522 E. HUXTIXGTOX SOLAE HYPOTHESIS OF CLIMATIC CHANGES 



Ir Xorth America Kullmer's figures point to an increase in the total 

 number of storms at times of maximum sun-spots, no matter in what way 

 we investigate them. In both Europe and Xorth America there seems to 

 be an unmistakable shifting of the zone of storminess in response to 

 changes in solar spots. Taking the evidence as a whole, we seem justified 

 in saying that, in spite of previous conclusions to the contrary, we actually 

 find as much agreement between climatic phenomena and sun-spots as 

 would be expected on the assumption that variations in the sun are the 

 main factor in producing variations in terrestrial climate. This, in brief, 

 is the outline of what may be called the '^'cyclonic'' solar hypothesis as 

 distinguished from the old ^'caloric*^ solar hypothesis. 



Tlie reduction of terrestrial temperature by cyclonic storms. — ^Let us 

 now return to a subject which has continually confronted ns, but which 

 it has not been possible properly to elucidate until the question of cyclonic 

 storms had been discussed. One of the most important objections to the 

 solar h^-pothesis is the disincHnation of astronomers to believe that the 

 mean temperature of the sun can have changed repeatedly to such an 

 extent as to cause the observed climatic changes of the geological past. 

 This view is supported by the fact that although the changes of climate 

 now in progress show a close relationship with changes in sun-spots, they 

 do not agree at all closely with changes in solar radiation as measured by 

 the pyrheliometer. This raises the question of the effect which varia- 

 tions in the intensity of storminess may have on the temperature of the 

 earth's surface. In answering this, as will shortly appear, we seem to be 

 led to the conclusion that the temperature observed on the earth's surface 

 can change in harmony with the sun-spots without demanding any change 

 of temperature in the sun. 



We have seen that in Xorth America the amount of storminess may be 

 as much as 15 per cent greater during years of the greatest sun-spot fre- 

 quency than during those of least. In Europe equally great variations 

 take place. For example. Kullmers unpublished charts show that in 

 1885 the number of storm centers passing over a small area between 

 Marseille? and Coi^ica was only 16. Four years later, in 1889, more than 

 three times as many, 55 in all, passed over the same area. Part of the 

 difference may be due to variations in the method of recording data, but 

 much of it is real, for we find many similar occurrences elsewhere, both 

 in Europe and America. Let us inquire into the necessary consequences 

 of such changes, if they take place in such a way as to cause a general 

 increase of storminess throughout the world. On the southern side of 

 ordinary cyclonic storms in the northern hemisphere, no marter whether 

 they are tropical hurricanes or the far more nTuneTOus storms of tem- 



