[andy58-in-nh]

97% of global CO₂ is naturally-occurring.

The human contribution (3%) applies to a gas CO₂ that itself comprises only 0.38% of the Earth's atmosphere.

Got that? Ok.

Now: of the man-made component (approximately 0.0114%), only 17% of that amount originates in the US and Canada, and much of that is attributable to agriculture, forestry, and other land use.

Even the most draconian, industry-ruining, economy-destroying regulations on U.S. power plants imaginable would result in a negligible reduction in global CO₂ levels, and might even result in an increase, owing to the need for humans to burn increased amounts of wood for heat.

[Reeses]

CO2 that itself comprises only 0.38% of the Earth's atmosphere.

You're off by a decimal point. The atmosphere CO2 percentage is 1/10th of that.

[Lonesome in Massachussets]

I’m not sure about the naturally occuring part. CO2 concentration has risen dramatically in the last 50 years, by an amount known to be consistent with human emmissions. I’m not so sure that that is bad thing. CO2 is definitely “green” in that it encourages plant growth. Linden (iirc) thinks that the amount of CO2 in the atmosphere is way beyond the saturation level for atmospheric warming. An increase in 50% in CO2 is likely to increase the CO2 absorption component of global temperature less than 1%.