Rising alcohol levels in wine is one of the hot-button issues of the wine world. Many wine lovers, including many readers of Vinography, think this is one of the most pressing problems with wine today and bemoan the fact that fewer and fewer wines can actually be drunk with dinner (as higher alcohol levels make it more difficult to pair wines with food). This concern is based in solid fact. Alcohol levels in California wine in particular have risen several absolute percentage points in the last two decades, and perhaps even up to 20% relative to earlier levels.

Today the San Francisco Chronicle’s W. Blake Gray takes a three part look at the alcohol levels in wines that is worth reading for anyone interested in the issue. In the first piece he summarizes the debate about higher alcohol wines.

In the second piece he looks at ways that California winemakers are managing alcohol levels in wine, from the low tech methods of adding water to the fermenting grapes to higher tech methods such as reverse osmosis and centrifuges.

Finally, he highlights one of the most interesting theories I have heard in a long time about high alcohol wines: it’s all about the rootstock. Some recent research at UC Davis has pointed to the possibility that the newer Phyloxerra resistant rootstocks that were widely planted in the mid-1980’s are partially responsible for higher alcohol wines because of their tendency to produce grapes with higher sugar content at ripening.

I’m sure Robert Parker is sighing in relief to know that the trend in higher alcohol wines isn’t his fault after all, and is merely a matter of plant biology. In all seriousness, though, this is a pretty intriguing theory. Unfortunately the article doesn’t have enough information about the specific rootstock clones that might contribute to this effect and whether these clones are also in use, say, in Australia, which also has seen massive jumps in alcohol levels.