water vapour does not. If it captured the same wavelength as water then the overall impact of added CO2 to the greenhouse effect would probably be less significant.