490 E. HI NTI>'GTOX SOLAR HYPOTHESIS OF CLIMATIC CHA^'GES 



is an inference, and he does not go into details to demonstrate its tmtii. 

 He has apparently failed to consider two important matters. One is the 

 effect which even a slight change of temperature may have on meteoro- 

 logical conditions, provided it be permanent. The other is the possibility 

 that while the mean temperature of the earth's atmosphere may van- only 

 slightly, the disiribwion of temperature may var}- considerably. In other 

 words, he has not considered the possibility that the mechanism whereby 

 solar heat is distributed may l)e so altered that the air at high altitudes 

 or in tropical latitudes may bec-ome warmer or cooler, while that at low 

 altitudes or in polar regions may suffer the opposite change. This might 

 occur without any appreciable change in the mean temperature of either 

 the earth as a whole or the sun. To put the matter in another way, cer- 

 tain climatic phenomena, such as cyclonic storms and their attendant 

 winds, may change their intensity and location, and may thus alter the 

 distriliution of temperature without any great change in mean tempera- 

 ture, provided all parts of the atmosphere are averaged together. The 

 possibility of this depends entirely on the cause of storms, a matter as to 

 which we are still in doubt. 



Relation of temperature changes during sun-spot cycle to glaciation. — 

 Turning now to the first objection to Xewcomb's conclusion, let us con- 

 sider the true importance which a range of 0.26° C. between the tem- 

 perature at times of maximum and minimum sun-spots would have, pro- 

 vided the temperature did not fluctuate between the extremes ever}* 1 1 

 years, more or less, but remained constant at one extreme for a few cen- 

 turies. As I have discussed this matter in detail elsewhere,^^ I shall here 

 merely summarize that discussion. 



The usual estimates of the change of mean temperature from the 

 height of the Glacial period to the present time range from 3° C. to 11°. 

 The average is 5° or 6°. This means that the Ijest authorities hold that 

 a change of temperature amounting to only about 2-1 times the change 

 that now takes place from periods of sun-spot minimum to sun-spot 

 maximum sufficed to cause the difference between an epoch when ice 

 covered all northwestern Europe and the northern ITnited States, and the 

 present epoch, when the ice has retreated almost entirely, except in Green- 

 land and Antarctica. If the conditions which Newcomb states to be those 

 characteristic of periods of minimum sun-spots should prevail steadily 

 for a few centuries and then should give place to those characteristic of 

 periods of sun-spot maxima for an equal length of time, the climate of 

 the world would be so altered that it would have gone one twenty-fourth 



"The climatic factor as iUiiKtratefl in arid America. Piib. 102. Carnegie Instftutlon 

 of Washington. 1914. pp. 242-24.3. 



