Ozone hole stable, possibly on the mend

Put the giant darning needle away, Ma

After last season's bumper ozone hole, this year things look set to be much less dramatic, and scientists even say the hole may have stopped widening.

At a conference in Washington, two of the scientists who first raised the alarm about the hole in the protective atmospheric layer said they were hopeful the hole would heal within 60 years.

The news comes 19 years after an international agreement was signed to phase out the use of CFCs, the chemicals known to have depleted the layer, and just 20 after Dr Susan Solomon and Dr David Hofman published the paper that drew attention to the problem.

"I'm very optimistic that we will have a normal ozone layer sometime, not in my lifetime, but perhaps in yours," Hofman is reported to have said.

The Ozone layer, for anyone who might have missed it, is a protective layer of the atmosphere which absorbs much of the harmful UV from the sun's rays. Its composition does fluctuate naturally during the year, becoming thicker in the summer months and thinner during the winter.

During the southern hemisphere winter the polar vortex keeps the atmospheric mass above the Antarctic continent isolated from exchanges with mid-latitude air. This keeps the air mass above the continent cold, and in the cold and dark, clouds that contain chlorine can form in the polar stratosphere.

Once the spring returns, this chlorine, much of it originating from man-made pollutants like chlorofluorocarbons, disrupts the ozone layer causing the hole we are all now so familiar with. ®

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