Effects of Temperature Increases on Wine Production

Let's get to the controversy first. This is not a debate about long-term shifts in climate on earth and what is or is not causing them. If that is the debate that you do want, there are plenty of places online that you can do that. Frankly, as someone who doesn't study climate science, my thoughts on the matter should no more influence yours than should any other random person's.

Here is a fact. The last 10 years or so have been warmer across essentially our entire planet than they have been over any other 10 year period since people started using thermometers and recording temperatures for posterity. Roughly 50 years ago back in the 1970s, we had a multi-year period during which temperatures were much colder than norms over the same periods of manually or electronically recorded temperatures. Each has an effect on wine.

Let's consider what this does to wine and to some extent why. And, before you think I've misled you, this is not about wine that might have been made in, for example, the year 2000 and stored in a cellar, this is about vintages during the recent global heat wave (I'd write about the cool period during the 1970s, but I was drinking mostly cheap beer then and wine was a complete rarity for me).

We'll start with some basics that don't require any wine knowledge.

Grapes are the fruit of a plant. Most of the ones that we drink in the US are classified as vitis vinifera. That is, they are genus vitis and species vinifera. Other species of vitis  that you might run across include vitis labrusca, vitis riparia, and vitis rotundifolia (that species is difficult to spell and might be misspelled, but you should know not to drink its grapes because it's Muscadine and any self-respecting wine drinker in Georgia knows that Muscadine wine is only for people with severely deformed sense of taste).

In any event, any tyype of plant will grow well in some climates and poorly in others. That's why, oversimplifying, we see palm trees in places like south Florida, southern California, and Hawaii, and do not see them in Alaska or the Dakotas.

Similarly, there are many varieties of vitis vinifera and each tends to grow better in its favorite climate conditions than it does in less favorite climate conditions. And, for purposes of this post, growing better does not necessarily mean that the grapevine grows taller or faster, but that the grape itself grows better or said a bit differently that the grape grows so that it produces tastier, more expressive wines when left in the hands of a great winemaker.

What does all this mean and why does it matter? Let's use France as an example. If we use Americans as our buying audience, we are used to buying wine based on what we see on the label. Most of us buy based on the grape, even if we don't know we are buying based on the grape and then there are some of us that like the monikers "red blend" or "white blend" or even "meritage" (generally a blend for which the wine producer pays money to the Meritage Association for the right to call their wine a Meritage). We've learned, for example, that Napa Valley produces big, bold Cabernet Sauvignon (whether we like that style or not is of course personal preference) and as a group, we've decided that is what Cabernet Sauvignon should be like.

That's fine. If I am making the buying decision, I set my parameters and if you are making the buying decision, you set your parameters.

Let's digress for a moment about big, bold wines. One of the first producers of big, bold red wines was Randy Dunn. For those who don't know, and I expect that is most people reading this, he was the winemaker at Caymus from roughly 1975 through 1985. But while he was at it, he found some land on Howell Mountain to grow his own grapes and produces his own wines under the Dunn label. Dunn Howell Mountain was as big as it they got. If you looked at a wine list back in the early to mid 80s and ranked the wines by ABV (alcohol by volume), Dunn's wines were almost in a class by themselves. The wines typically had an ABV between 13.5 and 14.0%, but Randy Dunn is alleged to have said he would never produce a wine with an ABV above 14.0%. Today, Napa Valley Cabernet Sauvignon routinely eclipses a 14.0% ABV with some exceeding 16.0%. 

What happened? Did winemakers think we should just get more drunk?

Grapes are a fruit and they naturally contain sugars. Fermentation is a chemical process during which those sugars are converted to alcohol. So, generally speaking, the more sugars in a grape, the higher the alcohol content that comes from it. And again, generalizing, the longer a grape stays on the vine, the more sugars that build up. So, if the growing season is longer, the grapes will tend to have more sugars meaning that a wine produced to be dry will have a higher alcohol content.

Science is cool. We should not ignore it.

When the growing season is warmer and the first post-growing season rains come later, the grapes can stay on the vines longer meaning more natural sugars meaning higher alcohol content. Is that good? It depends who you ask. Does this make Napa Valley Cabernet Sauvignon better than that from other parts of the US or the world? It depends who you ask. 

Many of us, however, have become comfortable with varieties that are somewhat synonymous with California wine country having high ABV, notably the aforementioned Cabernet Sauvignon and Zinfandel. Even in France, where high ABV is not viewed as desirable, alcohol content in recent vintages of Bordeaux, for example, is noticeably higher than in previous vintages.

This phenomenon has not been so good for some grapes though and as a result has not been good for certain regions. The grapes that grown better in cooler climates (notably thinner-skinned ones, so think Pinot Noir as an example) have not been happy with temperature increases. Their styles have changed, not because winemakers woke up one morning and said something like "Let's make bigger, bolder Pinot Noir," but because climate conditions forced this on them. As a secondary result, geographies with climates once considered too cold to effectively produce vitis vinifera wines are now doing it successfully (think England as an example) while France where each Appellation d'Origine Controlee (AOC) is limited in which grapes it can use is struggling. The Pinot Noir red wines from Bourgogne (Burgundy) are ceasing to taste like their traditional wines. The French are re-thinking which grapes may be used where.

We haven't even gotten into acidity which is also affected by climate, so perhaps we'll leave that for tomorrow or whenever I next decide to subject my keyboard to these flying fingers, but in the meantime, I hope you are convinced that temperature changes and shifts have significant effects on the wine you drink.