August 5, 1920] 



NATURE 



715 



Meteorological Influences of the Sun and the Atlantic J 

 By Prof. J. W. Gregory, F.R.S. 



''yHK prospects of lony^-period weather forecast- 

 ■*- ing and the explanation of major variations 

 of cHmate appear to rest on two lines of investiga- 

 tion. The effort of the first is to connect changes 

 in the weather with those in oceanic circulation ; 

 the second attributes the changes to variations in 

 the heat supply of the sun acting through the 

 atmospheric circulation. Each theory has its own 

 a priori probability. The oceanic control of climate 

 has the attraction that each ocean is a potential 

 refrigerator, since it is a reservoir of almost ice- 

 cold water, which, if raised to the surface, must 

 chill the air, disturb the winds, and enable polar 

 ice to drift further into the temperate seas. 

 Hence Meinardus, for example, connected the 

 range of ice in the Icelandic seas and harvests in 

 Germany with variations in the surface waters 

 of the North Atlantic. The alternative theory 

 has the recommendation that, since the earth re- 

 ceives its heat supply from the sun, variation in 

 solar activity is the natural cause of climatic change. 



The oceanic theory must be true in part. The 

 abnormal character of some coastal climates is 

 clearly due to the upwelling of cold water under 

 the influence of off-shore winds. Moreover, un- 

 usual spells of weather on some of the coasts and 

 islands of the Atlantic follow changes in the 

 quality of its surface water, as proved by Dr. 

 H. N. Dickson for North-western Europe, and 

 by Prof. H. H. Hildebrandsson's demonstration 

 that for fifteen years there has been constant co- 

 incidence between rainfall in British Columbia 

 and the weather in the following autumn in the 

 Azores. The alternative theory that the main 

 factor in controlling the temperature of the earth 

 is the varying heat from the sun acting through 

 changes of wind and atmospheric pressure has 

 been mainlv advanced by the work of Sir Norman 

 and Dr. W. J. S. Lockyer and of Prof. Frank 

 Bigelow ; they are now strongly reinforced by Dr. 

 B. Helland-Hansen, the director of the biological 

 station at Bergen, and Dr. Nansen, who remark 

 that these views have hitherto received but little 

 support. 



The important memoir by these Norwegian 

 oceanographers is based on a detailed study of 

 variations in the temperatures of the air and 

 surface waters along the steamer route from the 

 English Channel to New York. Their detailed 

 discussion of the results and associated problems 

 is accompanied bv a valuable series of tempera- 

 ture charts of the North .Atlantic for the months 

 of February and March from 1898 to 1910. The 

 data are often uncertain, and the inconvenience of 

 the Centigrade thermometer with its zero at freez- 

 ing point is illustrated by records of water tem- 

 perature of — '^° C. and —4° C, which have to 

 be rejected. Drs. Helland-Hansen and Nansen, 



1 BjSm Helland-Hansfn and Fridtjof Nansen, "Temperature Variation<! 

 in the Nonh Atlantic Ocean and in the Atmosphere " Introductory Studies 

 on the Cause of Climatoloeical Variation". Smithsonian Miscellaneous 

 Collections, vol. Ixx., Publication 2537. 1920. Pp. viii + 408+48 plates. 



NO. 2649, VOL. 105] 



after discussion of the theory of oceanic control, 

 reject it as quite inadequate. Thus the chilling 

 effect of the drift of ice into the North Atlantic 

 they estimate as "vanishingly small" in com- 

 parison with the heat transported by the air, or 

 even by ocean currents. They consider that, 

 though not yet fully established, the variations of 

 the air temperature preceded, and were therefore 

 not the result of, those of the water temperature. 

 They hold that the variations of temperature re- 

 quire some much greater and more general cause 

 than oceanic variations. 



Faith in the meteorological influence of oceanic 

 circulation was greatly favoured by the exagger- 

 ated estimates attached to what the authors refer 

 to as "the so-called Gulf Stream." Thus the 

 warmth of the water off the Norwegian coast was 

 attributed to that current even by Pettersson and 

 Meinardus ; this conclusion the authors describe 

 as surprising because the evidence of salinity 

 shows that the Norwegian waters are coastal and 

 quite different from those of the mid-Atlantic. 

 This sound criticism of the Swedish and Miinster 

 oceanographers renders it the more remarkable 

 that there is no reference, either in the long his- 

 torical discussion or in the bibliography, to the 

 pioneer work on this subject in the earlier papers 

 by Dr. H. N. Dickson, or to his observations as to 

 the seasonal entrance of the Atlantic water into 

 the North Sea. The authors agree with Schott 

 in terminating the Gulf Stream west of New- 

 foundland, and calling the current off Western 

 Europe the "Atlantic current," for which 

 Dickson's name of "European current" is more 

 descriptive and definite. The Atlantic is a large 

 mass, and has a whole system, of currents, of 

 which the so-called Atlantic current is by no 

 means the largest. 



Drs. Helland-Hansen and Nansen, after reject- 

 ing the oceanic theory, accept as firmly established 

 the dependence of variations in the earth's tem- 

 peratures on the solar variations proved by sun- 

 spots, the numbers of solar prominences, and ter- 

 restrial magnetic disturbances. They point out 

 that the influence of the sun on the weather of any 

 area on the earth depends upon so complex 'a 

 series of factors that the results at first sight 

 appear inconsistent. The crude expectation that an 

 increase of heat supply from the sun would raise 

 the temperature of the whole earth was early 

 dismissed, for the greater evaporation would 

 lower the temperature on the coastlands by in- 

 creased clouds, rain, and snow. Blanford pointed 

 out, for example, the see-saw of oceanic and con- 

 tinental conditions ; but. though his view has not 

 been fully confirmed, his principle is supported 

 by the proof that regions are oppositely affected 

 bv changes in the heat supplv from the sun. 

 B'Ofelow has divided the world into three groups 

 of regions: in the "direct" group the tempera- 

 ture conditions varv directly with the sun ; in the 



