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25 What is being done about ozone depletion?




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This article is from the Ozone Depletion FAQ, by Robert Parson rparson@spot.colorado.edu with numerous contributions by others.

25 What is being done about ozone depletion?

The 1987 Montreal Protocol (full text available on the world-wide web at
http://www.unep.org/unep/secretar/ozone/treaties.htm) specified that
CFC emissions should be reduced by 50% by the year 2000 (they had
been _increasing_ by 3% per year.) This agreement was amended in
London in 1990, to state that production of CFC's, CCl4, and halons
should cease entirely by the year 2000. Restrictions were also applied
applied to other Cl sources such as methylchloroform. (The details of
the protocols are complicated, involving different schedules for different
compounds, delays for developing nations, etc.) The phase-out schedule
was accelerated by four years by the 1992 Copenhagen agreements. A great
deal of effort has been devoted to recovering and recycling CFC's that are
currently being used in closed-cycle systems.

For more information about legal and policy issues, see the books by
[Benedick] and [Litvin], and the following web sites:

http://www.unep.org/unep/secretar/ozone/home.htm
http://www.unep.ch/ozone/ (European mirror site for above)
http://www.epa.gov/docs/ozone/index.html
http://www.ciesin.org/TG/OZ/ozpolic.html

Recent NOAA measurements [Elkins et al. 1993] [Montzka et al. 1996]
show that the _rate of increase_ of halocarbon concentrations in the
atmosphere has decreased markedly since 1987. It appears that the
Protocols are being observed. Under these conditions total stratospheric
chlorine is predicted to peak at 3.8 ppbv in the year 1998, 0.2 ppbv above
1994 levels, and to slowly decline thereafter. [WMO 1994] Extrapolation of
current trends suggests that the maximum ozone losses will be [WMO 1994]:

Northern Mid-latitudes in winter/Spring: 12-13% below late 1960's levels,
~2.5% below current levels.
Northern mid-latitudes in summer/fall: 6-7% below late 1960's levels,
~1.5% below current levels.
Southern mid-latitudes, year-round: ~ 11% below late 1960's levels,
~2.5% below current levels.

Very little depletion has been seen in the tropics and little is
expected there. After the year 2000, the ozone layer will slowly
recover over a period of 50 years or so. The antarctic ozone hole
is expected to last until about 2045. [WMO 1991,1994]
Some scientists are investigating ways to replenish stratospheric
ozone, either by removing CFC's from the troposphere or by tying up
the chlorine in inactive compounds. This is discussed in Part III.

 

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