HUMPHREYS: METEOROLOGICAL PARADOXES 1 69 



Now when cold dry oxygen, such as exists in the upper atmos- 

 phere, is acted upon by certain regions, at least, of the ultra- 

 violet spectrum, some of it is converted into ozone, a substance 

 known to be in the upper atmosphere to a far greater extent than 

 in the lower. Hence when sunspots are most numerous the upper 

 air should contain a minimum amount of ozone. But ozone is 

 intensely absorptive of earth radiation and that too in the spec- 

 tral region of its greatest intensity, and where water is least ab- 

 sorptive and carbon dioxide not at all. That is, at the time of 

 spot maxima when the solar constant is (apparently) greatest, 

 the earth's blanket of ozone is (presumably) least. Even, there- 

 fore, if the earth should be receiving an increased amount of heat 

 at this time it might, nevertheless, grow slightly colder because 

 of the coincident depletion of the heat-conserving blanket of 

 ozone. 



A greater general prevalence of cirrus and cirrus haze during 

 spot maxima than during spot minima (indicated by certain 

 observations) would also account for this paradox; because such 

 clouds, owing to the size of their particles, shut out the short 

 wave-length solar radiation more effectively than they shut in 

 the long wave-length earth radiation. And perhaps these 

 clouds really are generally most prevalent during spot maxima, 

 and, therefore, at least a contributing factor to the cause of the 

 corresponding temperature minima. At any rate the auroras 

 are then most frequent, and they obviously generate nitrous 

 oxide and other hygroscopic compounds which, because of their 

 density, slowly fall to the cirrus level where they may produce 

 cloud particles in an atmosphere whose humidity is much below 

 that which otherwise would be essential to cloud formation. 



The maximum, then, of the cirrus screen and the minimum 

 of the ozone blanket, coincident with the highest temperature 

 of the sun, may very well account for the above paradox — the 

 hotter the sun the colder the earth. 



THE COOLER THE SUN THE WARMER THE EARTH 



This paradox is practically included in the one just discussed. 

 It means that at times of sunspot minima, when the solar con- 

 stant seems to be least, the average temperature of the earth is 

 highest. 



