Have recent wines left you feeling unusually drowsy?

Have you noticed any tell-tale signs - a reddening of the cheeks, or sweaty palms and an aching head? Do you ever feel particularly thirsty or short of breath? If so, you could well be under the influence of an ongoing trend. As anyone in the wine trade will tell you, it is not just the world's climate that has been edging upwards by degree.

Hotter summers have helped boost the sugar content of grapes causing the average wine to increase in alcoholic strength from about 12.5% to around 14% in the space of a generation. To counter this, the growers can pick the grapes earlier, and right now wine regions in the southern hemisphere are facing one of their earliest harvests. Unfortunately picking earlier can mean losing out on flavour compounds that take longer to develop.

Yet perhaps more important than climate change, has been a conscious drive for maximum ripeness. At the cheap end where yields are stretched, a bit of extra alcohol can mask a multitude of sins, smooth out the texture and give an impression of sweetness - important in the more fruity styles of white wine. At the top end where bottles are herded into lines to be scored out of a 100, winemakers are predisposed to ramp up the intensity of flavour, aroma and alcohol to stand out from the crowd. These wines are rarely judged on their restraint, or even their drinkability.

"There's no doubt that the plush, deeply-coloured, high alcohol monsters win, or were winning, the medals and getting the high points," the consultant winemaker Philip Goodband told me, and while that was a few years ago, things haven't changed that much. To use a motoring analogy these are the gas-guzzling SUVs of the wine world.

Rising alcohol levels have blurred that sense of terroir that roots a wine to a particular place. The winemaker Sam Harrop who used to consult for Marks & Spencer believes it comes down to optimum ripeness. "As soon as you move beyond that into jammy, confected flavours you lose all flavour identity and it becomes just another over-ripe, warm-climate wine."

Add in the trend for super-sized wine glasses which can hold up to a third of a bottle and that may be another reason for the symptoms mentioned above.