Environmental Engineering Reference
In-Depth Information
temperature more, but we know that there has been no
runaway greenhouse effect on Earth where the feedbacks
turned the Earth into something like Venus. The histor-
ical record over the past few billion years shows that
although the climate has been both much hotter and
much colder than today, it has stayed within limits that
still support life. If the Earth were to become either very
hot or very cold compared with today it might not sup-
port our standard of living, but life would go on.
There are many climate models that have been created
by groups of experts around the world. The most sophis-
ticated and complex are called atmosphere
ocean general
circulation models (AOGCM). These models divide the
surface of our planet into small blocks, the atmosphere
into layers, and the oceans into layers too. Here the
-
rst
big problem arises. The surface of the land is not
smooth. The wind in the atmosphere is not uniform.
The ocean has currents that are narrow compared with
the size of the ocean. In size, the Gulf Stream that keeps
Europe warm is to the Atlantic Ocean as the Mississippi
River is to the North American continent. The Alps are
small compared with the total land area of Europe. All
are small compared with the scale of what they affect.
Models have to look at effects at an appropriate scale. On
the land surface, mountain ranges affect wind patterns
and therefore the transport of heat. In the oceans, cur-
rents such as the warm Gulf Stream off the US east coast
and the cold Humboldt Current off the US west coast
pierce the quiet oceans with water plumes that also move
huge amounts of heat. Land bottlenecks exist around
Greenland, for example, that restrict the
flow of water,
strongly affecting the heat
ow.
