[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.

[andy58-in-nh]

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

Thanks - you're right - I missed a "0" in the decimal-to-percentage conversion. Atmospheric CO₂ is 0.038%, the estimated human contribution toward which is 0.00114%, with a relatively small percentage of that tiny amount attributable to US power plants.