Some of the oldest and longest-running phenology records are those made by farmers, foresters, and… vintners. Wine grape harvest is closely tied to when the grapes ripen. And when the grapes ripen has a lot to do with climate. So centuries-long records of grape harvest dates can yield a lot of information about climate over centuries.
That’s exactly the information Isabelle Chuine and her collaborators set out to find when they examined the ripening dates of the Pinot Noir grape in Dijon and surrounding areas in Burgundy, France, dating back to 1370. They created a mathematical model of grape ripening for Pinot Noir grapes based on modern data, where the information on both ripening and temperature is known. Then they used this model to back-calculate historical summer temperatures based on the dates of grape ripening!
Their results, which were reported in the journal Nature, show the pattern of a lot of variation from year to year. This graph shows the harvest dates for the grapes, with earlier dates towards the bottom. You can see that some time periods had earlier harvests (and therefore warmer summers) than others. The red line shows 50-year averages.
In particular, the authors of this study, point out that the grape harvest in 2003 (the very end of the graph) was extremely early — earlier than any time in the past 6 centuries! They concluded that the very warm summer France experienced in 2003 was, indeed, extremely unusual.
Next time you raise a glass, consider that the wine you are drinking has an accompanying harvest record that might help future climate studies. Cheers!
Journal article: Chuine et. al. 2004. Historical phenology: Grape ripening as a past climate indicator. Nature 432, 289-290. doi:10.1038/432289a