Recently, however, convincing scientific evidence has shown that the ozone shield is being depleted well beyond changes due to natural processes.

The ozone shield keeps those rays from reaching the earth's surface.

If there were no ozone shield, plants and animals could not exist on land.

Let us look for a moment at the ozone shield.

The weakened ozone shield lets in more ultraviolet light, a cause of skin cancer.

But several said they were worried about the possible implications for both climate change and the earth's protective ozone shield.

Other possible catastrophes include nuclear winter and disruption of the ozone shield.

And sometime after that, the researchers said, the ozone shield should begin to recover.

The parties to the treaty plan to determine in 1990 whether further measures are needed to protect the ozone shield.

The group argues that, like the destruction of the earth's ozone shield, the mercury problem will be solved only by an international treaty.