Grapes basking under the Napa sun

Grapes basking under the Napa sun

11/05/2007

Tempest in a Wine Glass

by Iris Tse

This summer, I came home one afternoon to find my father frantically restocking our makeshift wine cellar with cases of wine. His action surprised me, as our “cellar,” technically a repurposed basement walk-in closet rigged with simple temperature control, was already well stocked with full-bodied Chilean Syrah and French Merlot.

Initially, I thought my father was falling for resveratrol, a reportedly anti-cancer, antiviral, anti-aging, anti-inflammatory and life-prolonging compound found in minute qualities in red wine. But I stood corrected. Between making space for his new case of Alsatian Gewürztraminer and Reislings, Dad explained that he found a few year-old news articles on the effect of global warming on grape. The gist was: the world is becoming too hot to grow grapes for quality wine.

His Y2K-esque stockpiling almost made sense. According to the worst case scenario projected by the Intergovernmental Panel on Climate Change, there can be “a global temperature increase of anywhere from 1.4 degrees to 5.8 degrees Celsius from 1990-2100.” With that, one can almost imagine the average daytime temperature in Yorkshire, England, soon becoming warm enough to ripen the warm-blooded cabernet sauvignon; and that Napa Valley would be too hot even for table grapes. If you buy into that argument, the Gewürztraminer, a finicky grape that matures best in the 13 to 15°C range, will be one of the first to go down the drain.

Yikes! No wonder Dad bought a whole case of that stuff … even though he doesn’t like white wine all that much.

It’s no news that global climate change has been changing the way plants grow all over the world. Exceptionally heavy rains across northern India in August threatened to cause extensive destruction to farmlands, possibly affecting food production. Gardeners in Pittsburgh are delighted, and concerned, when their rhododendrons bloom in mid October. The optimal range for sugar maples has increasingly inched across the US-Canadian border, forsaking the relatively tropical Vermont winter.

Wine connoisseurs worry that higher temperature will result in higher sugar ripeness and lower acidic levels that can ruin the fruity complex and balance of the wine. The extra sugar content will also ferment into a more alcoholic product, which won’t age as well or as long. Though most wine-growing region have yet to endure the kind of extreme precipitation fluctuations that create hyperbolic headlines, a summer of heavy rainfall or drought will easily ruin the year’s vintage.

The article that sparked Dad’s strong reaction was a study that appeared in Proceedings of the National Academy of Science, where it predicted that U.S. land area suitable for premium wine grape production could decrease by about 81% by the late 21st century if temperature trends continue. However, the researchers are quick to caution against blanket statements.

“The overall warming temperature places more challenge in producing well-balanced fruit for good wine. But it’s not impossible with our current technology and knowledge, “said Gregory Jones, a professor of climatology at Southern Oregon University who co-authored that paper. His research concentrates on viticulture and climate.

“So it’s not like the entire industry in Napa is going bust,” he said.

While Jones may have a point, most other experts doubt the magnitude of his findings. Some even questioned the calculations and assumptions behind that “81%” drop as it included desert or inaccessible land that one wouldn’t cultivate any vines to begin with. According to David Smart, a researcher at University of California, Davis, who also specializes in viticulture and climate effects, other assumptions that the PNAS article made was also “woefully bad.”

That article uses 14 growing season days with 35°C high temperature as the benchmark for lower quality. Yet, according to Smart, a shared secret among Pinot Noir growers in California is that some of the most outstanding vintages of the century vintages have occurred in unusually hot growing seasons, such as 1996 and 1997.

“The truth is that grape has tremendous flexibility in its ability to withstand both heat and water stress,” said Smart. “There are certainly some reasons to be concerned about grapes and climate change, and early bud break could be one. But the issues raised in that article needs better support.”

The effects of climate change may not drastically alter the world wine-making landscape. But the small changes are here. With warmer temperature, Canadian farmers have found favorable temperatures north of Okanagan Valley in British Columbia. Hotter summers in Europe have also prompted Spanish winemakers to transplant their vineyards to higher altitudes to avoid excessive heat. A side bonus of global warming is that red wines made from grapes that perform well in warmer climates, such as Zinfandel, Grenache and Shiraz, will do even better than their cool climate counterparts.

A week after my father and I spent a whole afternoon reorganizing his cellar to accommodate the new bottles of wine, we plucked a bottle of Riesling out of the shelf to accompany our dinner of mussels. As he poured the wine, I explained to him that there’s no reason we can’t have the same dinner, drinking the same wine, ten years later. Rest assure, the Riesling and other cool climate grapes are not going extinct.