Any time conversational genius flags, the weather is unquestionably the world's most honored subject. Yet with all their practice, languid prognosticators can seldom speak about the temperature tomorrow with so much authority as Harlow Shapley, seven other Harvard faculty members, and distinguished outside contributors can discuss the climate a million years ago--and a million years hence.
Two excellent essays describe climatic reasons for the evolution of certain races and bodily characteristics in various parts of the world. In mammals, the same body temperature must be maintained in the Arctic and in the tropics. This is the reason the equatorial zones produce long fingers, dark skin, and short bodies in monkeys as well as humans, and the high latitudes account for the opposite characteristics.
After the general introductory essays, the book's description of the effects of climate ends abruptly and there begins a more pedantic probing into the causes of glaciers and methods of dating them. Here the layman will be tempted to lay Climatic Change quietly down, and return to science fiction. But this would be a mistake, for the intensive study of glaciers is an unusual exhibition of all the--ologists from nuclear theorists to lake bed diggers (palcoliminologists).
Geologists have suggested that certain land mass configurations cause the glaciers. If, for an example, the Being Strait were to sink a few thousand feet, the Japanese current could pass through to melt the Arctic pack ice, and submerge the lower parts of all continents. Unfortunately for this theory, John Wolback points out that the four most recent glaciers have grown and died since the last significant distortion of the earth's crust.
Volcanos, enthusiastically cited by more imaginative geologists as the cause of glaciers, can actually produce enough dust to blot out much of the sun's radiant heat. Krakatoa's ash, sent sky high in 1833, cut 10 percent of France's sunlight for three years. But reductions in radiant energy cool the equator more than the poles, cutting temperature differences which create storms. Only an increase of the sun's general heating power will yield more snow, the sole food of glaciers. Yet if the sun's heat increases too much, the glaciers will melt.
So all the writers in Climatic Change agree that it is corpuscular radiation--such as comes from sun spot cruptions--that causes climatic variation. For corpuscles are charged, and are attracted to the earth's magnetic poles. When there are more sun spots than usual, the poles warm up; when there are fewer, they cool off, and glaciers can form. The sun spot theorics, explored mathematically and physically in Climatic Change, explain the relation of terrestial weather to the eleven year sun spot cycle, explain the fact that North American winters are colder than European winters at the same latitude, and they demonstrate that when the earth's magnetism and solar radiation are weakest, conditions are most favorable for an ice age.
Primarily because Climatic Changes contains the results of such widely differing scientific methods, it seems to evade the audience. The specialist will wait for reprinting in trade journals of the few articles in his field. And it will be the rare layman, unusually inspired by the stark mountain peaks on the book-jacket, who will decipher formulae for luminosity of the sun in order to lay bare an astronomer's scientific reasoning. The book would be improved by several additional papers on the earth's climate, how it molds the earth's terrain, and whether storminess is essential for human invigoration. Such essays could give Climatic Change the popular appeal Rachael Carson gave The Sea Around Us.