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Carleton S. Coon's THE LIVING RACES OF MAN:
The Interpretation of Weather Maps
WHATEVER we have said about weather maps, we find them excellent for depicting global variations in climate, such as temperature, light, and moisture, to which human beings are adapted.
Map, which indicates the winter temperatures of the land surfaces of the world, was made by combining the January means for the northern hemisphere with the July means for the southern. Because of the size of the pages of this book, it had to be drawn with intervals of no less than 20°F.
It shows that the northern hemisphere is the colder one. Siberia, Tibet, Canada, Alaska, and Greenland are--except for Antarctica--the winter iceboxes of the world. Most of Europe and Western Asian highlands lie during winter in zone within 8° to 12° of the freezing point, and all of the low-lying lands between the two tropics are warm. Adaptation to winter cold is primarily a Mongoloid problem; it is only secondarily a Caucasoid one.
Summer temperatures(See Map 19) are much more uniform. Only Tibet, Greenland, portions of the Arctic coasts of North America and Siberia, and high spots in the mountains of Europe and South America are below +40°F. Heat stress is concentrated in Africa north of 10 ° N. latitude, in the lands encircling the Persian Gulf, in India, and in Australia. Adaptation to summer heat is a problem principally for Mediterranean Caucasoids, the Bushmen, the peoples of India, Australian aborigines, and some of the Southeast Asians, many of whom are partly Australoid.
Although winter and summer temperatures show seasonal ranges for the different parts of the world, the total amount of global radiation that strikes the surface of the earth per year may be better measure of total heat. This is shown on Map 20. The global mean is about 150 kilogram calories per square centimeter of surface. The regions that receive the most radiant heat are situated on or near the Tropic of Cancer and Capricorn. Most of the world's land area which receives over 200 kg. cal./cm. per year lies in the Kalahari Desert, central Australia, the southwestern United States, and the Atacama Desert of northern Chile. The equatorial regions of the world, which are warm throughout the year, receive much less radiant heat annually, between 100 and 160 kg. cal/ cm. The world's largest area of low radiation in the tropics is in the Amazon and Orinoco valleys. Western Indonesia, New Guinea, and a sizable patch of equatorial Africa also receive relatively little radiation. An excess of radiant heat is therefore a problem affecting principally the Mediterranean branch of the Caucasoids, the Bushmen, the Australian aborigines, and a few of the American Indians. Reduced radiant energy, below the level of 120 kg. cal./cm per year, is largely confined to the and occupied by Europeans, Northern Asiatic Mongoloids, Eskimos, and some American Indians.
The last three maps have to do primarily with heat. Map 21 is chiefly concerned with light, as measured in terms of the total annual hours of sunlight. This map then reflects a balance between radiation, cloud cover, and humidity, and it matches the radiation map more nearly than it does the ones showing winter and summer temperatures. It shows that the sunniest parts of the world are, as expected, those occupied by Mediterraneans, Bushmen, Australian aborigines, Indians of the Southwestern United States and whoever is foolish enough to be found on the Atacama Desert. The most dimly lit places, except for certain regions in the far north, are Northwestern Europe, the foggy Northwest Coast of North America, the region of fjords and inland channels of southern Chile, equatorial South America, Tasmania and the southern tip of New Zealand, parts of West Africa, and, surprisingly enough much of southern China. Negroes, northwestern Europeans, the extinct Tasmanians, Amazonian Indians, and southern Chinese all inhabit or inhabited places where the sun shines on their faces less than three hours seventeen minutes and thirteen seconds a day; yet they have the fairest, the blackest, and the yellowest skin in the world.
