Bombs directed at missile silos would burst at ground level and throw a
huge amount of dust into the atmosphere, as the explosion of a volcano
does.  It is as much as a million tonnes from a large nuclear bomb
bursting at ground level.

 Bombs bursting over cities and surface installations, like factories or
oil stores and refineries, would cause huge fires and fire-storms that
would send huge amounts of smoke into the air.

 The 1980's research showed that the dust and the smoke would block out
a large fraction of the sunlight and the sun's heat from the earth's
surface, so it would be dark and cold like an arctic winter.  It would
take months for the sunlight to get back to near normal.

 The cloud of dust and smoke would circle the northern hemisphere
quickly.  Soon it could affect the tropics, and cold would bring
absolute disaster for all crops there.  Quite likely it would cross the
equator and affect the southern hemisphere to a smaller degree.

 While the temperature at the surface would be low, the temperature of
the upper part of the troposphere (5-11 km) would rise because of
sunlight absorbed by the smoke, so there would be an absolutely massive
temperature inversion.  That would keep many other products of
combustion down at the levels people breathe, making a smog such as has
never been seen before.  PYROTOXINS is a word coined for all the noxious
vapours that would be formed by combustion of the plastics, rubber,
petroleum, and other products of civilization.  It is certain that these
poisons would be formed, but we do not have quantitative estimates.  The
amount of combustible material is enormous, and it would produce
dioxins, furans, PCB's, cyanides, sulphuric and sulphurous acids, oxides
of nitrogen, carbon monoxide and carbon dioxide in amounts that would
make current concerns about atmospheric pollution seem utterly trivial.
There would also be toxic chemicals like ammonia and chlorine from
damaged storage tanks.

 Another bad environmental thing that would happen is destruction of the
ozone layer.  The reduction in the ozone layer could be 50% - 70% over
the whole northern hemisphere - very much worse than the current losses
that we are properly concerned about.  Nitrogen oxides are major
chemical agents for this.  They are formed by combination of the oxygen
and nitrogen of the air in any big fire and around nuclear explosions,
as they are on a smaller scale around lightning flashes.  So after the
smoke cleared and the sun began to shine again, there would be a large
increase of UV reaching the earth's surface.  This is bad for people in
several ways, but don't worry about the skin cancers ? not many of the
survivors would live long enough for that to matter.  UV is also bad for
many other living things, notably plankton, which are the bottom layer
of the whole marine food chain.  There would likely be enough UV to
cause blindness in many animals.  Humans can protect their eyes if they
are aware of the danger.  Animals do not know to do that, and blind
animals do not survive.  Blind insects do not pollinate flowers, so
there is another reason why human crops and natural food supplies for
animals would fail.

 Altogether, nuclear winter would be an ecological disaster of the same
sort of magnitude as the major extinctions of species that  have
occurred in the past, the most famous one being 65 million years ago at
the cretaceous extinction.  Of all the species living at the time, about
half became extinct.  The theory is that a large meteor made a great
crater in the Gulf of California, putting a trillion tons of rock debris
into the atmosphere.  That is a thousand times as much rock as is
predicted for a nuclear war, but the soot from fires blocks sunlight
more effectively than rock debris.  In nuclear winter there would also
be radioactive contamination giving worldwide background radiation doses
many times larger than has ever happened during the 3 billion years of
evolution.  The radiation would notably worsen things for existing
species, though it might, by increasing mutations, allow quicker
evolution of new species (perhaps mainly insects and grasses) that could
tolerate the post-war conditions.  (I should just mention that there is
no way the radioactivity from a nuclear war could destroy "all life on
earth".  People must stop saying that.  There will be plenty of
evolution after a war, but it may not include us.)

*Governments did not like the idea of Nuclear Winter*

The prediction of nuclear winter was published by a group headed by
Carl Sagan in 1983.  The initials of their names were T-T-A-P-S, so the
paper and their book has become known as "t-taps".  It caused some alarm
in government circles in U.S.A. and NATO countries, not so much because
this further disaster would follow a nuclear war, but because of the
boost it gave to the Peace Movement.

 A number of studies were published in the next few years, including
major reports by The Swedish Academy of Sciences (Ambio), the
International Council of Scientific Unions (SCOPE), and the U.S.
National Research Council.

 There was a drive by government and the military establishment to
minimize the matter, and after a few years the media were talking about
"nuclear autumn".  (The most astonishing lies were propagated, e.g. that
Carl Sagan admitted that his publication was "a propaganda scam".)  It
was true that islands and coastal areas would have less severe
temperature drops than the original predictions, because of the
modifying effect of the ocean.  They would have violent storms instead,
because of the big temperature difference between land and water.

