1. THE OZONE HOLE. (Image courtesy of NASA.)

This year's ozone hole over Antarctica was the second largest ever recorded, according to NASA. On September 11, 2003, the hole reached 10.9 million square miles, slightly larger than the size of North America, but smaller than the largest ozone hole ever recorded on September 10, 2000, when it covered 11.5 million square miles.

The Antarctic ozone hole is defined as thinning of the ozone layer over the continent to levels significantly below pre-1979 levels. Ozone blocks harmful ultraviolet rays. The thinning of the ozone layer is linked to skin cancer in humans and other adverse biological effects on plants and animals. Click here to go to an enlightening site about the ozone hole.

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