Global warming’s impact on Riesling

A Rheingau Riesling is considered one of the finest Rieslings in the world but that hallmark may come under threat from an unlikely source. Not a New World Riesling, or even a domestic knock-off; the threat is non other than global warming.

At the end of the 19th century, Riesling wines were fetching higher prices on world markets than Chateau Lafite claret and even Veuve Clicquot champagne. Then came the era of Liebfraumilch, sickly sweet and cheap. A good Rhine Riesling now has come full circle, once again winning accolades and fans all over the world.

The special quality of a Rhine Riesling is heavily reliant on a mix of cool nights and warm days that facilitate Riesling’s slow ripening. However, warmer than average temperatures are threatening to redraw the wine map. If current climate averages hold up, or regrettably increase, red grape varietals such as Cabernet Sauvignon and Merlot, traditionally grown in more southern climates will migrate north by anywhere from 125 to 250 miles and up hillsides by 100 to 150 yards. Following this trend, by the year 2040, Cabernet Sauvignon will flourish where Riesling does now.

It has been noted that German Riesling vines are developing shoots seven days earlier, blossoming 10 days earlier and starting to ripen 12 days earlier than the 40-year average, and are especially affected by warmer than average nights. Ernst Buscher, of the German Wine Institute states “Riesling vines are very sensitive to soil and climate.”

This impact has been felt already in the past few years. ‘Eiswein’, a delicious dessert wine made from grapes that are picked frozen on the vine at temperatures of 20 degrees or below, is becoming ever more rare. In the 2006 harvest, local growers had only two chances to pick at the proper temperatures; December 27 of 2006 and January 26 of this year. Arno Schales, whose family has grown Riesling since 1783 and has made Eiswein for 50 years says that these are the latest harvest dates ever for Eiswein. His current crop is approximately 200 bottles; well down in volume from the usual 1,000 to 2,000 bottles produced, and most was made from Pinot Noir grapes that survived the late warm temperatures without rotting.

Due to such dire weather for the past growing season, many Rheingau growers are giving up on Eiswein and instead picking the grapes for     - a wine made from grapes that have dried on the vine. German growers are leaning more towards red grapes, though favoring more traditional Pinot Noir and Dornfelder varieties over Merlot and Cabernet Sauvignon. This is due in part to German consumption of red wine, which has increased 17 percent in the four years between 2002 and 2006.

The demand is still strong for better and more expensive Riesling, particularly in the Unites States. Despite advances made by the USA and Australia, Germany still commands 60 percent of world production. Quality of Riesling has improved as a new generation of growers has invested in better processing, but the possibility of climate change could force them to adapt accordingly. Here’s just one more example of the impact around the world that is felt by global warming. Since terroir is so vitally important in the growing of grapes for the world’s best wines, it’s possible that it is only a matter of time before such nuances of flavor, or a particular varietal alone could be lost.

(photo courtesy www.winesof

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