Collection @0£¢-VowLeumana Review
2234
Box
EetEcls of Wenfo ns Gw The Werth
il
i.
23 February 1955
ION
US DOE cn GY
396 U.S. ATOMIMONE
MEMORANDUM TO DR. JOHN VON NEUMANN
O
a4
BJECT:
108529
Effects of Large Yield Thermonuclear Weapons Upon the Climate of
the World (U)
1, %In the fell of 1952 and 1953 the effects of large yield weapons upon
e climate of the world were studied. (See inclosures 2 and 3). Since that
me, however, additional information hes been obtained from atomic test oper
akions, especially from the study of rediosctive fallout (see inclosure 4),
which may throw some additional light upon this same subject. I have summari
below for your ready reference my present thoughts on the effects of nuclear
detonations upon the climate of the world:
a,
It is believed that if a total of 500 to 5000 megatons are conte.
barst on dry land or underground, the solar radiation reaching the earth may |
reduced by 10% (this refers to the 3000 to 7000 Angstrom region of the soler
ws ectrum).
The bombs must be in the yield range of from 10 to 200 megatons e:
ry The use of 50 to 100 MT bombs would enhance this effect. If the yield of eac!
"> bomb is very much less than 10 MT the majority of the particles would remain :
&
the troposphere or in the lower stratosphere thus producing a more transient
effect. For yields from 50 to 100 MT, a substantiel portion of the cloud wil:
be above 80,000 ft, and the maximum height may go above 150,000 to 200,000 ft.
thus producing a more permanent effect.
2. The following calculations indicete one of the methods used to arrivi
at the above-mentioned conclusion on the number of megatons required to produc
an effect on the world climate:
BEST AVAILABLE COPY
a. The specific activity of the fallout from surface burst weapons1
found to be 0.1 to 0.5 curies per gram extrapolated to the reference time of «
hour after bomb detonetion. At this same reference time, it is assumed that {
totel residual activity
yield,
percent of th®
residual
- time (see inclosure 4).
of the first shot of CASTLE Test Operation (14 MT tote
was
activity
he
bomb
It is believed that 75 to 85
fell out within 24 hours after s}
This means that the total weight of matter in the at<
BY
AU
RiTY OF DOE
CLASSIFIC ATION CANCELLED ye
WITH DELE TIONS
/OC
cloud due to fission procupts, bomd material and crater material was in the re
of from 6 x 1012 to 3 x 10
gm. This sppears reasonable since it is believec
that the CASTLE Bravo crater represents a mass displecement of approximately
1 x 1015 gm, It is believed that the crater dimensions are accurate within a
factor of 2,
30of the NY Operations
1
7
1
4
HH,Gaa
NOIS
Orrice adNO
shows that approximete
he totel activity of the IVI
Mike or CASTLE Bravo shots coule be foundthroughout the world due to long te:
fallout.
loft.
This means that
It is therefore beffeved
£ the totel activity of the bomb remains
reasonable to assume here that at least 5% of
the soil debris sucked into the cloud remsins aloft in the stratosphere, This
means that 3 x 1011 to 1.5 x 1012 gm of finely divided soil debris remeins alc
in the stratosphere from each 15 NT bomb surfece detonated on dry lend.
Inci-
dentelly, this represents spproximstely 0.0015 to 0.0003 of the total materia)
displaced by the creter. There is some evidence that the distribution of
particle radii at such heights (above 60,000 ft) is in the order of 0.5/(see
page 2, Incl 2).
bore,
ai
RatRIREEpRE
SE C5-40959
|