Energy and Changes in the Environment - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 49

TEMPERATURE CYCLES
Sulfates found in ice cores occur in a regular pattern throughout
150,000 years of the earth's history. The cycle appears to occur with a
shift in the earth's orbit that causes the North Pole to point toward the
sun when the earth is closest to it. The ice cores also showed that calcium
carbonate seems to have a cyclic pattern. This cycle occurs with the change
in the tilt angle of the earth's axis relative to the plane of its orbit. The
greater the tilt angle the hotter the seasonal extremes are. Changes in the
amount of carbon dioxide directly track the implied temperature changes
through the past 150,000 years. The same is true with methane, which is
20-30 times more powerful as a greenhouse gas than CO 2 .
Since methane is produced mainly by microbial decomposition
of dead organic matter in swamps, bogs and refuse piles, the close
correlations between changes in methane, CO 2 , and temperature suggest
that biological processes are involved.
It can take 500-1,000 years for the surge of warming temperatures
that take place as the ice ages vanish to pervade tundra and permafrost.
This warming could release methane to the air.
In bog formations extensive quantities of organic matter are stored
during glacial periods. These processes could be a critical link in the
explanation of large climatic changes that have occurred in the past.
A billion years ago the bacteria and algae of the earth began to
build up the oxygen that makes our planet livable. After another billion
years, multicelled creatures started to evolve into plants and animals. A
hundred million years ago, dinosaurs roamed the earth while the average
temperature was 10° to 15°C (18° to 27°F) warmer. During this period,
there was no permanent ice at the poles that can be detected from geologic
records. As the continents drifted, Antarctica became isolated at the South
Pole and India drifted northward crossing the equator and connecting
with Asia. The Tibetan plateau rose, and sea level dropped about 1,000
feet. Then, the planet cooled and permanent ice was formed.
The combination of forces that caused these changes is still in question
but it involves the stability of the climate. The climate has fluctuated
between limits of plus or minus 15°C (27°F) for hundreds of millions of
years. These limits are large enough to have a major influence on species'
extinction and evolution. A runaway greenhouse effect is thought to have
changed Venus where the oceans boiled.
There is almost as much carbon in the atmosphere in the form of CO 2