Increasing Alcohol Content

[Thomas]

Yeast cannot create alcohol without sugar (brix) so it isn't the yeast strain, it's the sugar levels.

In Ca. adding sugar to must is a no-no, so those high alcohol wines had to have started with quite ripe grapes. And grapes grown in the south will of course be even higher in sugar, sometimes adversely.

I must reiterate: in Ca. adding sugar is a no-no; do wineries cheat? That's a good question too.