NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 237 



(curves I) than for the other three regions (curves II to IV) and 

 that here as in other relations before mentioned the variations on 

 the Pacific coast are on the whole inverted to the variations of the 

 other regions. 



Since the winter temperature varies more than the summer tem- 

 perature the curves (as the difference between them shows) are 

 determined mostly by the winter temperatures. Hence the different 

 curves on the whole give an inverted picture of the curve of winter 

 temperatures. 



We can now compare these various temperature curves with the 

 curves for sun spots (SF) and prominences (P) at the bottom 

 of the figure. In the Pacific region (curve I) where, as we have 

 said, the variations are small, it seems as if the winter temperature 

 is especially low in the neighborhood of sun spot minimum, par- 

 ticularly 1890, 1910 and 1913. On the other hand, the difference 

 between the temperature in summer and winter at these times was 

 relatively great, but the variations are all so small and irregular 

 that nothing is to be concluded from them. In the other regions 

 there is a quite distinct agreement between the temperature rela- 

 tions in the two typical year seasons and the sun spot variations. 

 It appears that in the neighborhood of the sun spot minimum, as 

 well as of sun spot maximum, there is a relatively high winter 

 temperature and consequently a relatively small difference between 

 summer and winter temperatures. There is furthermore an indi- 

 cation of a halving of the sun spot period as we have found earlier. 

 It comes to view most clearly in the curves III S-W and IV S-W. 



INCOMING AND OUTGOING RADIATION DUST AND CLOUD FORMATION 



Our investigations do not appear to support the assumption that 

 variations in the temperature of the earth which accompany the sun 

 spot period depend directly on variations in the relation between 

 incoming and outgoing radiation of such a nature that the outgoing 

 radiation at sun spot minimum is diminished and the temperature 

 of the earth on this account increased. If this was correct we 

 should certainly have found it more definitely indicated in our curves 

 than we have done. 



If the temperature variations at the earth's surface are caused by 

 cosmic dust or volcanic ash in the atmosphere or by formation of 

 clouds (called forth perhaps by variations in atmospheric pressure, 

 which would be particularly active to diminish the temperature at the 

 tropics), the solar radiation which reaches the earth would be dimin- 



