|
A relatively warm Antarctic winter in 2004 kept the thinning of the protective ozone layer over Antarctica, known as the ozone 'hole,' slightly smaller than in 2003. Each year the 'hole' expands over Antarctica, sometimes reaching populated areas of South America and exposing them to ultraviolet rays normally absorbed by ozone. Scientists have new tools to study this annual phenomenon, and the human-produced compounds that contribute to ozone breakdown are decreasing. On September 22, 2004, ozone thinning over Antarctica reached its maximum extent for the year at 24.2 million square kilometers (9.4 million square miles). The largest maximum area on record was 29.2 million square kilometers, in 2000. On October 5, 2004, the ozone layer reached a low value of 99 Dobson Units.
|
