The ozone hole will likely close within 50 years, according to scientists who just ended a major conference on the issue in Buenos Aires. They said that the international ban on ozone-depleting chlorofluorcarbons, which resulted from the 1987 Montreal Protocol, is beginning to have an effect, but that the ozone recovery is not likely to start for a few more years and will not necessarily happen steadily because of natural fluctuations in weather patterns. The biggest ozone hole ever recorded occurred this October over Antarctica.