Environmental Engineering Reference
In-Depth Information
job that has to take into account a host of interactions
between very many elements of the systems that deter-
mine our climate.
The amount of incoming radiation from the Sun is
known very well. Not all of that radiation reaches the
ground. Some is re
ected back into space by clouds, and
some is absorbed by various chemicals in the atmosphere
and by the clouds themselves. Some is re
ected from the
surface, more strongly from snow and ice, less strongly
from deserts, and least strongly from the oceans and land
areas covered by vegetation. The oceans, the land masses
of the continents, and the atmosphere interact with each
other in complex ways. Changes in one thing change
other things as well. These effects are called feedback
loops and some were described earlier. I have mentioned
how increasing greenhouse gases increases the tempera-
ture; increasing the temperature increases water vapor
in the atmosphere; water vapor is also a greenhouse gas
so the temperature increases further; increasing water
vapor also increases clouds; more clouds re
ect more
incoming radiation into space, decreasing the tempera-
ture. We usually think that increased temperature should
lead to less snowfall, but one of the oddest feedback
effects increases snowfall in Antarctica when the global
average temperature increases slightly, because an
increase in temperature increases water vapor in the
atmosphere and that leads to more snow. Some of these
feedback loops amplify climate change effects while
others reduce them. Getting all of this right is the job of
the modelers and their computers.
Many of the feedbacks are positive in the sense
that given a temperature increase they increase the
