NO. 29 VOLCANOES AND CLIMATE — ABBOT AND FOWLE 19 



It appears that in 1903 as in 191 2, the presence of volcanic haze 

 caused a decrease of the transparency of the atmosphere, productive 

 of nearly as much effect in the infra-red as in the visible spectrum. 



VOLCANOES AND TERRESTRIAL TEMPERATURES 



We have made some preliminary study to determine if the hazi- 

 ness produced by volcanoes causes a decreased temperature at the 

 earth's surface. 



Taking- the year 1912, we find from the international ten-day 

 mean values published by the German Marine Observatory that the 

 high altitude stations of southwestern Europe, namely: Pic du Midi, 

 Puy de Dome, Brocken, Schneekoppe, Santis, and Hoch-Obir give 

 a very marked indication of a decrease in temperature with respect 

 to the normal beginning about the middle of July. The seven sta- 

 tions named are very consistent with one another in this indication 

 as shown in the table on page 20. 



In order to see if a similar effect was caused by the dust cloud 

 emanating from Krakatoa in 1883 we have studied the temperature 

 departures for Pic du Midi, Puy de Dome and Schneekoppe for the 

 years 1882 to 1884 inclusive, but there does not appear to have been 

 at that time any such marked decrease of temperature following the 

 eruption of Krakatoa, August 27, 1883. as occurred in July, 1912. 

 Nevertheless at Pic du Midi there was a very well marked decrease 

 in the daily temperature range beginning with September, 1883. 

 We have found for some other stations a similar decrease of the 

 daily temperature range following the volcano of Krakatoa. 



In table 6 temperature departures are given for seven stations 

 of the United States for 191 2. The stations selected are from 

 the most cloudless region of the country. They are arranged 

 in two groups with regard to whether they show a tendency to 

 lower temperatures during and after July. Leadville and Flagstaff, 

 two high stations, agree in this respect with the European high 

 stations. 



The temperature of the earth is a function of so many variable 

 quantities that general or cosmical effects are often greatly obscured 

 by local ones. From studies which have been made by various authors 

 it appears, however, that there is a periodicity of terrestrial tempera- 

 ture corresponding in time to the sun-spot cycle of about eleven 

 years. Koppen, Arctowski, Nordmann, Newcomb, Abbot and Fowle, 

 and others have found that there is an increased temperature at the 

 time of minimum sun spots. The increase of temperature is in fact 



