CO2 Through Geologic Time

CO2 Variation through Geologic Time

The above curves show the broad temperature and CO2 variations back to the beginning of the Paleozoic era. Our current era and the Late Carboniferous-Permian periods stick out as having extremely low temperatures and low atomospheric CO2. Both of these times were also distinct in having glaciations.

This data covers from 600 million years ago to the present. What it shows is that CO2 decreased from the Cambrian high of 7000 PPM through the Paleozoic with the lowest levels reached in the glacial ages of the Late Carboniferous-Permian. During the Mesozoic, CO2 was generaly greater than 1000 PPM and then it decreased to the current low level, which is very similar to that in the Carboniferous-Permian ice ages. There is no evidence for a "runaway greenhouse effect" through all of this Earth history. Why should we worry about such an effect being caused by man's release of CO2 by burning fossil fuels? The answer is we shouldn't. It is never going to happen. If we burned every ounce of coal and petroleum available to us, it would never raise CO2 levels higher than the Mesozoic norm of 1000 PPM. I doubt we could even double the current CO2 level. It is thought that man's current input of CO2 into the atomsphere is about 70 PPM, so you judge what it would take to drive CO2 higher than the Mesozoic norm.