The surgeon general warning came along with a large number of other measures to reduce smoking. If that warning had an effect, I would guess that effect was to prime the public for the other measures and generally to change consensus.

BUT, I think it's very likely that the surgeon general warning was closer to a signal that consensus had been achieved. That voice of authority didn't actually _tell_ anyone what to believe, but was a message that anyone could look around and use many sources to see that there was a consensus on the bad effects of smoking.