(TheTennessean) - When it comes to alcohol content, all wines are definitely not created equal.

A German riesling may contain only half the alcohol of a riesling from California or Australia. A French Champagne may be 25 percent more potent than an Italian spumante. And a big California zinfandel might approach fortified-wine levels.

One thing many wines do have in common is that over the past couple of decades, average alcohol content has increased significantly. That’s primarily because higher-alcohol wines have found a lot of consumer appeal as they tend to have rich, ripe fruit flavors.

Those flavors come from really ripe grapes, and really ripe grapes come from warmer growing conditions. Those grapes contain more sugar, and more sugar produces more alcohol during fermentation.

California is a good case study in how climate affects grapes. Over the past 15 or 20 years, many California wine-growing regions have seen steadily increasing seasonal temperatures — and a correspondingly rise in sugar/alcohol levels. Similar reports come from Australia, Spain and South America.

Of course, not all wine regions are in hot climates. German Rieslings are low in alcohol because grapes struggle to ripen that far north. Cool climate pinot noirs, such as those from Oregon, illustrate the climate/alcohol relationship especially well. Oregon pinots tend to be lighter, drier and lower in alcohol than California pinots, because grapes in the northwest are not supercharged with heat.

If you have any doubts about alcohol being a key component of wine, just take a sip of “dealcoholized wine.” Alcohol content affects both flavor and texture, and it’s evaporating alcohol that carries the aroma of wine to our senses. Alcohol also adds viscosity and helps balance sweetness and acidity. On the other hand, too much can damp-down flavors and aromas, and make a wine seem “hot” on the palate.