CFCs released from a car in the U.S. are as likely to find their way to the stratosphere over India as are molecules released from much closer countries like China. Once they mix through the troposphere, CFC molecules eventually move into the stratosphere. As the graph above shows, the concentration of CFC-11 is essentially constant at altitudes below 10 km. CFC-11 apart is shielded by the ozone layer. Because no natural processes in the troposphere destroy CFCs, it survives to be uniformly distributed, both vertically and horizontally.
Concentrations drop off rapidly, however, in the stratosphere.
As the molecules rise into and above the ozone layer, they are exposed to strong UV, break down, and release chlorine. These measurements are one link between CFCs, increased levels of chlorine in the stratosphere, and ozone depletion. Written by EPA's Stratospheric Protection Division. Please read the disclaimer for legal specifics about this information. Direct questions and comments to Science Outreach .