ased on various scientific surveys, we know that temperatures will continue to become warmer on average between now and 2100, and that will have a direct impact on the growing of grapes and the resulting types of wines that the various established wine regions can produce. It could also change the typical characteristics that we associate with various wine-growing regions.

At the moment, we have more questions than answers. Among them are, “Will Napa Valley soon be too warm to grow classically structured (age-worthy) Cabernet Sauvignon? Will Bordeaux soon be warm enough to grow California-style Cabernet? Will Pinot Noir be all but impossible to grow in California and Oregon in just a few years? How far north must we go to plant grapes that will emulate the best wines we once made with regularity in California? What grape varieties will we have to plant and which varieties will be removed by this change in climate? And what will become of the typical regional character we have come to associate with various regions of the wine world?

The topic of global warming was on the lips of everyone at the Adelaide technical conference, in part because Australia’s wine industry has already seen the impact of global warming. The drought it has been suffering through for the last several years is not only a reality for the Aussie wine industry, but it figures to get worse. And high temperatures during the 2007 harvest caused a drastic drop in production.

It is certainly true that a hotter planet is projected over time. From the July 2006 Proceedings of the National Academy of Sciences, co-author James Hansen concluded that, because of rapid warming in the past 30 years, the earth is approaching and will soon surpass the warmest temperatures in the past 12,000 years - since the end of the last ice age.

Recent warming “has brought global temperature to a level within about one degree Celsius of the maximum temperature of the past million years,” said the report, which also added that the higher latitudes are warming faster, as are the Indian and western Pacific Oceans.

Many experts also predict that drought conditions could well affect many of the more prestigious wine-growing regions of the world.

So well recognized is this subject that, in 2004, for an April Fool’s issue of my weekly newsletter, I did a global warming “story” in which I reported on a Swedish farmer who was growing Cabernet Sauvignon. And not one reader realized the story was a spoof.

However, at least one Champagne house has already planted grapes in England and another, the house of Roederer, has admitted the idea is intriguing. Until recently, England was too cold to make drinkable table wines on a consistent basis. And of the approximately 350 wineries in Great Britain, most produce sparkling wine. Recently, many have reported making the best bubbly they’ve ever made.

When news stories about global warming first made headlines, some of them indicated that the Napa Valley was destined to collapse as a fine wine region. Stories implied that the area would soon be a desert that would make only simple, hot-climate wines.

Soon after the stories hit, growers began to see what they could do to slow the impact. One strategy: the Napa Valley Vintners set up a Climate Change Task Force that would team with geophysicists from Scripps Institute of Oceanography to investigate what was occurring in their vineyards.

The Proceedings of the National Academy of Sciences has said that unless wine makers intervene with plant-protection systems, the total area suitable for wine growing in this country could shrink by up to 80 percent by the end of the century.

Even so, most studies on climate change have not been very specific about how a projected 1 to 3-degree Celsius increase in the average temperature by the end of the century will affect grape growing. The assumption is that increased solar radiation and the possible reduction in available water could be disastrous.

How About Some Good News

Curiously, over the short term, there may well be some good news. Early studies show that Napa, Sonoma, and to a lesser degree Mendocino and Lake counties, may actually be cooler for a number of years as the interior valleys grow warmer. This effect may also be seen for other coastal regions, such as the Salinas Valley of Monterey County (which gets cooling breezes off Monterey Bay), as well as San Luis Obispo County; Santa Maria Valley and Santa Barbara, and Ventura County.

This is due to a sort of suction effect that occurs, say the studies. As the vast San Joaquin Valley gets hotter, it creates a vacuum that draws in cooler marine air.

Fog from the Pacific Ocean can cause slower morning warming during daylight hours - one of the key factors in why Russian River Valley is one of the coolest of California’s growing regions. Such cooler mornings may give way to high daytime temperatures during the summer, but the total duration of excessive heat may well be less than in the past, and nights cooled by marine air can keep acid levels high.

Dr. Andy Walker of UC Davis says that the average temperature drop in Napa and Sonoma could well be so significant over the next few years that it could radically change the character of many wines over the next decade.

The cooling trend is evident from the last three vintages, 2005, 2006 and 2007, all of which were considered about as cool as any in the last two decades. Nationally, 2005 was one of the warmest years on record, but in California’s two most famous wine-growing counties, Napa and Sonoma, it was rated as a very cool year.

Moreover, the practice of farming by greener methods (sustainability, organic or biodynamic) has grown significantly in the last decade as farmers realize the need to become proactive in protecting the vine from the ravages of global climate change.

