John Williams has been making wine in California’s Napa Valley for nearly 30 years, and he farms so ecologically that his peers call him Mr. Green. But if you ask him how climate change will affect Napa’s world famous wines, he gets irritated, almost insulted. “You know, I’ve been getting that question a lot recently, and I feel we need to keep this issue in perspective,” he told me. “When I hear about global warming in the news, I hear that it’s going to melt the Arctic, inundate coastal cities, displace millions and millions of people, spread tropical diseases and bring lots of other horrible effects. Then I get calls from wine writers and all they want to know is, ‘How is the character of cabernet sauvignon going to change under global warming?’ I worry about global warming, but I worry about it at the humanity scale, not the vineyard scale.”

Williams is the founder of Frog’s Leap, one of the most ecologically minded wineries in Napa and, for that matter, the world. Electricity for the operation comes from 1,000 solar panels erected along the Merlot vines; the heating and cooling are supplied by a geothermal system that taps into the earth’s heat. The vineyards are 100 percent organic and — most radical of all, considering Napa’s dry summers — there is no irrigation.

Yet despite his environmental fervor, Williams dismisses questions about preparing Frog’s Leap for the impacts of climate change. “We have no idea what effects global warming will have on the conditions that affect Napa Valley wines, so to prepare for those changes seems to me to be whistling past the cemetery,” he says, a note of irritation in his voice. “All I know is, there are things I can do to stop, or at least slow down, global warming, and those are things I should do.”

The Climate DeskWilliams has a point about keeping things in perspective. At a time when climate change is already making it harder for people in Bangladesh to find enough drinking water, it seems callous to fret about what might happen to premium wines. But there is much more to the question of wine and climate change than the character of pinot noir. Because wine grapes are extraordinarily sensitive to temperature, the industry amounts to an early-warning system for problems that all food crops — and all industries — will confront as global warming intensifies. In vino veritas, the Romans said: In wine there is truth. The truth now is that the earth’s climate is changing much faster than the wine business, and virtually every other business on earth, is preparing for.

All crops need favorable climates, but few are as vulnerable to temperature and other extremes as wine grapes. “There is a fifteenfold difference in the price of cabernet sauvignon grapes that are grown in Napa Valley and cabernet sauvignon grapes grown in Fresno” in California’s hot Central Valley, says Kim Cahill, a consultant to the Napa Valley Vintners’ Association. “Cab grapes grown in Napa sold [in 2006] for $4,100 a ton. In Fresno the price was $260 a ton. The difference in average temperature between Napa and Fresno was 5 degrees Fahrenheit.”

Numbers like that help explain why climate change is poised to clobber the global wine industry, a multibillion-dollar business whose decline would also damage the much larger industries of food, restaurants, and tourism. Every business on earth will feel the effects of global warming, but only the ski industry — which appears doomed in its current form — is more visibly targeted by the hot, erratic weather that lies in store over the next 50 years. In France, the rise in temperatures may render the Champagne region too hot to produce fine champagne. The same is true for the legendary reds of Châteauneuf du Pape, where the stony white soil’s ability to retain heat, once considered a virtue, may now become a curse. The world’s other major wine-producing regions — California, Italy, Spain, Australia — are also at risk.

If current trends continue, the “premium wine grape production area [in the United States] … could decline by up to 81 percent by the late 21st century,” a team of scientists wrote in a study published in the Proceedings of the National Academy of Sciences in 2006. The culprit was not so much the rise in average temperatures but an increased frequency of extremely hot days, defined as above 95 degrees Fahrenheit. If no adaptation measures were taken, these increased heat spikes would “eliminate wine grape production in many areas of the United States,” the scientists wrote.

In theory, winemakers can defuse the threat by simply shifting production to more congenial locations. Indeed, champagne grapes have already been planted in England and some respectable vintages harvested. But there are limits to this strategy. After all, temperature is not the sole determinant of a wine’s taste. What the French call terroir — a term that refers to the soil of a given region but also includes the cultural knowledge of the people who grow and process grapes — is crucial. “Wine is tied to place more than any other form of agriculture, in the sense that the names of the place are on the bottle,” says David Graves, the co-founder of the Saintsbury wine company in the Napa Valley. “If traditional sugar-beet growing regions in eastern Colorado had to move north, nobody would care. But if wine grapes can’t grow in the Napa Valley anymore — which is an extreme statement, but let’s say so for the sake of argument — suddenly you have a global warming poster child right up there with the polar bears.”

A handful of climate-savvy winemakers such as Graves are trying to rouse their colleagues to action before it is too late, but to little avail. Indeed, some winemakers are actually rejoicing in the higher temperatures of recent years. “Some of the most expensive wines in Spain come from the Rioja Alta and Rioja Alavesa regions,” Pancho Campo, the founder and president of the Wine Academy of Spain, says. “They are getting almost perfect ripeness every year now for Tempranillo. This makes the winemakers say, ‘Who cares about climate change? We are getting perfect vintages.’ The same thing has happened in Bordeaux. It is very difficult to tell someone, ‘This is only going to be the case for another few years.'”

The irony is, the wine business is better situated than most to adapt to global warming. Many of the people in the industry followed in their parents’ footsteps and hope to pass the business on to their kids and grandkids someday. This should lead them to think farther ahead than the average corporation, with its obsessive focus on this quarter’s financial results. But I found little evidence this is happening.