 November 4, 2003
A study of the world's top 27 wine regions' temperatures and wine quality over the past 50 years reveals that rising temperatures have already impacted vintage quality. As for the next 50 years, climate modeling for these same wine regions predicts a 2°C temperature rise that is likely to make cool growing regions better producers of some grape varieties, and already warm wine regions less hospitable for viticulture. The details of what rising temperatures and longer growing seasons have done and are likely to do to wine quality was presented by Southern Oregon University's Gregory Jones at the Geological Society of America's annual meeting on Monday, November 3, in Seattle, WA. Jones worked on the study with Michael White of Utah State University and Owen Cooper of the University of Colorado/NOAA Aeronomy Lab. "Grapes are a good indicator crop," explains Jones regarding the broader applications of their wine-specific work. Because wine grapes are grown in temperate climates - what's called a "Mediterranean" climate - and wines are almost obsessively tasted and rated for quality, wine grapes are a particularly good indicator of changes that are probably effecting other crops in the same areas, says Jones. Jones and his colleagues used records of Sotheby's 100-point vintage rating scale data (where wines scoring over 90 are "excellent to superb" and under 40 are "disastrous") along with climate records dating back to 1950 to look for trends in wine quality or growing season temperatures. What they found was an average temperature rise of 2°C rise over the past 50 years and higher vintage ratings. "There were no negative impacts," Jones said of the apparent temperature rise in the world's most renowned wine producing regions. Included in the study were five southern hemisphere wine regions, including three in Australia, one in South Africa and one in Chile. While it is clear that improvements in grape growing and wine making technology have produced better wines, climate will always be the wild card in determining year to year variations in quality, said Jones. "If the climate is more conducive in general or less variable, then higher quality should be easier to obtain." To project into the future, Jones and his team used the HadCM3 coupled atmosphere-ocean general circulation model (AOGCM) developed at the Hadley Centre in the UK. It is a model that has been used previously for predicting future agricultural conditions, Jones says. Based on the modeling, the same top wine-growing regions can expect another 2°C over the next 50 years. Does that mean even finer wines? Not necessarily, says Jones. Warmer temperatures could mean that cool growing regions should ripen fruit more consistently and should experience less year-to-year wine quality variability. In addition, already warm wine-growing regions could experience challenges in terms of overripe fruit, added water stress, and increases in diseases and pests. For example, Italy's famous Chianti region, which already is very warm in the summer, could be hotter, making harvest earlier during hotter periods and giving some pests more time to mount an attack on the vineyards. On the other hand, the Rhine Valley region in Germany could benefit with greater ripening potential, but might eventually have to produce different wines in the changing climate. On the other hand, warmer temperatures are already allowing wine grapes to be grown at higher latitudes and elevations - places that were once too cold. For instance, vineyards are on the rise in southern England. Along with the climate and grape-growing changes, there are also bound to be some big shifts in thinking for people of the wine growing regions, says Jones. "There is a huge historical and cultural identity associated with wine producing regions." A region known for a superb merlot, for instance, might need to shift to another kind of grape, changing the cultural identity that has developed over centuries. The bottom line, says Jones, is that growers need to pay attention to what might be happening in terms of climate. "In the coming 20 to 30 years they may have to work to replace varieties or change management strategies," he said. Survival of today's wine regions will depend on how well viticulturists adapt to and mitigate the effects of climate change.
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