Environmental Engineering Reference
In-Depth Information
surface. The net effect would be to drive
temperatures down. Since none of this could be
measured directly, estimates were based on the
results of a series of mathematical simulation
models.
According to the TTAPS baseline scenario, a
5,000 megatonne nuclear war would inject 960
million tonnes of dust into the atmosphere (1
megatonne is equivalent to 1 million tonnes of
TNT). Eighty per cent would reach the
stratosphere, and remain there for more than a
year. This dust veil would be augmented by as
much as 225 million tonnes of smoke, produced
over a period of several weeks by the massive fires
ignited by the initial explosions. Incorporated
into the atmospheric circulation, the dust and
smoke would first spread over the northern
hemisphere—where it was assumed most of the
nuclear explosions would take place—before
being carried into the southern hemisphere,
eventually to blanket the entire globe.
The net result of this massive increase in
atmospheric turbidity would be the reduction of
incoming solar radiation by as much as 95 per
cent, causing an average land surface cooling of
10-20°C and maximum cooling of up to 35°C
in the the interior of the continents in a matter
of weeks. The temperature reductions over the
oceans and in coastal areas would be perhaps
only 1-3°C because the cooling would be offset
by the great heat capacity of the oceans. The
juxtaposition of these relatively mild conditions
with the cold over the land masses would create
strong horizontal temperature and pressure
gradients and lead to severe coastal storms.
Changes in the vertical temperature structure of
the atmosphere, induced by the absorption of
large amounts of solar energy in the upper
atmosphere, would also contribute to a much
modified global circulation. It was estimated that
recovery from all of these changes would take
more than a year. The potential environmental
impact of gases such as CO
2
and NO
X
, released
into the atmosphere along with the particulate
matter, was recognized, and the biological
consequences of nuclear winter were noted, but
neither was elaborated.
The TTAPS hypothesis elicited a strong
response from the scientific community. The
assumptions underlying the estimated endurance
and intensity of the smoke and dust clouds were
strongly criticized, for example, and the
magnitude of the postulated temperature decline
was regarded as questionable (see e.g. Maddox
1984; Singer 1984). Much of this initial criticism
merely detailed perceived flaws in the study itself,
and did little to develop the concept or to
invalidate it (Teller 1984).
Other investigators examined the mechanics
of the study, and replaced its simplistic one-
dimensional atmospheric model with two- and
three-dimensional versions. The state-of-the-art,
3-D, general circulation models (GCMs)
ultimately used included a greater number of
variables and finer geographic resolution than
the TTAPS model, and incorporated earth/
atmosphere feedback loops. In general they
indicated that planetary cooling would be much
less than postulated in the TTAPS scenario, and
it was suggested that the cooling following a
nuclear war would be more appropriately
referred to as 'nuclear autumn' (or 'nuclear fall')
than nuclear winter (Thompson and Schneider
1986).
The environmental consequences of nuclear
war (ENUWAR) received little attention in the
TTAPS scenario, but a contemporary study by a
group of life scientists indicated that the net effect
of a large scale nuclear war would be the global
disruption of the biosphere, and the disruption
of the biological support systems of civilization
(Ehrlich
et al.
1983) (see Figure 5.11). The
severity of the impact has been mitigated in line
with the successive modifications of the nuclear
winter hypothesis, but the situation is still
considered serious. The report of the Scientific
Committee on Problems of the Environment
(SCOPE) concerning the ecological and
agricultural impact of nuclear war (Harwell and
Hutchinson 1985) sponsored by the International
Council of Scientific Unions (ICSU) identified
indirect biological effects as a major threat to
society, and subsequent studies by the SCOPE-
ENUWAR researchers have confirmed this
