Visions of climate catastrophe drew upon a widespread fear that
nuclear war could wreck the global environment. Scientific calculations,
publicized in 1983, suggested that the bombs could pollute the air with
enough dust and chemical smog to severely cool the planet a "nuclear
winter." The lesson about the atmosphere's fragility was meanwhile
reinforced by evidence that such a climate catastrophe had actually happened
long ago. Something, perhaps a single asteroid-bomb, had caused an atmospheric change that exterminated the dinosaurs.
| In the 1950s, as the world's arsenals filled with hydrogen bombs,
people worried about how a thermonuclear war might injure the entire
global environment. Poignant novels and movies showed radioactive
dust, borne on the winds, extinguishing all life on Earth.(1*) Experts dismissed the scenarios as impossible.
But secret studies supported by the U.S. military suggested that a
war's effects on the atmosphere could be quite serious. In an openly
published, but little noticed, 1958 review of climatology, a leading
expert wrote that a nuclear war could throw up enough dust to alter
the climate for a few years. The U.S.Weather Bureau had gone farther
in an unpublicized 1956 study, saying it was conceivable that enough
dust might be thrown into the stratosphere to launch a new 'ice age."
In the 1960s a few scientists tried to publicize the threat. The public
scarcely noticed it, amid countless apocalyptic warnings about how
nuclear weapons could bring the end of civilization or even all life
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|Most experts agreed
that the effects of a nuclear war on climate deserved little attention.
A National Academy of Sciences panel that reviewed the issue in 1975
concluded that a war could kick up as much dust and smoke as a large
volcanic eruption. Scientists suspected that such eruptions in the
past had cooled the Earth a degree or so for a year or two. Moreover,
recent spacecraft observations of Mars had showed that a planet-wide
dust storm could severely cool the climate, and in a self-sustaining
way. Still, the authors concluded that the effects "would probably
lie within normal global climatic variability," and it seemed like
a minor problem next to the other horrors of a nuclear war. The panel
also pointed out that the nitrogen compounds (NOx)
created by the fireballs could sharply reduce the Earth's ozone layer,
but again the damage would be only temporary. The authors did admit
that little was known about climate, so that "the possibility of climatic
changes of a more dramatic nature cannot be ruled out." A few scientists
criticized the report for brushing aside possible calamities. Some
pointed to the vast firestorms that a war could ignite, exclaiming
that might pollute the atmosphere so severely as to "force Homo
sapiens into extinction."(3) These scientists were in tune with a public
attitude that grew strong during the 1960s and 1970s. For the first
time, many people found it plausible that we could bring about an
atmospheric catastrophe so terrible that it would destroy the human
Full discussion in
<=Venus & Mars
| This commonly held attitude may have helped
scientists to admit into their thinking a new answer to an old puzzle.
Geologist Walter Alvarez and his physicist father, Luis Alvarez, proposed
that the fall of a huge asteroid had caused the extinction of the
dinosaurs some 65 million years ago. They figured that the dust thrown
into the air by an impact could have obscured sunlight long enough
to kill much of the Earth's plant life through simple darkness, so
that the dinosaurs perished of starvation. Stephen Schneider recalled
that when he heard Luis Alvarez explain the new idea in a 1979 lecture,
"I commented from the floor that such a cloud could have climatic
effects, particularly a sharp, but short-term climatic cooling on
land." Schneider was just then involved in studies that emphasized
how smoke, smog, and other aerosols could cool the atmosphere and
perhaps even precipitate an ice age. Calculations soon confirmed that
an asteroid strike could indeed have brought on a global cooling severe
enough to kill off the dinosaurs directly.(4)
| Other scientists scoffed at the idea, especially geologists and
paleontologists who stuck to their old theories about dinosaurs. These
theories, however, failed to fit observations of world-wide peculiarities
preserved in rock layers 65 million years old. Some geologists proposed
that the damage to the atmosphere had been caused not by an asteroid strike, but by carbon dioxide (CO2) and poisonous gases from a "paroxysmal" spate of enormous volcanic eruptions. There was evidence of just
such a volcanic outpouring at about the right time. Either way, the
killer had been a shocking atmospheric change.(5)
|The dinosaur-extinction debate became passionate, sometimes personal
and embittered, carrying forward a tradition of geological controversy
that stretched back to the 18th century. On one side had been traditional
"catastrophists," whose historical roots connected them with Bible
fundamentalists and Noah's Flood. They had argued ardently that
vast cataclysms in the past had suddenly extinguished entire sets
of species. By the late 19th century these views had been driven
from the field of professional scientific discussion by the views
of so-called "uniformitarians" (a more precise term would have been
"gradualists.") These scientists had amassed convincing evidence
that evolution acted over millions of years, responding to the slow
rise of mountain chains or the parting of continents.
|By 1980, however,
some paleontologists were beginning to be persuaded that species
could evolve in a "punctuated" pattern. In short, the catastrophist
viewpoint was raising its head again. Anyway that was how the opponents
caricatured the movement; the actual scientific arguments
were of course more complex.(6) Underneath the science,
what mattered was a picture in which dinosaurs did not decline gradually
over eons, but fell in their prime, struck down swiftly by a random doom.
