One of the stupidest claims in climate science, originally pushed by the constantly stoned Carl Sagan, is that increasing CO2 will lead to a runaway greenhouse effect.
This is a spectacularly stupid concept. The only IR bands which are not saturated are ones which CO2 doesn’t affect.
The IPCC says :
a “runaway greenhouse effect”—analogous to Venus– appears to have virtually no chance of being induced by anthropogenic activities.