384 
of sudden solar outbursts on the large-scale pressure 
changes. 
HYPOTHESES OTHER THAN SOLAR VARIABIL- 
ITY AS PRIMARY FACTORS CONTROLLING 
THE ENTIRE SPECTRUM OF ANOMA- 
LOUS WEATHER CHANGES 
The irregular weather changes described above have 
many characteristics that seem to indicate solar vari- 
ability as a primary causative factor. These arguments 
cannot be considered as definite proof of the existence 
of an atmospheric reaction to solar variability. At 
least, however, they pomt out the importance of fur- 
ther studies of the question. 
Perhaps the most striking feature of these changes is 
the fact that the entire spectrum of weather variations 
reveals a similar oscillation between two definite types 
of weather pattern. The severe, stormy weather of the 
glacial epochs, glacial stages, glacial substages, peat- 
bog period, and stormy centuries could be satisfactorily 
explained in terms of the predominance over varying 
periods of time of the low-index patterns that are ap- 
parent in our weather today. Thus, all these weather 
patterns indicate an expansion of the circumpolar vor- 
tex, with extension into middle latitudes of polar condi- 
tions, a retreat southward of the zone of westerlies and 
the storm tracks, a contraction and equatorward move- 
ment of the subtropical high-pressure systems, and 
probably a contraction and intensification of the inter- 
tropical convergence zone. On the other hand, the rela- 
tively mild and dry weather which has predominated 
at various times in the earth’s history is similar in nature 
to our mild seasons characterized by high-index pat- 
terns. 
This similarity of pattern is strongly indicative of 
similarity of the disturbing impulses for all fluctuations. 
The necessity of some wniversal disturbing impulse 
which varies irregularly in long as well as short cycles 
is indicated by the fact that the amplitude of the fluc- 
tuations increases with the period. No random com- 
bination of localized centers of disturbance of the cel- 
lular patterns of the circulation could be expected to 
produce such globally consistent and integrated patterns 
of change. 
Unfortunately, the physical basis for present-day 
changes between high-index and low-index weather pat- 
terns is not understood. Rossby [17] has shown that 
relatively high pressure near the poles (anticyclonic 
polar vortex) is dynamically unstable and that cold 
anticyclonic domes tend to move southward with a 
resulting mcrease in the meridional austausch. 
Starr [23] considers the latitudinal transport of mo- 
mentum and heat and arrives at the conclusion that 
relatively high pressure in higher latitudes is a neces- 
sary condition for, but does not require, poleward 
transport of heat and kinetic energy. Thus Rossby’s 
interpretation is essentially dynamic and Starr’s is 
thermodynamic. Correlation studies based on Starr’s 
hypothesis have yielded coefficients considerably higher 
than those based on any other hypothesis of the me- 
chanics of the general circulation. 
COSMICAL METEOROLOGY 
Irregular weather changes also seem to be world- 
wide in extent. Certainly the glacial epochs and prob- 
ably the glacial stages have been essentially simul- 
taneous throughout the Northern Hemisphere. This 
also applies to the climatic fluctuations. For the secular 
and week-to-week changes, we cannot be so certain, 
but even there evidence indicates the same tendency. 
The difficulties of calibrating the geological time-scale 
in the Southern Hemisphere with that in the Northern 
Hemisphere are great; however, the evidence now avail- 
able indicates the coincidence of the gross weather 
variations in the two hemispheres. 
If the two premises are accepted that irregular 
weather variations of all periods have a common cause 
and tend to be world-wide in extent, it is natural to 
look to solar variability as the controlling factor. All 
that we know about solar variability indicates a strik- 
ing similarity between the patterns of solar changes 
and of weather changes. The sun is capable of short- 
term changes in emission of ultraviolet light and charged 
particles. It also shows a secular change in these emis- 
sions that is only roughly periodic. The meagre evidence 
available from sunspot observations indicates also 
changes extending over centuries that might correspond 
to climatic weather changes. Quite probably the sun 
has varied even more in the geological past than in the 
immediate past where records are available. 
In spite of these considerations, many previous in- 
vestigators have suggested other causes for various 
types of weather changes. Hach of these suggestions 
has encountered serious objections. None, except solar 
variability, is capable of explaining all irregular weather 
variations. Nevertheless it is of interest to consider the 
various weather changes in turn and to discuss the 
alternative suggestions that have been offered. 
Geological Weather Changes. The cause of the ice 
ages has been and still is a subject of lively debate. Of 
the many theories that have been propounded, three 
have seemed particularly attractive and have received 
the most attention. These are (1) the theory of distri- 
bution of insolational heating, (2) the theory of mountain 
or continent building, and (38) the theory of solar vari- 
ability. 
1. The theory of distribution of insolational heating 
holds that variations in the earth’s orbital elements 
(eccentricity, inclination of the earth’s axis, and preces- 
sion) affect the distribution of solar radiation over the 
earth and thus cause cycles of weather. The cyclic 
variation of these elements is such as to predict the 
pattern of Pleistocene glaciation (four glacial stages 
and three interglacial stages), and at one time was used 
to establish a Pleistocene chronology. The arguments 
against this theory are: 
a. These same cyclic changes carried back beyond 
the Pleistocene Epoch predict similar patterns of 
glaciation, whereas pre-Pleistocene time was rela- 
tively free of glaciation for some 250 million years. 
b. These solar effects require that changes in the 
Northern and Southern Hemisphere be out of phase, 
contrary to present opinion and available evidence. 
c. This solar variation does not affect the total 
