Science / Medicine : Depletion of Ozone Layer

Depletion of the Earth’s life-protecting ozone layer goes on with or without sunshine, during the Arctic winter as well as spring, Italian scientists report. Researchers have known since 1984 that a “hole” in the ozone layer, the atmospheric stratum that shields the Earth from the sun’s lethal ultraviolet rays, appears in September over the South Pole. The hole is caused by a chemical reaction set off by the spring sunshine.

But scientists reporting in the current issue of Nature magazine found that the ozone is also depleted during June and July, the Arctic winter, even though the sun never appears.

Measurements taken last year at the South Pole found holes in the ozone layer between June 11 and July 24 similar to those that appear in September.

The team, led by Georgio Fiocco of the University la Sapienza in Rome, said polar stratospheric clouds that form during the Arctic winter apparently provide places in which the chemical destruction of ozone can occur even without sunshine.

Scientists believe that the earth’s ozone layer is slowly being destroyed in part by the large amount of chlorofluorocarbons released into the atmosphere from aerosol sprays, air conditioners and refrigeration materials.