Independent (UK): It was perceived as one of the greatest environmental threats of the late-20th century. Twenty-five years ago this month, a hole in the ozone layer was detected high in the atmosphere over the frozen wastes of Antarctica; scientists warned it might spread to other parts of the world, leading to dangerous increases in cancer-causing radiation from the Sun. The Earth’s protective layer of ozone shields all life from the damaging effects of ultraviolet (UV) rays, and its gradual …