The ozone hole
The ozone hole is more a thinning of the ozone layer than a real hole. It occurs every spring above Antarctica since the end of the 1970s. The size of the ozone hole has increased in the last two decades, and it covers now an area of about 25 million square kilometers. The thickness of the ozone layer in the ozone hole can be as low as 100 DU while it should be between 300 and 400 DU at that time. The figure below shows the ozone hole in black.