For the average wine drinker, whether a Bordeaux chateau harvests its grapes in September or August may seem like a matter of little concern, but in fact harvest dates (and heat) play a huge role in wine quality. After studying more than 500 years of European harvest records for a recent paper on climate change and wine grape harvests, Harvard's Elizabeth Wolkovich, Associate Professor of Organismic and Evolutionary Biology, together with researchers from NASA, has determined that French wine grape harvest dates saw a major turning point after 1980, getting earlier and earlier. I talked with her about what this development might mean.
How long did you work on this study?
The last ten years of my life, really. I was interested in wine grapes because they're hyper-diverse, and I thought they'd be able to help us answer a lot of questions about wild species, too.
You used historical information as well as current climate data, correct?
Yes. Wine grape harvest records are just phenomenal in terms of how far back they go. They compare pretty much only with cherry blossom records out of Asia, which are the longest records of that sort on Earth. Those go back to the 800s.
So are harvest dates actually changing?
Yes. Since 1980 the harvest timing of wine grapes is getting much earlier across France; 10 to 14 days, depending on where you are. That's a significant change, especially when you think about climate as it's related to quality. You can accurately say that harvests are getting significantly earlier and they're getting significantly hotter. The real question is how much more heat these regions like Bordeaux and Burgundy can sustain. I think the answer is a fair bit—if you are willing to plant different varieties.
Does that mean you might not see Cabernet in Bordeaux in the future?
Well, the good news is that there's room in wine grapes to grow them across diverse climates. The bad news is that you can't expect to get high quality years in Bordeaux and Burgundy if you keep pushing the climate systems. We've seen only a fraction of the climate change we expect to see in the next 50 to 80 years. For instance, 2003, when we saw many days in a row over 104 degrees in Bordeaux? We're going to see much more climate like that. And I think that will push many of the grapes that people currently plant in their current locations to the limit. We just don't know yet, because we haven't seen those extreme years, what that limit will be. But my suspicion is that given the current rates of climate change and greenhouse gases, we will see those extreme situations in the next 20 to 50 years.
What's the difference between climate and weather, roughly?
People will say, oh, it was so cold last year, how can we be having climate change? It's like, well, we can look back 500 years and find years that are super-cold followed by years that are super-hot. But the signature that you see since 1980 is that harvests are just getting earlier. There are still hot years and cold years, but we're not getting the super-cold years and we're getting more and more super-hot ones.
Could this spell the end for Pinot Noir in Burgundy, for instance?
Pinot needs colder weather than I think it will have in Burgundy in eighty years, at least if we continue a sort of business-as-usual situation in terms of how the human race is acting. But the research I'm doing now is more about how different wine grapes respond to different climate conditions, for exactly that reason. We want to project across the globe when you might need to start switching varieties, how quickly you will need to do it, and what those varieties might be. Will you be growing Mourvèdre really successfully across France in the future? Because I'd would argue that right now it's hard to get a really high quality Mourvèdre in many areas. But you may start having a lot of trouble with Pinot Noir in the central regions that grow it now, for instance.
It's difficult to predict what will happen in any given year, though, isn't it?
It's really hard to predict fine-scale weather. That's why people still get weather forecasts wrong—I live in Boston, and I know! But we've robustly predicted a significant proportion of the large-scale climate change we've seen to date. And then there are these fundamental giant questions we can't answer, like when will the ice sheets go? Exactly when will we start to have huge sea level rise? Or, related to that, this huge fear that the jet stream will shift, which may be really good for some places, but really bad for others. The least of your troubles at that point will be whether you can still plant Cabernet in Bordeaux.