 In 1990 another paper was published by the T-TAPS group reviewing in
detail the later studies, and showing that some modifications to their
1983 paper were necessary.  Some of these were in the direction of more
severe changes, others towards milder changes.  The general picture was
little changed.  The book: "A Path Where No Man Thought" by Sagan and
Turco (one of the T's), also published in 1990, gives an account of
current conclusions for the serious non-specialist reader.  It gives
detailed descriptions of nuclear winters of different severity according
to how many weapons were used, and against what targets.  If oil
refineries and storage were the main targets, 100 bombs would be enough
to cause a nuclear winter, and the smallest sizes of nuclear bombs would
be effective in starting the fires.

*A new study needed*

Nuclear Winter seems to be a matter that the peace movement has largely
forgotten about, and the general public has completely forgotten about.
As far as I can find out, no new scientific study has been published on
the matter since 1990.  I feel sure we ought to be reminding the world
of it.  A new scientific study is surely warranted by now.  Computer
modelling is a main tool in atmospheric research, and the capacity of
computers available to university scientists and in government
laboratories has increased very much in the last 10 years; other
atmospheric research has not been dormant.  The advances need to be
applied.  If a new study happened to show that the aftermath of nuclear
war would *not* include severe changes in the weather and climate it
would be great news for the nuclear weapon establishments, and slightly
good news for those who are working for elimination of nuclear weapons,
but we should carry on just the same.  If, as seems more likely, the new
study largely confirmed the T-TAPS results it would strengthen our
position in dialogue and provide a focus for a publicity campaign to
re-awaken the voting public to the need to eliminate nuclear weapons,
and the urgent need to de-alert them.

 An important area where more information is needed is to show whether
spread of the cold is likely to affect the tropics.  A new study could
be expected to add valuable information.  Many developing countries have
such serious problems of violence, military spending, and sickness, that
we can hardly expect the activists there to spend much of their effort
in the necessary task of uniting the world to urge the nuclear weapons
states to eliminate their weapons.  If it were shown that frost is
likely to reach tropical latitudes in the event of a nuclear war in the
northern countries, scientists and governments in the tropics would know
it would be an ecological disaster for themselves.  Even a fall of
temperature to 10º Celsius destroys a rice crop.

 I should emphasize that this is not a question of preventing
"proliferation".  The weapons that pose the danger of nuclear winter are
the existing big arsenals.  It is these that need most urgently to be
eliminated.  A war between Pakistan and India with the arsenals they are
believed to have at present, or the use of the few weapons that a "rogue
state" might make clandestinely, would be a regional disaster of the
most terrible magnitude; but it would not cause nuclear winter.

 Efforts are being started to interest atmospheric scientists and to
solicit funding for a new study.

       Alan Phillips aphil@cujo2.icom.ca
       Oct. 2000.
========================================

References (in chronological order):

Peterson, Jeannie (ed)  "Aftermath: The Human & Ecological Consequences
of Nuclear War, Pantheon, New York, 1983 (Based on a special issue of
Ambio, Vol.II, nos 2,3, 1982.)

Turco, R.P., Toon, A.B., Ackerman, T.P., Pollack, J.B., Sagan,
C.[TTAPS], "Nuclear Winter: Global Consequences of Multiple Nuclear
Explosions", Science 222, 1983, 1283-1297.

Turco, R.P., Toon, A.B., Ackerman, T.P., Pollack, J.B., Sagan,
C.[TTAPS], "The Climatic Effects of Nuclear War", Scientific American,
Aug.1984.

U.S. National Research Council, "The Effects on the Atmosphere of a
Major Nuclear Exchange," 1985.

SCOPE (Scientific Committee on Problems of the Environment of the
International Council of Scientific Unions) Report #28, "Environmental
Effects of Nuclear War" v.1, 1986; v.2, 1985.

Turco, R.P., Toon, O.B., Ackerman, T.P., Pollack, J.B., Sagan, C.,
Science 247 (1990) 166-176.

Sagan and Turco in 1990: "A Path Where No Man Thought" (Random House,
1990: out of print but available at moderate cost from www.alibris.com).

Robock, Alan, 1996: Nuclear winter: in Encyclopedia of Weather and
Climate, vol. 2, edited by Stephen H. Schneider, (Oxford Univ. Press,
New York), 534-536. [This cites no work later than 1990.]