Abstract
Abstract. This paper presents a unique 517-yr long documentary data-based reconstruction of spring-summer (MAMJJ) temperatures for northern Switzerland and south-western Germany from 1454 to 1970. It is composed of 25 partial series of winter grain (secale cereale) harvest starting dates (WGHD) that are partly based on harvest related bookkeeping of institutions (hospitals, municipalities), partly on (early) phenological observations. The resulting main Basel WGHD series was homogenised with regard to dating style, data type and altitude. The calibration and verification approach was applied using the homogenous HISTALP temperature series from 1774–1824 for calibration (r = 0.78) and from 1920–1970 for verification (r = 0.75). The latter result even suffers from the weak data base available for 1870–1950. Temperature reconstructions based on WGHD are more influenced by spring temperatures than those based on grape harvest dates (GHD), because rye in contrast to vines already begins to grow as soon as sunlight brings the plant to above freezing. The earliest and latest harvest dates were checked for consistency with narrative documentary weather reports. Comparisons with other European documentary-based GHD and WGHD temperature reconstructions generally reveal significant correlations decreasing with the distance from Switzerland. The new Basel WGHD series shows better skills in representing highly climate change sensitive variations of Swiss Alpine glaciers than available GHD series.
Highlights
Cereals are the most widely grown crops in Europe since the Neolithic Revolution
The Basel WGHD series is well documented for the pre-instrumental period, whereas it is of somewhat lower quality from 1870 to 1950, i.e. during a considerable part of the instrumental period
All available figures needed to be annually averaged. After having taken these homogenisation steps, we may speak from the Basel Winter Grain Harvest Date series (Basel WGHD)
Summary
Cereals are the most widely grown crops in Europe since the Neolithic Revolution. Bread was the basic food in most European societies, and before the advent of the railway, grain prices were known to be the key indicator of economic activity (Persson, 1999), comparable to oil-prices today (Pfister, 2010). This paper presents a 517-yr long reconstruction of spring-summer (MAMJJ) temperatures from documentary-based winter rye (secale cereale) harvest starting dates covering the period from 1454 to 1970. From the twelfth century onwards, chroniclers occasionally referred to (bio) physical evidence as a means to provide data on pronounced temperature anomalies that could be compared over time (Wegmann, 2005; Pfister et al, 2009). Annual average rainfall provided a May to July temperature reconstruction of Bu- varies between 800 mm (in the lee of the Jura Mountains) and dapest based on five vine- and grain-related historical pheno- more than 2500 mm in the High Alps, with a summer maxilogical seriesFfirgo.m2.
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