Are you sure? Because my understanding is, in the past what has happened is that some other force causes a bit of warming, and then the oceans heat up, which causes co2 to bubble out, which then causes more warming, which causes more co2 to bubble out, and so on. So co2 is an active part of the picture but it wasn’t the independent variable, so to speak. Whereas now we’re mining fossil carbon and squirting it directly into the atmosphere, which is new.

And climate scientists are very smart and have worked out how much the added co2 amplified the original warming, and have been able to work out how much warming you would get by doubling co2 levels, which appears to be around 3 degrees C.