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OCR for page 185
APPENDIX:
Evolution of Knowledge About
Long-Term Nuclear Effects
The first nuclear explosion (the Trinity event)
near Alamogordo, New Mexico, on July 16, 1945. During
development of nuclear weapons, which has spanned four decades, the
outcome of nuclear events have repeatedly impressed, and occasionally
surprised, nuclear scientists and engineers.
The only two nuclear bombs to be used in war time (detonated over
occurred in the desert
the subsequent
Hiroshima and Nagasaki, Japan, in August 1945) each destroyed an entire
city, although both were of quite low energy yield by today's
standards. The 15-Mt Bravo test on Bikini Atoll in March 1954
underlined the hazard of radioactive fallout. The residents of
Rongelap Atoll, more than 150 km downwind of Bikini, were exposed to,
and suffered from, serious doses of nuclear fallout radiation even
though they were quickly evacuated (Glasstone and Dola-n' 1977~.
Following the first successful detonation of a fusion device in 1952,
the pace of nuclear testing, the size of individual nuclear warheads,
and the total nuclear arsenals of the United States and the USSR
expanded rapidly (the USSR detonated the largest weapon, a ~58-Mt
device, in the atmosphere in October 19611.
Throughout this period and into the early 1960s, a debate developed
among nuclear strategists as to whether blast or thermal (fire) effects
should be considered the primary destruction mechanism in formulating
nuclear strategy. Blast effects were finally settled on because they
were certain to occur with each explosion; fire was considered a
secondary effect, as was prompt radioactive fallout from surface
bursts.
With the growth of the arsenals, scientists became concerned that
severe global environmental effects might occur if even a fraction of
the existing nuclear weapons were detonated. Such concern led, for
example, to projects Gabriel and Sunshine--from 1949 through 1959--to
evaluate the danger of radioactive fallout. Batten (1966) later
assessed the possible climatic impact of dust raised by nuclear surface
bursts, while Ayers (1965) undertook a broad analysis of the
environmental and biological consequences of nuclear war, including the
effects of blast, fires, and fallout. These early studies were
hampered by a lack of critical data (some of which are now available)
and were based on assumptions that seemed reasonable at the time but in
retrospect appear to have been incorrect. They were not quantitative
185
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186
in many important details. Ayers noted that very severe effects were
possible in his scenarios, but he could not marshal the data to make a
· ~
convincing case.
During the period of assessment of the global impacts of supersonic
flight, Foley and Ruderman (1973) pointed out that the nitrogen oxides
(NOX) produced in nuclear fireballs by megaton-size explosions would
be carried into the stratosphere. There NOX would react with and
deplete the ozone layer, which shields the earth from harmful
ultraviolet sunlight. Hampson (1974) suggested that a full-scale
superpower nuclear exchange could result in the nearly complete
depletion of the ozone shield, possibly subjecting the earth to high
levels of ultraviolet radiation for a year or more.
The 1975 National Research Council study (NRC, 1975) attempted to
resolve some of these questions about the long-term effects of nuclear
war. Much of that analysis centered on the recently identified ozone
depletion problem. The report concluded that large reductions (about
50 percent) of the global ozone burden could occur. The NRC report
judged that the likely climatic impact of nuclear dust from 10,000 Mt
of high-yield surface explosions would probably be no more than the
slight cooling produced by the great Krakatau eruption of 1883; but it
noted a large uncertainty in these findings.
The recent renewal of interest in long-term effects arose from two
independent activities. One started in a seemingly unrelated field.
Analysis of a thin clay layer found widely distributed at the
stratigraphic boundary between the Cretaceous and Tertiary periods led
Alvarez et al. (1980) to theorize--on the basis of anomalous levels of
such noble metals as iridium--that the mass extinction of species that
occurred 65 million years ago could be attributed to an asteroid
striking the earth. The asteroid, they proposed, had raised a global
dust cloud that blocked out sunlight so effectively that the
terrestrial and marine food chains supporting the dinosaurs and many
other species collapsed. Recognizing a possible parallel between the
dust-lofting effect of an asteroid and that of a sizeable exchange of
nuclear warheads, William J. Moran, in March 1981, stimulated
discussions and preliminary calculations within the NRC. This work led
to two meetings of an NRC study panel (December 1981 and April 1982) to
further investigate the effects of dust lofted by nuclear detonations.
The second key event was the realization of the possible effects of
smoke. Prior to this time, assessments of the effects of nuclear war
did not include the potential effects of the smoke emitted by fires
ignited by nuclear detonation. Attention to fires had focused instead
on the immediate damage caused by burning and high temperatures. As
part of a study that had been launched in 1980 by the Royal Swedish
Academy of Sciences, Crutzen and Birks in early 1982 circulated a draft
paper (published in June 1982) that provided the first quantitative
evidence of the possible importance of smoke in blocking solar
radiation, and suggested consequent alterations of weather and
short-term climate in the northern hemisphere.
