Huge swathes of California's wine areas may disappear by 2050 if world temperatures continue to rise at their current rate, warn two separate studies on wine and global warming.
There were some worried looks among conference guests as wine and climate change expert Gregory Jones unveiled a map showing where California's famous Napa Valley wine region used to thrive.
A 2°C rise in temperatures up to 2050, already predicted by some scientists, could be enough to make this vision a reality, he said.
The warning highlights growing concern about the possible effects of global warming on the world's wine growing areas.
Jones' presentation, made at the International Wine Business and Marketing Conference in France last week, was backed up by similar research published by the US National Academy of Sciences this week.
That report said half of America's top wine growing areas could be unviable by the end of this century.
Whether that prediction comes true will depend heavily on events in California, which lies at the heart of the US wine industry.
Jones, a professor at Southern Oregon University, said Napa Valley was of particular concern because a rise in temperatures would see it move to the "upper limit of its capability".
Jones has spent the last few years developing a model to compare the average temperature of different wine regions around the world and their suitability for growing the grape varieties they are most famous for.
Different grape varieties work best at different temperatures.
Minimum temperatures in Napa have risen 1.7°C over the last 50 years, largely in line with the 2°C rise average temperatures around the world.
This has made Napa perfectly placed to produce top wines from its most popular grape varieties, but more temperature rises will be a test of how the region is able to adapt, Jones said.
In contrast, and just to fuel extra tension between the Old and New World wine producers, France's Bordeaux region comes out of Jones' climate model rather well.
Bordeaux, despite its high reputation, is actually slightly on the cold side for several of its specialist grape varieties, and notably Cabernet Sauvignon, Jones said. If temperatures rise, Bordeaux may end up better positioned to produce top vintages.
Still, winemakers in California's Napa Valley remain upbeat about the challenges they face.
Karen Ross, president of the California Association of Winegrape Growers, told BeverageDaily.com that the region's wineries were acutely aware of the impact of weather and climate on vintages.
"It is important to point out that many fine wines are produced from warm climate varietals in countries with high temperatures and little rainfall.
"California winegrape growers have a history of being resourceful and adaptable," she said, adding that reports of the challenges facing the region would stimulate new debate on whether "the California wine community has the right research and extension programmes in place".
Wine and climate change is set to be a big part of the 2007 Unified Wine & Grape Symposium in California.
Research on how to handle the effects of climate change is likely to focus on plant breeding techniques, in an attempt to create strains that will enable vines to cope more easily in hotter weather.