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CFCs: Double Danger
The CFCs present a double danger to the global environment because
they have the potential for both ozone depletion and global warming, since
they also are greenhouse gases. Figure 1 shows the energy absorbing
potential (band strength) for various gases at different wavelengths.
Infrared radiation from the earth has substantial energy at wavelengths between 7 and 10 micrometers. The graph shows that the CFCs (underlined in blue) have moderate to high absorbing capabilities at these wavelengths and thereby contribute to global warming.
Figure 2 gives the combined global warming and ozone depleting effects of the chlorinated compounds.
Molecules located in the upper right part of the chart have large detrimental effects for both reasons and are candidates to be replaced with more benign molecules located in the lower left part of the chart. The process of making an HCFC from a CFC reduces the environmental impact of the molecule but it negates one of the reasons the CFCs were created in the first place, namely because they are so non-reactive. The result is that when HCFCs are used in, say, a refrigerator they also interact with the lubricating oil added to the working fluid. This means that the lubricating capability is diminished, which reduces the lifetime of the refrigerator's compressor. Also, the compressor may require a higher operating pressure which demands more energy and puts more strain on seals and other components, making the refrigerator less energy efficient and subject to malfunction. The CFCs are very convenient chemicals, except for their environmental hazard, and several negative factors that must be considered in the search for suitable replacements. The Upper Atmosphere Research Satellite (UARS) measures temperature, pressure, wind variability and gas species concentrations in the stratosphere at altitude ranges from 10 to 100 km.
