Environmental Engineering Reference
In-Depth Information
has already reached the decision-making stage,
whereas in the study of global warming the
technical aspects of the issue—such as the
establishment of the nature, extent and timing
of the warming—continue to receive much of the
attention. This may reflect the relative complexity
of the two issues. Controlling CFCs is relatively
easy, for example, because their uses are limited,
the small number of producers can be easily
identified and production can be monitored.
Substitutes for many CFCs have been developed
quite easily. In contrast, greenhouse gas
production is widespread, with a mixture of
natural and anthropogenic sources which are
difficult to monitor with any accuracy. The size
and complexity of the problem is such that there
has been little development of replacements for
the products and processes releasing greenhouse
gases. The greater progress in dealing with
thinning ozone is also an indication of the
different ways in which the problems are
perceived. Of the two, ozone depletion is usually
seen as having the most serious consequences.
The discovery of the Antarctic ozone hole was
followed closely by the initiation of international
efforts to save the ozone layer, which gained
momentum with every new report of ozone
depletion.
The Vienna Convention on the Protection of
the Ozone Layer, which emerged from a 1985
conference, was followed in 1987 by the
Montreal Protocol. Signatories to the Protocol
agreed to reduce production of CFCs by 50 per
cent (of 1986 values) by 2000. The concluding
statement of the World Conference on the
Changing Atmosphere, held in Toronto, Canada
in mid-1988, also included reference to CFCs. It
called for them to be phased out by the year 2000,
and, later that year, delegates at the World
Conference on Climate and Development in
Hamburg, Germany recommended a global ban
on the production and use of CFCs by 1995. In
March 1989, the members of the European
Community agreed to eliminate production and
use of ozone-destroying chemicals by the end of
the century. The US government endorsed the
effort, but stressed the importance of finding safe
substitutes for CFCs. In Australia in 1989, the
government passed the Ozone Protection Act
which, with supplementary regulations, was
aimed at eliminating CFC and halon use by 1994.
At about the same time, major, government-
sponsored conferences in London and Paris
provided international support for a worldwide
ban on CFCs and other environmentally harmful
chemicals. Subsequent meetings have confirmed
the willingness of the nations of the world to deal
with the issue, and the second half of the 1990s
will see the progressive elimination of CFCs and
other ozone-destroying compounds. There is
already evidence of a decrease in the growth rate
of atmospheric halons (Butler
et al.
1992) and
certain CFCs (Elkins
et al.
1993). The growth of
CFC-11 and CFC-12 is slowing, for example, and
if this continues as expected, the volume of these
gases in the atmosphere will reach a peak by the
end of the century, and then begin to decline.
Even with such developments, the ozone layer
will take time to recover, and levels of UV-B rays
reaching the earth's surface will remain high. In
October 1993, for example, the US National
Oceanic and Atmospheric Administration
announced that the amount of ozone in the
atmosphere above Antarctica had reached a
record low, being virtually absent between 13.5
km and 18 km above the surface. Announcements
such as this apparently confirming the progressive
thinning of the ozone, have prompted
government agencies from as far apart as
Australia and Canada to issue warnings about
exposure to excess ultraviolet radiation, and these
warnings are currently among the most obvious
manifestations of the ozone problem.
Like ozone depletion, global warming has been
the subject of a large number of conferences and
workshops—from Villach in 1985, where the
original investigative framework was set up, to
Rio in 1992, where it was considered as a major
element in the broader study of global change.
The net effect has been the accumulation of a
considerable body of knowledge on all aspects
of global warming, and a recently published
annotated bibliography lists several hundred
publications on the topic (Handel and Risbey
