Changes in viticulture due to climate alteration

Chateau la France Bordeaux is where I did my first few days of field work. Chateau la France is situated in the Entre deux Mer region, which a popular region for mix varities. For example, most of the bottles are mixed with 20% merlot and 80% sauvignon cabarenet. Many of the vinyards in Bordeaux have been donated to climate research due to high rise in estate tax. Bordeaux University is a research center for viniculture. Scientists from the university and all around Bordeaux have been studying the possible effects of climate change on vines. The chief question is how would rising CO2 levels affect the vines.

The photo above is showing the type of work Dr. Morin's team has been working on for their research. In a large outdoor testing area, the researchers are pumping grape vines with artificially high levels of carbon dioxide (CO2). The gas is being sprayed out of tiny jets mounted on circular rings suspended above the vines and then evenly spread through the air with the help of ventilators. While this work is being done, I was doing interviews with vineyard management group. The video is in French but I'm transcribing the content below.

Here is a summary of what I've learned from talking to the growers:

Climate change can impact wine grapes through effects on both quantity (yields) and quality, and both aspects have been examined carefully by the university of Bordeaux. Alcohol content of the wine productions have been increasing. Table wines used to hover around the 12% mark: now it’s rare to find them below 13%, and wines with 14 or 14.5% alcohol are commonly encountered. And it’s not all that unusual to see wines tipping the scales at 15%. Alcohol is produced by the fermentation of sugars by yeast, and so it follows that the higher the sugar level in the grapes, the higher the final alcohol level in the wine when it is fermented to dryness. Sugar accumulates in grapes during the ripening process, being produced by the process of photosynthesis in the leaves and stems of the grapevine.The rate of photosynthesis is determined by the intensity and duration of light, plus the temperature. Photosynthesis is maximized in warm, sunny conditions where there is lots of light and the elevated temperatures cause chemical reactions to occur at a faster rate, but if it is too hot, photosynthesis stops because the vine closes its stomata (gas exchange pores) to reduce water loss. Thus we can have a situation where in hot regions, development lags or weakens because photosynthesis will have ceased during the warmest hours of the day.

There are also expected to be repercussions to pest and disease dynamics in wine grapes in an altered climate. and though many studies have recognized this potential, nothing is being done about it to prevent the issues. On the whole, wine grape quality appears to be more sensitive to climate change than yields, and greater problems with pests and disease can be expected in the future climate conditions. From the interview, I gather that severe weather patterns and shifts have been conerning to the viners. Although nothing has been done to prevent heavy precipitation and hailstorms, 40-50% of loss in production is painful to accept.