A new report co-authored by the World Meteorological Organization and the UN Environment Program has revealed that the ozone layer that shields the earth from cancer-causing ultraviolet rays is showing early signs of thickening after years of depletion. The ozone hole that appears annually over Antarctica has started shrinking, although it will take about a decade before it shrinks completely.

The largest ozone hole on record was about 30 million square km in 2006. The hole now covers about 20 million square km, which is still big enough for the moon to pass through.

Experts credited the recovery to a 1987 ban on emission of CFC gases that damage the fragile high-altitude ozone layer. The ozone layer had been depleting since the late 1970s and it led to destruction of ozone molecules high in the air. Countries around the world agreed to the 1987 Montreal Protocol that banned or phased out ozone-eating depleting chemicals, including chlorofluorocarbons (CFCs) that were once widely used in refrigerators and spray cans. This political determination has declined the levels of CFCs in the air and this would certainly help prevent millions of cases of skin cancer and other conditions.

However, the good news on ozone has come at the time when bad news on the gases that cause climate change has surfaced. The atmospheric greenhouse gases have attained a high record due to the rise in the chemicals that replaced CFCs.

For now, the ozone layer is on track to fully recover by the middle of the century, but a rapid increase in certain substitutes still threatens to undermine the recovery. It has a long way to go before it is fully healed or recovered as the hole in the layer still appears over Antarctica every spring.