VOLCANOES AND CLIMATE 

 By C. G. ABBOT and F. E. FOWLE 



During- the summer of 191 2 we were engaged, respectively, at 

 Bassour, Algeria, and at Mount Wilson, California, in measuring 

 with the pyrheliometer and spectrobolometer the intensity of the 

 radiation of the sun. On June 19 Mr. Abbot began to notice in 

 Bassour streaks resembling smoke lying along the horizon, as if 

 there were a forest fire in the neighborhood of the station. These 

 streaks continued all summer, and were very marked before sunrise 

 and after sunset covering the sky then towards the sun nearly to 

 the zenith. After a few days the sky became mottled, especially 

 near the sun. The appearance was like that of the so-called 

 mackerel sky, although there were absolutely no clouds. In the 

 months of July, August, and so long as the expedition remained in 

 September, the sky was very hazy, and it was found that the inten- 

 sity of the radiation of the sun was greatly decreased by the uncom- 

 monly great haziness. Mr. Fowle noted similar appearances at 

 Mount Wilson especially noting the streakiness beginning with June 

 21. Publications in European journals and elsewhere have indicated 

 that this haziness was world-wide. We adopt the view expressed by 

 Dr. Hellmann 1 that the haze in question was due to the eruption of 

 the volcano of Mount Katmai in Alaska in June, 1912. In the 

 present paper we give the effects of the haze on the quantity and 

 quality of the solar radiation as determined by our measurements, 

 and also the effect which the presence of the haze and that of 

 similar occurrences in former years appear to have had on the 

 climate of the earth. 



Before passing to the numerical results it will be interesting to 

 recall briefly the circumstances attending the eruption of Mount 

 Katmai and of other extraordinary volcanic outbreaks which resulted 

 in periods of prolonged haziness similar to that of the summer of 

 1912. 



1 Zeitschrift fur Meteorologie, January, 1913. 



Smithsonian Miscellaneous Collections, Vol 60, No. 29 



