Climate Change and Wine Growing: One Farmer’s Opinion

December 7th, 2009 → 12:37 pm @ Josh Hermsmeyer


A couple items in the news and the on the blogs prompted this post. First was the recent discussion by Jeff over at Good Grape about Tom Johnson’s (author of Louisville Juice) contention that wine bloggers don’t link to each other.

One of the reasons for this, Jeff says, is because of the dearth of meta stories that are news-driven and thus have universal effect and interest. I think he’s right.

Two other stories this morning also prodded me to post. One is this story on CNN talking about winemakers fighting climate change.

Another is this recent post on Palate Press discussing where to plant a vineyard in 2099 due to effects of anthropogenic global warming (AGW).

EDIT: Another one from today (12/8): French wineries join Greenpeace.

Bottom line – it looks like we have a universal, news driven wine story, and so I thought I’d provide some perspective from a farmer/winemaker in the Russian River Valley.

Global Warming and Wine Grape Growing.

First, some context. I believe that the earth has been warming over the past century. I think this is pretty well established. The question is: why has it warmed? Also, I am not going to take a stand on the global policy implications of warming. I’ll leave that to the politicians.

In terms of the wine industry, the relevant questions are: how will the warming affect grape growing, and will the the warming be detrimental or will it have a positive impact? In making these determinations, it is also very useful to have an opinion as to whether the rise in temps is due to CO2 “forcing”, or if warming is a cyclical thing and should be regarded as temporary.

How Will Warming Affect Wine Grape Growing?

The short answer is: we don’t know. The reason we don’t know is because the climate isn’t homogenous, and warming on a global scale may or may not adversely impact viticulture on a meso scale.

In 2007 I wrote about UC Davis Climatologist Richard Snyder’s work studying Napa temps.

I wrote the following as a conclusion (click through to see slides and a link to a news article on his talk):

What’s interesting is that the single biggest danger global warming poses for wine growers is that the incidence of these extreme weather events will increase, not that average temps will increase. San Pablo Bay protects Napa Valley from overheating quite well, and as temps increase Dr. Snyder predicted that fog due to evaporation from the bay will increase and stretch farther up the valley, insulating the grapes.

And given the fact that it is in nighttime temps that we are seeing the real effect of the temperature increase, what we have is a recipe for better grape growing conditions. Since grapes can continue to ripen at night when temperatures are relatively warm, global warming – paradoxically – might be just the thing to help out growers losing tonnage late in the season because phenological ripeness hasn’t kept pace with sugar accumulation.

It’s tempting to speculate that other maritime winegrowing regions might react in a similar way, but more studies for each region would need to be undertaken. The truth is we just don’t know.

Indeed, we simply have no evidence to suspect any sort of universal calamity to befall grape growers due to an increase in global average temperatures, and this needs to be noted in any discussion about wine and global warming.

Global Warming’s Cause: Man, Nature or a bit of Both?

Why does it matter what the cause is, if most people agree there is warming?

The answer is: if it’s man made, it will continue. If it’s an artifact of natural cycles, it will likely reverse course in the future. In one future the climate never cools. In the other the climate behaves like a sine wave, with global temps rising and falling with a relatively flat trend line.

In practice, a winegrower’s stance on the issue has profound implications.

As one example, I was sent this link to a Decanter story about Hugh Ryman of Chateau de la Jaubertie in Bergerac pulling out his Merlot vines due to warming. His actions are predicated on his belief that the warming will either continue, or that current temps will stabilize as the new normal.

This is not a cheap endeavor on his part, and pulling old vines is always a cringe-inducing affair. In the Russian River and Sonoma, the lack of many old vines is frequently lamented, even though they were replaced with the best of intentions at the time, in the name of progress.

There are of course consequences to inaction as well. If your wine quality is suffering for whatever reason, change is usually required. Grafting over to new varieties is typical in the New World, for instance, when the whims of the market change.

For those with skin in the game, it behooves us all to take a hard look at the science behind the cause of the warming and determine how big a bet we want to place on the accuracy of any prediction where climate is concerned.

My Current Opinion, Subject to Change

Until just very recently, I was a firm believer in AGW. We have purchased extremely marginal land up north and began vineyard planning and collecting temperature data in anticipation of future warming. In the face of what I saw as overwhelming consensus on AGW, our family put our money where the science told us to.

I’m now a skeptic.

In general, viticulturists and vineyard developers are used to and comfortable with trusting science and the researchers producing it. Science is a good bet. Sometimes it works out (phylloxera) and sometimes it doesn’t (UC Davis in the 70′s advised most folks to plant on the valley floor in Alexander Valley if they wanted the best quality). But we’ve never had reason to doubt that the researchers were only after the truth and had out best interests at heart.

I don’t have that same confidence anymore for the top-tier scientists in Climate Modeling. And I don’t think I’m alone.

Why? In a recent editorial in Nature, the evidence for AGW is characterized as the following:

Denialists often maintain that these changes are just a symptom of natural climate variability. But when climate modellers test this assertion by running their simulations with greenhouse gases such as carbon dioxide held fixed, the results bear little resemblance to the observed warming. The strong implication is that increased greenhouse-gas emissions have played an important part in recent warming, meaning that curbing the world’s voracious appetite for carbon is essential.

If the leaked CRU emails show anything, it is that the public was wrong to confer to scientists a level of deference that is utterly unmatched in any other professional endeavor. They are as petty as everyone else, and the sausage-making behind the scenes is ugly indeed.

Programming code and comments from the leaked archive indicate that data massaging was taking place. It is not clear if this code was used to produce published results, but it was present, uncommented, in a finished version of an influential temperature reconstruction.

Regardless though, the fact that such manipulative code exists is reason enough to demand a full and transparent accounting of how the models provide the predictions they do.

The extent to which the raw data and metadata used to build temperature reconstructions was destroyed is incredibly worrisome as well. It means that replication will be extremely difficult, if not impossible, and replication is at the heart of the scientific method.

Ultimately the above is important because, as the Nature editorial points out, the evidence for AGW rests on the inability of the climate models to account for warming without CO2 “forcing” and its attendant feedbacks (cloud cover, water vapor etc.) which are not well understood. The models are validated with past data, and are an accumulation of much good science. However the models are a product of a complicated set of assumptions, not observations, and can’t account for the lack of warming in the past decade. In fact, the warming in last decade is below even the most optimistic predictions the models made back in 1999.

Indeed NCAR scientist Kevin Trenberth (now famously) wrote

“The fact is that we can’t account for the lack of warming at the moment and it is a travesty that we can’t.”

Looking at all this, I’m forced to confront the uncomfortable idea that I can no longer credulously accept the notion of AGW. It may well be that man is the cause of the recent warming, but we are not ready to grub up any vineyards, buy any more property, or do much of anything else based on the evidence at hand.

Let me be clear, the above is not evidence that AGW isn’t occurring. It is simply a wake up call. Appeals to authority are no longer (and should never have been) acceptable as explanations.

Unfortunately for the climate scientists, the predictions of warming they provide us are entirely predicated on us trusting them and the closed-source climate models they create.

So, I’m a skeptic. It is a noble intellectual position, and I won’t let ad hominim cries of “denialist” sway me.

What will sway me? A clear accounting of the issues raised by the leaked data and emails, complete and transparent reconstructions of key paleoclimatic data, and public disclosure of all code used to predict future climate change. In short, good science.

My mind is open to whatever may come.

UPDATE: A very good discussion of the problems with AGW by Joe D’Aelo