I was in Germany and Austria in late April and early May, when there were a number of days in the mid- and high 80s (30C). I’d seen the temps were still high in Vienna the last week or two, so I checked wine areas. Ouch! The highs seem higher than usual, and worryingly high in a number of cases.
I don’t want to speak with too much authority about the specific growing regions, because I’m sure there’s a lot of specific effects that vary on a grape-by-grape/region-by-region basis…but I think you can make a few generalizations:
The first thing that’s going to be true is that mid-season heat tends to encourage grapes to thicken their skins as a way to prevent moisture loss through respiration and protect against sun exposure. The degree to which this is true depends a bit on how intense the heat is/how long it’s there for/when in the season it shows up.
It advances the growing season. To me, this might be the bigger effect on the style of the finished wines because it means that the final stages of ripening happen when the weather is likely to be warmer and the hours of daylight longer. That shrinks the margin of error for picking decisions. Think of it like roasting a chicken: You can absolutely cook it properly in a hot oven, but your window to pull it out at the correct doneness is much smaller if you’re finishing the roast at 500 vs. 350. [Edit: but also, this is reversible, to some extent: If you get a cool end of summer and/or some well-timed rains, mother nature can push harvest dates deeper into the fall.]
Weird, my spouse was just in Vienna for a half-week business trip and said that the weather was pretty similar to how it is here back home (gray, pretty cool, rainy).
Not only do Beaune temps look forbiddingly high for this time of year (or really even for full summer), nighttime lows averaging 70 (!) are at least as scary. 70 - 95 is not an optimal diurnal swing.
Harvesting in Bordeaux will take place 1-2 weeks in advance of last year, which was already the earliest vintage in history for numerous estates. Perhaps the biggest danger is the potential for tropical conditions which can happen due to the combination of warm temperatures and excess water, causing botrytis.
Warm temperatures alone don’t make the vintage. But, as a guess, lesser terroirs without the ability to retain water in the soil could have a difficult year. Vineyards with water retentive soils could produce very good wine. That being said, there’s a long way to go before the fat lady sings.
We have had a run of warm vintages. Lafleur decided existing AOC rules were no longer relevant; enacted at a time when the weather often meant wines struggled with ripeness, and alcohol levels could end up below sub12%.
I think it makes sense for the various AOCs to start to revisit the rules about hydration. If they continue to hogtie producers, particularly on the Right Bank, others must surely follow, knowing that they are being prevented from making the best wine possible.
I remember there was a proposal five or seven years ago to permit additional grapes, at least in AOC Bordeaux, to add more heat-tolerant varieties. There was a thread here about it. Tempranillo was on the list, I remember. Whatever happened with that?
If you asked me what change was less radical and more likely to preserve the Bordeaux-ness of Bordeaux, permitting irrigation vs planting Tempranillo, I would say irrigation hands down.
Going from memory they approved some additional grapes on a trial basis in some lesser appellations within Bordeaux. I assume the lack of updates (that I’ve seen) means the trial continues, but you know what they say about assuming.
Why? My understanding is that higher nighttime temperatures allow for ripening into the night without the sugar accumulation from photosynthesis thus allowing for maturity to be reached at lower sugars.
