Many consumers perceive wines nowadays as more alcoholic than they used to be. This is actually quite true. This has to do with a lot of things (and not only global warming): grapes are harvested riper, wineries use better clones, consumers drink more wines from warmer climates, such as southern Italy, the New World, etc, which automatically gives a higher alcohol.
Producers are aware of the problem and are seeking solutions. For example, researchers in Australia have for three years experimented with shading a vineyard planted with Syrah after le véraison, the period when the grapes change colour and turn blue. A net was put over the vineyard that softened the sun’s radiation. When harvested, the grapes had less sugar than normal and a little bit more acidity. But they had more or less the same phenolic maturity. This is an interesting experiment, but you would have to put up many meters of nets if you want to do this on a larger scale. Maybe a similar effect can be achieved by not doing efeuillage (manual leaf plucking).
Here is more information about this shady experiment vitisphere.com
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