To one significant figure, the mass of CO2 in Earth's atmosphere is 3 trillion tonnes. Annual fossil fuel emissions of CO2 are about 37 billion tonnes:
https://www.iea.org/reports/co2-emissions-in-2023/executive-...
https://www.iea.org/reports/co2-emissions-in-2023/executive-...
I haven't checked against the GeoPhys journals (I should, but ...), FWiW wikipedia has it that:
In October 2023 the average level of CO2 in Earth's atmosphere, adjusted for seasonal variation, was 422.17 parts per million by volume (ppm).
Each part per million of CO2 in the atmosphere represents approximately 2.13 gigatonnes of carbon, or 7.82 gigatonnes of CO2.
~ https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_at...
That's total, not just the excess portion added in by human activity and sourced from the bowels of the earth via mining for concentrated old sunlight energy.
Still, despite the fractional ppm composition that's a full atmospheric total of 3,301 billion tonne.
Here in W.Australia we move approx one billion tonne of iron ore from the Pilbara to (mostly) China per year. That takes some effort and energy.
A simple calculation in units(1) shows that your figure is the right order of magnitude:
You have: 400ppm 4pi earthradius**2 atm / gravity
You want: trillion tonnes
* 2.1080571
/ 0.47437046
You have: 422ppm (carbon + 2 oxygen) 4pi earthradius**2 atm / gravity (21% 2 oxygen + 79% 2 nitrogen)
You want: trillion tonnes
* 3.3925982
/ 0.29475934