ENVIRONMENT: Hole in Ozone Layer Does not Reach Inhabited Areas

By Gustavo Capdevila Reprint | | Print |

Gustavo Capdevila

GENEVA, Sep 22 2001 (IPS) - The effects of the hole in the ozone layer on the people living in the southernmost parts of South America have not been as serious this year as in the past, according to a bulletin released by the World Meteorological Organisation (WMO) Friday.

The WMO reported that inhabited areas this year remained outside the direct influence of the ozone hole, which grows every southern hemisphere spring.

The vortex over Antarctica is more circular in shape this year, which means it is almost completely located over the South Pole, and does not extend to the continental territories of Chile and Argentina, as it has in previous years.

The ozone layer absorbs a large part of the sun’s ultraviolet radiation, exposure to which can cause serious damage to life on earth.

The WMO reported that “in the past few days, the area of the ozone hole edged up to 25 million square kilometres, still shy of the 28 million square kilometre record reached” on Sep 12, 2000.

Every year, the WMO puts out periodic bulletins on the state of the hole in the ozone layer in the southern hemisphere from mid- August to November, when the vortex begins to shrink.

The agency’s statistics are closely followed by governments and populations in the southernmost portions of South America, as well as by the rest of the international community, which has embarked on a struggle to secure recovery of the ozone layer in the stratosphere.

The Vienna Convention for the Protection of the Ozone Layer and the Montreal Protocol established the rules governing those efforts, and the norms and targets for achieving a steady reduction of the use of ozone-depleting chemicals.

The main culprits in the thinning of the ozone layer are chloroflourocarbons (CFCs), the use of which will be banned worldwide as of 2010. Scientific studies have also warned of the destructive effects of methyl bromide and methyl chloride.

The bulletin, released Friday in Geneva, also reports on the amount of ozone loss, as measured in millions of tons of ozone and estimated from the daily ozone data available.

“This ‘ozone mass deficit’ is calculated within the area more than 10 percent below pre-ozone-hole norms and provides a means of measuring the progress of the depletion and of comparing the depth of ozone holes from year to year.”

Using that procedure, the WMO found that last year’s hole reached a peak of 57 million tons of ozone by the second week of September, “a value higher than all previous years.”

“This year the ozone mass deficit has reached about 54 million tons of ozone, well above most previous years,” it adds.

The report, which also describes the meteorological conditions in which the ozone hole is forming this year, said the minimum temperatures registered in the lower stratosphere were steadily rising, as expected this time of year in the southern hemisphere.

“The area with temperatures low enough to form polar stratospheric clouds is 20-25 million square kilometres, which is large compared to the past ten years, and remains a significant portion of the polar vortex, presently about 37 million square kilometres.”

The polar stratospheric clouds “activate chemical processes, that in the presence of sunlight” – which returns to Antarctica around Sep 21 after six months of darkness – “result in rapid ozone depletion, and these conditions ultimately result in the ozone hole.”

“The extremely low ozone values that characterise the ozone hole are generally confined to the interior of the vortex,” the report adds.

The WMO points to “another noteworthy observation”: the fact that this year’s hole is more circular than last year’s indicates that it is more stable and will last longer.