What does it mean to ban chlorofluorocarbons (CFC's) and what does this mean in terms of the global warming issue?
CFCs had widespread use in the United States when it was discovered in 1973 that chlorine acts as a catalyst in ozone depletion. CFCs have a large effect because chlorine is not absorbed in the catalytic reaction, therefore the same chlorine molecule can reduce hundreds of O3 molecules before being absorbed by some other species in the atmosphere. Later, it was found that in the same areas of the atmosphere where CFC concentrations were rising, ozone concentrations were falling. This discovery was followed by agreements to freeze production of CFCs at 1986 levels and to reduce production by 50% by 1999, and ultimately to phase out CFCs entirely by 1996. Hence, these chemicals are banned in the United States.
There is little to directly link ozone depletion with global warming. The primary impact of O3 is to absorb ultraviolet rays which can in high doses damage skin and plants. While there was never any direct evidence that plants or animals were negatively impacted by the atmospheric reductions in O3, there is reason to believe that ultimately increased levels of ultraviolet radiation would raise occurenses of skin cancer in humans and harm plankton and other ultraviolet light-sensitive eco-systems. Worry over increased exposure to UV light was the main motivation in moving quickly to ban CFCs.