A giant man-made hole in Earth's atmosphere is finally closing up

by Jessica Orwig

Now that summer is here, you'll likely be slathering up with sunscreen.

Earth, it turns out, is doing the same, according to an encouraging study recently published by a team of scientists at NASA Goddard Space Flight Center and Goddard Earth Sciences Technology and Research at the Universities Space Research Association.

Earth has its own layer of sunscreen called the ozone layer, or ozone shield, which makes up part of the stratosphere and absorbs most of the sun's ultra-violet (UV) radiation. But it doesn't absorb all of the UV light, and what gets through can cause skin cancer and cataracts in humans as well as reproductive problems in fish, crabs, and frogs.

the hole should finally, permanently shrink below 8 million square miles by 2040 and could even be fully recovered by the end of the century

Since 1983, scientists have observed a scary phenomenon: Earth's ozone was extremely weak over parts of Antarctica, letting in bouts of harmful UV radiation. The reason, in part, was because a series of man-made chemicals — namely chlorine and bromine — were eating away the planet's protective, sunscreen-like layer.

They called this weaker region Antarctica's ozone hole. Although the hole's size varies each year, it has been consistently larger than 8 million square miles since 1990 — more than twice the size of the entire United States!

In recent years, scientific reports have noted that the hole is slowly healing — thanks to a decrease in ozone-depleting chemicals in the atmosphere — but scientists were not sure when the hole would be completely regenerated.

Now, according to a study published in journal Geophysical Research: Atmospheres, the hole should finally, permanently shrink below 8 million square miles by 2040s and could even be fully recovered by the end of the century.

The source of the problem

For the middle half of the 20th Century, companies used ozone-depleting chemicals, called chlorofluorocarbons (CFCs), in refrigerators and aerosol sprays that, through use, were getting released into the atmosphere. By the early '80s scientists were beginning to understand the damage that these chemicals were doing to the planet.

When CFCs float up to the troposphere, above the ozone, they interact with UV radiation from the sun releasing chlorine, which destroys ozone. As a result of this discovery, an international treaty called the Montreal Protocol was enacted in 1989 that began phasing out the production and subsequent emission of ozone-depleting chemicals.

By that point, however, the damage had been done.

These chemicals can hang out in the atmosphere for years after they've entered the atmosphere. Like a series of dominoes, the ozone hole continued to grow even after CFCs were banned. Here's a chart showing the size of the ozone hole, in blue, from 1979 through 2012:

Ozone depletion above the planet's north and south poles was exceptionally bad because Earth's wind currents were sweeping the chemicals toward either end of the planet.

Once these chemicals reached the poles, a large-scale cyclone, called the polar vortex, was trapping the chemicals where they accumulated over time to high concentrations, ravenously eating away the ozone (see the GIF below). This led to the Antarctic ozone hole as well as the Arctic ozone hole, which in 2011 reportedly had half the ozone it used to.

Using NASA'S Aura satellite — an instrument orbiting Earth that sniffs out certain chemicals, including chlorine — the team of scientists studied the amount of ozone-eating chemicals above Antarctica from 2004 to 2012. From that, they identified a clear relation between the level of chlorine in the atmosphere and the size of the ozone hole.

They then looked at ozone hole sizes from 1979 through 2013 and predicted what future hole sizes will be based on how quickly chlorine levels are decreasing in the atmosphere above the Antarctic.

"With this new information we can look into the future and say with confidence that ozone holes will be consistently smaller than 8 million square miles by 2040," said Susan Strahan, a senior research scientist at NASA Goddard Space Flight Center, in a video about the study. "And that will really be a milestone that we're finally past the era of big ozone holes."

Check out the full video below: