New research from Harvard University and NASA shows that higher temperatures in France are producing exceptional vintages. However, this trend may not last forever.
Wine grape maturation is largely driven by warmer temperatures and delayed by rain. Researchers examining records dating back more than 500 years revealed that wine grapes across France are now being harvested two weeks earlier on average than they were in the past.
"There are two big points in this paper, the first is that harvest dates are getting much earlier, and all the evidence points to it being linked to climate change," explained Elizabeth Wolkovich, an assistant professor of organismic and evolutionary biology at Harvard University. "Especially since 1980, when we see a major turning point for temperatures in the northern hemisphere, we see harvest dates across France getting earlier and earlier."
While earlier harvests are generally associated with higher quality wines, researchers warn the trend may end soon, as climate change continues to drive temperatures higher and higher.
"The bad news is that if we keep warming the globe, we will reach a tipping point," Wolkovich added. "The trend, in general, is that earlier harvests lead to higher-quality wine, but you can connect the dots here... we have several data points that tell us there is a threshold we will probably cross in the future where higher temperatures will not produce higher quality."
Prior to 1980, grape growers basically needed a drought to generate warm enough temperatures for a really early harvest. But that is no longer the case.
In other words, human-induced warming has become so pronounced that even drenching summer rains cannot offset the heat that helps ripening grapes develop sugars, acids and tannins.
"It's become so warm thanks to climate change, grape growers don't need drought to get these very warm temperatures," added Benjamin Cook, lead author and a climate scientist from Columbia University's Lamont-Doherty Earth Observatory and NASA's Goddard Institute for Space Studies. "After 1980, the drought signal effectively disappears. That means there's been a fundamental shift in the large-scale climate under which other, local factors operate."
In terms of when this trend may end, researchers reference the extremely dry, warm 2013 growing season that preceded one of France's earliest harvests on record.
"But the wine quality was kind of middling," Cook said. "That suggests that after a certain point, it could just get to be so warm, and the harvest so early, that you move into a situation where the old rules no longer apply."
What's remarkable about the recent study is that is addresses vineyards all across France and paints a clear picture of what the region can expect with future grape harvests.
"These records come from... Burgundy, Bordeaux, Loire and even from Switzerland, so we're looking at an aggregate of many data sets that are put together to get one picture of how a large region is changing," Wolkovich said.
However, what the study lacks is specificity.
"If you are on a certain slope with a certain soil type in Bordeaux, you will see a slightly different response than if you were on a wet soil in Burgundy," Wolkovich continued. "So there is a lot of local climate that matters to when you harvest your grapes, and, especially, what kind of quality you get, and this type of analysis is not targeted to answering those questions about local climate."
There is a French word, terroir, that vintners use to describe environmental factors that impact wine grape quality. Even still, "at the heart of good wine is climate," Wolkovich concluded.
Their findings were recently published in the journal Nature Climate Change.
