Environmental Engineering Reference
In-Depth Information
them—which will help in the creation of disaster
prevention programmes (Climate Institute
1992b).
Even in those areas not completely inundated,
the relationship between sea level and regional
hydrology would allow the effects to be felt some
distance inland in the form of altered streamflow
patterns and groundwater levels. In time, the
impact of higher temperatures on the rate of
ablation of ice caps and sea ice in polar regions
might be sufficient to cause a rise in mean sea
level of between 3 and 4 m (Hoffman
et al.
1983).
Should this ever come to pass, most of the world's
major ports would not survive without extensive
and costly protection.
This disruption of commercial activities by
rising sea-level in coastal regions is only one of a
series of economic impacts which would
accompany global warming. Others range from
changes in energy use, particularly for space
heating, to the development of entirely new
patterns of recreational activity. Because of its
northern location, Canada is especially
susceptible to such changes, and as a result
Environment Canada has invested a great deal
of time and effort in viewing the greenhouse effect
from a Canadian perspective (see Figure 7.12).
The results of the studies, although specific to
Canada, may also give an indication of future
developments in other northern regions such as
Scandinavia and Russia (Kemp 1991).
that this imposes on the results have long been a
source of criticism. One of the earliest and most
vociferous critics of the theoretical modelling
approach was Sherwood Idso, who attacked the
established view of future global warming
through numerous publications (e.g. Idso 1980,
1981, 1982, 1987). He suggested that increasing
CO
2
levels would produce negligible warming,
and might even cause global cooling. His
conclusions were based on so-called natural
experiments in which he monitored temperature
change and radiative heat flow during natural
events—such as dust storms, for example. From
these he estimated the temperature change
produced by a given change in radiation. Since
the effects of increasing CO
2
levels are felt
through the disruption of the radiative heat flow
in the atmosphere, it was therefore possible to
estimate the temperature change that would be
produced by a specific increase in CO
2
. Initially,
Idso (1980) suggested that the effect of a
doubling of atmospheric CO
2
would be less than
half that estimated from the models. Later he
concluded that increasing CO
2
levels might
actually cause cooling (Idso 1983). Idso received
some support for his views (e.g. Gribbin 1982;
Wittwer 1984), but for the most part, his ideas
were soundly criticized by the modelling
community, sometimes in damning terms (NRC
1982, Cess and Potter 1984). Although they
initiated an intense—and sometimes
acrimonious—debate on the methods of
estimating climate change, in the long term Idso's
natural experiments did little to slow the growing
trend towards the use of GCMs. However, even
with the growing sophistication of the models,
those who used them were often the first to note
their limitations (e.g. Rowntree 1990), and many
of the criticisms of the estimated impact of
elevated CO
2
levels have arisen out of the
perceived inadequacies of the models used (Kerr
1989).
Many of the problems associated with GCMs
arise from their inability to deal adequately with
elements that are integral to the functioning of
the earth/atmosphere system. The roles of clouds
and oceans in global warming are poorly
Alternative points of view and the problems
of GCMs
The global warming scenario, in which a
doubling of atmospheric CO
2
would cause a
temperature increase of 1.3-4.5°C, is widely
accepted. This consensus has evolved from the
results of many experiments with theoretical
climate models which indicate the considerable
potential for change in the earth/atmosphere
system as concentrations of atmospheric
greenhouse gases increase. Even the most
sophisticated General Circulation Models
(GCMs) cannot represent the working of the
atmosphere exactly, however, and the limitations
