A year ago, a scientific report showed that global warming may create conditions that will be too warm for the traditional great wine regions of France and the United States to make great wine. 

  Scientists said that by the middle of this century, average temperatures will rise just enough to pose a hazard to the making of classic wines. 

 Does this mean that cabernet sauvignon will soon be planted in Wisconsin; chardonnay in Alaska; and that Napa is destined to become a tropical housing paradise for San Francisco commuters?

 Hardly. Sure, gradual warming of California’s wine areas may well, in a few decades, affect many of the wines we know now, but climate change is slow. Wine scientists planning now for the future may be able to counteract, for a prolonged period of time, the weather-driven problems that may face wineries and grape growers in the near future.

However, what we can forecast is that, over time, some grape varieties may have to be torn out and replaced by other grapes that do better in slightly warmer regions.

With the cool Pacific Ocean providing temperate breezes in the afternoons, many winemakers can take solace that simple pruning and trellising techniques could well provide solutions for at least another few decades.

The fear that warmer temperatures will cause grapes to gain sugar too quickly, before vine-ripened flavors are attained, seems to be a lot greater in places where grapes don’t make classic wines. Which means interior valleys.

What is clear, however, is that coastal vineyards, those with direct access to marine air, are cooled more regularly than are vines growing in inland valleys.

 Grapes growing in California’s hot, vast central San Joaquin Valley may be more negatively affected than those in coastal areas. In the inland valleys, summer daytime highs routinely reach triple digits, allowing a lot of grapes to flourish and make wines with uninteresting flavors.

Marine influences aren’t the only factors in wine quality, of course, but they were so compelling for at least one man that they led him on a multiyear quest to get a federal ruling on the issue.

 Jess Jackson, head of the Kendall-Jackson brand, as well as an empire of superb smaller wineries, was denied in his quest to have the phrase “California Coastal” approved as the largest appellation in the nation.

Had his proposal been approved, it would have covered an area stretching from the Mexican border to northern California  roughly 700 miles. It would have excluded the hot central interior, where some 70 percent of the grapes in the state are grown.

And Jackson was right: Coastal wines are better than Central Valley wines, in almost all cases.

 But sea views and cooler mountain regions are not only beneficial to wines. They are also attractive to homebuilders, who know that it’s a lot easier to sell a home for $2 million on an acre of hillside land than it is to sell that same site for a vineyard that — even in an optimistic projection — would gross $50,000 a year in revenues from the growing of grapes.

Such competition for land has caused some of the more sophisticated wine companies to seek cooler regions that aren’t necessarily as attractive to homebuilders.

 In California, that’s not as easy as it is in places like Australia and New Zealand, where vast land masses and small populations (just about 25 million between the two nations) combine to allow well-financed wine companies to plant new vineyards.

  Moreover, emerging wine regions in Spain, South Africa, Argentina and even Romania, in which climate change has been taken into account, could well provide reasonably priced alternatives to California wine if and when global warming becomes a huge problem.

Wine of the Week: 2004 Charles Krug Merlot, Napa Valley ($22).  Stylish blueberry fruit with hints of red currants and plum. A soft entry and supple tannins make this fine red wine excellent to pair with light red meat or chicken dishes. Often discounted below $20.

Dan Berger publishes a weekly newsletter on wine and can be reached at danberger@VintageExperiences.com.