Ozone hole gets smaller

23:41, Sep 15 2010

As much of New Zealand struggles to see the end of winter, sun-lovers will be pleased to hear that the ozone hole appears to be smaller this year.

However, scientists cannot definitively say whether this marks the start of a steady decrease in its size.

Today is International Ozone Hole day, occurring as New Zealand enters its ozone season, which runs until the end of November.

Niwa atmospheric research scientist Olaf Morgenstern said this year's season was "slow to kick in".

There were substantial variants in the size of the hole from year-to-year because, just like the weather, there were many contributing factors such as the solar cycle varying the heat of the sun.

The largest ozone hole occurred four years ago in 2006.

"What we will see is a shrinking of the ozone hole, the ozone hole will disappear," Dr Morgenstern said.

Until the 1980s, chlorofluorocarbons, or CFCs, and other man-made halogen compounds were used in refrigeration, aerosol sprays and numerous other applications throughout the world.

UV radiation breaks down these chemicals once they are in the stratosphere, releasing chlorine and bromine atoms, which then deplete ozone.

Dr Morgenstern said it was during spring that the UV rays heated up the chemicals which is why scientists are able to see the hole now.

After the destructive properties of chlorine and bromine were discovered in the 1980s and the Montreal Protocol was introduced in 1987 there was an agreement to phase out the usage of the destructive chemicals.

"In the future we expect [ozone] to recover.

"We might have more ozone over New Zealand than we had say 50 years ago, we might have less UV, and fewer skin cancers."

He said he expected the ozone hole to disappear by about 2060.