In the 1980s, scientists discovered that the ozon layer over Antarctica had thinned dramatically. In an effort to curb the terrifying effect, the world agreed to reduce the use of hydrofluorocarbons in the Montreal Protocol.
Today, tests indicate that the "hole" has shrunk by some 4 million square kilometers (1.5 million square miles).
"It's wonderful to see that this most untouched part of our planet that we actually did touch in a very unusual way by creating the ozone hole is going back to its original state," celebrates study lead author Susan Solomon, an atmospheric chemist at the Massachusetts Institute of Technology.