ENVIRONMENT: Ozone Protection Measures Bearing Fruit

By Gustavo Capdevila Reprint | | Print |

Gustavo Capdevila

GENEVA, Jun 22 1998 (IPS) - Measures taken by the international community to protect the ozone layer are beginning to bear fruit, the World Meteorological Organisation (WMO) and UN Environment Programme (UNEP) announced in Geneva Monday.

The latest evaluation of the state of the ozone layer, carried out this month, found that the concentration of ozone-depleting chemicals had begun to diminish in the troposphere, the portion of the atmosphere extending outward about 12 kms from the earth’s surface.

The ozone layer is located in the stratosphere – extending from 12 to 27 kms above the earth – and protects the earth’s surface from the sun’s harmful ultraviolet rays.

The 1998 Scientific Evaluation of Ozone-Depletion, released by the WMO and UNEP Monday, documents for the first time that emissions of greenhouse gases have begun to level off, said Dr. Rumen Bojkov, the WMO’s top adviser on ozone.

But although emissions have been cut, the reduction has not yet had any effect on the ozone layer, because it takes four to 10 years – six on average – for greenhouse gases to reach the stratosphere, he told a media briefing.

WMO Secretary-General G.O.P. Obassi said the measurements taken by a network of 200 scientists worldwide confirmed the efficacy of the Montreal Protocol, the international agreement regulating the use and emissions of ozone-depleting substances.

The measurements show that the Montreal Protocol is fulfilling its purpose, because the rate of increase of ozone-depleting chemicals is being reduced, and emissions of some substances are even starting to diminish, said Bojkov.

Concentration of bromine compounds, extremely harmful, was previously growing in the troposphere at a rate of 12 percent a year, but is now only doing so at an annual rate of five percent. Studies also show that the concentration of chlorine has even begun to diminish, albeit slowly.

But the positive results have only been found in the troposphere. It takes six years for greenhouse gases to reach the stratosphere from the earth’s surface, where the destruction of the ozone layer occurs.

Concentrations of chlorine in the stratosphere will peak between the years 2000 and 2002, the result of gases emitted before industrialised countries began to implement the Montreal Protocol in 1995.

But before greenhouse gases start to diminish in the stratosphere, they will level off for around a decade, “due to the complexity of the chemical processes in space,” Bojkov explained.

The definitive recovery of the ozone layer to levels seen in the 1960s or 1970s is not expected until the middle of next century.

The WMO/UNEP study warns “that we will not see the start of recovery for at least another 20 years,” said Bojkov. That is because ozone depletion is not only caused by the presence of chlorofluorocarbons (CFCs) and other harmful substances, but also depends on the temperature of the stratosphere, which regulates the speed of ozone-depletion.

The study also found that the close to 50 percent loss of ozone seen every year over the Antarctic in September and October has not diminished, and it predicted that it would continue occurring for several decades.

The study found nothing new with respect to the effects of ozone on ultraviolet rays, said Bojkov, who added that for every one percent of depletion of the ozone layer, ultraviolet rays increased one percent in intensity.

Exposure to strong ultraviolet rays can cause skin cancer, lower crop yields and damage the food chain, starting with microscopic plankton in the world’s oceans, the UN agencies pointed out.

“Without the Montreal Protocol, we would be in a much worse situation today,” Bojkov underlined.

Developing countries have until 2004 to apply the Montreal Protocol, which was agreed on in its original form in 1987 in the Canadian city from which it drew its name, and later updated in London in 1990, Copenhagen in 1992 and Vienna in 1995.