Published by the Students of Johns Hopkins since 1896
October 28, 2021

Climate change may decrease wine quality

By RACHEL WITKIN | October 11, 2012

With global warming causing extreme weather around the world, it may seem like a glass of wine is the only thing people can count on.  As climate change worsens though, the harvest season for wine grapes will change. This will affect the quality of wine produced and force vineyards to be relocated in the future, chasing the cold weather that the crops require.

The wine type is dependent on the length of the grape harvest season. Photosynthesis occurs between 10 and 30 degrees Celsius, and once temperatures rise above that window, the grapes stop growing. Wine production is also heavily dependent on the change in temperature between night and day that help the grapes maintain their acid levels.

This acidity determines the flavor of the wine. “If a wine does not have that acidic backbone, it’s referred to as flabby [and] it doesn’t have that character. It’s the acid that gives the wine the thirst quenching aspect of it,” Antonio Busalacchi, advanced sommelier and Earth Systems Science professor at the University of Maryland, said.

Busalacchi first became interested in global warming’s effect on wine when he read a journal article on the subject in 2003, which was also the year that Europe suffered from a devastating heat wave. He decided to look at wineries around the world to try to figure out how much of an effect increased temperatures will have on wine grapes.

Busalacchi started with models from the Intergovernmental Panel on Climate Change (IPCC), which predict temperatures using various carbon dioxide emissions scenarios.  He corrected any biases in the models and took the average of three different scenarios. Busalacchi also used observations from 24 wine regions around the world to try to predict what will happen to vineyards in the future.

He took into account the number of days that grapes will able to grow, the amount of heat over the entire harvest season, and rainfall predictions. The models show that by 2050 there will be a two degree Celsius increase in the yearly average temperatures in most of the regions that produce wine.

This number jumps to four degrees Celsius by 2095. There will also be a 10 to 30 percent decrease in precipitation and serious droughts in Australia and South Africa. Some regions, including Bordeaux, France, will have much shorter growing seasons, which will make it harder for the grapes to ripen and develop flavor.

However, some areas with high latitudes and altitude like Alsace and New Zealand will benefit because the grapes will be able to grow for a longer period of time and develop the amount of acid necessary for a high quality wine.

Currently, the warm temperature allows for the production of the best wine, labeled “premium” by wine experts. However, as the climate warms, vineyards will produce “standard” wine, which is a downgrade. “Wines are going to lose their traditional character,” Busalacchi said. “The grapes are going to change and the wines are going to change.”

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