A Note On Saturation of the Carbon Dioxide 15-micron Band
.
.
.
.
....Considerations along these lines have sometimes been used erroneously to imply that carbon dioxide increase is not a concern for global warming. The sophisticated reader should immediately see the problem with such an analysis. The atmosphere is not a single-layer system. The temperature and pressure of the atmosphere change significantly with altitude. One might naively think that simply taking the average pressure and temperature would address this issue, but that is not the case. Unfortunately, it is necessary to understand the atmosphere and atmospheric processes at a more detailed level.
Before we congratulate ourselves too much in this realization, it is worth noting that no less of a scientist than Knut Ångström made this error when considering the pioneering work of Svante Arrhenius.
The most important consideration here is that layers of the atmosphere do not just absorb radiation; they also emit radiation. The emission of radiation from a layer in the atmosphere depends on its temperature.
When I introduced Beer's Law, I treated the transmittance as a simple ratio between the spectral radiance of the sample and the spectral radiance of a source or radiation (Is/I0). This assumption was based upon the source of radiation being much hotter than the sample (as would be expected under laboratory conditions.).
Once this assumption no longer holds, the transmittance is no longer equal to the indicated ratio. We have to take into account each layer in the model and its thermal radiance.
This post is part of a primer on infrared spectroscopy and global warming . The previous post discusses Beer's Law, and is a necess...
how-it-looks.blogspot.com