Environmental Engineering Reference
In-Depth Information
All of these effects make the design of the calculations
extremely complicated, and the description above only
begins to take into account the wide variety of conditions
over the entire surface of the Earth. The most sophisti-
cated calculations start off with the surface divided into
squares which might be as small as
miles on an edge
where the terrain is highly variable and as large as several
hundred miles on an edge where the terrain is smooth and
fairly uniform. The atmosphere is divided into layers and
there can be as many as
of them. Similarly the
oceans are divided into layers, and the number of layers
has to take into account the depth of the oceans as well. In
the actual calculations there can be hundreds of thousands
of these cells. Heat and
or
fluids (water in the oceans and air
in the atmosphere)
flow into a cell from one side or top
or bottom, and
flow out of another to adjacent cells. The
calculations require enormous computers, and even the
largest computers available today cannot do the job
quickly. These AOGCMs are not run very often because
of the huge amounts of computer time needed. There are
different AOGCMs that the IPCC takes into account
in its climate synthesis.
The problem is so large that it cannot be solved from
first principles on any existing computer. That would
require starting off with oceans uniformly full of water
and an atmosphere full of the proper mix of gases both at
the average temperature of the Earth (
C), and
running the program for long enough to allow the cur-
rents in the ocean and the air to develop, the temperature
to stabilize, the ice caps to form, etc. Perhaps when com-
puters become at least
For
times more powerful than
those of today it can be done. Today, what is done is
