Prolonged cold snaps over the past 1,000 years in Eastern Europe coincided with plague outbreaks, civil unrest and declines in human settlement, according to a new study that also finds the region is warmer now than it has been for the past millennium.

“It is not accurate to say that whenever it is cold you have problems, that is not the case, but there is a tendency,” study leader Ulf Buntgen, a paleoclimatologist at the Swiss Federal Research Institute in Zurich, told NBC News.