We now have first direct proof that the ozone hole is shrinking

5 Jan 2018

A view of Earth’s atmosphere from space. Image: NASA

In one of few good news stories about our planet’s environment, scientists find the first proof that the ozone hole is shrinking.

While the world’s coral reefs are suffering irreparable damage, there was some good news announced by NASA scientists who have found the first direct proof that ozone depletion is in decline as a result of a global ban on chemical chlorofluorocarbons (CFCs).

Published in the journal Geophysical Research Letters, the findings showed that the ban has resulted in about 20pc less ozone depletion during the Antarctic winter than there was in 2005.

This the first year that measurements of chlorine and ozone during the Antarctic winter were made by NASA’s Aura satellite.

The stratospheric ozone hole over Antarctica was first discovered in 1985, sparking fears of immeasurable damage to the Earth as a loss of the ozone layer would lead to our planet being bombarded with harmful ultraviolet radiation from the sun.

Damage of CFCs

Two years after its discovery, regulations on chemicals that would contribute to ozone decline were signed by the nations of the world, with CFCs being the key target due to their prevalence in many household items, such as refrigerators and aerosols.

These long-living chemical compounds eventually rise into the stratosphere, where they are broken apart by the sun’s ultraviolet radiation, releasing chlorine atoms that go on to destroy ozone molecules.

Previous studies in this area used statistical analyses of changes in the hole’s size to argue that ozone depletion is decreasing.

However, this study is the first to use measurements of the chemical composition inside the ozone hole to confirm that not only is ozone depletion decreasing, but that the decrease is caused by the decline in CFCs.

“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.

Decades of recovery ahead

With help from the Aura satellite and its Microwave Limb Sounder (MLS) instrument, the team was able to take measurements of depletion from 2004.

Unlike other satellite instruments that require sunlight to measure atmospheric trace gases, the MLS uses microwave emissions and thus can measure trace gases over Antarctica during the key time of year, the dark southern winter, when the stratospheric weather is quiet and temperatures are low and stable.

Looking to the future, NASA scientists believe that as long as the ban of CFCs is maintained, the ozone hole should shrink gradually, but it could take decades to recover.

The paper’s co-author, Anne Douglass, said: “CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time.

“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.”

Colm Gorey was a senior journalist with Silicon Republic