French wine quality boosted by climate change - but effects will be short lived

The quality of wine in France has been given a boost by climate change over recent years, with warmer temperatures minus droughts leading to earlier harvests. However, this effect on wine will not last, scientists say, with future projections of global warming set to pass a tipping point for good wine production.

Nasa and Harvard scientists Elizabeth Wolkovich and Benjamin Cook looked at 500 years of wine grape harvest records to find out what effect climate change has had on production. The study, published in the journal Nature Climate Change, showed global warming has led to harvests across France taking place two weeks earlier than past times.

In wine production, warmer temperatures normally speed up wine grape maturation, while increased rainfall normally delays it. High-quality wines are normally associated with earlier harvest dates.

Analysis of the harvest data showed between 1600 and 2007, early grape harvests took place when there were droughts in spring and summer, and were delayed in wetter years. However, their findings also showed this relationship has broken down since the 1980s, when global temperatures began increasing at a faster rate.

Canary in the coal mine

Cook said: "It's become so warm thanks to climate change, grape growers don't need drought to get these very warm temperatures. 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."

The team says the increasing global temperatures does not mean wine quality will continue to improve. They looked at the wine quality produced in 2003, when a massive heatwave hit Europe. That year saw the earliest harvest of the whole study, yet the wines were of mixed quality.

She said current climate change has led to global warming of around 0.6C. If current projections of 2C warming by the end of the century come to pass, there could be significantly earlier harvests.

"The bad news is that if we keep warming the globe we will reach a tipping point," Wolkovich said. "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.

"At the heart of a good wine is climate. So (the grapes) are a very good canary in the coal mine and that's something you see in this paper, which is that temperature is the biggest driver on when you harvest winegrapes."