Do those New World Cabernets and Zinfandels make your head spin? Fed up with having to stop drinking after just one glass?

Plenty of wine lovers around the world will have noticed their favourite tipples are getting stronger, and many of them are unhappy about the hangovers that come with increased alcohol levels.

But it seems they have only themselves to blame as experts say that changing consumer tastes are mainly responsible for driving the trend.

Wine critics and advances in winemaking techniques also shoulder some of the blame for what experts say are unbalanced wines that can cause health risks and safety issues, casting a pall over the pleasure of imbibing.

"The rise in alcohol content of wine is primarily man-made," reported a working paper by the American Association of Wine Economists in 2011.

Over the last two decades, drinkers have developed a passion for fruity, aromatic wines with round, silky tannins, encouraged by high ratings from critics.

Even for growers who favour elegance over "fruit bombs", the quest for ripe tannins has led to grapes with more sugar, which transforms during fermentation into higher alcohol levels.

"I would stress that higher alcohol levels are never our aim, but rather the logical consequence of the way we work in the vineyards today, which has evolved considerably compared to how it was 20 or more years ago," says Christian Seely, managing director of AXA Millesime's wine estates in France and Portugal.

A couple of decades ago, yields were twice what they are today, and very little sorting was done to select the best fruit.

The alcohol levels might have been lower, but the tannins were often unripe, requiring years of cellaring to soften.

Today vintners look for mature tannins in the grape skins and seeds -- phenolic ripeness in the industry jargon -- before the harvest, even if it means higher sugar content.

"It is important to understand that the effect of achieving more regularly greater phenolic ripeness is not just to achieve higher sugar levels and so higher potential alcohol levels, but also, crucially, riper and finer tannins," Seely told AFP.

"We choose the date of picking based on our tasting of the grapes, but also on our analyses of polyphenols and IPTs (total phenolics), which usually indicate the optimum phenolic ripeness a couple of days after the desired sugar levels," he said.

But wine drinkers now say the alcohol levels have gone too far.

"Going from drinking two glasses of wine with 12-percent alcohol to a similar amount of wine that contains 14-percent alcohol could put you from under to over the legal limit for driving," said Michael Apstein, a columnist, gastroenterologist and assistant professor at Harvard Medical School.

"We all enjoy wine, but we enjoy balanced wine. As soon as you get 14, 15 and 15.5 percent, you don't have balanced wines," added Laurent Audeguin, a selection, research and development manager at the French Vine and Wine Institute (IFV).

-- Climate change compounds problem --

At the same time, there is little interest in spoiling the party with the return of thin wines with unripe tannins.

Climate change, while not the only factor, is compounding the problem.

"Global warming is a bigger and bigger concern in the industry, because every year we have higher sugar content," Audeguin said.

"We now face erratic rainfall, and less rainfall during the growing season, mainly in the Mediterranean vineyards, so we have to find varieties well-adapted to those conditions."

One option, says Audeguin, is to introduce grape varieties that deliver lower alcohol in hot, dry growing conditions.

With this in mind, the IFV has scoured southern Europe for likely candidates to import into France.

"We are selecting grape varieties from south Italy, the Greek Peloponnese islands, Spain and Portugal. We don't breed these, we just try to import these varieties and see how they perform in France. The plan is to have some varieties authorised in France within five years," said Audeguin.

Vintners are also experimenting with new strategies in pruning, leaf canopy management and irrigation.

In the meantime, low-alcohol wines are increasingly popular.

Domaines Auriol, based in Languedoc-Roussillon, produces So' Light, a wine with nine-percent alcohol content that appeared on American store shelves last January.

In Britain, according to Chris Wisson, a senior drinks analyst at Mintel, the low-alcohol wine market is worth 23 million pounds ($36 million, 27 million euros) with strong growth pushed by government taxes on alcohol and health concerns.

"The rising price of wine has made people try low-alcohol wines, and there is certainly a health side to it," said Wisson. Demand, he says, is driven primarily by women and young drinkers aged 18 to 24.

For fine-wine stalwarts, there is another option.

"Naturally if one sees a high alcohol level on the label of a bottle you need to adjust the amount you might decide to drink accordingly, but that is just common sense," Seely said.

Common sense? Maybe. Common practice? Maybe not!