(It remained uncertain how much was due to the asteroid strike and how much to volcanoes; meanwhile geologists moved on to investigating the other great extinctions in the geological record, all of which turned out to be caused by climate catastrophes.) The
unspoken and repugnant implication was that a spoiled atmospheric
could extinguish entire species — maybe even our own.
| The most likely way that could happen was
through nuclear war. The effect of bombs on climate had been taken
up again in 1981 by Paul Crutzen. A Dutch scientist interested in
aerosols, Crutzen had helped set off the stratospheric transport controversy
of the early 1970s (described here)
by showing how airplane emissions could destroy ozone. After working
at the Air Quality Division of the U.S. National Center for Atmospheric
Research, he was now employed in Germany. Crutzen had recently been
in Brazil, collecting samples of smoke to check the contentious claim
that slash-and-burn destruction of forests was a major source of atmospheric
CO2. Reviewing the 1975 National Academy report,
Crutzen worried that the study group had focused on dust without taking
full account of how much smoke, NOx,
and other smog could arise from the firestorms of industrial centers
and forests torched by bombs. People had known for many decades that
the smoke from great forest fires could dim the sunlight thousands
of miles downwind. Crutzen concluded that nuclear war, much like the
Alvarez asteroid, could send the world into a frozen twilight.(7)
| Atmospheric scientists were well-placed to
take up the question of smoke from a nuclear war. Measurements like
Crutzen's of the effects of soot and the like had greatly advanced
since the 1975 study. Richard Turco and others, working on the dinosaur
extinction problem, had developed a computer model of a haze-filled
atmosphere, and it had occurred to them that dust lofted by the explosions
of a nuclear world war might have effects comparable to the dust from
an asteroid impact. Meanwhile the surprising observation that a giant
dust storm was cooling the atmosphere of Mars had inspired two more
scientists, James Pollack and Brian Toon, into new calculations of
dust effects. This led them into work with Carl Sagan on how the aerosols
emitted by volcanic eruptions could affect climate. Now these scattered
scientists joined forces to calculate the consequences of an exchange
of hydrogen bombs. Their ominous conclusion was that the sooty smoke
from burning cities could bring on a "nuclear winter" months
or even years of cold so severe it would gravely endanger living creatures.(8)
| The scientists did this work mainly for public consumption. When they announced
their results in 1983, it was with the explicit aim of promoting international
arms control. Surely the likelihood that all-out nuclear war was literally suicidal, even if the other side did not retaliate, would persuade nations to reduce their arsenals? As a side
effect, the studies helped to improve scientific understanding of
how aerosols could affect climate.(9)
| The computer models were so simplified, and the data on smoke and
other aerosols were still so poor, that the scientists could say nothing
for certain. Critics, mostly people opposed to nuclear disarmament,
quickly pointed out the deficiencies. In the mid 1980s, detailed studies
confirmed that a nuclear war would probably alter global climate temporarily.
But as Schneider and a coauthor explained in a widely read article,
it was not likely to bring an apocalyptic winter, although it would bring a damaging
"nuclear fall." (According to more recent research, smoke following even a limited, regional war would probably dim sunlight enough to kill many more people through starvation than would die directly under the bombs.)(10)
The vociferous dispute over nuclear winter (along with dinosaur extinction) made scientists and the public more sensitive to the idea that stuff we emitted into the air could provoke a severe climate change. An asteroid strike, however, told us little about greenhouse warming. The controversy did provoke studies by geologists who would eventually show that the other great extinctions of the past, some even worse than the doom of the dinosaurs, had been caused by massive injections of greenhouse gases from volcanic outbursts — an all too relevant demonstration of the power of the gases.
|The nuclear winter warnings probably influenced some government policy-makers, but only some. Most people already believed that nuclear war was too horrible to consider as
an actual option. Others, who did think it was possible to "win"
a nuclear war, scoffed at the shaky science and strident polemics
of nuclear apocalypse. It was an old debate in nuclear policy, but
remarkably similar to another debate that was just then getting underway:
how should we address global warming from the greenhouse effect?
|In 1939 the physicists Leo Szilard and Enrico Fermi had
joined forces to see if they could create a chain reaction that
would release the nuclear power in uranium. "Fermi thought
the conservative thing was to play down the possibility," Szilard
later recalled, "...and I thought the conservative thing was
to assume that it would happen and take the necessary precautions."
