Environmental Engineering Reference
In-Depth Information
2
340
-
2
260
6
-
180
-
10
400 000
300 000
200 000
100 000
0
Years BP
Temperature Variation
CO
2
Concentration
Vostok ice core data. Carbon dioxide concentration in
parts per million by volume (left scale) and temperature in degrees
centigrade (right scale) relative to today
fig. 4.2
s average temperature back
through the last four ice ages. (Source: J. R. Petit et al. Climate and
atmospheric history of the past
'
years from the Vostok ice
core, Antarctica.
Nature
,
-
,
).
The temperature cycles seem to cool slowly and warm
rapidly. There are occasional spikes of abrupt warming
and cooling,
the most dramatic occurring about
years ago. The spikes are not understood, but
their existence is the source of concern about possible
sudden climate instabilities. Since the main cycles have
about the same period as orbit changes they have to be
driven by orbit changes, not greenhouse gas changes. It is
most likely that the greenhouse gases play a role in the
relatively rapid warming through the feedback effects
mentioned earlier (in which higher temperature increases
water vapor in the atmosphere, increasing temperature
further; higher temperature decreases the amount of
CO
that can be dissolved in the surface layer of the
The Vostok data have been extended to back to
years ago. The
new data show the same periodic warming and cooling as the
original data.
