488 E. HUNTINGTON SOLAR HYPOTHESIS OF CLIMATIC CHANGES 



For polar regions we have as yet no good compilation of data. If the 

 decrease, which hoth Xewcomb and Koppen notice as one passes away 

 from the equator, continues indefinitely poleward, it would appear that 

 in polar regions the difference between periods of sun-spot maximum and 

 minimum may almost disappear. The importance of this will appear 

 later. Other authorities, as well as the two just mentioned, have found 

 differences in terrestrial temperature corresponding to variations in sun- 

 spots. For example, Arctowski,^^* shows that according to his geograph- 

 ical method the difference between the mean temperature of the earth in 

 1893, a year of maximum sun-spots, and in 1900, when the spots were 

 almost at a minimum, amounted to about 0.5° C. The agreement among 

 the various authorities is so complete that we may safely consider that the 

 relation of solar changes and terrestrial temperature is an established 

 fact. This, however, does not necessarily prove that the earth's climate 

 is appreciably influenced by changes in the amount of heat emitted by the 

 sun. Newcomb holds that this is not the case, and Hann, the great au- 

 thority on climate, is inclined to agree with him. although he expresses 



the century from 1811 to 1910. Hence the results are even more reliable than those 

 of Xewcomb. They are summed up in the following table : 



Departures from Mean Temperature during the Sun-spot Cycle 



.., .. Sou til North 



Year of sun-spot cvcle. y^no Tt-mperate Temperate World (lands). 



'^°"^- Zone. Zone. 



Approx. sun-spot minimum.. +0.36° C. +0.2.".° C. +0.31° C. +0.32° C. 



1 year after minimum +0.11 +0.08 —0.04 +0.11 



2 years after minimum +0.07 +0.08 0.07 +0.07 



3 years after minimum —0.11 +0.03 —0.07 —0.08 



4 years after minimum —0.23 —0.20 —0.06 —0.13 



Appro.x. sun-spot maximum. —0.11 —0.20 —0.12 —0.14 



6 years after minimum —0.13 —0.03 —0.08 —0.11 



7 years after minimum —0.11 —0.08 —0.20 —0.16 



8 years after minimum —0.13 —0.04 0.07 —0.04 



years after minimum +0.02 +0.00 —0.04 —0.02 



10 years after minimum. .. . +0.24 +0.2.J +0.07 +0.18 



These figures agree with those quoted above except that the amplitude of the change 

 of temperature from maximum to minimum is somewhat less. Koppen shows further 

 that the new figures strengthen the conclusion that the variation during the sun-spot 

 cycle is most regular and of greatest amplitude in the tropics, while in the far north, 

 although it can still be detected, it is unimportant and there are often contradictions. 

 Another important matter is that, so far as the data go. there does not seen to be a 

 compensation of low temperature in one region by high temperature in another. Inas- 

 much as the data cover only about one-sixth of the earth's surface, the rest being either 

 water or lands where no data are available, this can not be regarded as positive proof 

 that the mean temperature of the earth's surface as a whole actually suffers a reduction 

 at times of many sun-spots, but It points in that direction. When one sun-spot cycle 

 is compared with another. KOppen does not find reason to think that the mean tem- 

 pi'rature varies in harmony with the range of spottedn»>ss — that is. when the difference 

 between maximum and minimum spots is great, there does not seem to be a corre- 

 spondingly great diflference In the mean temperature. In support of this he gives the 



