From the abstract:
The database of Prof. Rogers (1887), which includes wheat prices in England in the Middle Ages, was used to search for a possible influence of solar activity on the wheat market. We present a conceptual model of possible modes for sensitivity of wheat prices to weather conditions, caused by solar cycle variations, and compare expected price fluctuations with price variations recorded in medieval England.
Usually the articles on astro-ph relate more to the state of astronomy today, rather than historical applications of astronomical data. Astronomer William Herchel noted that a relationship between wheat prices and sunspots in 1801. This work is a more detailed account of that relationship.
The authors found that during the 17th century, minimums in solar activity directly correlated with higher wheat prices. A BBC article talks about some of the theories sparked by this relationship.
The effects of the solar activity on Earth’s weather is not clearly understood yet, and is still being studied . A recent study has shown that, at least in the United States, periods of increased solar activity are usually accompanied by periods of greater cloud cover. In addition, storm tracks are pulled north by about 400 miles during solar peak activity.