Warmer climates in wine regions and changing grape-growing techniques are two key components combining to raise the alcohol level in wine. These warmer summers result in ripe, sweet berries, which are higher in fermentable sugars, boosting the average percentage of alcohol in wine from roughly 12-12.5% in the 1980s to 13.5-14.5% and even higher 15.5% during the past decade plus.
Researchers along with grape-grower and winemakers have observed that grapes have been accumulating these sugars that ferment into alcohol much faster than they have been accumulating other desired elements that result in a wine’s flavour profile, texture, colour and tannins - the grapes phenolics.

 

As with any change, there has been criticism directed towards producers of high-alcohol wines, though there is little interest in the opposite when they produce wines from under-ripe grapes. Some wine authorities have commented on several occasions - that global warming is of concern to the industry, because every year they have higher sugar content, which ferment into levels of alcohol that can over power the finished wine. Many wine regions due to climate change are facing erratic rainfall, and this low rainfall during the growing season, has resulted in viticulturists choosing varietals which are better-adapted to these conditions.
Experts suggest one option is to introduce varietals which produce lower alcohol wines in these hot, dry growing conditions. With this in mind, the IFV (French Institute of Vines) has been searching southern Europe for likely candidates to import into France. They have been selecting varietals from southern Italy, the Greek Peloponnese islands, and several regions around Spain and Portugal. The market for ‘alternative’ and varied grapes is already established, with many international varietals been grown and produced in a large number of wines regions, around the world.
In an effort to deal with climate change, viticulturists are also experimenting with new strategies in the vineyard, including later pruning, leaf canopy management and controlled irrigation to better manage potential alcohol levels.
Another issue and way to adapt; the Chilean industry, have concerns about increasing grape musts, so they recently altered their wine regulations to allow up to 7% water to be added. Though winemakers can be sent to jail for doing the same in the neighbouring Argentina, and in several regions of the world, large fines and serious penalties can be enforced. Though for example the adding of water, within set limits, has long been allowed in California, and is also permitted in Australia - ‘as an aid to mixing an additive’. If done with the aim of making a better, more balanced wine, - then there are few to comment with serious objections.
Meanwhile, Australia’s practical wine scientists are trying to isolate yeast strains which convert sugars into alcohol less efficiently so that lower-alcohol wines result - (as was the case not so long ago). But for many winemakers the world over, what makes balanced wines are balanced vines, which tends to mean older vines, dry farmed. And those who have adopted these sustainable viticultural practices - have vines which ripen well-balanced grapes earlier and more harmoniously than their commercially farmed neighbours.
But we must remind ourselves - wine has been made in hot regions for centuries, and yet you never used to find bottles with ABVs of 14% or 15% as sometimes come out of several wine regions today. Similarly, there have always been warm vintages in temperate regions such as Bordeaux, but alcohol levels rarely approached 13-14%.
So what has changed is the way grapes, particularly red varietals, are being grown. A key factor is the resulting phenolic ripeness: the moment when the pips and stalks lose any green traces. Over the past two - three decades winemakers the world over have focused on techniques such as cutting back yields early in the season to concentrate fewer bunches, along with waiting as long as possible to harvest. But the longer you wait for phenolic ripeness, the higher the berry sugars climb, and the lower the acidity. So wines with smooth tannins, and a lack of green flavours tend to come with higher levels of alcohol, frequently at the expense of freshness and varietal typicity.
Individual winemakers have set themselves personal limits over which their wine should not exceed. For some wines styles and varietals reaching levels above 14%, the finished wine can lose its fine, elegant notes. There are even a select few independent retailers and sommeliers around the world that avoid anything over 13.5%. I am sure nobody is disappointed at this focus towards more elegant wines. Though it should be said that this urge to control natural alcohol should not prevent some of the great warmer climate wines, from Barolo to the Douro, from Languedoc to Barossa, all of which tend to be around 14% and higher. The best producers in these regions don't try to push ripeness to its limits. Tasting them you realise, what really matters is not the number on the label, but a concept as elusive and subjective in wine as it is in life - ‘balance’.