That's measured already since the 60s. You never see any reference to it because what it shows is a constant rate of increase that is entirely unaffected by literally anything you can think of. Rise of China? No impact. Lockdowns and the global air travel shutdown? No impact. Renewables revolution? Invisible. Great recession? Of course not. And all the international conferences and agreements.... well, you get the picture.

This fact is discouraging which is why the media and government enforce a blanket silence about it. Along with many other aspects of climate science.