Everyone seems to agree the earth's temperatures are on the rise and storm cycles have increased both in number and ferocity as climatic changes have occurred. Admittedly there are arguments as to the cause of these changes but prevailing science seems solidly on the side of man's intervention in the atmospheric conditions of today.
Regardless of its cause, climate change (referred to by some as global warming) is having a profound effect on the well known winegrowing regions of the world and what grapes will be grown there and elsewhere as new cooler areas emerge. Dramatic changes are occurring and great minds are exploring countless options to stem their detrimental effects. Some will inevitably prove successful and others not necessarily so.
While winemaking is a complex web of interconnected influences such as soil type, exposure, trellising (i.e. vine training), canopy management, row orientation, clonal selection and of course the direct influence of the winemaker, temperature is perhaps the most critical and least subject to corrective intervention.
Warmer temperatures result in higher sugar levels (translating to higher alcohol) and lower acidity that declines as sugar increases. Warm temperatures can also have a negative affect on color, flavor and tannin development through decreased phenolic production.
Harvest decisions are often guided by chemistry in the analysis of sugar levels (aka Brix) that is a preliminary indicator of ripeness and determines the potential alcohol of the finished wine. The skilled winemaker will always temper the chemistry in making the final harvest decisions based on "phenolic maturity" developing in the later part of the growing cycle by tasting the berries from several parts of a vineyard. This cycle is greatly accelerated as temperatures rise with the resulting wines showing lesser character and complexity.
Climate change is a multifaceted phenomenon not easily explained and not consistent from one area to the other. Along with temperature it involves many factors from drought to increased precipitation and storm surge, rising sea levels, increased incidence of pests and disease along with others.
Cooler growing areas such as Tasmania, southern England and even Sweden will most probably benefit from the warmer temperatures but the vast majority of premier growing areas face decisions from changing farming practices to the introduction of different varietals in order to survive.
Bordeaux, perhaps the world's most renowned winegowing region, has begun the search to find which varietals can withstand the anticipated temperature increases over the coming generations. In 2009 an experimental planting of 52 different varietals (from Italy, Greece, Spain and Portugal) in the Pessac-Lèognan appellation was begun under the leadership the French National Institute for Agricultural Research and Bordeaux Wine Council. The aim of this experiment is to maintain the character of great Bordeaux wine with varietals more acclimated to warmer temperatures. A lofty goal indeed with results many decades away.
And in 2007 under the direction of Henri Lurton owner of Chateau Brane Cantenac in the Margaux appellation planted about one acre of the somewhat forgotten and late developing Carmenere. With the uneven and warm 2011 vintage Carmenere was used in the Grand Vin for the first time since the late 19th century.
Kimberly Nicholas wrote a comprehensive article in the January 2015 Scientific American covering many aspects of the subject. Nicholas, a Sonoma native now working as an associate professor in sustainability science at Lund University in Sweden, recently visited a Carneros vineyard and happened on to a "handful of alien vines" planted among the Pinot and Chardonnay and later identified as several Bordeaux varietals in an experimental block.
But as Nicholas deftly points out, it is not only the question of finding the varietals that will survive in warmer temperatures it is also a function of finding the varietals that will carry on the character of the original growing area. It is simplistic to think of growers successfully moving their Napa Cabernet plantings to Oregon for cooler temperatures given the reality of different soils and other conditions. The grapes may survive the change but will the character of the wine be vastly different? Probably so.
Long ago, and over many generations, the French were able to isolate the proper growing environment (terroir) for numerous varietals and growing areas. Yet this relationship of vine to terroir is at risk according to Nicholas and others because even small climatic change can lessen the relevance of the local skills that have taken generations to perfect.
Change is definitely here and only time will tell what direction it dictates.