The harmful chemicals that destroy the ozone layer have to be carried up into the stratosphere by clouds in order to react with ozone. The land mass at the South Pole (Antarctica) creates the necessary weather conditions for this to happen, while the North Pole is covered in water, causing winds in the upper atmosphere to blow away pollutants. The bad news is that some scientists fear that increasing levels of pollution may result in a hole in the ozone at the North Pole in about 20 years.