Has Something Happened to the Weather?
The weather is no longer quite as unpredictable as it used to be. Yet we
are hardly ever sure of it even a few hours in advance. One week is
about the limit of the period of any prediction. Where the best men lack
knowledge untrammeled fantasy has a field day. Weather has so far
remained a safe topic of conversation and of speculation.
Nuclear explosions have, of course, been made responsible for the
weather—for any kind of unusual weather. Be it rain or drought or a hard
season of hurricanes—the nuclear tests are dragged in. The weather
bureau says: no. But then—the weather bureau has not always been
correct. Indeed it would be a miracle if the popular talk and the
popular press would not have seen some connection between atomic
explosions and the wayward behavior of the seasons.
In one case—and to our knowledge only in one case—there has occurred a
chain of events starting with a nuclear test and ending in a copious and
unusual downpour. In the spring of 1955 a test shot of moderate size was
fired in Nevada. At the same time the last storm of the season was
blowing itself out in California. According to the usual rules of
meteorology the radioactive cloud should have been carried east by the
steady westerly winds which blow over the temperate zone. But this time
the cloud was caught up by the swirl of the dying California storm and
some of the radioactivity was carried to the west coast.
Hours after the explosion radioactive rain began to fall in California.
The activity was weak enough and did not give rise to any worry. But a
remarkable thing happened. As the active cloud arrived over California
the storm revived. It developed into an abundant rain which is not usual
at that place and time. Did we—quite unintentionally—do something about
the weather?
The weather bureau said: no. One must certainly admit that this single
case proves nothing. Only greatly improved methods of weather
observation and weather prediction would make it possible to decide if
such a chain of events consists of the strong links of cause and effect
or else of a simple sequence of haphazard occurrences.
Even though our knowledge is incomplete there is at least one simple
fact which should be borne in mind. All the energy in that Nevada
explosion was not quite sufficient to evaporate the water droplets in a
cloud one mile broad, one mile wide, and one mile deep. This is not a
very big rain cloud. Such a cloud would give about one third of an inch
of rain water over one square mile—not an impressive amount. Even the
biggest hydrogen bomb would give only energy enough to evaporate a cloud
ten miles by ten miles and towering to the top of the “boiling” portion
of our air, which we call the troposphere. This would give roughly three
inches of rain over a hundred square miles—a more impressive amount but
vanishing in the vastness of the Pacific Ocean.
Nuclear explosions are violent enough. But compared to the forces of
nature—compared even with the daily release of energy from not
particularly stormy weather—all our bombs are puny. Offhand one might
guess that our nuclear fireworks could not swing the scales in the
massive energy changes that we see around us in the common occurrences
of wind and rain.
But the interplay of clouds and sunshine, of water evaporating,
freezing, dropping and thawing—in short the vagaries of weather—are both
involved and tricky. Small causes can give rise to big effects. Some
processes of air masses sweeping over oceans and continents are
irresistible and predictable. Others, like the first upsurge of hot air
from the overheated ground, may be a question of close competition and
trigger action. This is what makes it so difficult to predict the
weather.
One of the most delicate processes we must think about is the formation
of water droplets. When some water molecules are mixed with air
molecules, we have moist air. If such air rises, expands and cools, the
water molecules lose some of their agitated motion and have a greater
tendency to stick together to form droplets. But it is not easy to get
them started on this joint enterprise.
If two or three molecules stick together, they soon are shaken apart.
If, however, two or three dozen are collected, this is enough to start a
growth which ends in a droplet of water. If moist air is cooled,
droplets will form, provided there is a meeting place from which the
growth can start. If there is no such meeting place, there are no
droplets and we get no cloud. If there are few meeting places, each will
collect a rather great amount of water, we will get big drops, and we
may get rain. If there is an abundance of meeting places many tiny
droplets are formed which will remain suspended as a cloud. The present
attempts at rain-making are connected with a birth-control of droplets.
We have seen earlier that in each radioactive decay charged particles
are emitted. As these move along their paths, they tear up more atoms
and leave in their wake an assembly of charged particles. These charged
particles strongly attract the molecules of water. They attract the
molecules of air much less. The reason is that in a water molecule
positive and negative charges are separated to a considerable extent
whereas in the nitrogen and oxygen molecules of air the charges are
distributed more evenly. As a result the track of each particle emitted
in a radioactive decay provides many meeting places for the formation of
water droplets.
