Historical records indicate that, worldwide, witch hunts occur more often during cold periods, possibly because people look for scapegoats to blame for crop failures and general economic hardship. Fitting the pattern, scholars argue that cold weather may have spurred the infamous Salem witch trials in 1692.
The theory, first laid out by the economist Emily Oster in her senior thesis at Harvard University eight years ago, holds that the most active era of witchcraft trials in Europe coincided with a 400- year period of lower-than-average temperature known to climatologists as the "little ice age."Oster, now an associate professor of economics at the University of Chicago, showed that as the climate varied from year to year during this cold period, lower temperatures correlated with higher numbers of witchcraft accusations.
The correlation may not be surprising, Oster argued, in light of textual evidence from the period: popes and scholars alike clearly believed witches were capable of controlling the weather, and therefore, affecting food production.
The Salem witch trials fell within an extreme cold spell that lasted from 1680 and 1730 — one of the chilliest segments of the little ice age. The notion that weather may have instigated those trials is being revived by Salem State University historian Tad Baker in his forthcoming book, "A Storm of Witchcraft" (Oxford University Press, 2013). Building on Oster's thesis, Baker has found clues in diaries and sermons that suggest a harsh New England winter really may have set the stage for accusations of witchcraft.