We have a COMPLEX system between solar input
and the response of Earth to that energy input
because of different reasons: the coupled system
of oceans and atmosphere, plus the variation of
solar energy due to the tilt of the earth spin
axis. The precession of the spin axis, the
variation of the obliquity with time, and the
variation of the location of perihelion (the point
of closest approach to the Sun of a body orbiting
As a simple example consider the amount of
incoming solar visible radiation that is reflected
back into space. Currently this is about 30% for
Earth. That is to say, out of each 1 joule of
visible radiation that the Sun pours down upon us
about 30 % is reflected back into space. The
amount is controlled by the area of land versus
area of ocean and by the areal extent of glaciers.
Ice has a very high reflectivity. So now let us
imagine, because of astronomical forcing, the
Earth grows a little colder and more ice forms.
The response of the Earth system will be to
increase the reflectivity and hence make the earth
even COLDER!! This is a positive feedback; if the
planet gets a little colder due to one effect,
ANOTHER effect kicks in to amplify the first
The reason why the issue of climate prediction is
so difficult is because MANY SUCH feedbacks both
positive and negative exist!!!!!
Hence understanding the real response is a
complex summation of all these simultaneous
effects. This is why we call the Climate and
example of a COMPLEX system. Another example of a
complex system with feedbacks is YOU!!!!!
You go outside on a warm or hot day and your
body sweats. But because it takes energy to
evaporate water, as your sweat liquid water goes
to the gas, it removes heat from your body cooling
you off!!!! This is an example of a negative
feedback: the more you heat up and sweat the more
cooling effect you get.
Complex systems all share this phenomena of
positive and negative feedbacks.
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