No More Antarctic Ozone Left to Destroy

The seasonal hole in the ozone layer, first observed over the Antarctic in the 1980s, has reappeared each year since then. This year's ozone loss is "comparable to the previous record-setting years," he says.

"We have reached the bottom," Bojkov says. "All the ozone contained within the polar vortex area between nine miles and 14 miles is destroyed. That's it. We cannot have lower values than that. There is no more ozone (over the Antarctic) to be destroyed."

Ozone is a naturally occurring form of oxygen found in the stratosphere which acts as a protective shield to life on Earth by absorbing most of the sun's cancer-causing ultraviolet radiation.

The United Nations WMO says sustained surges in radiation reaching the Earth could lead to a rise in cancer in humans and animals, lower crop yields and damage the marine food chain, starting with microscopic plankton in the world's oceans.

"Holes" in the ozone layer appear each year over the Arctic and Antarctic and the layer has become generally thinner because of the effect of ozone depleting chemicals. The WMO studies show a one percent drop in ozone levels causes an average 1.3 percent rise in ultraviolet radiation.

The ozone loss is expected to peak between 2001 and 2005 provided that countries abide by the 1987 Montreal Protocol aimed at reducing the use of certain chemicals. The pact calls for a 50 percent reduction in volume of chloroflurocarbons (CFCs) by the year 2000.

This year's ozone depletion was detected by the U.S.-built Total Ozone Mapping Spectrometer system, carried on board the U.S. Earth Probe satellite and the Japanese Advanced Earth-Observing Satellite. The data were confirmed by ground-based instruments and other satellite-based instruments.

The average size of the Antarctic ozone hole during 1996 has been almost as large as in the peak year of 1993, although ozone values are higher than the record lows seen in September 1994, according to preliminary analysis of satellite data by scientists at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

This year the hole covered a surface area over the South Pole roughly equal in size to the North American continent.

"Although its area climbed briefly over that of the previous peak, that is not as great a concern as the average size, because meteorological conditions can cause large day-to-day fluctuations," explains Dr. Paul Newman, research scientist in the Laboratory for Atmospheres at Goddard.

Scientists at the South Pole from the National Oceanic and Atmospheric Administration (NOAA), working with balloon-borne measurements, say the measurements are similar to last year when ozone depletion was more severe than in the past.

Dr. Dave Hofmann of the NOAA Climate Monitoring and Diagnostics Lab in Boulder, Colorado says last year's measurements showed complete destruction of the ozone layer at an altitude of 10 miles between September 24 and October 14.

"These deep and large ozone holes are likely to continue to form annually until the stratospheric chlorine amount drops to its pre-ozone hole values," says Dr. Richard Stolarski, who is also at Goddard.

Bojkov warns that world should now watch out for potentially more life-threatening depletion over Europe and America. He told a media briefing in Geneva last week that up to 10 percent of the ozone had been depleted over Europe and North America by man-made chemicals in the past 20 years.

"Over Geneva, for example, we have lost nearly eight to 10 percent of the ozone compared to the 1960s," he said. "Within the next 10 or 15 years, we may expect a stronger ozone depletion. We'll always have a little bit of ozone left over our heads but it may not be sufficient to protect biological species."

Reducing the use of ozone depleting chemicals, however, still faces problems. The CFCs once used universally as refrigerants have been replaced largely by hydrochlorofluorocarbons (HCFCs) which are less harmful to the ozone layer but still destructive.

The Montreal Protocol signatories agreed last December that the developed world would phase out production by 2020 and the developing world by 2040. But so far there is no suitable substitute for HCFCs. Another problem is methyl bromide, a pesticide used mainly as a soil fumigant, which is even more damaging than CFCs.

In 1985, the world produced about 1.1 million tons of CFCs. By the end of 1995 it was less than 400,000 tons. Most of the remaining production is being used in Russia and the newly independent states of the former Soviet Union.

Developing nations, which account for a smaller share, have another decade to phase out CFCs. But their use is predicted to grow enormously as countries like China continue to develop economically.

To help poorer countries phase out these chemicals, the Montreal Protocol allowed for a special Multilateral Fund, to be paid for by the industrialized world. So far the Fund has financed more than 1,000 projects at a total cost of $440 million.

These are supposed to allow the elimination of 30 percent of all ozone depleters used in the developing world by the turn of the century. But the Fund has received about 20 percent less money than was pledged for 1996.