The frigid 2013/14 Midwestern winter was 20–100 times less likely than in the 1880s due to long-term warming, while winter temperature variability has shown little long-term change.
K Wolter, M Hoerling, JK Eischeid, GJ van Oldenborgh, XW Quan, JE Walsh, TN Chase, RM Dole. How Unusual was the Cold Winter of 2013/14 in the Upper Midwest?
published, Bull. Amer. Meteor. Soc., 2015, 96