Historically speaking, when Jews talked about the weather, it wasn’t just idle chatter.

These days, everyone is worried about the effects of global warming. However, a new study indicates that the Jews have been dealing with the negative repercussions of climate change for centuries already. But rather than rising temperatures being the problem, Jews’ woes occurred when the mercury started to drop.

The Jewish communities of Europe, whose persecutions in the medieval and early modern periods are well-documented, provided the data necessary for economics professors Warren Anderson of the University of Michigan and Noel Johnson and Mark Koyama of George Mason University, who sought to determine when exactly medieval Europe transitioned into the protective, religiously tolerant region of the post-industrial era.

In their paper “From the persecuting to the protective state? Jewish expulsions and weather shocks from 1100 to 1800,” the researchers explain that historical Jewish expulsions were associated with colder temperatures during the growing season, typically April through September.

When chillier-than-usual weather led to crop failure, European rulers gave the Jews more than just the cold shoulder. During the 15th and 16th centuries, an average decrease of one-third of a degree corresponded with a 1-2 point increase in the likelihood that a Jewish community would be expelled in a given five-year period.

If you had been a Jew of that era and region with an average lifespan of 50 years, you would have faced an 18 percent chance of expulsion during your lifetime. If you happened to have lived in a city with poor soil quality, or during particularly cold years, your fortunes would have been even worse.

For Jews living in pre-modern agrarian societies, there was a serious probability that a cold snap could lead to political unrest, resulting in scapegoating and expulsion. In later centuries, it was developments like the rise of powerful states capable of resisting anti-Semitism; increased religious tolerance; and changing attitudes toward historically Jewish occupations like commerce, money lending, and banking, that mitigated the effects of weather shocks that had earlier left Jews out in the cold.