How much Carbon dioxide (CO2) is in Earth's atmosphere
today?
a) 10% or greater
b)
2% to 10%
c) less
than 1/10th of 1%
You are correct!
Carbon dioxide is such a small
component of Earth's atmosphere (380 parts per million or 0.038%) that
it shows up on the chart below as only a thin line (shown at 2x actual
thickness, just so you can see it!). Compared to former geologic times,
Earth's atmosphere is "CO2 impoverished."
In the last 600 million years of Earth's
history only the Carboniferous Period and our present age, the Quaternary
Period, have witnessed CO2 levels less than 400 ppm.
Global Temperature and Atmospheric CO2 over Geologic
Time
 |
Late Carboniferous to Early Permian time (315 mya -- 270
mya) is the only time period in the last 600 million years when both
atmospheric CO2 and temperatures were as low as they are
today (Quaternary Period ).
Temperature after C.R. Scotese http://www.scotese.com/climate.htm CO2 after R.A. Berner, 2001 (GEOCARB III)
 |
There has historically been much more CO2 in our atmosphere than exists
today. For example:
During the Jurassic Period (200
mya), average CO2 concentrations were about 1800 ppm or about 4.7
times higher than today.
The highest concentrations of CO2 during
all of the Paleozoic Era occurred during the Cambrian Period, nearly
7000 ppm -- about 18 times higher than today.
The Carboniferous Period and
the Ordovician Period were the only geological periods during
the Paleozoic Era when global temperatures were as low as they
are today. To the consternation of global warming proponents, the Late
Ordovician Period was also an Ice Age while at the same time CO2
concentrations then were nearly 12 times higher than today-- 4400 ppm.
According to greenhouse theory, Earth should have been exceedingly hot.
Instead, global temperatures were no warmer than today. Clearly, other
factors besides atmospheric carbon influence earth temperatures and global
warming.