22nd June, 2011 by Patrick Schmitt - This article is over multiple pages: 1 2
Different viticulture techniques and later picking times – rather than climate change – have caused alcohol levels in Californian wines to rise, according to Christopher Howell, winemaker and general manager at Cain vineyard and winery.
Speaking at the Napa Valley Climate Seminar at Vinexpo in Bordeaux yesterday and referring to data collected since 1991 in Napa and Sonoma, Howell (left) said: “Temperatures have changed but nothing like as dramatically as the [grape] sugars… just over a period of two decades we have seen a huge increase in sugars and our claim is that most of this is due to fashion and winemaker choice.”
The overriding influence on the surge in sugar levels – and hence eventual abv – Howell ascribed to harvest times. “We are picking later than we used to, even if we have more warmth,” he stated.
He also explained that altered approaches to viticulture in the Napa Valley had affected alcohol levels, such as the use of different rootstocks, increasing the planting density and changing the trellising techniques. “Historically Napa looked like a big jungle, what was known as the Californian sprawl – visualise a teenager on the sofa – and so the fruit was buried in the leaves and it didn’t ripen properly,” he said.
Today however, more efficient training techniques such as the vertical trellis with shoot-positioning system (VSP) which, when combined with closely spaced vines, are producing grapes with a higher sugar content than 15 to 20 years ago.
As for climate change in the region, he pointed out that records over the last 15 years showed a slight average temperature increase but more dramatic changes when it came to nightime and morning temperatures.