The size of the ozone hole fluctuates on a regular basis. From August to October, the ozone hole increases in size—reaching a maximum between mid-September and mid-October. When temperatures high up in the stratosphere start to rise in the southern hemisphere, the ozone depletion slows, the polar vortex weakens and finally breaks down, and by the end of December ozone levels return to normal.
DB2
Lead author Hannah Kessenich, PhD candidate in the Department of Physics, says they found there is much less ozone in the centre of the ozone hole compared to 19 years ago. “This means that the hole is not only larger in area, but also deeper throughout most of spring.”…
“More study is warranted to determine the precursors for the changes we identify…”
DB2
At least one cause is illegal CFC emissions from China.