Al Gore won the Nobel Peace Prize last week for his work to publicize global warming and this got me to thinking about climate change and wine. Global warming (and Al Gore) seem to be very controversial issues in the media, but climate change and wine are not: I don’t know anyone in the wine business who does not take the fact of climate change seriously.

You have only to look at these two maps to understand why. They are based upon research by Gregory V. Jones, a geographer at Southern Oregon University. Professor Jones is my “go-to-guy” when it comes to climate and viticulture. He impresses me as a seriously good scientist and I visit his research website frequently to see what he has been working on.

As you can see from these maps, the geography of wine in the western U.S. is likely to undergo very significant changes in the coming years (click on the map to enlarge the image). Some areas that are currently in the “hot climate” range, like Lodi California, and currently specialize in hot climate grapes like Zinfandel may become too hot to make quality wines at all. Some “cool climate” Pinot Noir areas, like Santa Barbara and Oregon’s Willamette Valley, may bet too warm for those varietals and the Pinot will have to be replaced with more heat-friendly varietals such as Merlot, Malbec, Syrah or Cab. And some areas that are now considered too cold for quality wine production may become viable.

I have been reading some of Professor Jones’s scientific articles and it seems to me that the case for a general if uneven warming of grape growing regions in the western U.S. and around the world is very strong. The trend is weakest in coastal regions where maritime influences come into play and strongest inland — areas like California’s Central Valley and Washington’s Columbia Valley on the map.

There are a variety of climate factors that affect a region’s winegrowing potential including average temperature during the growing season (that’s what the map is showing), the length of the season (number of days between the last spring and the first fall frosts), the severity of vine-damaging winter freezes and the number of very hot days during the critical ripening phase.

In general heat is beneficial up to a point, improving the quality of wine by raising sugar levels and developing flavor factors without affecting acidity. Too much heat, however, and too many very hot days means that the grapes don’t ripen properly. Grapes picked when the sugars are right may lack flavor and those allowed to hang on the vine until the flavors develop lose acidity and are unbalanced. Growing seasons must provide sufficient time between frosts for plants to develop and grapes to ripen. Killing frosts obviously limit how close to the two poles vines can successful produce.

All four of these factors are changing and in some cases the shifts are dramatic. The maps give a sense of how temperatures have been changing (and let me say that the projections shown here appear to be consistent with the long term trends reported in Professor Jones’s research). Growing seasons are expanding, too. One study indicates that the frost-free period for the North Coast region of California increased by 68 days between 1949 and 2002. That is an incredible change. (The average increase for all winegrowing areas studied was 34 days — one whole month!). The number of very hot days has increased in many areas while the threat of deep freeze has diminished.

There are winners and losers from these trends. A front page article in the October 15, 2007 Wall Street Journal reported on one winner, the owner of a vineyard in Tappen, British Columbia, 70 miles north of the Okanogan Valley. Warmer temperatures, a
longer growing season, and relative freedom from killing frosts all helped put this spot on the world wine map (albeit still on the edge of the map). This gain in the Canadian west will perhaps offset a loss back east where, I am told, there are growing problems with the profitable ice wine business. Not enough cold weather to make that sweet wine the natural way.

In fact, researchers have found that most wine regions have been winners from climate change so far. Research has found a strong direct correlation between rising temperatures and scores in the wine magazines. The quality of wine has improved, the correlations suggest, although there are other possible explanations. Perhaps winemakers have become more skilled at the same time that the climate has changed. Or maybe Robert Parker just prefers Chateau Al Gore — big, ripe global warming wines.

I’ve seen the Canadian case before, I think, when Sue and I visited New Zealand in 2004. I can’t get over how many similarities there are between the evolution of the Canadian and Kiwi wine industries (the wines, of course, are very different, at least for now). A wine consultant once advised the New Zealand growers to plant Muller Thurgau, which is the most cold-tolerant grape variety. Now New Zealand grows Pinot Noir in Central Otago, where you would think is would be too cold, and makes nice hot weather Cabs in Hawks Bay, especially in the Esk Valley. In the far north, where New Zealand wine really began, I am told it is almost too warm to ripen grapes properly.

When people talk about climate change causing the ocean level to rise, flooding out coastal areas — well it may be hard to imagine how relatively small changes in natural conditions could have such large effects. But there is nothing imaginary about how the wine map is being redrawn by small (and large!) changes in climate.