Why are so many wines higher in alcohol than before?

If you prefer lighter wines it can be difficult at times to find anything that registers at less than 14 per cent alcohol. There are two reasons why alcohol levels in wine have been creeping up over the past decade or so.
In warmer climates grapes accumulate higher levels of sugar, which then ferment into more alcohol. It’s a simple equation; more sugar means more alcohol, unless you stop the fermentation, which will leave you with a sweet wine. As many of the traditional wine-producing regions have heated up because of climate change, their wines are becoming higher in alcohol. At one time areas such as Bordeaux struggled to ripen grapes in some years, and their wines were usually 12.5-13.5 per cent ABV. Nowadays many are 14 per cent, 14.5 per cent or even a very heart-warming 15 per cent. In hotter regions such as California, they can sometimes go higher, to 15-17 per cent alcohol.
The second reason is simple: consumers like it. Lighter wines tend to be fresher with higher levels of acidity. Fuller-bodied wines, sometimes called fruit bombs, taste riper and smoother and slip down easily. The demand for full-bodied wines is not exclusively Irish. There is a preference for these in many of the world’s biggest wine markets. It is not just wine drinkers who prefer bigger wines. A great many judges and critics score them higher too.
Producers can pick their grapes earlier if they want to keep alcohol levels down. Or they can plant vines in cooler areas. But, although some regions are worried about their long-term future as our climate changes, many are happy to produce wines at 14-14.5 per cent ABV. It is worth remembering that producers are allowed a tolerance of .5 per cent either way when labelling a wine (it is 1.5 per cent in the US) so your 13.5 per cent wine may actually be 14 per cent or 13 per cent.