Most surprisingly, Europe winter 1939/40 was the coldest for 100 years.
Unfortunately, back in summer 1939 there was no voice that warned Adolf Hitler and his consorts that a major war in general, and a naval warfare in particular, would bear a high risk of dangerous interfering with weather and atmospheric conditions, with unknown consequences.
In addition, no one mentioned how foolish it would be to start with naval war activities in northern European waters in early autumn. It would release the heat stored in the North Sea and Baltic earlier than in other years. This heat is an essential contributor to moderate winters in Europe. No, Reichskanzler Adolf Hitler and the High Command of the Wehrmacht had no idea of the risks, neither did their professional advisers. Meteorology failed then and over all decades ever since. Meteorology is still unable to explain what happened seven decades ago, and the few who did, presents unproven claims, as e.g. Professor Stefan Brönnimann assuming a correlation to an El Nino event. Current El Nino winter 2015/16 proves: it as nonsense. MORE Adolf Hitler’s personal responsibility, for weather and climate modification in winter 1939/40 and beyond, was never raised. That is irresponsible and a great failure of Meteorology and Climatology.