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UNIT 5 The Villain in the Atmosphere
There is one gas present in the air we
breathe that is essential to life. Unfortunately,
one can have too much of a good thing
and the growth in carbon dioxide threatens to
warm up our planet to a dangerous
extent. Isaac Asimov introduces us to this villain
in
the atmosphere, explaining how it
works and what can be done about it.
The villain in
the atmosphere is carbon dioxide.
It
does
not
seem
to
be
a
villain.
It
is
not
very
poisonous
and
it
is
present
in
the
atmosphere in so small a
quantity
—
only 0.034
percent
—
that it does us no
harm.
What’s
more,
that
small
quantity
of
carbon
dioxide
in
the
air
is
essential
to
life.
Plants absorb carbon
dioxide and convert it into their own tissue,
which serve as the basic
food supply
for all of animal life (including human beings, of
course). In the process they
liberate
oxygen, which is also necessary for all animal
life.
But here is what this
apparently harmless and certainly essential gas is
doing to us:
The sea level is rising
very slowly from year to year. In all likelihood,
it will continue
to rise and do so at a
greater rate in the course of the next hundred
years. Where there are
low-lying
coastal areas
(where a large fraction
of the world’s population lives) the water
will advance steadily, forcing people
to retreat inland.
Eventually
the
sea
will
reach
two
hundred
feet
above
its
present
level,
and
will
be
splashing
against
the
windows
along
the
twentie
th
floors
of
Manhattan’s
skyscrapers.
Florida will disappear beneath the
waves, as will much of the British Isles, the
crowded
Nile valley, and the low-lying
areas of China, India, and Russia.
Not
only
will
many
cities
be
drowned,
but
much
of
the
most
productive
farming
areas
of
the
world
will
be
lost.
As
the
food
supply drops,
starvation will
be
widespread
and the structure of society
may collapse under the pressure.
And
all
because
of
carbon
dioxide.
But
how
does
that
come
about?
What
is
the
connection?
It
begins
with
sunlight,
to
which
the
various
gases
of
the
atmosphere
(including
carbon
dioxide)
are
transparent.
Sunlight,
striking
the
top
of
the
atmosphere,
travels
right
through
miles
of
it
to
warm
the
Earth’s
surface.
At
night,
the
Earth
cools
by
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radiating
heat into space in the form of infrared radiation.
However, the atmosphere is not quite as
transparent to infrared radiation as it is to
visible light. Carbon dioxide in
particular tends to block such radiation. Less
heat is lost
at
night,
for
that
reason,
than
would
be
lost
if
carbon
dioxide
were
not
present
in
the
atmosphere. Without the small quantity
of that gas present, the Earth would be distinctly
cooler, perhaps uncomfortably cool.
We
can
be
thankful
that
carbon
dioxide
is
keeping
us
comfortably
warm,
but
the
concentration of carbon dioxide in the
atmosphere is going up steadily and that is where
the
villainy
comes
in.
In
1958,
carbon
dioxide
made
up
only
0.0316
percent
of
the
atmosphere.
Each
year
since,
the
concentration has
crept
upward
and
it now
stands
at
0.0340
percent. It is estimated that by 2020 the
concentration will be nearly twice what it
is now.
This
means
that
in
the
coming
decades,
Earth’s
average
temperature
will
go
up
slightly. As a result, the polar ice
caps will begin to melt.
Something
like
90
percent
of
the
ice
in
the
world
is
to
be
found
in
the
huge
Antarctica
ice
cap,
and
another
8
percent
is
in
the
Greenland
ice
cap.
If
these
ice
caps
begin to melt, the sea level will rise,
with the result that I have already described.
But why is the
concentration of carbon dioxide in the atmosphere
steadily rising?
To blame
are two factors. First of all, in the last few
centuries, first coal, then oil and
natural
gas,
have
been
burned
for
energy
at
a
rapidly
increasing
rate.
The
carbon
contained in these fuels, which has
been safely buried underground for many millions
of
years, is now being burned to carbon
dioxide and poured into the atmosphere at a rate
of
many tons per day.
To
make matters worse, Earth’s forests have been
disappeari
ng, slowly at first, but in
the
last
couple
of
centuries
quite
rapidly.
Right
now
it
is
disappearing
at
the
rate
of
sixty-four acres per
minute.
Whatever replaces
the forest
—
grassland or
farms or scrub
—
produces
plants that
do not consume carbon
dioxide at an equal rate. Thus, not only is more
carbon dioxide
being added to the
atmosphere through burning of fuel, but as the
forests disappear, less
carbon dioxide
is being removed from the atmosphere by plants.
But this gives us a new perspective on
the matter. The carbon dioxide is not rising by
itself. It is people who are burning
the coal, oil, and gas. It is people who are
cutting down
the forests. It is people,
then, who are the villains.
What is to be done?
First,
we must save our forests, and even replant them.
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