War winter 1939/40 has already received considerable attention with its dramatic development and appearance. Over a very short period of just four months of naval war, a lot of heat was exhausted from Northern European seas, to an extent that they could not prevent arctic air from taking reign of the northern part of the continent during January and February 1940. After huge sea areas had been churned and turned about by naval ships and military means again and again, in short succession, most of summer-stored heat has been gone. Riparian countries immediately plunged into icy winter conditions not experienced for many generations. Circumstances give a clear indication about who is to blame.
However, as already indicated in the opening section of this chapter, there is more evidence to prove the link between naval activities and Europe’s three cold war winters 1939-1942. Cold, very cold, and extreme cold still leave a lot of uncertainty as long as a baseline is not established for comparison. After having shown two extraordinary exceptions with regard to the unexpected return to Little Ice Age, to the conditions and the exceptionality of three successive cold winters, the third massive piece of evidence is based on record conditions in combination with the intensity of naval activities.
Even a record is not necessarily a record if not clearly defined. Record cold winter can cover many dozen events. Human 100-meter sprint record needs a long precision before being reckoned as an Olympic record. Even identifying the “coldest winter” may raise a number of questions. With respect to the three initial war winters, one can do better by concentration on the cold centre of a record cold region in connection with a major naval activity area. But if naval activities reached their full extent in a wider area (Northern Europe), the cold centre of this wide region during a war winter was exactly where pronounced naval activities had taken place during previous autumn months, and this would prove the connection between the two of them. First war winter (1939/40) is the first excellent example in this respect.
Cold Center Hamburg (North Germany)
North Germany reported a record cold winter. Hamburg is a focal point between the North and Baltic Sea. North Ger-many is equally central to both seas. For Hamburg and for Northern Germany, war winter 1939/40 was the coldest of the three initial war winters. Other riparian countries (the Netherlands, Norway, Sweden) experienced their ultimate arctic winter during one of the following war winters.
For Berlin it was the coldest winter in 110 years. The assessment is based on the ‘summary of the daily mean data from November to March, with a ‘cold sum’ figure of -791°C in 1829/30. The corresponding figure for the winter 1939/40 is -736°C. Hamburg was even colder than Berlin, with an extraordinary temperature of –29°C from 14-15 February 1940.
Since early December 1939, Hamburg’s mean temperatures were below zero degrees Celsius, which were an extreme deviation from the long-term average, close to 0°C throughout the whole winter period because of the maritime weather characteristics between the two seas. Why did the situation change so much during the winter of 1939/40?
naval activities started on the 1st of September 1939 and, only a few
months later, cold air temperatures were close to breaking the record, viz.
Southern Baltic Sea from Gdansk to Kiel and Helgoland
Bight. Not only had been several ten thousand sea mines already been laid
within the few weeks since war commenced, but uncountable ship-coast and
ship-ship encounters took place off the Polish coast, in September, while
the German Navy trained several ten thousands of navy personnel off its
coast and send hundreds of ships in surveillance operations, patrols, mine
detecting, mine sweeping, battle missions and so on. Evidence of a
connection between the weather change and the naval war emerged soon.
Massive naval activities and record cold occurred concomitantly in the
 This applies correspondingly to a number of German cities e.g. Halle and Dresden about 150 km south of Berlin.
 Stellmacher, R. and Tiesel R.; ‚Über die Strenge der mitteleuropäischen Winter der letzten 220 Jahre – eine statistische Untersuchung’, Z. Meteorol.39 (1989) 1, p.56-59.