The average temperature in Sussex is a degree warmer than it was for most of the 20th century, with practical implications for the region's vineyards

Spring really shouldn't be this cold. Standing on a gently sloping field in the South Downs, with nothing but rows and rows of freshly planted, knobbly vines for shelter, the wind seems to be picking up the snow on the distant hilltops and blowing it right into our faces.

As a snapshot of global warming, then, the Rathfinny vineyard in April leaves a lot to be desired. Nevertheless, despite the unfortunate weather conditions, this small part of the South Downs National Park, three miles from the south coast, is as good an example as any of what's happened to our climate over the last 20 or so years.

There are various reasons why ex-fund manager Mark Driver chose Rathfinny to plant what will be, when it's finished in 2020, one of the biggest single-site vineyards in Europe. Perhaps the most important, though, is that, according to the weather station at nearby Eastbourne, average temperatures in this area have been climbing since the 1980s to, in 2011, almost a degree higher than they were for most of the 20th century.

This might not sound much but, in the temperature-sensitive world of viniculture, it can make the difference between a bad year and a good one. Until relatively recently, the English wine industry tended to rely on high-yield, cold climate Germanic vines with names like tractor manufacturers: Huxelrebe and Dornfelder among others.

Although these are still present in many vineyards, Mark is taking a lead from his Sussex neighbours and planting the classic "champagne" grapes: chardonnay, pinot noir and pinot meunier. The sparkling wines produced with those varieties by local producers, such as Nyetimber and Ridgeview, among others, have regularly beaten champagne in international competitions and blind tastings. "The temperatures in this area are now pretty much where champagne's were in the 1980s," says Mark Driver. "And they made some pretty good champagne in the 70s and 80s."

Currently the UK produces between 3m and 5m bottles of wine a year but Rathfinny alone plans to produce around a million a year by 2020. This fits with the narrative of English wine as a kind of cheery "and finally" story at the end of the relentlessly glum news about global warming.

But not everyone's convinced that there will be such clear-cut "winners" in our current game of climate change roulette. Farmer Guy Watson, whose Devon based organic-produce company Riverford delivers vegetable boxes to houses across the country, has no plans to plant a vineyard. "On average we may be getting warmer," he says, "but it tends to be extremes that are important, rather than averages. We're certainly still getting extreme wetness. A few years ago people were talking about growing new crops but now most growers I work with have retreated to things that will reliably do well. I will never plant another strawberry outside. Not in my lifetime! I've had 25 years of trying and I've absolutely had enough of it."

However, other experts believe that climate change will force farmers to abandon previously reliable crops. Geologist and viticulture expert Professor Richard Selley, who worked as a consultant at the UK's biggest vineyard, Denbies, claims that, if temperatures continue to rise, within a generation or so the Drivers or their successors will have to start thinking about replacing their current vines with varieties better suited for a warmer climate. He's produced a speculative wine map of Britain in 2080 showing chardonnay grown mostly in northern England, the Welsh mountains and Scotland, merlot in much of the rest of the country, with the south coast of England fit only for raisins.

This, of course, implies even greater devastation elsewhere. But moving vineyards to cooler parts of the world has its own problems. A recent report by the US-based journal, Proceedings of the National Academy of Sciences, claimed that it could have disastrous effects for animals, including pandas, that currently live in places that could become prime viticulture land. This dilemma was summed up in many publications as "pandas vs pinot". In which case the argument for planting vines in the arable land of the South Downs seems pretty strong. If God gives you lemons, and you don't have to shoot pandas to get at them, why not make lemonade?

However, anyone who thinks that climate change will provide a simple good news story for English wine-lovers may be deluding themselves. In England, depending on what happens to the gulf stream and other variables, it might become hotter, wetter or, perhaps, even colder. All that climate change really promises is chaos and instability, which are not conditions that are beneficial for grapes or any other crop.