In truly fascinating new reasearch, scientists have searched historical records to collect data about when the grape harvest began each year. Their research wasn’t published in the Journal of French Wine (I don’t know if there even is one), it was published in the journal Climate of the Past. That’s because the date when the grape harvest begins is a clue to temperature.
The importance of clues like this is that they extend farther back in time than thermometer records. The grape harvest dates (GHD) start in the year 1354 — centuries before the thermometer was even invented. Also quite important: they are all for the same location: Beaune, France.
When the temperature is hotter, the grapes are ready to harvest earlier. When it’s colder, they harvest later. If climate is really heating up, the grape harvest should be getting earlier. And what did they find? This:
There’s no doubt about it: since about 1980, the grape harvest has been getting earlier in Beaune, France. I don’t say so simply based on “eyeballing” the graph — I’ve run the numbers, done the statistical tests, and there is no doubt about it.
Visually, the change seems to start right around 1980, so I used changepoint analysis to estimate when it really started to heat up (when the grape harvest really started getting earlier). It suggests that it actually began around the year 1978:
Before 1978, the harvest was getting earlier by about -0.007 +/- 0.007 d/yr (days per year. That means the real rate is most likely between -0.014 d/yr and 0 d/yr. It certainly wasn’t changing much, if at all.
But since 1978, the trend is a whopping -0.53 +/- 0.23 d/yr. It’s definitely trending earlier, and at a half day a year, since 1978 it has gotten earlier by about 20 days. Here’s a close-up on the data since the year 1800:
Interestingly, the earliest GHD (Grape Harvest Day) in Beaune, France was in the year 2003 when France suffered through its worst heat wave ever.
I can also estimate the trend with a smoothing function, and regular readers know I’m fond of the lowess smooth (but different methods give essentially the same result):
It fluctuated before 1978 — real data does that — but since 1978 it has been declining precipitously. This is not natural. It’s because of man-made climate change.
We can get an “image” of how this indicates temperature has changed throughout the years, simply by turning the graph upside down:
That is one steep rise since 1978. Just as obvious as the recent steep rise, is the lack of such things in the previous 600 years. This is not natural. It’s man-made climate change. Does the shape of this graph remind you of anything? Maybe … something like … a hockey stick?
Whenever new evidence of climate change emerges, climate deniers try to dispute it by any means necessary. They especially hate anything that looks like a hockey stick because it shows so clearly how what’s happening today is not like what we’ve seen before. It’s not natural. Perhaps they’ll claim that French wine-grapes are communists who want to destroy our freedom and impose world government.
I’m looking forward to seeing their response. This is such a wonderful opportunity for them to embarrass themselves! I’m sure they’re up to the task.
This blog is made possible by readers like you; join others by donating at My Wee Dragon.