Thursday, July 20, 2017


Three years ago Carl Sagan and a few other scientists proposed a new theory of Armageddon. 

They called it "nuclear winter,"and their message was chilling.

The end  of  the  world,  they  said, would come not by fire during a nuclear attack but by ice afterward

After a nuclear war, the Earth would become encircled with smoke, dark, and cold. No one could  expect to survive the frost, not the innocent New Zealanders or the remotest tribes of  Africa. Even a small atomic  war  could  end  human  life , Sagan  concluded  in  the  Winter 1983-84  issue of Foreign Affairs  that  all  nuclear weapons should  be eliminated, or at least 99 percent of them.

This insight did not come from a rereading of the book of Revelation, It rested on modern physics and a very sophisticated computer program. It had the glint of hard science. 

Sagan, who is an expert on the solar system and an adviser to NASA on the Voyager space probe, may be America's most famous popularizer of science.  In  1983  several  other  scientists,  including  biologist  Paul Ehrlich  of  Stanford,  joined  Sagan  to  endorse  the view  that  nuclear weapons  were  a  threat to  the  human species, quite  apart  from the obvious threat to civilized life north of the equator.  They launched a media blitz that included heavy technical articles, political essays, and TV interviews.  It  still  reverberates  through  literature.

The message was always the same:
 scientific analysis "proves" that nuclear
weapons are useless. To employ them is
to commit global suicide. Even owning
them is dangerous because it increases
The best thing to do is to get rid of them.
This message came nine months after 
Reagan's "Star Wars" speech,  matching
his technician's dream  with a technician's 
nightmare of equal force.

The nuclear winter theorists wanted
publicity back then, and they got it.
But now the situation has changed.
The death-by-ice theory seems moribund,
riddled with problems, and of diminishing
relevance to strategic policy. The same can
be said of  Reagan's idea  of  using  space 
weapons to protect cities.

The main technical challenge to nuclear
winter comes from Stephen Schneider
and Starley Thompson, researchers at
the National Center for Atmospheric 
Research in Boulder, Colorado. They agree
with Sagan that the number of nuclear
weapons should be reduced, but they
say the integrity of atmospheric science
should not be sacrificed to make that

Schneider claims that it has been
clear for perhaps two years that Sagan's
original description of nuclear winter is
not the most accurate. But coaxing has
not brought any acknowledgment that
this is so. Sagan said recently that he
found "nothing new" in a state-of-theart
computer analysis by Schneider and
Thompson to change his view of

Schneider and Thompson laid out
their doubts in a Foreign Affairs article last
summer, reporting that the chance of
human extinction after a nuclear war is
"vanishingly low," They find no risk of
a new ice age. Some open, dry areas in
the war latitudes might undergo temporary
"quick freezes," But, on average,
the temperature drop in the Northern
Hemisphere would not be worse than 12
degrees during the first week or so after
an attack.

At a private gathering of experts at the
National Academy of Sciences in January,
it became clear that this new mild
version of "nuclear autumn" is credible
and may even overstate the temperature
drop. This does not mean the climatic
impacts of war would be mild, Schneider
and Thompson say that rice and soybeans
are sensitive to small temperature
changes and that global rainfall patterns
might be disrupted. Millions (billions?)
might starve. But there would be no ice
in the tropics; that is certain. Schneider
says: "Carl's idea was brilliant. He proposed
an invasion from Mars," It just
didn't hold up under scrutiny.

The more apocalyptic version of nuclear
winter has become a part of the
anti-weapons dogma of the 1980s, As a
result, some people may be reluctant to
let it go. Others will delight in its agonies...

Although Schneider's milder scenario
has more credibility today, the technical
argument has a long way to run.

This is because the Pentagon has been
cajoled into taking nuclear winter seriously.
The Defense and Energy Departments
have increased research on nuclear winter
from around $300,000 a few years ago
to around $5.5 million now. It is embedded
in the budget. The amount is nothing like 
the $5 billion spent on the other millennial
fancy of  the 1980s, "Star Wars," and not
enough—the vested researchers  say—to
provide definitive answers to the questions
Sagan has raised.

But even without definitive answers,
it may be time to say goodbye to nuclear
winter as a policy issue. If Schneider and
Thompson are right, and atmospheric
scientists seem to think they are, the climatic
impact is just one of a dozen "secondary
effects" of nuclear war that would make 
life hardly worth living.

The main policy debate will continue to
focus on the "primary" effect: the use of
weapons. In this sense, nuclear winter
was a diversion, providing little insight
on how to cooperate on arms reductions,
an area rife with distrust.

The freeze movement may have gained
a tactical victory through the promotion
of nuclear winter. It helped get attention.
But the advantage appears to have been
short-lived. Now, as the computer termites
gnaw at the data, the structure creaks and
totters. Soon it may be gone.

Perhaps if we are lucky, 1987 will bring
the final debunking of two great science
fictions of the Reagan era: nuclear winter
and Star Wars.

Thanks to Eliot Marshall for  providing the pdf from which this was excerpted- 
Copyright 1987 , The New Republic

Some of the true believers are still  re-running the TTAPS models parameters and deny that anything much went wrong :