In 1987 there was a major breakthrough when the Montreal Protocol was signed to outlaw cholorfluorocarbons - gases used in refrigerators - in order to combat the ozone hole. The ozone layer shields us from dangerous ultraviolet radiation of the sun. The ozone hole occured in particular in the Southern hemisphere. Now the hole is smaller and appears later in the year than ever since. It is a big sign that shows that international agreements can be effective.