Dealing with the Inevitable Lack of Water

One impact may well be a lack of water and the possible need to pay more for it. If drought conditions persist, it would be better to have plants trained to be self-sufficient than to be dependent on irrigation, fertigation and other man-made solutions.

In a report on global climate change, Paul Newman of NASA Goddard Space Flight Center said his research into clouds indicated that water (or a lack of it) could be the major impact of global climate change. “Water is a tremendous greenhouse gas,” he said. “It can condense and form…clouds. Clouds can reflect radiation and clouds can actually insulate the surface - if you've got a cloud layer overhead, the surface stays a little bit warmer. So water is really crucial to the whole process.”

Cooler temperatures for Napa and Sonoma, if that does occur over the next decade, won’t affect how sunlight directly impacts grapes. Could there be a major impact of solar radiation here? Many growers now are looking at their trellising systems and trying to determine if they can still get proper ripening with slightly greater leaf cover, to protect grapes from direct sunlight. There is legitimate concern about the effect of direct sunlight on berries.

Dr. Walker of UC Davis said the vertical shoot positioning (VSP) trellis system, so widely employed in California, “is bad for [most vineyards in] California, but it is the most easily mechanized and it’s easy to train people to work on.” He suggested, interestingly, that grape breeding programs could become more important over time as scientists develop crosses of grapes that do better in different climates.

One possible effect of increased daytime temperatures, when that occurs, could well be accelerated sugar accumulation in berries, which could call for harvesting grapes at higher and higher Brix levels with consequently a greater need for alcohol-removal techniques. And still it may be that certain grapes will be harvested that have a green, vegetative character.

“… warming will clearly force changes in the varieties grown and wine styles produced in particular regions,” wrote Jancis Robinson in her recently released The Oxford Companion to Wine. She added that there might well be increased incidence/impact of plant disease and/or pests.

The effect of global climate change will obviously vary depending on the region. Look at how Germany grows Riesling, for example. For centuries, south-facing German vineyards were considered optimum for ripeness; vineyards facing north received far less sunlight and thus ripened less reliably. So on-the-edge were even Germany’s best regions that in the 1980s and before, the country’s wine growers could anticipate rarely more than three great years a decade, and occasionally it was only two or one. The rest were rated as serviceable.

In the last 14 years, however, Germany has, arguably, had 10 great vintages, and no flat-out disasters. As temperatures have risen in recent years, German production of Spatburgunder (Pinot Noir) has risen and so has quality. Until recently, this rare red wine from Germany was unlikely to arouse much interest from wine lovers. Now it is.

Orly Ashenfelter, an economist at Princeton, recently published a study on sunlight and vineyard values in Germany. He concluded that, as a result of the recent warming trends, the Mosel is a great place to invest since warming could provide Germany with regularly exceptional vintages in the coming years.

Researchers at UC Davis, the Australian Wine Research Institute, and in particular Greg Jones at Southern Oregon University, are among those delving into this problem. But because each growing region in the world is so different from the others, it’s likely that no overall solution will be proposed.

Jones, an associate professor of geography, wrote a paper recently on global climate change in which he noted: “On a global scale, one of the first analyses to examine climate changes in many of the world’s best wine regions found that average growing season temperatures warmed 1.3°C over the last 50 years. The warming was not uniform across the regions, showing more warming in the western U.S. and Europe, with lower warming in Chile, South Africa, and Australia. The greatest warming was seen in the Iberian Peninsula, Southern France, and parts of Washington and California with warming greater than 2.5°.”

As for solutions to localized issues, each region will have to personalize the general conclusions to fit individual needs. As Walker indicated, grape breeding, new trellising systems, and matching grapes to regions are now far more important topics than they were a decade ago. Look at just two grapes, Pinot Noir and Cabernet Franc.

“We have - what? - 28,000 acres of Pinot Noir in California? I know some of that is planted in regions which are too warm,” he said, adding that a re-thinking of what is planted where would be a good start for many growers.

As for Cabernet Franc, I have spoken with numerous Napa Valley wine makers over the last few years who are quietly in love with this little cousin of Bordeaux, and they say they have seen a marked improvement in the wine it makes over the last decade. As Jones’ research shows, Cab Franc ripens in cooler climates than does Cabernet Sauvignon. So for the foreseeable future, will Cab Franc become the newest Napa red wine superstar?

No one is quite sure what to make of global climate change at this point, but almost all agree that it’s a huge challenge to wine makers around the world. And it figures to grow even more challenging.