427 



a rise of 8° — 9° together with a more uniform distribution of 

 the heat over the globe would be produced, if the percentage 

 of carbonic acid rose to 0.08 or thereabouts (p. 268). 



In a second contribution ^) Arrhenids pubhshed a series of 

 experimental determinations of the absorption of heat by car- 

 bonic acid and revised his former calculations on this new 

 basis, by which revision he obtained somewhat lower values for 

 the influence of the atmospheric carbonic acid. It appears, 

 however, from investigations by Angstrom^) that the density of 

 of the gas has a very marked influence upon its absorption ; I m. 

 of COo at the pressure of 4 atmospheres absorbs 16.2 ^/o of a dark 

 radiation, whereas 4 m. at the pressure of 1 atm. absorb only 

 13.3"/o. This effect of the pressure was not taken into account 

 by Arrhknius, who made his determinations by means of varied 

 pressures in a tube of unalterable length. His figures must 

 therefore at all events undergo a considerable reduction, and 

 it seems to me to be rather doubtful whether variation in the 

 percentage of carbonic acid in the atmosphere will have any 

 appreciable influence upon the climate. Angström expresses the 

 opinion, for which he gives several reasons, that a rise in the 

 percentage will have no influence whatever, while a decline 

 will lower the temperature only if it is carried below 20 "/o of 

 the present value. 



ToLMAN (Journ. of Geol. vol. 7, 1899, pp. 610 — 16) discusses at 

 some length the combined influence upon the ocean-tension of 

 a decreasing percentage of carbonic acid in the atmosphere and 

 the lowering of the temperature, which he supposes to take place 

 in accordance with the original estimates ofARRHENiis. He arrives 

 at the conclusion that the decline of the percentage of CO^ in 



') Svenska Vet. Akad. Forhandl. 1001, pp. 25 — 58. 



^) Ueber die Abhangiglieit der Absorption der Gase, besonders der Kohlen- 

 säure, von der Dichte. Svenska Vef.Akad. Forhandl. 1901, pp. .371—380 

 and: Einige Bemerliungen zur Absorption der Erdstrahiung durch die 

 atmosphärische Kohlensäure. Ihid. pp. 38t — 89. 



I 



