I agree with your post but the CO2 concentration is 400/1,000,000 which is .04%
You are correct on the concentration on CO2.
I typed that in on a cell phone and did not notice the location of the decimal point.
The concentration of CO2 in the atmosphere is such a small trace amount that it's contribution to atmosphereic solar heating is negligible and will continue to be negligible even if we increase it several times over.