Earth's blackbody radiation curve and greenhouse gases / global warming?

Question

This post has various questions related to it that I am curious about. Kano believes the planet is warmer than what it would be if solar input were only taken into account from pressure. However if we look at the blackbody curve of the Earth we see that this isn't the case. Gases retain energy at specific frequencies and we can see the amount of energy they retain.

http://www.giss.nasa.gov/research/briefs/schmidt_05/curve_s.gif

You can clearly see the dips of both CO2 and ozone as well as the continuum outside of the atmospheric window of water vapour. How much warming, given the graph above or the data to output that graph, does CO2 alone contribute?

Co2 and other gases absorb at more than just within the Earth's blackbody curve. If we look at solar input we see this: http://upload.wikimedia.org/wikipedia/commons/4/4c/Solar_Spectrum.png

Would the net effect of absorption of gases be one of cooling or warming with regards to solar input and how did you come to that conclusion mathematically?

Kano · Answer

Well to start with the Earth is not a blackbody (more like a greybody) your second graph shows that the overwhelming greenhouse gas is H2O,
While I do not deny that CO2 does cause warming, I point out that it is not the only factor, it is only a small factor among many.
For Young if you work out the what the temperature for Venus should be, according to the IPCC's doubling of CO2, 95% CO2 should give about 120C surface temperature, as Venus is 460C there is certainly another factor involved, unless of course the laws of physics are different on Venus.

Ottawa Mike · Answer

I ended up at this article:  http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap7.html which discusses blackbody radiation and the greenhouse effect.

But I'm not confident I can give a good answer.  I did note from your second graph though (and from what I think I understand), that CO2 absorbs very little shortwave energy from the Sun.

Bernard A · Answer

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Earth's blackbody radiation curve and greenhouse gases / global warming?

3 Answers