At first, scientists at the British Antarctic Survey thought their equipment was playing up. In the late 1970s and early 1980s the field workers at Halley research station, on the Brunt ice shelf, reported that their ozone monitoring machine was producing remarkably low results.
“Numbers were falling off the graph,” says Jonathan Shanklin. He does not mean this metaphorically. Readings in those days were taken by hand and plotted on paper, but the results were so low that they had dropped off the bottom of the page.
This was the first sign of what within a few years would become clear was a huge hole in the ozone layer — the atmospheric shield of O3 oxygen molecules that absorbs harmful UV rays from the sun.