Low temperatures may be the key to ozone loss in the atmosphere, according to recent studies.

Now, he said, scientists suspect that chemical reactions at lower altitudes actually cause most of the ozone loss.

The team said that within a decade winter ozone losses over the northern hemisphere would be double those recorded by the end of the 1980s.

Satellite measurements show that ozone loss worldwide has amounted to 2.9 per cent over the past 10 years.

Some political conservatives have questioned the connection between the chemicals and the ozone loss.

Scientists hope to get the best picture yet of the extent and location of ozone loss in the upper atmosphere.

Dr. Prather said the forecast of ozone loss over the next 30 years would range from 1 to 4 percent.

They said the finding could portend even greater ozone loss over highly populated parts of the world than in the past.

Smaller ozone losses have been observed in other parts of the globe.

Computer models suggested this reduction would hold the global ozone loss to 1 percent, compared with 6 percent without controls.