As the historian Lawrence Badash remarks, "Fermi was thinking
of a scientific phenomenon, while Szilard had progressed to the
political consequences." The same divergence on what it means
to be "conservative" permeated the debate about controlling
greenhouse gases. As with nuclear winter, so with global warming,
scientists were estimating the size of the problem by using
computer models, standing on a pile of uncertain assumptions. As
with nuclear winter, so with global warming, many people thought
it would be foolish to introduce radically new policies just because
a bunch of scientists had come up with a hypothesis as unlikely-sounding
as anything in science fiction. Only a few scientists were prepared
to reply that the scientific uncertainty itself was an
argument for action. As Sagan said in reference to nuclear war,
injuring the atmosphere was "an experiment that can be performed
once, at most."(11)
The Public and Climate (2)
1. Weart (1988), chap.
12. Warning of a "Fimbulwinter" caused specifically by dust
that blocked sunlight appeared on p. 68 of Poul Anderson and F.N.Waldrop,
"Tomorrow’s Children," Astounding Science-Fiction,
March 1947, pp. 59-79, reprinted as first part of Poul Anderson, Twilight
World (NY: Torquil, 1961), according to Bartter
(1988), pp. 220-21. On nuclear winter see also Masco (2010); Hamblin (2013), pp. 237-41. BACK
2. Landsberg (1958); for classified studies in the 1950s and 1960s see Dörries (2011), pp. 202-05; Badash (2009), pp. 24-25; Hecht
and Tirpak (1995), p. 375. Weather Bureau study: Hewlett
and Holl (1989), p. 369, referencing Atomic Energy Commission, Division
of Biology and Medicine, "Summary Discussion of Effects on Humans,
Agricultural Products, and Weather of a Projected Nuclear War," Oct.
9, 1956 (Washington, DC: AEC). Warnings: Lapp (1962),
pp. 102-103; Commoner (1966), pp. 76-77, referencing
Hudson Institute, "Special Aspects of Environment Resulting from
Various Kinds of Nuclear Wars," Part II, H1303-RR, Jan. 8, 1964 (Harmon-on-Hudson,
NY: Hudson Institute); Ehrlich and Ehrlich (1970),
p. 192, speculating about smoke as well as dust. On nuclear apocalypse
see Weart (1988).
3. National Academy of Sciences
(1975), quotes p. 7; criticism, extinction: Ehrlich
et al. (1977), pp. 690-91. Ozone effects were announced in 1974, see
New York Times, Sept. 6, 1974, p. 1; Nov. 12, 1974, p. 38. See also Dörries (2011) for developments to 1983.
4. Schneider and Londer (1984),
p. 205n; Alvarez et al. (1980); cooling of up to 40°C for
up to a year over continents was calculated by Pollack et al.
5. McLean (1981); McLean (1985); Officer et al.
(1987) ("paroxysmal" in their title); for the controversy, see Glen (1994); for a general discussion of issues, Palmer (1999); for a short summary, Huggett (1990), pp. 171-78.
6. Huggett (1990); Palmer (1999).
7. Crutzen and Birks (1982); on
the history, see Levenson (1989), pp. 214-18; Davidson (1999), pp. 360-71.
8. A one-dimensional radiative-convective model.
Turco et al. (1983). The paper is known as TTAPS from the
initials of Turco, Toon, Thomas P. Ackerman (who collaborated with Toon),
Pollack and Sagan. For full details see Badash
(2009). The biological consequences were discussed by Ehrlich
et al. (1983), a paper whose prestigious authors included Carl Sagan,
George Woodwell, Stephen J. Gould, Ernst Mayr, etc. BACK
9. Poundstone (1999), pp.
292-319; Badash (2001).
10. Thompson and Schneider
(1986). See Sagan and Turco (1990); Schneider (2009), pp. 95-108. Recent work: Toon et al. (2008); Robock and Toon (2010) includes references to scientific papers.
11 Szilard, Sagan quoted by Badash
(2009) pp. 303, 61. BACK
© 2003-2018 Spencer Weart & American Institute of Physics