You actually do need to be a rocket scientist of a sort. You think CO2 increasing by that much is a problem because you've been told it is, probably since birth. It's not something you can observe directly with your own eyes, because it's all about small long term trends.
In practice it's rocket science because:
- The climate is a function of a bazillion factors, many of which aren't well understood at all, and climatologists suck at programming them anyway. That's why the models are so unstable and frequently go crazy to Venus or ice-age like conditions even when simulating a theoretically stable climate with no CO2 emissions.
- There is evidence the CO2 greenhouse effect may saturate logarithmically, which if so would completely change the discussion around climate (in reality it wouldn't be allowed to change, but in theory)
- Nobody knows what the effect on temperature of doubling CO2 is! This is called ECS and over the decades, different teams of climatologists have estimated it yet their estimates have been drifting apart not closer together. The much vaunted consensus has actually been collapsing, with some researchers claiming ECS is a high number and others that it's a low number.