By Sam Wilson
BBC News, Napa Valley
Creating wine is all about getting the balance right.
You have to find the best location, with good soil, the right range of temperature, and rain at certain times of year. You must plant the right grapes.
And then you must get lucky with the weather.
Napa Valley's temperature range makes it ideal for wine grapes
So it is no wonder that winemakers are especially aware of the issue of climate change.
Some studies have suggested that the wine map could be changed completely if global warming proceeds apace over the coming decades.
In North America's most renowned wine-growing region, Napa Valley in California, current conditions are near-perfect.
"You have the climate, you have ideal soils and a history of winemaking that goes back to the turn of last century. It's a combination of those things that makes Napa Valley unique," says Jeff Virnig, winemaker at Robert Sinskey Vineyards.
A subtle variation of temperatures and conditions in different places means "you can pretty much grow any grape variety here in this valley".
Some scientists say global warming could turn that all on its head.
A study by the America's National Academy of Sciences last year suggested that the area of the US suitable for growing premium wine grapes could decline by 81% by the end of the century.
Findings like that have alarmed wine industry figures around the world.
Pancho Campo, a Spaniard who put on the first international Global Warming and Wine conference last year, urged attendees to "spread the word... It might not help sell wine today, but global warming will bite us all in 20 years' time".
He had particular reason for concern, as studies suggest Spain would be one of the first wine-growing areas to become unviable.
The effects on cooler regions, however, might be beneficial, at least initially.
In Bordeaux, for instance, recent vintages have been acclaimed, following a succession of warm summers that have allowed it to ripen its grapes more consistently than before.
The US study suggested that climate change could make viticulture much more successful in northern parts of Europe, at the expense of Spain, Italy and the south of France.
At Napa's Sinskey Vineyards, they believe the worst-case scenarios are alarmist.
"The sensational aspects that you hear - that's doom and gloom," says owner Robert Sinskey.
As a farmer who has seen many unexpected weather events in his time, he is reluctant to say definitively that the climate is in flux.
Chardonnay grows at the cooler end of the Napa Valley
"What we can say is we have an impression that change is happening. Are we in crisis mode? No we're not."
In any case, Napa Valley growers believe their proximity to the Pacific coast may protect them from the worst effects of climate change.
"As the interior of California heats up, coastal regions actually cool off," says Terry Hall, a spokesman for Napa Valley Vintners.
This is because hot air inland rises, drawing in cool, moist air from over the sea.
"2005 was the warmest year ever in the US," he says. "For us [in Napa], it was a very cool year.
"The headlines read that Napa's going to hell in a handbag," he says. In fact, he says, "microclimate cooling may be as big an issue for us as global warming."
Napa's refusal to panic over climate change does not mean it is unconcerned, however.
Mr Hall says it is vital not just to accept that climate change is under way, but to "make that a cornerstone of your agricultural decisions".
That might mean planting different varieties, or thinning fewer leaves from the vines to provide more shade.
In Sinskey's case, it means trying to make practices as environmentally friendly as possible.
Walking round the vineyard, winemaker Jeff Virnig shows how he allows grass and plants to grow between the vines, to recycle organic material into the soil. The grass is grazed by sheep.
"One of the reasons we've gone to organic farming practices is we figured we'd be better able to buffer against extremes of weather," says Mr Virnig.
By raising the level of organic material in the soil, he explains, it can hold more water, which is useful both in dry and wet periods.
The winery is also decked with solar panels, that produce 75% of the power needed on the site. Its trucks and tractors run on biodiesel.
Robert Sinskey believes that as someone who makes a living off the land, he has a responsibility to work in "the most efficient, least intrusive way possible".
Sheep help Sinskey Vineyards keep their operations organic
He says that also makes good business sense.
"Our customer base are highly educated. If they're not practising green, they're thinking about it. If we can inspire in any way and also be true to the spirit, and non-damaging, there's a security in doing business that way."
And if the worst-case scenarios come to pass, getting the right acidity and crispness in his pinot noir will be the least of his problems.
"If we were to see dramatic change, we'd have to kiss our business goodbye," he says.
"But I think there'd be bigger concerns than our business. We'd be concerned about basic survival."