Wine: A barometer of global warming Vintners in France forced to change ways grapes are grown

ROUFFACH, France - On a cobweb-encrusted rafter above his giant steel grape pressers, Rene Mure is charting one of the world's most-tangible barometers of global warming.

The evidence, scrawled in black ink, is the first day of the annual grape harvest for the past three decades. In 1978, it was Oct. 16. In 1998, the date was Sept. 14. This year, harvesting started Aug. 24 - the earliest ever recorded, not only in Mure's vineyards but in the entire Alsace wine district of northeastern France.

"I noticed the harvest was getting earlier before anybody had a name for it," said Mure, 59, the 11th generation of his family to produce wine from the clay-and-limestone slopes of the Vosges Mountains near the German border. "When I was young, we were harvesting in October with snow on the mountaintops. Today, we're harvesting in August."

Throughout the wine-producing world, from France to South Africa to California, vintners are in the vanguard of confronting the impact of climate change. Rising temperatures are forcing unprecedented early harvests, changing the tastes of the best-known varieties of wine and threatening the survival of centuries-old winegrowing regions.

In the hot Mediterranean vineyards - the first to feel the effects of longer, drier summers - vintners are harvesting grapes at night to protect the fragile fruit at the critical picking stage. Growers in Spain, Italy and southern France are buying land at higher terrains for future vineyards.

Some champagne producers in northern France - whose grapes were ready for harvest in August, earlier than in any year on record - are eyeing properties in southern England, the current beneficiary of planet warming. The British wine industry is re-emerging for the first time in the 500 years since a minor ice age cooled Europe.

While Provence and other southern regions of France have suffered through debilitating droughts and high temperatures for several seasons, scientists and growers have been stunned by the dramatic evolutions in the northernmost regions of Alsace and Champagne, long considered less susceptible to global warming.

"Usually, Alsace is one of the last regions to harvest in France, and this year, we were the first ones," said Gerard Boesch, president of the Alsace Wine Association. "That's astonishing."

In a chain reaction of nature, climate change is also sending new insects and diseases north. The leafhopper is migrating north with warmer weather, spreading yellow leaf disease in Alsatian vineyards for the first time, according to a regional research institute.

Scientists and vintners say wine grapes are the best agricultural measure of climate change because of their extraordinary sensitivity to weather and the meticulous data that have been kept concerning the long-lived vines.

"The link of wine to global warming is unique because the quality of wine is very dependent on the climate," said Bernard Seguin, an authority on the impact of global warming and viniculture at the French National Agronomy Institute. "For me, it is the ultimate expression of the consequences of climate change."

Nowhere is the impact more acute or better documented than in France. Here, the $13 billion wine industry is not only crucial to the economy but also more inextricably entwined in the culture and heritage of the people than in any wine-producing country on Earth.

For centuries, the "vendange," or annual grape harvest, has been treated as a nearly religious ritual, with parish churches maintaining meticulous records in dusty, crumbling ledgers.

In France, winegrowers are subject to the world's most-rigid cultivation restrictions: Vintners can grow only varieties authorized for their region, harvests are tightly regulated and, until this year, no irrigation was allowed. Year after year, the climate is the single greatest variable in France's wine production, making its vineyards the perfect climate-change laboratory for scientists.

Rene Mure's family has been growing grapes and producing wine in the hills surrounding the picturesque village of Rouffach since 1648. The family tree, with its 12 generations of winegrowers - Rene's children, Veronique, 31, and Thomas, 27, are the newest Mure vintners - is tacked to a wall in his cellars, which produce 350,000 bottles of wine a year.

Mure and other French vintners have tasted global warming in their wines for the past three decades. Their red pinot noirs were more aromatic, and their white Gewurztraminers were sweeter with fragrances of litchi and roses.

All over France, vintners abandoned their forefathers' practice of adding sugar to the wines to improve their flavors and alcohol content. The sun and warmer summers were doing the job for them. Through the 1980s and 1990s, French wines won higher and higher ratings from domestic and international wine critics.

But the climate warming has accelerated faster than vintners or French scientists anticipated. That has forced sugar levels, and consequently alcohol levels, higher in the wines. Some producers in Provence are adding acidic compounds to their wines to keep them from becoming too sweet and undrinkable.

Vintners in Alsace are now facing similar problems. The average temperature in Alsace, which is bordered by the Rhine River and Germany, has risen 3.5 degrees in the past 30 years, a dramatic increase for sensitive grapevines, according to the French National Agronomy Institute.

"For 10 years, our problem has been to keep the acidity," Mure said. "Wines need to be balanced to have fresh, crisp flavor."

Mure has already started changing the way he cultivates his grapes, growing some vines closer to the ground with fewer leaves in the style of southern grape growers, giving his vines less exposure to the sun.

He wants to experiment with growing southern Syrah grapes in Alsace. The way Mure sees it, if the southern climate is moving north, he should be prepared to grow grapes that can withstand the heat. -washingtonpost