Ozone, a gas that is produced naturally up in the stratosphere, surrounds the Earth like a protective blanket. This ozone layer keeps us safe because it absorbs many of the sun’s harmful ultraviolet (UV) rays.
But that protective blanket gets holes in it because of man-made chemicals known as ozone-depleting substances—ODS for short—which destroy ozone and our protection from UV rays.
Scientists report that this year the hole over Antarctica is a record-breaker: “From September 21 to 30, the average area of the ozone hole was the largest ever observed at 10.6 million square miles (27.4 million square kilometers),” said atmospheric scientist Paul Newman with NASA’s Goddard Space Flight Center.
That’s larger than the surface area of North America. The hole is also the deepest ever recorded.
Two things account for the record-breaking hole. The first is that even though more than 180 countries agreed to phase out ODS use in 1987, there are still a lot of these substances up in the stratosphere from years past. That’s because they last a long, long time, some of them more than a hundred years.
The second factor has to do with clouds and cold temperatures over the South Pole.
“The polar stratosphere is a very cold, dry place,” explains Newman. “It is hard for clouds to form there. But polar stratospheric clouds form when it gets extremely cold: minus 109 degrees Fahrenheit (minus 78 degrees Celsius).” Newman says that’s when some interesting chemistry takes place: “The cloud releases chlorine in a form that rapidly destroys ozone.”
The good news, however, is that the situation would be a lot worse if people hadn’t started doing things to protect the ozone layer. By the year 2070, the big ozone holes will be a thing of the past, predicts Newman.
- Ozone occurs naturally 10 to 30 miles (16 to 48 kilometers) above the Earth’s surface.
- Ozone protects us from the sun’s harmful UV rays.
- Human-produced compounds that release chlorine and bromine gases into the stratosphere cause ozone depletion.
- The Antarctic ozone hole was first discovered in 1985.
- The Montreal Protocol was signed in 1987 to fight ozone depletion.
Text by Catherine Clarke Fox