DCSIMG

The hole truth about global warming

With the discovery of the hole in the ozone layer marking its 20th anniversary, Martin Hickes asks Antarctic scientists what the future holds for global warming. Twenty years ago, in those seemingly impossible years when computers were only used in business and the internet was an almost exclusive military and academic reserve, three scientists studying the wastes of Antarctica looked up and noticed part of the sky was missing, metaphorically speaking.

The dramatic discovery of a sizeable hole in the earth's crucial ozone layer above the world's least-populated continent sent shock waves around the world – and both stunned and spurred the international scientific community into action.

Next year, 2006, marks the "coming of age" of the "hole" which, while not

as large as it used to be, still hangs over the continent like an invisible

sword of Damocles in the spring months.

And while the original discoverers still keep a watchful eye on what lies

above – this year's hole was one of the largest on record – for the first time in more than a decade, they claim they may be seeing not the beginning of the end for the hole, but, to paraphrase Churchill, perhaps the very start of the end of the beginning.

The discovery of the annual spring depletion of ozone above the continent was first announced in a paper – which appeared in Nature magazine in May

1985 – by scientific researchers Joe Farman, Brian Gardiner and Jonathan Shanklin.

Later, NASA scientists re-analysed their satellite data and found, to their fascination and horror, that the whole of the Antarctic was affected.

Unnoticed, a 20 million square km hole, the size of the United States, had formed over the continent, thanks to the slow attrition of ozone through a complex process involving CFCs – chlorofluorocarbons – and sunlight.

After intensive research, it was found that the hole began to form in the Antarctic winter, and reached its largest extent every September, before disappearing again by mid-summer.

Scientists also discovered that during the winter, temperatures in the high atmosphere (the stratosphere), where most of the ozone was present, dropped below -80C, and thin clouds began to form.

Chemical reactions took place in the clouds and, when the sun returned in spring, further reactions took place which destroyed ozone – on a monumental scale.

While the scientific community remained both fascinated and alarmed in equal measure about the discovery, the political reaction ranged from apathetic to the cataclysmic.

The discovery that CFCs and other compounds – produced by aerosols and refrigerators among other sources – were a major contributing factor to ozone depletion, not only spurred some countries into phasing them out, but

also lit the blue touch paper on the subject of global warming in general,

and led to the signing of the Montreal Protocol to control 96 different ozone-depleting chemicals

Today, one of the hole's original discoverers, researcher Shanklin, says that while the monster still hasn't gone away, it remains on a firm leash – and has every chance of being diminished – but only as long as international agreements are

maintained.

"Our atmosphere consists of nitrogen (78 per cent) and oxygen (21 per cent) and a small amount of other gases. Ozone is quite a rare gas: even in

the ozone layer there is less than one ozone molecule for every 100,000 molecules of air," says Shanklin.

"In the polluted air from large cities, ozone may be present in higher concentrations and this can cause severe health problems. In its

proper place higher in the atmosphere, ozone provides a safety screen

against harmful ultra-violet light from the Sun.

"The 2005 Antarctic hole is larger and deeper than the holes that formed when the discovery was made, but the situation would be much worse if the Montreal Protocol had not come into force.

"We are still experiencing large losses of Antarctic ozone each spring because CFCs and other chemicals live for a long time in our atmosphere.

"However, the ban ensures that we will see an improvement in the future. We now need to take similar actions to control greenhouse gases, otherwise we will bequeath future generations a significantly different climate from that

of today.

"Covering an area of around 22 million square kilometres, this year's hole is a little smaller than the record-breaking

event in August 2003. It's certainly not going away in any hurry, but there is a glimmer of hope that we may be able to put the 'genie back in the bottle'."

Measurements made during August

and September 2005 at BAS Halley and Rothera Research Stations reveal a 50 per cent reduction on normal ozone levels over the base of the Antarctic peninsula and the Weddell

Sea, and a 20 per cent reduction over the tip of South America and the Falkland Islands.

"The area of the Antarctic ozone hole has been steadily increasing,"

says Shanklin. "But it is unlikely to become much deeper than in the

past.

"During October 1993, most of the ozone between 12 and 20 km altitude disappeared. The 2003 hole was the largest yet observed, covering more

than 23 million sq km. The shape of the hole is continually changing; sometimes it is circular and at other times very elongated.

"But if CFC releases had continued at the high rates of the mid-1980s, a continental-sized ozone hole might have appeared over the Arctic as well.

"I think there is a reasonable chance that the hole will have disappeared by the end of the 21st century if all protocols are adhered to. Of course, we don't know what other discoveries will be made in that time, but that, of course, is why we are here.

"It's exciting to have played a small part in the discovery of something big, as part of a dedicated team... and we'll keep watching."

 
 
 

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