Page 367 - Earth's Climate Past and Future
P. 367
CHAPTER 19
Future Climatic
Change
The climatic effects of rising CO levels will become increasingly significant
2
in the future. Consumption of estimated reserves of fossil fuels (mainly coal) in
the next two or three centuries will add far more CO to the atmosphere than
2
has accumulated so far, unless technology or extreme conservation efforts
reduce this influx. Atmospheric CO concentrations will increase to levels at
2
least twice and possibly four or more times those that have existed during all
of human existence. Concentrations will be comparable to levels last seen
millions to tens of millions of years ago when a much warmer greenhouse world
existed. This warming will completely overwhelm natural variations in climate
and cause changes unprecedented in human experience. Atmospheric CO
2
levels will eventually decrease as the ocean slowly absorbs much of the excess
carbon, but concentrations will still remain well above natural values for thou-
sands of years into the future.
