 Furthermore, the journals contain information or proxy data that admits statements on climatic variation.When e.g.transforming the data on potatoes and barley yields into 10 years moving averages, both crops show similar chronological yield variations, with good harvests in the early 1830s, early 1860s and mid-1880s, separated by poorer periods with minima around 1825, 1844 and the 1870s.