In the atmosphere, carbon dioxide acts
rather like a one-mirror--the glass in the roof of a green-house which allows
the sun’ s rays to enter but prevents the heat from escaping.
According to a weather expert’ s prediction, the atmosphere will be warmer
in the year 2050 than it is today, if man continues to burn fuels at the present
rate. If this warming up took place, the ice caps in the poles would begin to
melt, thus raising sea level several meters and severely flooding coastal
cities. Also, the increase in atmospheric temperature would lead to great
changes in the climate of the northern hemisphere, possibly resulting in an
alteration of the earth’ s chief food-growing zones.
In the
past, concern about a man-made warming of the earth has concentrated on the
Arctic because the Antarctic is much colder and has a much thicker ice sheet.
But the weather experts are now paying more attention to West Antarctic, which
may be affected by only a few degrees of warming: in other words, by a warming
on the scale that will possibly take place in the next fifty years from the
burning of fuels.
Satellite pictures show that large areas of
Antarctic ice are already disappearing. The evidence available suggests that a
warming has taken place. This fits the theory that carbon dioxide warm the
earth.
However, most of the fuel is burnt in the northern
hemisphere, where temperatures seem to falling. Scientists conclude, therefore,
that up to now natural influences on the weather have exceeded those caused by
man. The question is: Which natural cause has most effect on the
weather
One possibility is the variable behavior of the sun.
Astronomers at one research station have studied the hot spots and "cold" spots
(that is, the relatively less hot spots) on the sun. As the sun rotated, every
27.5 days, it presents hotter of "colder" faces to the earth, and different
aspects to different parts of the earth. This seems to have a considerable
effect on the distribution of the earth’ s atmospheric pressure, and
consequently on wind circulation. The sun is also variable over a long term: its
heat output goes up and down in cycles, the latest trend being
downward.
Scientists are now finding mutual relations between
models of solar-weather interactions and the actual climate over many thousands
of years, including the last Ice Age. The problem is that the models are
predicting that the world should be entering a new Ice Age and it is not. One
way of solving this theoretical difficulty is to assume a delay of thousands of
years while the solar effects overcome the inertia of the earth’ s climate. If
this is right, the warming effect of carbon dioxide might thus be serving as a
useful counter-balance to the sun’s diminishing
heat. |
