With a palate honed on four decades in the wine industry, Eben Archer can taste it: Global warming has come to the southern tip of Africa.

Archer doesn't know about melting glaciers or rising sea temperatures, or whether catastrophic events like Hurricane Katrina are related to a changing climate. But at 58, having devoted his professional life to studying and cultivating wine grapes, he knows that the deep, earthy, grassy flavors of sauvignon blanc -- the flagship of South Africa's globally popular white wines -- seem to become less common with each vintage.

And he thinks he knows why.

"There has been all sorts of freakish weather over the past five years, more than before," Archer, trim and white-haired, said as he sat in an office adorned with a chart showing how temperatures in February -- deep summer in South Africa -- have been rising. "Surely we are facing global warming."

Such declarations border on treason in the Western Cape, home to the nation's sprawling, lucrative wine industry. The extent of climate change, and its consequences, are the subject of fierce debate here.

But prudent winemakers have begun to adapt, offering perhaps a glimpse of what lies ahead for the world if predictions of an overheating climate prove true.

Faced with a string of unusually hot, dry summers, and frightened by climatological models suggesting that things will only get worse, winemakers have begun seeking predictable cool. They are moving their grape vines -- especially sauvignon blanc -- to higher altitudes. They are finding patches open to sea breezes. And they are beating a retreat from the equator, planting heavily in southern, coastal regions once regarded as too cold.

Not everyone is ready. The South African wine industry traces it roots to 1659, when Jan van Riebeeck, the Dutch founder of what would become Cape Town, pressed the first wine from grapes grown from French cuttings. In the past decade, with apartheid-era sanctions gone and a stultifying government quota system scrapped, South African winemakers have forced their way into the front ranks of global producers with increasingly sophisticated, though generally still affordable, red and white wines.

Yet given that it takes many years for fickle vines to start producing top-quality grapes, the industry remains deeply conservative, dominated by cautious Afrikaners -- descendants of Dutch and French settlers from centuries ago -- whose families often have owned their wine estates and farms for generations.

One recent cold morning, climate researcher Peter Johnston, of the University of Cape Town, presented findings from recent studies of weather trends in South Africa's wine country to farmers and winemakers in Paarl, one of the industry's historic centers.

Johnston cautioned that climate models are not perfect but then revealed several showing a trend toward hotter weather and fewer rainy days during winter months, when grape vines need them most.

"There is no question," Johnston told the stony-faced farmers, "everywhere is getting warmer."

Even skeptics in the industry acknowledge that the last several summers have been unusually warm, damaging some crops. But they maintain that other heat waves have been balanced out by cool years, and that major climate change -- if it's coming -- remains decades away.

"The warming has been very gradual," said Jan Booysen, a wine industry researcher, speaking by phone from Paarl.

Yet industry analysts such as Francois Knight see disruption already beginning. Knight advises winemakers on where to plant various grapes in order to take advantage of the region's evolving climate. He suggests putting hardy cabernet, for example, in hotter spots while planting sauvignon blanc in cooler ones.

(Grapes that make red wines are generally more thick-skinned and resistant to heat than those that make whites, with the exception being the finicky pinot noirs, a red wine variety attempted by only a handful of South African winemakers.)

For some warm, dry farms, Knight suggests avoiding sauvignon blanc because the grapes are so easily damaged by heat. It's a tough message for winemakers to hear. Not only are sauvignon blancs popular but they are fairly cheap to make. Because they are best consumed in the year they are produced, sales often keep wineries profitable at a time when their reds, in need of aging, are years from the market.

"Every winemaker wants to make a good sauvignon blanc," Knight said.

Yet his data suggest trouble. He has charted average February temperatures since 1965 in Stellenbosch, the lush, mountainous university town that is home to some of South Africa's most prestigious wineries. The first 20-year period looks pretty steady, with an average temperature of 70.1 degrees. The second, from 1985 to 2005, shows a jump to an average of 72.3 degrees, with the trend line slanting upward.

Two degrees would not damage most agricultural products. But wine, with its fragile chemistry and discerning clientele, is the agricultural equivalent of the canary in the coal mine. When something changes, the grapes show it first.

That is not to say that winemakers don't have some tricks. For example, it has become popular to harvest sauvignon blanc early, ahead of full ripeness, to avoid a heat wave that could ruin a promising vintage in just a few hours.

Eben Sadie, who produces some of the country's finest wines, compares such tactics to plastic surgery: They prettify flaws, but something authentic is lost.

Sadie, who also owns a small winery in Spain and has worked elsewhere in Europe, predicts that winemakers around the globe, reacting to the same trend toward hotter climates, will spend the next few decades scrambling to protect their products.

Outside Paarl, Sadie already has planted his grapes far up the slopes of one breezy mountainside.

"Sauvignon blanc is on a roll," he said. "But if the weather changes . . . if we have to absorb another 3 degrees Celsius, it's going to get very messy."

Eben Archer, a viticulturist, is convinced that global warming has affected wine production in South Africa, and will continue to do so in the future.