for National Geographic News
Wine production in the United States could take a drastic hit if global warming continues unabated, a new study says.
The grapes needed for premium wines are more sensitive to weather conditions than those used for table wine or grape juice.
If human-caused carbon dioxide emissions continue to rise, average temperatures in wine-producing regions will increase, the study says, as will the number of extremely hot days.
And a hotter, more variable climate will harm wine-grape ripening.
"We project a greater than 80 percent reduction in total premium wine production in the U.S.," said Noah Diffenbaugh of Purdue University in West Lafayette, Indiana.
Diffenbaugh co-authored the study, which appears today in the journal Proceedings of the National Academy of Sciences.
According to his team's data, warming could lead to a "more than a 50 percent [acreage] reduction in areas suitable for the highest-quality, most expensive wines."
In premium grapes, photosynthesis breaks down at temperatures above 95°F (35°C). Flavor ripening can fail with prolonged exposure to temperatures above 86°F (30°C).
Diffenbaugh's team found that as carbon dioxide gases increase, average growing-season temperatures might rise by about 5°F (3°C) by the year 2100.
Although that's a fairly significant change, an average of warmer days isn't by itself catastrophic for grape-growers, Diffenbaugh said.
The scientists also found that California's Napa and Sonoma wine regions, which currently see fewer than 14 superhot days each year, will see 55 or 60 of them by late in this century (California map, facts, more).
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