According to a recent article on www.decanter.com, a report from the American Association of Wine Economists, analysed climate data from1992-2009 and found that the heat index in most wine-making countries grew less than the rise in alcohol, and could not be attributed as the major factor driving the steady increase.

The heat index was created by averaging the daily high and low temperatures over the relevant growing season in the various countries sampled. The research indicates, the authors say, that the average alcohol content in wine has increased by 1.12% over 18 years, from a mean of 12.7%.’ This, they say, is considerably higher than would be expected when set against the heat index, which predicts an average rise of 0.05% in alcohol per year. ‘It would take a whopping 20 degree Fahrenheit (6.67 Celsius) increase in the average temperature in the growing season to account for a 1 percentage point increase in the average alcohol content of wine.

Other factors that could have influenced the rising levels have been cited, including changing consumer and market preferences.