Actually, cooled moist air has been used for many decades to make the
tracks of fast charged particles visible. In one of the photographs you
can see a picture of such “vapor trails.” It is a photograph through an
apparatus called the Wilson Cloud Chamber. The myriads of radioactive
disintegrations in the debris of a nuclear explosion can give vapor
trails which coalesce into a real cloud. In this way weather might be
influenced. (See pictures 11 and 12.)
In spite of all this it remains highly probable that testing of nuclear
explosions, as practiced at present, does not influence the weather.
Radioactivity does furnish an opportunity for droplets to form. But
other abundant sources are also available for droplet formation. Dust,
smoke and many forms of air pollution will do the trick. Foam scattered
from ocean waves evaporates and leaves a speck of salt behind. This
particle of salt may be carried by the winds for many miles and may
eventually become the germ around which a new drop will condense. The
cosmic rays by which we are bombarded give rise to vapor trails similar
to those produced by the radioactive decay products. Among the many
processes of nature and the usual by-products of civilization the few
atomic tests do not play an important role. This statement can stand,
not as a certainty, but as a very good guess.
Among the many surprises that the future holds one may be closely
connected with the weather. In the age of the airplane we are getting
more and more information about the air masses around us. Air travel
demands this information and also furnishes it. New techniques, such as
radar, can detect the formation of a cloud and can measure the size of
droplets at a great distance. In fact the information received is so
plentiful that one may doubt whether we can properly understand it and
utilize it.
Fortunately we no longer need to rely exclusively on our own brains.
Human thought is a remarkable thing but it is slow. The modern computing
machines, the “electronic brains,” are simpletons as compared to the
apparatus which each of us wears in his skull. But the electronic
computers have one advantage: they are fast. Soon they will be a million
times as fast as our mental processes. The expression “fast as thought”
is dated—it is a contemporary of the horse-and-buggy.
The electronic machines can digest weather information as fast as it is
received. Some progress has already been made. In a few years all
weather predictions may be machine-made.
This need not mean that weather can be predicted with certainty or for a
long time ahead. The trigger processes which, starting from an
insignificant and unnoticed spot of turbulence, can grow into the
dimensions of a cyclone will set a limit to any art of prediction.
But to the extent that weather cannot be predicted it may be influenced.
If small causes may have big effects then even the puny means available
to man may change the weather—provided we know how and where to apply
the lever.
First we shall have to acquire a better understanding of the
weather-science of meteorology. Then we shall have to look for the
appropriate trigger mechanism. This may be a cloud of dust of the right
kind—or else a chemical—or perhaps a great number of radioactive
particles. In one way or another atomic explosions may be used as the
trigger but the trigger will not be effective until and unless the rest
of the machinery is understood.
Of course atomic explosions cannot be used in really significant numbers
unless we learn how to avoid those radioactive by-products which are
really dangerous. Fortunately the use of nuclear fusion, best known from
the hydrogen bomb, makes it possible to regulate the kind of
radioactivity one obtains. We may make only such kinds of activity which
decay before they have a chance to get into the human body.
Experience has proved that to talk about weather is not dangerous. To do
something about the weather will be more risky. Shall the weather become
a ward of the government? Shall we have Republican Rainstorms and
Democratic Droughts? In this way we shall certainly lose the last safe
topic of conversation.
In the narrower confines of Europe where sovereign nation is a few hours
from sovereign nation (as the wind blows) the situation will be much
more serious. But even the whole planet may prove too small for fiercely
conflicting interests when more knowing fingers are placed on more
sensitive triggers.
To govern the weather can be most useful. It could give ample livelihood
to all the people of the earth and to many more billions. Such endeavor
is surely good and it would appear peaceful. But in this case as in many
other cases knowledge will lead to power and power will lead to disaster
if it is not tempered by wisdom.
Yet this knowledge or some similarly dangerous knowledge will come to us
in our lifetimes. Nuclear explosions do not stand alone as a potential
source of mischief.