Ozone depletion

Ozone Depletion

Ozone is a highly reactive molecule that contains three oxygen atoms. It is

constantly being formed and broken down in the high atmosphere, 6.2 to

31 miles (10 to 50 kilometers) above Earth, in the region called the

stratosphere.

Today, there is widespread concern that the ozone layer is deteriorating

due to the release of pollution containing the chemicals chlorine and

bromine. Such deterioration allows large amounts of ultraviolet B rays

to reach Earth, which can cause skin cancer and cataracts in humans and

harm animals as well.

Chlorofluorocarbons (CFCs), chemicals found mainly in spray aerosols

heavily used by industrialized nations for much of the past 50 years, are the

primary culprits in ozone layer breakdown.

One atom of chlorine can destroy more than a hundred thousand ozone

molecules, according to the the U.S. Environmental Protection Agency.

The ozone layer above the Antarctic has been particularly impacted by

pollution since the mid-1980s. This region’s low temperatures speed up

the conversion of CFCs to chlorine. In the southern spring and summer,

when the sun shines for long periods of the day, chlorine reacts with

ultraviolet rays, destroying ozone on a massive scale, up to 65 percent.

This is what some people erroneously refer to as the "ozone hole." In

other regions, the ozone layer has deteriorated by about 20 percent.

About 90 percent of CFCs currently in the atmosphere were emitted by

industrialized countries in the Northern Hemisphere, including the

United States and Europe. These countries banned CFCs by 1996, and

the amount of chlorine in the atmosphere is falling now. But scientists

estimate it will take another 50 years for chlorine levels to return to their

natural levels.

Causes

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Ozone depletion and climate change

There is a complex relationship between ozone loss and climate change.

Ozone-depleting substances are also greenhouse gases, so the Montreal

Protocol contributed significantly to international attempts to fighting

global warming. However, since HFCs are also greenhouse gases, it's

possible their increasing use could erase the benefit of phasing out ozone-

depleting substances.

In addition, greenhouse gases can affect ozone cover, by affecting

temperature in the stratosphere and by altering atmospheric circulation

patterns in a way that changes the distribution of ozone over the planet,

moving it away from the tropics.

As ozone-depleting substances disappear from the atmosphere, other

greenhouse gases, such as carbon dioxide and methane, will become the

most important factors determining ozone levels, Newman said.