A 500 year pheno-climatological view on the 2003 heatwave in Europe assessed by grape harvest dates

In 2003, Europe was affected by a record-breaking heatwave in summer, which is statistically extremely unlikely. However, there are indications that comparably anomalous warm summers might have occurred in the more distant historical past, for instance in 1540. Dates of grape harvesting in Western Europe, starting in 1484, allow a concise assessment of growing season temperatures. The maturity of grapes strongly depends on growing season temperatures, and 84 % of the year-to-year variability is explained by April to August temperature. When reconstructing the growing season temperatures by these historical grape harvest dates, the heatwave of 2003 stands out as an extreme, not only for the instrumental period, but also during the preceding 500 years.