[TStro]

CO2 levels during the Carboniferous Period were 400 times higher than present levels.

http://www.geocraft.com/WVFossils/Carboniferous_climate.html#anchor147264

[zeestephen]

Thanks - that’s an excellent link.

I read all of it, some parts twice.

One correction to your comment, though.

You said CO2 was 400 times higher than present.

Sorry - in the Early Carboniferous CO2 was about 1500 parts per million.

Today, it’s 400 ppm, so the difference is about 4 times.

You probably made your error when you looked at the “percentage” of CO2, which is expressed 0.04%.

Percent is expressed in “parts per hundred.”

PPM is expressed like this - 0.000400 and 0.001500.