Environmental Engineering Reference
In-Depth Information
in some greenhouse gases. The logic is simple: green-
house gases are known to increase the temperature, and
if we add more of what increases the temperature, we will
increase the temperature more. How much more is the
question that thousands of scientists are trying to answer.
Looking again at our two nearest neighbors in the Solar
System, Venus and Mars, tells what happens when the
greenhouse effect goes very wrong. I began this chapter
with what a science
fiction story might be like. Here is the
real story. Both planets have been extensively studied
from Earth by telescopes and radar, observed by orbiting
spacecraft, and sampled by probes sent into the atmos-
phere (Venus) and by landers (Mars).
Venus is closest to us in size. Its diameter is
% of ours
and its surface gravity is
% of ours. If you weigh
pounds (
kg) here, a scale would show that you
weigh only
kg) there. However, you
would not enjoy a trip to the Venusian spa. Venus is closer
to the Sun, having an orbit that is
pounds (
% the size of ours
(Earth
'
is orbit radius is about
millionmiles or
million
kilometers, that of Venus is about
million miles or
million kilometers, and that of Mars
is about
million kilometers). This means
that the incoming radiation on Venus is almost twice as
intense as on Earth and has to be balanced by a higher
temperature to radiate enough energy to maintain a con-
stant temperature. In the absence of any greenhouse effect,
the average temperature of Venus would be about
million miles or
F
C), uncomfortable, but livable at least in the cooler
areas near the poles. Instead, its temperature is above
(
F(
C), way above the temperature reached in a self-
cleaning oven. Venus has what
is called a runaway
