CO2 levels data from the ice ages makes a laughing stock of global warming. It needs more attention.
Ref: http://www.climatedepot.com/2013/05/14/co2-nears-400-ppm-relax-its-not-global-warming-end-times-but-only-a-big-yawn-climate-depot-special-report/
...Scientists also note that geologically speaking, the Earth is currently in a “CO2 famine” and that the geologic record reveals that ice ages have occurred when CO2 was at 2000 ppm to as high as 8000ppm. In addition, peer-reviewed studies have documented that there have been temperatures similar to the present day on Earth when carbon dioxide was up to twenty times higher than today’s levels. And, a peer-reviewed study this year found that the present day carbon dioxide level of 400 ppm was exceeded — without any human influence — 12,750 years ago when CO2 may have reached up to 425 ppm.