From September 21-30, 2006 the average area of the ozone hole was the largest ever observed, at 10.6 million square miles. In this image, from Sept. 24, the Antarctic ozone hole was equal to the record single-day largest area of 11.4 million square miles, reached on Sept. 9, 2000. The blue and purple colors are where there is the least ozone, and the greens, yellows, and reds are where there is more ozone. (UPI Photo/NASA) | License Photo
The concentration of ozone in the Earth's upper atmosphere is essential to life, as it absorbs and reflects from harmful radiation emitted by the sun -- thus protecting the planet's inhabitants.
Scientists first noticed the ozone layer was weakening in the 1970s; they quickly fingered a class of chemicals called chlorofluorocarbons, or CFCs, commonly used in refrigerants and aerosol cans, as responsible. Strict regulation followed. In 1987, world leaders signed the Montreal Protocol, which helped phase out CFC use around the world. The ban has apparently helped the ozone layer regain its strength.
But scientists warn the Earth's atmosphere isn't entirely out of the woods yet. While the ozone layer is showing early signs of recovery, the U.N. report says it will likely be another 35 years before the ozone returns to the relatively healthy levels of the 1980s.