The largest-ever hole in ozone layer over the Arctic has closed, the Copernicus' Atmospheric Monitoring Service announced recently.   In late March, scientists spotted signs of a rare hole forming and it was thought to be the result of low temperatures at the north pole, reports Euro News.   Earth’s ozone layer shields it from most of the Sun's ultraviolet radiation, a major cause of skin cancer. A hole in ozone layer would pose a direct threat to humans if it moves to populated areas.   Copernicus, the EU's earth monitoring programme, announced the closure of the hole on April 23. The development is unrelated to the reduction in pollution because of lockdown across much of the world.