The hole in the Southern Hemisphere's ozone layer will start shrinking within a decade and should close completely in the next 50 years, an international panel said. Date unveiled at a conference in Argentina suggests that the global effort to reduce the use of chloroflurocarbons (CFCs), the main menance to the ozone hole is succeeding, just three months after NASA revealed that the size of the ozone hole in the Southern Hemisphere had grown to 11 million square miles and had reached the tip of South America.