>> While increased CO2 is something to pay
>> attention to, after all we need air to breath,
>> the current CO2 levels are still low on a
>> geologic timeframe,
>
> It looks quite high to me:
>
> http://www.mongabay.com/images/external/2005/co2_var.jpg
>
> Around 375 ppmv today compared to the usual cycle of 200-300 ppmv over the 
> last half a million years.

By some estimates mamals have existed at times when it was over 2000 ppm.
http://www.nytimes.com/imagepages/2006/11/06/science/earth/20061107_CO2_GRAPHIC.html
http://www.nytimes.com/2006/11/07/science/earth/07co2.html

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