It is the driftice of the Labrador-current which attacks the Gulf- 

 stream south of Newfoundland and compels its warm water to 

 spread eastwards towards the submarine base of the Acores and 

 the coastal bank of Europe. There it is joined by the warm outflow 

 from the Mediterranian, which the Danish expedition on Thor in 

 1910 found extended as far as the weastcoast of Ireland, and 

 forms the vast area of warm water over which the great low-pressure 

 belt south of Iceland forms in winter. When no ice was carried 

 by the Labrador current and this current consequently played a less 

 conspicous part in the oceanic circulation the Gulfstream »could 

 take a more westerly course », as Ekholm says. Then the icemel- 

 ting took place in higher lat:s; in Baffins Bay, in the arctic sea 

 and even in the Polarbasin. 



Western and northwestern Europe then possessed a more 

 continental climate with colder and calmer winter weather. 



At the end of the 13 century the first signs of an iceblockade 

 of Iceland appeared and at the close of the 14th century the 

 drift-ice outside East-Greenland had developed so far, that the 

 sailing-route had to be altered. At the close of the 13th century 

 the invasion of Greenland by the Eskimos appears to have begun 

 and in the 14th century came the destruction of the west Green- 

 land settlement followed by that of the eastern settlement 

 and the loss of communications over sea. In 1200 — 1300 Ice- 

 land was again and again subjected to ice-blockades. The icedrift 

 from the polar sea steadily increased towards the time of the 

 maximum of the tidegenerating force. 



In the Baltic the effect was to increase the influx of salt water 

 which carried the herring shoals into Oresund and gave rise to 

 an abundant fishery which attained its maximum from 1100 to 

 1500 and then declined or removed to northern Cattegat and 

 the North Sea. The swelling of the bottomlayer compelled the sur- 

 facewater to escape and to spread as a thin coating over Skage- 

 rak and Cattegat which there, as well as in the Baltic proper, 

 became excessively heated in summer and cooled in winter, when 

 there was a tendency for anticyclonic development over the snow- 

 covered Scandinavian penninsula surrounded as it was by a broad brim 

 of ice-cold or frozen Baltic water. Cyclones originating in the 

 lowpressure-belt south of Iceland could as a rule not pursue their 

 present course over Skagerak and south Sweden, which then was 

 the centre of an anticyclone. They bent their course to the South, 

 south of Hven, passing over the coast of north Germany where, 

 in conjunction with the high-water at spring-tide, they caused the 

 destructive stormfloods of the winters and the torrential rains and inun- 

 dations of the summers described in the chronicles. This is proved 

 by yet another circumstance. The Volga is the. only considerable 

 tributary to the Caspian Sea. Bruckner and Huntington have shown 

 (see later) that the Caspian Sea had an exceedingly low waterlevel 

 in the 11th century. This must mean that the conflux from the 

 Volga decreased in consequence of the continental meteorologic con- 

 ditions in Europe at this time. This conditions must have altered 

 entirely at the end of the 12th century for then the level of the 

 Caspian Sea again rose according to Huntington: 



»In 1106, if the pilgrim Daniel has not erred in his distances, 

 the Dead Sea stood higher than to day. Next comes a dry period. 

 The caravanserai in the waters of the Caspian Sea off Baku appears 

 to date from the twelfth or thirteenth century, to judge from its 

 architecture. The aridity of this time was not permanent, however, 

 for in 1306 a. D. the Caspian sea again rose to a height of thirty 

 seven feet above the present surface. » 



It was the Volga, which had increased its watersupply, its 

 sources feeding on the rain brought by the Atlantic cyclones 

 which, as Ekholm says, passed over Europe south of the island of 

 Hven. From the Atlantic cyclones were sent out, partly to the 

 Norwegian Sea and the coast of Norway, partly over the North 

 Sea and the coast of middle Europe. Sweden, Denmark and the 

 Baltic countries generally appear to have suffered less from cyclones, 

 according to Tycho Brahe's observations, owing to the fact that 



the Baltic in winter formed part of the anticyclonic area which 

 probably at that time was joined to the great Siberian-Russian an- 

 ticyclonic belt. 



These climatic conditions had a bad effect on the harvest and 

 economic conditions of Iceland, Greenland and north Europe. As 

 regards Greenland and Iceland I refer to a previous chapter of 

 this paper. 



