Carbon dioxide does not cause warming because it cannot hold heat - cuz its a heavy gas that stinks to ground level. Humidity holds heat so that would make atmospheric water a huge problem
People working in greenhouses that burn propane to increase CO2 levels far beyond 1000 ppm are not suffocating...Are they? Early Homo species were surviving quite nicely with CO2 levels above 2500 ppm. Early mammals and dinosaurs at 8000 ppm.
If the planet ever warms to its optimal 69F temperature (It is at 60F today), then atmospheric CO2 will be about 1200 ppm. It is really too bad man can't cause global warming...It would be ideal.