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Global Warming: Napa Valley Cools its Heels

by David on December 22, 2007

As I dragged myself out of bed to 27 degrees F. this morning, one of many freezing mornings in recent weeks, I thought there just might be something to this very interesting article from Appellation America. There wasn’t an actual comment on winter weather but, jeepers, it’s cold!!!Anyway, to get to the point, the article quotes Dr. Andy Walker, of UC Davis, as saying what those of us who live here have noticed (and appreciated!) – that the last three growing seasons have been cool ones. Last summer’s weather was so wonderfully mild that it had a veteran grower crowing about the great conditions and predicting the vintage of the century in August, before harvest even started. Growers, wisely, tend to reserve comment until it’s all in the barn, but he may be right. It was a heckuva good harvest!!Dr. Walker thinks it’s more than a coincidence about the mild weather. As more wine grapes are planted in southern England and Germany enjoys improving fruit maturity, presumably, due to warming, he predicts that the vast, already-toasty San Joaquin Valley, in California’s interior, will heat up, too (yikes!), and work like a vacuum to pull in marine air from the Pacific into Napa, Sonoma, Mendocino and Lake Counties. That makes perfect sense. We’ve been boring you for years explaining the way the summertime heat rises in our very small valley, and then lures the cooling San Pablo Bay fog up-valley in the evening, conveniently trapped between our two mountain ranges. I guess we’re just looking at a much grander scale, here.

Dr. Walker said that “the average temperature drop in Napa and Sonoma could well be so significant over the next few years that it could radically change the character of many wines over the next decade.” He thinks Lake and Mendocino counties will experience only a slight change – probably a relief to the Mendocino growers.

Now, that might sound a little scary until you think about the hot – no pun intended ;-) topic on everyone’s lips lately – hangtime. How to get full fruit maturity without also getting outrageously high alcohols. Well, if it’s cooler it will take longer for the sugar to accumulate while we wait for flavor development and seed maturation. We won’t have to worry as much about the sugars, and therefore alcohols, climbing too high. Will the “radical change” take the form of enjoying wines with ripe, wonderful flavors that are 13 or 13.5% instead of 14 or 14.5%? Works for me! Seems to me we’re already on our way. I can hear myself reporting harvesting mature fruit and moderate sugars in recent harvest updates and Winemaker Notes. Yippee!!!Of course, water will become an even greater issue than it is now and already there’s greater discussion about dry farming and “off-dry farming”. We know that there’s a history of dry farming wine grapes in California, just because irrigation used to be so difficult, so perhaps we’ll revisit the past to plan for the future. Using rootstocks that send the roots down rather than out, more frequent cultivation and widening the spacing (again, moving forward to the past) are other recommended ways to decrease water use. It sounds like a manageable challenge if we’re smart about it and think ahead when we replant.So, I hope he’s right! I can certainly live with a cooling trend although, at the moment, I’m still waiting for my feet to thaw out on this freezing-cold first day of winter! Happy solstice!

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