That climate change report? Let’s look at the facts
22 Apr 2013
Instead of reading second- and third-hand accounts of that notorious
National Academy of Sciences report on the impact of climate change on
the world’s grape growing areas, let’s do something radical: look at the
actual report itself, to see what it does–and doesn’t–say.
I don’t know about you, but after reading different articles about it in newspapers and magazines, and hearing about it on the tube, it seems to me that all the reporters are fastening onto the sexy prediction that coastal California will be too hot for premium winegrowing by 2050. (In reporting lingo, that’s known as a Wow! headline.)
So onto the report. Its most attention-grabbing sentence is “the impacts of climate change on viticultural suitability are substantial,” but this is, of course, a sweeping statement, and the devil is, as usual, in the details. If we grant that “25% to 73%” of suitable areas in “major wine producing regions” are in jeopardy (a big assumption), we have to ask if coastal California is among them. We have also to look at the water situation; the NAS study suggests that warmer climates may increase the need for water use (such as to combat heat stress), although it does not state categorically that climate change will bring decreased precipitation. It “may,” in “some regions,” says the report; but again, that’s pretty abstract, and can mean whatever the reader wants it to mean (which if often true of these long-range predictions).
The report does flat out say that the suitability of “the Bordeaux and Rhone valley regions [and] Tuscany” is “projected to decline.” It also predicts that “more northern regions in America” should have increased suitability (hence all those silly headlines about “Chateau Yukon Cabernet”). As for California, the part of the study that has gotten the most attention in the media here is the map, on page 2, that seems to suggest a swathe of prime coastal land, from Santa Barbara up well north of the Golden Gate and including Napa and Sonoma, will experience “decreases [in suitability] by mid-century.” But look closely at the map: I did, zooming in to 200%. From the coast to what looks like about 50 miles inland, there are alternating stripes of (from west to east), blue [indicating “novel” or increased suitability for premium grape growing], dark green and light green [both indicating “current suitability that is retained"], then red [“current suitability that decreases by mid-century”]. So you can appreciate that defining precisely where the boundaries are between colors is important. But this is nowhere explained in the text. The map, then, with its generalized colors, is the only guide we have, and an imprecise one at that.
So what are we to make of it? The blues along the immediate coast seem to indicate that the narrow coastal strip where, say, the Russians found viticulture impossible at Fort Ross, in 1812-1813, might by 2050 be warm enough to grow Chardonnay. The greens, where suitability is retained, look like they include most of the tenderloin growing areas from the Santa Ynez Valley, up through the Central Coast and into Napa-Sonoma. The reds seem to this observer to lie from about 35 miles inland to the borders of the Great Central Valley–if you’re familiar with the Bay Area, the red zone would start on the east side of the East Bay Hills, in what is now Livermore Valley. Other red regions include the far eastern parts of San Luis Obispo and Santa Barbara counties and, perhaps, Lake County (although Clear Lake would have a cooling effect, wouldn’t it?).
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