Ozone Depletion in the Stratosphere 233CFC, carbon tetrachloride, and methyl chloroform
production was almost completely phased out in the
United States and other highly developed countries in
1996, except for a relatively small amount exported to de-
veloping countries. Developing countries were on a dif-
ferent timetable and phased out CFC use in 2005. Methyl
bromide was phased out in highly developed countries,
which were responsible for 80 percent of its global use, in- HCFCs will be phased out in 2030.
Unfortunately, CFCs are extremely stable com-
pounds and will probably continue to deplete strato-
spheric ozone for several decades. Human-exacerbated
ozone thinning will reappear over Antarctica each year,
although the area and degree of thinning will gradually
decline over time, until full recovery takes place some-
time after 2050. - What is the stratospheric ozone layer, and how
does it protect life on Earth? - What is stratospheric ozone thinning? What
role do CFCs play in ozone thinning? - How have governments responded to ozone
thinning?
states have banned indoor tanning for children. Malig-
nant melanoma, the most dangerous type of skin cancer,
is increasing faster than any other type of cancer.Reversing Ozone Layer Thinning
In 1978 the United States, the world’s largest user of
CFCs, banned the use of CFC propellants in products
such as antiperspirants and hair sprays. Although this
ban was a step in the right direction, it did not solve the
problem. Most nations did not follow suit, and propel-
lants represented only a small portion of all CFC use.
In 1987 representatives from many countries met in
Montreal to sign the Montreal Protocol, an agreement
that originally stipulated a 50 percent reduction of CFC
production by 1998. Despite this effort, stratospheric
ozone c ontinued to thin over the heavily populated mid-
latitudes of the Northern Hemisphere, and the Montreal
Protocol was modified to include even stricter limits on
CFC production.
Industrial companies that manufacture CFCs quickly
developed substitutes, such as hydrofluorocarbons (HFCs)
and hydrochlorofluorocarbons (HCFCs). HFCs do not
attack ozone, although they are potent greenhouse
gases. HCFCs attack ozone but are less destructive than
the chemicals they are replacing.that warm the troposphere also contribute to stratospheric
cooling, presumably because heat trapped in the troposphere
is not available to warm the stratosphere. The stratospheric
temperature has been dropping for the past several years, and
these lower temperatures provide better conditions for ozone-
depleting chemicals to attack stratospheric ozone. Record ozone
holes over Antarctica are attributed to cooler stratospheric
temperatures. Some scientists speculate that if the cooling
trend in the stratosphere continues, recovery of the ozone layer
may be delayed. This means climate warming could prolong
ozone depletion in the stratosphere despite the success of the
Montreal Protocol.
Scientists now know environmental problems can’t be
studied as separate issues because they often interact in
surprisingly subtle ways. As global climate change, ozone
depletion, and acid deposition are studied further, it is likely that
other interactions will be discovered.Most environmental studies examine a single issue, such as
acid deposition, global climate change, or ozone depletion.
In the past few years, however, some researchers have been
exploring the interactions of all three problems simultaneously.
One study of such interactions found that North American
lakes may be more susceptible to damage from UV radiation
than the thinning of the ozone hole would indicate. The reason:
Organic matter in the lakes, which absorbs some UV radiation
and protects the lakes’ plant and fish life, is affected by acid
deposition and global climate change. Acid deposition reacts
with organic matter in lakes, causing it to settle to the lake
floor, where it does not absorb as much of the UV radiation
as it once did. And a warmer climate increases evaporation,
which reduces the amount of organic matter washed into
lakes by streams.
Several studies report a link between human-caused
climate warming and polar ozone depletion. Greenhouse gases
EnviroDiscovery
Links Between Climate and Atmospheric Change