Understanding temperature data? Not so easy!
One of the toughest parts of my job—of any wine writer’s job, actually—is finding reliable, historic data on which to base conclusions about terroir.
Lord knows, we have endless discussions about terroir, yet most of them are based on anecdotal information and as we all know anecdotes are not reliable. They may be interesting, they may be well-meaning on the part of the teller, and they may even be true. Yet there’s nothing like accumulated, provable data to underscore a scientific claim.
Having been in this business for a long time I can’t tell you how often I’ve been given directly conflicting info by winemakers who often couldn’t agree on the characteristics of their region’s terroir even when their vineyards were right next to each other! Or, along similar lines, they couldn’t agree on the qualitative aspects of the wines from the appellation they shared. Needless to say, this makes the wine writer’s job more difficult, so in the end, we’re forced to come to our own conclusions—for which the winemakers who couldn’t agree in the first place then criticize us. Sigh…
A nice example of my current challenge is to determine, precisely and clearly, the temperature and climate differences between the Santa Maria Valley and the Santa Rita Hills, especially for growing Pinot Noir. The two AVAs are, of course, close together. Both are open to the west winds from the Pacific; both are east-west-running valleys. Is one cooler than the other? How does one define “cooler”? This is where the tough part of my job kicks in. Where is the data? Who controls it? Is it a government agency, like NOAA? Do individual vineyards have weather sensors that could tell us? Is that data proprietary or is it sharable? Over how many years does the data span? I don’t want data only from a single year; to be credible the data should span multiple years. Who’s been measuring degree days or daytime and nighttime lows for a decade? How long does the high temperature remain high during the day—for 30 minutes? An hour? Both AVAs are long, in an east-west direction: how much does the daily high temperature vary as you move inland? A degree a mile, as is commonly cited? What part does elevation play (both AVAs contain significant hills). This only begins to describe the complexities. As the great Saintsbury winemaker David Graves notes, “What do you mean by cooler? Hours above or below a threshold? Nighttime lows? Daytime highs? The period between veraision and harvest? Bloom-harvest? And what role does relative humidity play?” For the wine writer these are difficult things to determine, but they seem central to me, if you’re trying to pick apart the differences between neighboring appellations. After all, if an appellation means anything to begin with, it consists of these very complexities and ambiguities.
Yet if a writer wants really to tackle issues of terroir, these data points need to be accumulated. The trouble is, where are they?
It’s hard work, which is why there are so many shibboleths and myths in this business. Who’s got the time to research this stuff, or even to figure out how to begin? So, too many wine writers look up something Matt Kramer, or Oz Clarke, or Steve Heimoff or Larry Walker or somebody else once said, and repeat it, as though it were the gospel truth. Which it might or might not be. It’s not that any of these individuals would deliberate misstate something (Heaven forbid!) but that they might have got it wrong to begin with, without knowing it and without having subsequently been corrected.
Anyhow, this is one reason why the more I last in this business the less I trust “the conventional wisdom.” Still, understanding appellations is as central to my job as breathing is to life. I hope to just be able to contribute some small part to it that will stand the test of time.