

CLIMATIC CYCLES AND TREE GROWTH 



A STUDY OF CYCLES 



I. INTRODUCTION 



While seeking information regarding climatic influence on tree-ring growth, 

 we have developed an improved method of studying and expressing certain 

 climatic changes that have been disappointing to students of cycles. The 

 chief purposes of the present writing are to describe and discuss this method 

 of cycle analysis, to place on record the results obtained on ring growth in 

 favorable regions, to outline the similarities over certain geographical areas, 

 to present the resemblance of climatic cycles to certain solar cycles, and to 

 begin the study of their use in long-range weather prediction. 



The present work is based on a view sustained by recent advance, namely, 

 that having developed an appropriate method, we should specialize upon those 

 climatic changes which seem to occur in non-permanent but still obviously 

 cyclic form. It is hoped that this treatment will receive consideration in 

 connection with problems of reclamation and hydraulic engineering as well as 

 in climatology. Although this volume is the third 1 in a series begun in 1919, 

 a large mass of basic material still remains unpublished. It is hoped that it 

 will be made available in the near future. 



Since presentation of the material involves the facts obtained in the 

 measurement of rings of trees, especially the western yellow pine and Douglas 

 fir of Arizona, certain formal tests upon our ring records, such as the uni- 

 formity of ring records within a tree, the uniformity over local areas, and the 

 like will be referred to. In other respects, without undue repetition, we 

 desire to bring the basic material up to date. We believe that this should be 

 investigated in the district and upon the trees with which we have worked, 

 thus avoiding misleading results that have been found in distant localities and 

 other environments and different biological material. 



In presenting a new description of the analytical method used now for a 

 score of years, we shall endeavor to make clear to those familiar with harmonic 

 analysis that the new method is simply a way of finding and expressing the 

 facts of climatic change in a more detailed and useful form. The use of the 

 word "accidental" will be avoided as far as possible in regard to climatic 

 changes because that word begs the question by implying uselessness to human 

 welfare. We believe that some of the results will prove useful. From the 

 viewpoint of climatology, our investigation is a study of the geographical ex- 

 tension of certain climatic similarities, because in this type of expression 

 (the cyclogram method) similarities not hitherto observed can be recognized. 



1 References in this book to the preceding volumes are sometimes indicated by I 

 and II. 



