Environmental Engineering Reference
In-Depth Information
ed life
forms: the growth of giant plants and trees in the Carbon-
iferous era
From then to now saw the rise of many diversi
million years ago whose decay and burial
gave us the supply of the fossil fuel we use today; a mass
extinction about
million years ago whose cause is not
understood; the rise and disappearance of the dinosaurs in
another mass extinction about
million years ago,
thought to have been caused by the collision of a giant
meteor with the Earth. Life is old; we are young. Homo
habilis, thought to be our African
rst ancestor,
lived
about
million years ago. Our particular subspecies,
Homo sapiens, is only about
years old. Our civil-
ization is a mere
years old, a time period so short as
to be only the blink of a geological eye. Yet in that eye
blink our numbers and economic activity have begun to
have effects on a global scale. If we continue increasing
emissions at the rate we are now, these effects will become
of a size comparable to major geological effects.
The earliest reliable data showing a correlation between
temperature and greenhouse gases come from material
million years old. In an era called the Eocene, there
was a rise in global temperature that seems to have reached
a maximum of about
C) higher than it is now.
This was accompanied by an atmospheric CO
F(
level that
recent work puts at about
ppm at least, about
ve
times the preindustrial level of the
s and perhaps much
higher. There may have been other greenhouse gases that
increased sharply at the same time contributing to the
temperature increase as well. This temperature rise lasted
about
years before the oceans absorbed whatever
caused the rise. Though our world was very different back
then (no ice in either the Arctic or the Antarctic, the
Search WWH ::




Custom Search