As to south Europe I here reproduce the following description 

 from the 14th century contained in Jessop's Historic Essays p. 175: 



»It seems established that during the year 1347 there was 

 an atmospheric disturbance extending over a large area of Southern 

 Europe resulting in extensive failure of the harvest and con- 

 sequent famine and distress. In January 1348 one of the most vi- 

 olent earthquakes in history wrought immense havoc in Italy the 

 shocks being felt in the islands of the Mediterranian and even 

 north of the Alps. » 



All through the 14th century earthquakes occurred continu- 

 ally over all Europe (which was the case in Iceland also). The earth- 

 quake in Jan. 1348 became famous because it occurred in Avignon 

 simultaneously with the outbreak of the plague (in January accor- 

 ding to Guido de Chauliac). 



It does not seem strange that the maximum of the tidegenerating 

 force which so greatly influenced the ocean's movements should be 

 accompanied by earth-quakes. The Committee for earth-quake- 

 statistics appointed by the B. A. has found a periodicity of 18 

 years in this phenomenon, which seems to hint at a connection 

 with moon periods. Also in the Scandinavian countries the cli- 

 matic variations appear to have brought bad years. 



Of corresponding events in Iceland during the 14th century 

 Professor P. A. Munch relates 1 ). 



»So many tales are still told of the many scourges and vio- 

 lent catastrophes in Nature which visited Iceland in this year that 

 one feels tempted to conclude that this must have been one of 

 the sometimes recurring periods in which the volcanic forces in 

 the interior of the earth are extraordinarily active and the elements 

 are in extraordinary commotion*. 



On examining the historic dates from the last centuries of the 

 Middle-ages, Dr. Bull of Christiania has come to the conclusion 

 that the decay of the Norwegian kingdom was not so much a con- 

 sequence of the political conditions at that time, as of the frequent 

 failures of the harvest so that corn for bread had to be imported 

 from Liibeck, Rostock, Wismar a. s. o. The Hansa-union under- 

 took the importation and obtained political power by its econo- 

 mic influence. The Norwegian landowners were forced to lower 

 their rents. The population decreased and became impoverished. 

 The revenue sank 60-70 %. Even the income from Church-property 

 decreased. In 1367 corn was imported from Liibeck to a value 

 of 34 million kronor. The trade-balance inclined to the disadvan- 

 tage of Norway whose sole article for export at that time was 

 dried fish. Dr. Bull draws a comparition with the conditions 

 described in the Sagas when Nordland produced enough corn to 

 feed the inhabitants of the country. At the time of Asbjdrn Sels- 

 bane the chieftains in Trondenas grew so much corn that they 

 did not need to go southover to buy corn unless three successive 

 years of dearth had occurred. The province of Throndhiem 

 exported wheat to Iceland a. s. o. Probably the turbulent political 

 state of Scandinavia at the end of the Middle-ages was in a great 

 measure due to unfavourable climatic conditions, which lowered 

 the standard of life, and not entirely to misgovernment and political 

 strife as has hitherto been taken for granted. 



I have already pointed out that these conditions must be due 

 to cosmic causes. But the influence of cosmic agents is not purely 

 local, it is felt all over the earth. If the absolute maximum of the 

 tidegenerating force in the beginning of the 15th century 

 really affected the climate of the earth, then its effects should be 

 traced also outside the area whose climate is domimted by the 

 Atlantic. 



VIII. 



Climatic Variations outside Europe at the end of the Middle=age. 



The areas that can come under consideration are North Ame- 

 rica and Central Asia. In these parts of the world an intense 

 research work is carried on which I can only slightly touch upon 

 here. Professor E. Huntington 2 has studied the climatic variation 

 both in Asia and Amerika from an archeological point of view. 



In America he has obtained results of considerable interest by me- 

 asuring the annual growth of the big Californian firtrees Sequoia 

 gigantea some of which are 2000—3000 years old. I reproduce 

 here Huntington's diagram of the growth pro decade of their 

 annual rings (i. e. the width of 10 annual rings in mm. corrected for the 



1 P. A Munch: Det Norske Folks Historie III. 



2 E. Huntington, The fluctuating climate of N-America. Geogr. Journ. Oct. 1912. The Pulsa of Asia; Palestine and its Transformations. 



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