As an input to the April 1982 meeting, Turco, with the assistance
of Toon, Pollack, and Ackerman--drawing upon the work in progress of
Toon et al. (1982) on the climatic impact of dust lofted by an
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187
asteroidal impact--presented preliminary calculations on the climatic
impact of nuclear dust emissions. The work of Crutzen and Birks on
smoke was also reported by Turco and Eric Jones, and its potential
importance was immediately recognized by the NRC study panel. A letter
report (Moran, 1982) concluded that sufficient scientific data were
available to warrant a thorough examination of the environmental
effects of a nuclear exchange. Discussions then began between the NBC
and the Department of Defense that culminated in the request for the
present study. Meanwhile, Turco and his colleagues continued their
studies presented at the April meeting and soon made the first
quantitative estimates of the climatic effects of smoke and dust
mixtures (Turco et al., 1982, 1983a,b). Related work by Crutzen et al.
(1984), scientists at the Lawrence Livermore National Laboratory (e.g.,
MacCracken, 1983), and climatologists at the National Center for
Atmospheric Research (Covey et al., 1984) underscored the potential
seriousness of the problem.
Thus, nearly four decades after the introduction of nuclear weapons
technology, a series of unplanned, separate scientific developments has
led to a reevaluation of our understanding of the global effects of
nuclear war. One can ask whether even now the full range of physical
consequences--let alone the biological effects--of nuclear warfare is
within our comprehension.
REFERENCES
Alvarez, L.W., W. Alvarez, F. Asaro, and H.W. Michel (1980)
Extraterrestrial cause for the Cretaceous-Tertiary extinction.
Science 208:1095-1108.
Ayers, R.U. (1965) Environmental Effects of Nuclear Weapons. Vols.
1-3. Report HI-518-RR. Harmon-on-Hudson, N.Y.: Hudson Institute.
Batten, E.S. (1966) The Effects of Nuclear War on the Weather and
Climate. Memorandum RM-4989-TAB. Santa Monica, Calif.: RAND Corp.
50 pp.
Bethe, H. (1976) Ultimate catastrophe? Bull. At. Sci. 32:36-37.
Covey, C., S.H. Schneider, and S.L. Thompson (1984) Global atmospheric
effects of massive smoke injections from a nuclear war: Results
from general circulation model simulations. Nature 308:21-31.
Crutzen, P.J., and J.W. Birks (1982) The atmosphere after a nuclear
war: Twilight at noon. Ambio 11:114-125.
Crutzen, P.J., C. Brahl, and I.E. Galbally (1984) Atmospheric effects
from post-nuclear fires. Climatic Change, in press.
Foley, H.M., and M.A. Ruderman (1973) Stratospheric NO production from
past nuclear explosions. J. Geophys. Res. 78:4441-4450.
Glasstone, S., and P.J. Dolan (eds.) (1977) The Effects of Nuclear
Weapons. Washington, D.C.: U.S. Department of Defense. 653 pp.
Hampson, J. (1974) Photochemical war on the atmosphere. Nature
250:189-191.
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188
MacCracken, M.C. (1983) Nuclear war: Preliminary estimates of the
climatic effects of a nuclear exchange. Paper presented at the
International Seminar on Nuclear War, 3rd Session: The Technical
Basis for Peace. Ettore Majorana Centre for Scientific Culture,
Erice, Sicily, Aug. 19-24, 1983.
Moran, W.J. (1982) Letter report to Frank Press, chairman of the
National Research Council, April 20, 1982.
National Research Council (1975) Long-Term Worldwide Effects of
Multiple Nuclear Weapons Detonations. Washington, D.C.: National
Academy of Sciences.
Silver, L.T., and P.H. Schultz (eds.) (1982) Geological implications of
impacts of large asteroids and comets on the earth. Geol. Soc. Am.
Spec. Pap. 190. 328 pp.
Toon, O.B., J.B. Pollack, T.P. Ackerman, R.P. Turco, C.P. McKay, and
M.S. Liu (1982) Evolution of an impact generated dust cloud and its
effects on the atmosphere. Geol. Soc. Am. Spec. Pap. 190:187-200.
Tur co, R.P., O.B. Toon, J.B. Pollack, and C. Sagan (1982) Global
consequences of nuclear warfare. Eos Trans. AGU 63:1018.
Turco, R.P., O.B. Toon, T.P. Ackerman, J.B. Pollack, and C. Sagan
(1983a) Nuclear winter: Global consequences of multiple nuclear
explosions. Science 222:1283-1292.
Turco, R.P., O.B. Toon, T.P. Ackerman, J.B. Pollack, and C. Sagan
(1983b) Global Atmospheric Consequences of Nuclear War. Interim
Report. Marina del Rey, Calif.: R&D Associates. 144 pp.
Representative terms from entire chapter:
climatic impact
