The evening news on TF1 carried an interesting report on climate change and Loire Valley wines a couple of evenings ago. The grape harvest is beginning earlier and earlier all around France, the report said, with the Loire Valley being no exception. Grapes are ripening faster because of increased sunshine.
One grape-grower over in the Saumur-Champigny wine district, west of Tours, said that when he started his career back in the mid-1970s, his (and his father's) challenge was to produce wines with an alcohol content of 10%. That was not easy then. Nowadays, however, he says he regularly produces Saumur-Champigny reds with 12% or 13% alcohol.
Rather than harvest his grapes earlier, he says he has kept the schedule he always followed, meaning that the grapes are much riper when they are picked than they used to be. They contain more natural sugar, which means the wines are more puissants, more alcoholic. The fruity, light wines of 30 years ago are no more.
Saumur-Champigny and the nearby appellations of Chinon and Bourgueil produce red wines using the Cabernet Franc grape exclusively. Warmer, sunnier weather also makes white wine grapes mature more quickly (or reach a greater stage of ripeness), and the local white wines are more alcoholic than they used to be as well.
Here's a link to the TF1 report on climate change and Loire wines
Overall, the TF1 report said, the grape harvest occurs two weeks earlier than it used to. And the wines are different. For the time being, the warmer, sunnier climate trend is a boon to wine producers. Studies done by France's INRA (the Institut National de la Recherche Agronomique) show that hours of sunshine recorded in the Saumur area have increased by 25% since 1980.
Further warming of the climate might turn into too much of a good thing, the experts say. Right now, Cab Franc and other grapes are benefiting. But grapes need the first cool nights of autumn to develop good flavors, so if they ripen too early that becomes a problem. INRA researchers are studying new grape varieties and hybrids that will not ripen so fast in today's sunnier, warmer Loire Valley (or in other wine districts).