In June 2007, the Intergovernmental Panel on Climate Change of the United Nations published the three-part UN Climate Report, on which some 2,500 researchers from 124 countries had worked for years. Among other things, it is based on around 40 computer simulations. For the first time, the panel agreed on a formulation according to which humans are to blame for climate change (which is still disputed in some places today). The highly developed countries are responsible for heating up the atmosphere (global warming) and "exporting" the effects. The main causes are rapid population growth, increasing consumption of fossil fuels, deforestation and urbanisation.
The relentless burning of fossil fuels such as petrol, oil or coal produces huge amounts of additional carbon dioxide, which causes the so-called greenhouse effect. In many regions of the world, a decrease in the number of frosty days and an increase in the number of days with extremely high temperatures has been observed in recent decades. This was particularly the case in central and northern Europe, the USA, Canada, China, Australia and New Zealand. In the central and northern latitudes, especially in the northern hemisphere, the frequency of heavy precipitation increased significantly in the second half of the 20th century. In contrast, some regions of Africa and Asia are experiencing increasingly frequent severe droughts, as well as desertification.
Since industrialisation, the average temperature has risen by +0.7 to +0.8 °Celsius, with +0.6 °Celsius alone being attributable to the past 30 years. By 2100, temperatures on Earth will probably rise twice as fast as in the last century. Eleven of the past twelve years have been among the twelve warmest since records began in 1850, with the Earth's surface warming at best by 1.1 to 2.9 degrees by 2100 and at worst by 2.4 to 6.4 degrees. The average warming is predicted to be 1.8 to 4 degrees Celsius. For the most favourable scenario, a rise in sea level of 18 to 38 centimetres has been calculated. In the worst case it could rise by up to 59 centimetres. Floods, crop failures and hurricanes are on the increase. About a fifth of animal and plant species are threatened with extinction.
The climate has a significant influence on the vines and the quality of the wine. Therefore, climate change naturally has an impact on viticulture, although according to recent research results, this impact is assumed to be less pronounced in the case of the vine compared to other agricultural crops. Records of climate values and viticultural data such as grape harvest times, yields and vintage quality have been kept in Europe for over a thousand years. During this period there have been repeated fluctuations and also exceptional conditions such as the Medieval Warm Period (900-1300) with on average higher and the so-called Little Ice Age (1450-1850) with on average lower temperatures. However, the causes and effects of today's climate change are incomparably more dramatic, more lasting and faster. In the past, major climate changes were caused by natural phenomena such as global warming or cooling (ice ages) and occurred very slowly over many millennia. The present situation, on the other hand, is a reaction to man-made circumstances and is proceeding at an alarming rate.
Dr. Edgar Müller of DLR Rheinhessen-Nahe-Hunsrück is a profound expert on the subject and has written many documentations on the subject. At the DLR site in Bad Kreuznach (Nahe cultivation area), precise records are available for one Riesling and one Müller-Thurgau plot each since 1959. Detailed phenological data such as budding, flowering, véraison and the start of the grape harvest have been recorded. One of the findings is that between 1959 and 2006 the number of summer days (> 25 °C) and hot days (> 30 °C) increased dramatically. The average annual temperature rose by 1.0 °Celsius. A large temperature increase is particularly noticeable from the end of the 1980s onwards. The following changes are to be expected in southwest Germany by 2050, although this probably also tends to apply to other Central European wine-growing regions:
On this basis, changes of varying degrees are to be expected. These are shorter growth intervals, stronger vegetation with more foliage area, higher water consumption or the resulting need for artificial irrigation, fluctuating yields, increased pest infestation and vine diseases and thus declining grape quality. Dry summers can result in a higher number of generations of grape berry moths and other pest insects, as well as more frequent problems with bacteria, phytoplasmas and viruses. This has a negative effect on the quality of the wine in the affected wine-growing areas. White wines will have more alcohol and less acidity due to earlier ripening. This will be a problem above all for the Riesling that ripens late today, but also for early ripening varieties with low acidity.
The frequency of UTA (untypical age tone) and fermentation disorders will increase. This has negative effects on the aromas paired with phenolic notes. In addition, there will be a lower ageing potential. Diseases such as Pierce Disease, which have so far only been present in warm areas, could then also occur in Europe. The viticulture will have to change or adapt with regard to vineyard care and vinification. This will affect the grape varieties, the choice of rootstocks, fertilization, the form of cultivation, and in connection with this, pruning, the question of greening, plant protection and, last but not least, certainly also the wine styles.
High-quality viticulture is possible in only one narrow geographical band, the so-called vine belts from 40 to 50 degrees north and 30 to 40 degrees south latitude (see also under vine). Wine-growing areas in the northern hemisphere, near the equator and inland are more affected by climate change than those in the southern hemisphere, at higher altitudes or near the coast. However, there will be global consequences for all wine-growing regions to varying degrees. Regions that have already been dry and hot will probably have to contend with even greater problems. In Australia and California a strong decrease in precipitation is expected. Parts of southern Europe could become too hot for quality viticulture. In Champagne and Bordeaux, on the other hand, improvements through improved grape ripeness are likely.
Better and new perspectives are opening up for the previous climatic border locations. The wine-growing regions will expand towards the poles. In Europe, Denmark, England, Croatia, Netherlands, Poland, Sweden and Ukraine are candidates. Outside Europe Argentina, Australia (parts), China (north), Chile and New Zealand. In a study published at the end of May 2008, the British wine trading company Berry Bros & Rudd sees China as the most important wine-growing country in the world in 50 years. Not only in terms of quantity will the Middle Kingdom then be the most important wine-growing nation, but in terms of quality it will also be able to compete with Bordeaux. The big loser is said to be Australia, as it would be too hot for quality viticulture in most areas.
Dr. Edgar Müller draws the following conclusion from this: "The effects of climatic changes can be mitigated in many respects by appropriate changes in cultivation techniques as mentioned above. If the sceptical prognoses of the climate scientists are correct, our children, or at the latest our grandchildren, will be able to cultivate vines in a way that differs considerably from today's cultivation techniques. This may also apply to grape varieties and locations. Regardless of the considerable problems, German viticulture would still be on the winning side compared to other large European wine-growing regions. The problems we would face could probably be mastered. For large wine-growing regions, such as central Spain, for example, where wine-growing is already reaching the limits of its potential due to a severe lack of water, the prospects are far gloomier. However, the winegrowing problems of a climate change would still be marginal compared to the possible global problems.
Nobody can say with certainty whether the optimists or the sceptics are right in the discussion about the expected changes. Everyone should know, however, that the current generation, out of responsibility towards future generations, cannot afford the luxury of not waiting for action to be taken to let our grandchildren see who was right. They would probably have little sympathy for the fact that today's opportunities for climate protection, such as saving energy or expanding alternative energies, are largely wasted because many people see them as an unreasonable financial burden or a restriction on personal development. If the sceptical forecasts were to come true, these restrictions or burdens would be ridiculous in comparison to the problems of our descendants (end of quote).
The Climate Change and Wine Congress, created in 2006, is dedicated to this problem area. The threat to biodiversity posed by climate change has given rise to the often-used term biodiversity, which plays an important role in organic wine growing. The division of European wine-growing regions into wine zones according to climatic conditions in terms of wine-growing worthiness will perhaps have to change as a result of climate change. From the mid-1990s onwards, Cool Climate Winegrowing has become popular (also) due to the fact of global climate change, by which winegrowing in higher areas with continental climatic conditions is to be understood. See also under Globalisation and Pollution.
Source: Dr. Edgar Müller from DLR Rheinhessen-Nahe-Hunsrück