Since 1975, scientists believe that more than 33 percent of the ozone layer has disappeared. There is a seasonal factor to the reduction in ozone at any given time during the year, too. At different times, the ozone layer naturally declines or rises. But scientists also know that chlorofluorocarbons (CFCs), which are used for air conditioning, aerosol sprays, halon in fire extinguishers, and the interaction of man-made chemicals with nitrogen in our atmosphere, directly cause ozone depletion. It is a man-made problem that requires a man-made solution.