The Washington Post published a hopeful article earlier this week about the ozone hole over Antarctica, which has been shrinking ever since chlorofluorocarbons (CFCs) and related chemicals were banned from use as refrigerants. This year the ozone hole is the smallest it has been since 1988. It was the largest in 2000. The presence of an ozone hole means that high-energy ultraviolet light can reach the surface of the earth, increasing cancer in humans and livestock and increasing genetic mutations in crops. You can read more about how the ozone hole was caused and how big it is this year here.