A good reason you don’t find too many Bordeaux wines at 10-11% alcohol by volume anymore. Warm temperatures and dry summers increase the sugars in the grape which when fermented result in higher alcohol. Here is the drawback though. Grapes that mature quickly lose their acidity which gives the wine that balance. Here are how some French vineyards are coping. Click the title to view.
AFP: Fickle weather worries French wine growers