There's a scene in the film “Sideways” in which the four main characters go to an author's talk at a winery. After five seconds of high-flown blather about the origins of the Pinot Noir grape and an eye roll by Stephanie, the group sneaks off to the winery's barrel room. The author in the movie is apparently modeled on Oz Clarke, the prolific British wine writer.

If so, Mr. Clarke's portrayal in “Sideways” seems unfair. Although his descriptions of wine are elaborate and at times overblown, he has been a major force behind the “democratization” of wine. In his latest book, Red & White: An Unquenchable Thirst for Wine, Mr. Clarke describes his introduction to wine as a student at Oxford in the 1980s, and how he became convinced that consumers needed options besides the top wines from France and the sea of mediocre wine that was most of everything else produced in Europe at the time.

He would find his accessible, affordable, and delicious wines in the New World. After graduating from college, Mr. Clarke would land on the BBC program “Food and Drink.” As co-host of this long-running and popular show, he helped to create a generation of British wine-drinkers by introducing them to “exuberant, juicy, fruity wine” from Australia, California, New Zealand, and elsewhere. With the rise of New World wines, European producers would soon follow suit: the New World “showed that France's domination of great wine could be challenged. California started it. Australia continued it. Now Europe could do it, Italy leading, with Spain, Portugal, and others following behind.”

Red & White is part memoir and part travelogue. Mr. Clarke recounts his first surreptitious drink of wine at the age of three, joining the Oxford wine tasting club in an unsuccessful attempt to impress women, and learning the hard way not to store wine at friends’ houses (cases of Lafite ’61 and Pétrus ’64 were among the wines never recovered). Mr. Clarke started as a stage actor, but wine took the place of acting when the wine taster for “Food and Drink” dropped out at the last minute, with the producer of the program reportedly saying, “Get me that actor who knows about wine.”

The bulk of Red & White is a tour through the wine regions of the world. The trip begins, predictably enough, in France. The reader is guided through the French appellations, with sincere attention given to small (the Jura) and less renowned (the Languedoc) areas. Mr. Clarke has an unsurpassed curiosity about and passion for wine, delighting especially in rare varietals and wines whose quality is not yet reflected in prices. His writing combines wine history and science, personal anecdotes, and descriptions of individual wine-makers. The style is light and refreshing, not unlike a glass of rosé on a hot summer day.

Unlike most books about the wines of the world, France is not the primary destination. I found a 2001 edition of Hugh Johnson's Wine Companion on my book shelf and calculated that 40% of its pages on wine regions are devoted to France, with only 20% given to non-European countries. Red & White quickly moves from France to Australia, New Zealand, the United States, and Canada, and from there to places expected (e.g., Italy, Spain) and not (e.g., India, Uruguay). Mr. Clarke brings his enthusiasm for wine wherever he goes, but that is not to say his views on wine are uncritical. For example, he thinks that there is too much Tempranillo produced in Spain, yielding much “unconvincing” wine, and that Merlot is overplanted in France, where “loads of the early-ripening Merlot is broiling away in the unsuitable suntraps of the south.” Japanese wine? Drink their beer instead.

Red & White does not have a central thesis, but it does have recurring themes. One is that New World winemakers, and some European producers, have gone too far in their pursuit of ripeness. Mr. Clarke has played a central role in promoting accessible, fruit-forward wines from the New World, but laments the trend toward massive, high-alcohol reds. In his chapter on Australia, he describes the abuse of Barossa grapes “at the hands of the over-ripening brigade crazy for a 100-point wine.” He celebrates wine-makers around the world who are trying to produce wines that make a “statement about the vineyards they came from,” even if that means a break from the traditional European varietals. His view is that the “world doesn't want any more big, oaky clunkers, but it does want tasty, fresh reds at lower alcohol levels.”

Another theme, which for me is the book's highlight, is the effect of climate change on wine. Mr. Clarke was an early voice of warning. His keynote address at the 1993 New York Wine Experience, a high-profile event featuring top wine-makers from around the world, focused on the adjustments the wine industry would inevitably have to make in a warming world. He spoke of how wine-makers were going to have to change the style of their wines and adopt new grape varieties. He predicted the French system of appellation contrôlée would become obsolete as Spanish varieties like Tempranillo made their way into Bordeaux and Syrah was planted in Burgundy. The French producers made a noisy exit from the auditorium, and the Wine Spectator, the host of the event, departed from tradition by not publishing the address in the next issue.

Of course, Mr. Clarke has been proven correct, and Red & White is filled with fascinating examples of climate change impacts on wine and the adaptive responses by wine-makers. The Yarra region in Australia has become too warm for Pinot Noir and vineyards are being replanted with Shiraz. Mr. Clarke sees the same change coming to the Marlborough region in New Zealand as well. Merlot and Cabernet Sauvignon are being planted in southern Germany, and, in Lebanon, harvest dates have moved back by a month over the past 50 years. The highly-regarded 1982 Bordeaux vintage ushered in a more fruit-forward style of wine in the region, which Mr. Clarke declares to be “the first marked by what we now know is the relentless charge of climate change.”

And then there's the second French invasion of England (the first being the Norman Conquest of 1066). As Mr. Clarke explains, part of the allure of sparkling wine from Champagne comes from the use of barely ripe grapes, which have been difficult to produce in the region in recent decades. Since 1990, the ripening season temperature in Champagne has risen by more than 2° C. French producers have been buying land in southern England, which is cooler than Champagne and has the same chalk soils. Taittinger was the first producer to establish a vineyard in southern England, with Pommery following soon after. Five million bottles of wine, most of it sparkling, are now being produced each year in Britain.

I enjoyed Red & White. Mr. Clarke's writing is lively and humorous and clearly conveys his unabating excitement about wine. He explains that he has always been able to put his experiences with wine into words. Thus, we get this description of Amarone from Italy:

Maybe not entirely believable, but fun to read.

My main complaint about the book is that it goes on for too long. After the tour of all of the places in the world that make wine, Mr. Clarke turns to a description of each of the major grape varietals, often returning to locations the reader has already been to. By this point, I was ready for the trip to be over and yet, sections with names like “Cabernet Sauvignon and Canada” stretched out before me. Despite the excessive length, I still recommend the book. It's highly entertaining and full of absorbing information from one of the world's experts on wine. This is the perfect book for a hot summer day, accompanied by a chilled glass of rosé.