PRFA)ICTIOi\ OF CLIMATIC J'ARIATIOXS 



101 



outward in the form of a \va\t". Svicli 

 waves move irregularly in \arious direc- 

 tions and with differing speeds. It is 

 possible to trace them, provided enough 

 work is done in the way of tabulating 

 and mapping the weather records. 



Let us return now to the question of 

 sunspots and climate, for the sunspots 

 are the most im])ortant solar \ariation 

 that we are yet familiar with. The 

 contradictions that \vd\e been described 

 above are not really so contradictory as 

 they seem. They are perhaps explica- 

 ble on the following hypothesis. When 

 sunspots are numerous the earth re- 

 ceives more heat than usual, and there 

 is also a greater degree of electrical 

 activity, as is known from many years 

 of observation. These two conditions, 

 either separately or together or in 

 conjunction with other conditions not 

 yet understood, lead to unusual stormi- 

 ness and to an unconmionly rapid circu- 

 lation of the air. Practically all storms 

 are of a cyclonic nature. This does not 

 mean that they are tornadoes, for to the 

 meteorologist the word cyclone merely 

 means a vast slow-moving whirl, or 

 area of low pressure extending o\er 

 hundreds of miles. Such whirls, or 

 storm areas are surrounded by inblow- 

 ing winds, while in their centers great 

 volumes of air move slowly upward. 

 This air is always comparati\ely warm. 

 Therefore it drains the heat away from 

 the earth's surface. Hence if storminess 

 increases, the amount of warm air that 

 goes upward must also increase. This 

 perhaps accoimts for the fact that when 

 sunspots and storms are numerous the 

 earth's mean temperature falls. 



The apparent contradiction between 

 the relation of sunspots to storms in 

 Kansas and in Arizona or Canada, is 

 another case where careful study shows 

 that a definite law is at work, although 

 the cause is not vet understood. Kull- 



iiicr has (h'awn a series of maps showing 

 the areas where storms increase or 

 diminisli at times of many or few sun- 

 spots. He finds that when sunspots are 

 munerous there is a tendency for stormi- 

 ness to increase in the Southwest from 

 southern California to Texas, and also 

 in the North along the southern Ijorder 

 of Canada. In the center of the coun- 

 try however, from Oregon southeast- 

 ward to the middle Mississippi and then 

 northeastward to New England, the 

 storminess tends to tlecline. The aver- 

 age location of the areas of increase and 

 decrease may be seen on the accompany- 

 ing map taken from the author's volume 

 CiriJizaiio)) and Clinuiir. The heav- 

 ily shaded areas are the places where 

 storminess increases at times of many 

 sunspots. Essentially the same condi- 

 tions are found in Europe as may be 

 seen in the low^er map. When sunspots 

 are numerous the areas around the North 

 and Baltic Seas are stormy, and the 

 same is true in a southern belt around 

 the Mediterranean. The intermediate 

 areas, on the contrary, are unusually- 

 dry at such times. 



The phenomena shown in the maps 

 repeat themselves with each sunspot 

 cycle. The exact limits of the shaded 

 areas howe\'er, by no means remain 

 the same from cycle to cycle. The 

 southwestern area of increased stormi- 

 ness in the United States contracts or ex- 

 pands; the tongue that projects south- 

 ward near Lake Michigan sometimes lies 

 west and sometimes east of its average 

 position. This accounts for the dis- 

 agreement already described between 

 the le\-el of Lake Michigan and the sun- 

 spot numbers. In general the shaded 

 area lies over the lake's drainage basin. 

 So long as that is the case the water 

 rises when sunspots are nvmierous and 

 falls when they decline. Sometimes 

 however, the tonuue shifts so far to 



