Environmental Engineering Reference
In-Depth Information
make no attempt to estimate changing conditions
during the transient phase of the model run,
although these conditions may well have
important environmental impacts long before
equilibrium is reached. The development of
transient or time-dependent models which would
provide the interim information currently lags
behind that of the equilibrium models. The few
existing transient models are of coarse resolution,
but yield results which are broadly consistent
with those from the more common equilibrium
models (Bretherton et al. 1990). They incorporate
a coupled ocean-atmosphere system with full
ocean dynamics, and require increased computer
power and improved ocean observation data,
before they can make a greater contribution to
the study of future climate change.
Despite the increasing complexity of current
GCMs, the fact remains that like all models they
represent a compromise between the complexities
of the earth/atmosphere system and the
constraints imposed by such factors as data
availability, computer size and speed and the cost
of model development and operation, which limit
the accuracy of the final result. The quality of
specific simulations can be tested by comparing
model predictions with the results obtained by
direct measurement or observation. This
approach shows, for example, that GCMs can
simulate short-term changes such as seasonal
cycles remarkably well (Schneider 1987), and
their portrayal of atmospheric responses to sea
surface temperature anomalies is usually
considered as satisfactory. Simulations of
Holocene climates, which provide an indication
of the long-term capabilities of the models, have
given results supported by palaeo-environmental
indicators, such as fossil pollen distribution and
former lake levels, revealed in lake and ocean
sediment cores (Gates et al. 1990). These tests
indicate that most simulations can represent the
large scale characteristics of climate quite well,
but significant errors remain at regional scales
as a result of the coarse resolution common to
most models. The accuracy of coupled models is
also restricted by inadequate data on which to
base the oceanic component. More powerful
computers and improved parameterization will
take care of some of these problems, but the
general consensus is that the gap between climate
simulation and reality will remain for some time
to come.
SUMMARY
Changes in such elements as the composition of
the atmosphere, global circulation patterns and
the earth's energy budget are now widely
recognized as components of most current global
environmental issues. The relationships involved
are complex, and remain imperfectly understood
despite major advances in the acquisition and
analysis of atmospheric data. Global climate
models have been developed to investigate the
processes further, and provide forecasts of future
developments. These investigations and forecasts
will allow a more effective response to the
changes with the ultimate aim of minimizing their
environmental impact.
SUGGESTIONS FOR FURTHER READING
Ahrens, C.D. (1993) Essentials of Meteorology,
Minneapolis/St Paul: West Publishing
Company.
Barry, R.G. and Chorley, R.J. (1992)
Atmosphere, Weather and Climate, London:
Routledge.
Briggs, D., Smithson, P. and Ball, T. (1993)
Fundamentals of Physical Geography,
Mississauga, Ontario: Copp Clark Pitman.
Hidore, J.J. and Oliver, J.E. (1993) Climatology:
An Atmospheric Science, New York:
Macmillan.
Levenson, T. (1989) Ice Time: Climate, Science
and Life on Earth, New York: Harper and
Row.
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