NASA study provides first proof of ozone hole recovery | News | DW | 06.01.2018
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NASA study provides first proof of ozone hole recovery

Scientists at NASA have shared evidence proving that levels of ozone-destroying chemicals in the atmosphere are declining. For the first time, there is full scientific proof that a worldwide ban on CFCs is working.

Direct satellite observations by NASA show that the global ban on chlorofluorocarbons (CFCs) has caused the hole in the ozone layer to shrink.

In a new study published in the journal Geophysical Research Letters, scientists said ozone depletion had dropped by about 20 percent since 2005.

CFCs are long-lived, chlorine-based chemicals that rise into the stratosphere layer of Earth's atmosphere, where the sun's ultraviolet radiation breaks their compounds apart, releasing chlorine atoms that destroy ozone molecules.

Stratospheric ozone protects life on Earth by absorbing ultraviolet radiation, which is potentially harmful as it can cause skin cancer and cataracts, compromise the immune system and damage plants.

"We see very clearly that chlorine from CFCs is going down in the ozone hole, and that less ozone depletion is occurring because of it," said lead author Susan Strahan, an atmospheric scientist at NASA's Goddard Space Flight Center.

Read more: What happened to the ozone layer? 

Strahan and co-author Anne R. Douglass used data from the Microwave Limb Sounder (MLS) aboard the Aura satellite, which has been making measurements continuously around the globe since mid-2004.

"The Antarctic ozone hole is healing slowly because levels of the man-made chemicals causing the hole have long lifetimes," the study stated.

Ozone layer still decades away from full recovery

The study is the first to use measurements of the chemical composition inside the ozone hole to confirm that ozone depletion is decreasing as a direct result of the decline in use of CFCs. Past studies have had to rely only on statistical analyses of changes in the ozone hole's size to suggest that the ozone is healing.

The Antarctic ozone is expected to continue to recover gradually as CFCs leave the atmosphere; however, a complete recovery is expected to take decades, as the ozone layer faces other threats.

Read more: Ozone layer under threat, again?

"CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time," Douglass said. "As far as the ozone hole being gone, we're looking at 2060 or 2080. And even then there might still be a small hole."

Two years after the discovery of the Antarctic ozone hole in 1985, countries around the world agreed to sign the Montreal Protocol on Substances that Deplete the Ozone Layer, which regulates ozone-depleting compounds. The agreement was ratified in 1989 and has been amended multiple times since in order to completely phase out the production of CFCs.

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