ENVIRONMENT: Ozone Hole Divides in Two

By Gustavo Capdevila Reprint | | Print |

Gustavo Capdevila

GENEVA, Oct 1 2002 (IPS) - The hole in the ozone layer over Antarctica divided in two last week, an unprecedented phenomenon that caught the scientific community by surprise, say officials at the World Meteorological Organisation (WMO).

Michael Proffitt, WMO expert on the Earth’s atmospheric ozone layer, declined to comment on whether he thought the double ozone hole might have positive or negative implications.

"To me it is just a very surprising thing. Scientists did not expect to see this occur," he said.

Frederic Delsol, director of the WMO atmospheric and environmental programme, related the event to the extremely unusual air currents in the Southern Hemisphere’s atmosphere recorded this year.

The currents have meant that the cyclic formation of the ozone hole has not come about in its normal way and has taken a totally different shape, said Delsol.

The ozone layer, located 15 to 50 km above the Earth’s surface, filters out ultraviolet (UV) radiation that is harmful to all fauna and flora on the planet. Among the public health problems caused by the thinning of the ozone layer are damage to vision and increased incidence of skin cancer.

Since 1980, there has been a cyclical thinning of the ozone layer over Antarctica, usually lasting from August to December. The consequences are the equivalent of a hole measuring millions of square km in area.

The phenomenon is blamed on the emissions of man-made gases, such as chlorofluorocarbons (CFCs) and halons, that break apart the three-oxygen molecule of ozone.

In 1987, 180 countries signed an international agreement, the Montreal Protocol, to eliminate the production and use of those gases by 2010.

The WMO is tracking the evolution of the ozone hole, or holes, through data obtained from the Global Atmosphere Watch Network, with ground stations located around the world, several in Antarctica.

"We also look at satellite images that there are produced almost in real time," said Proffitt. "We always are very careful to be sure that all sources of data support the same conclusions."

Two weeks ago, the WMO reported the appearance of one of the smallest holes in the ozone measured in the last decade, but predicted that it would grow wider in the following weeks.

But the Sep 25 observations of the hole caught scientists by surprise. They showed that the hole had divided into two smaller areas, and the centre of each with less than half the density of ozone gas considered normal for the atmospheric layer from January to June.

After Sep 25, one of the holes remained unchanged, located over the Antarctic area to the southeast of Africa. The other, over an area closer to South America shrank considerably.

Proffitt commented that the strangest aspect this year is that the vortex and the ozone hole have behaved in an unusual way.

The vortex is the meteorological term for the phenomenon and involves the extremely low temperatures needed to cause the chemical process of accelerated ozone loss over Antarctica, he explained.

This chemical process is well known, but scientists have not yet been able to determine the influence of meteorological conditions on how the ozone hole occurs or how wide it will become.

Some of these meteorological conditions could be a response to other conditions that are chemical, said Proffitt.

"In fact, it could be that the ozone hole itself has changed the temperature structure in the vortex, in this cold pool of air over the Antarctic," which has produced the unexpected event of two smaller holes.

But the WMO expert stressed that the recent data do not point to a new trend. "This is an indication of meteorological conditions. It may be that meteorological conditions are changing. Maybe global circulation of currents is changing," he said.

The double ozone hole "has nothing to do with the limitations that have been put on CFCs and the various compounds that destroy ozone. It’s another issue," Proffitt added.

Delsol summarised that the Southern Hemisphere has seen an anomalous pattern in its air currents and that in the stratosphere the circulation is behaving differently. This has a strong impact on the structure and shape of the ozone hole, including its division into two.

Meteorologists do not know why there have been changes in the Southern Hemisphere’s air circulation, and it will be difficult to determine, he said.

Regardless of any potential explanations for the double ozone hole, the prediction remains in place that at least another 50 years will be needed for the Earth’s ozone layer to completely recover.

And that will only be possible if all countries comply with the Montreal Protocol’s timeline for phasing out production and use of ozone depleting substances, according to the WMO.

ENVIRONMENT: Ozone Hole Divides in Two

By Gustavo Capdevila Reprint | | Print |

Gustavo Capdevila

GENEVA, Oct 1 2002 (IPS) - The hole in the ozone layer over Antarctica divided in two last week, an unprecedented phenomenon that caught the scientific community by surprise, say officials at the World Meteorological Organisation (WMO).
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