Sunlight is reduced by rainfall which creates shady forest, and by water vapor pressure plotted independently of temperature. The latter is more useful than a map of relative humidity. As Map 22 indicates, with minor exceptions the greatest mean annual precipitation is found in the tropics: in Central and South America, West Africa and the Congo, Madagascar, India, Southeast Asia, Indonesia, and New Guinea. The exceptions are the Northwest Coast of North America, the archipelago of southern Chile, parts of Norway, Scotland, Iceland, Japan, Tasmania, and new Zealand. The driest part of the world is a great zone that stretches from the Atlantic coast of the Sahara Desert , across Arabia, down into Somalia, around the Zagros into Iran, and then northward and eastward all the way to Manchuria. It is broken only by the spine of Asia, the Tien Shan and Altai mountains, which long separated the Caucasoid and Mongoloid regions. Smaller areas of little rainfall are found in North America, South America, southern Africa, and Australia.
Map 22 coincides to a considerable extent with Map 20, which shows global radiation. But the resemblance holds only for the parts of the world lying between 40° N. Latitude and 40 ° S. latitude. Once we go polewards from the forties, it ends. In the latter regions, radiation is low with or without much rainfall. Our last maps in this series are 23 and 24, which show the mean water vapor pressures from winter and summer. They are constructed by the same technique as Map 18 and 19, the temperature maps. Water vapor pressure, measured in millibars, indicates the total amount of moisture in the air at a given point. It is independent of rainfall and cloud cover. For example, in the ring of land around the shores of the Persian Gulf, water vapor pressure reaches a world peak in summer. Yet this region is also one of the driest and sunniest on the earth. When high pressure is combined with high temperature, as it is in the Persian Gulf, the heat load becomes almost insufferable.
In the damp tropics, where the thermometer seldom rises above 80°F., the high water-vapor content of the air intensified small changes in temperature. One seldom feels completely comfortable, for a rise of two or three degrees brings on sweating, and an equally slight fall may make one shiver.
As Maps 23 and 24 indicate, it is always damp near the Equator, except in the Andes and the highlands of East Africa and New Guinea. In summer the dampness spreads to the Gulf Coast of the southern United States, the coasts of the Indian Ocean, and to China and the Philippines. The Sahara Desert, and to a lesser extent the Arabian Desert, have dry air the whole year; the deserts of Central Asia, from Iran to Manchuria, are more humid. In this respect the Australian and Kalahari deserts resemble the Sahara. Northwestern Europe, although cloudy, rainy, and cool, does not have damp air. In China, where there is also much cloud cover and considerable rainfall, the air is damp in summer.
The effective thickness of the earth's atmosphere is about 30 kilometers, or 14 miles. Through this protective skin the sunlight that reaches the earth screened. The atmosphere is 14 miles thick when the sun stands exactly overhead, as on the Equator during the equinoxes and on the Tropics of Cancer and Capricorn during their particular solstices. During the equinoxes, at a latitude of 54° north, which is just south of Scotland and Scandinavia, the sun's rays have to pass through one and a half times as much atmosphere as they do at the Equator, and at the Arctic Circle they pass through twice as much.
On a global average, 50 percent of solar radiation is absorbed at the earth's surface; 16 percent is absorbed by atmospheric gases and clouds; and 34 percent is reflected back into space. Where the sun is nearly overhead and the land is covered with vegetation, nearly 70 percent is absorbed, but the ratio falls to 30 percent on a cloudy day.
If the air is saturated, much of the infrared radiation is trapped in it, making the air hot and sultry. But if the air is dry, as on the deserts, only the air close to the ground, the private atmosphere of lizards and snakes, is excessively hot. Most of the infrared radiation bounces back into space. This is why maritime and continental climates are different, and why the equatorial lowlands of the world, being excessively humid, receive no more infrared radiation than do many places forty degrees of latitude to the north or south.
Ultraviolet radiation is more efficient at penetrating the atmosphere than infrared radiation is, and that is why a person can be severely sunburned on a New England beach on a hazy June day, and why hand-line fishermen on the foggy Grand Banks get lip cancer from glare off the water.
The maps we have looked at and the information just reviewed concerning the role of the atmosphere indicate quite clearly that the subspecies of man have been moulded into different shapes and hues by a variety of special climatic combinations. The Caucasoid region is divided into two parts, the northern and the southern. In the northern part, and particularly in Northwest Europe, winters are chilly to cold, summers are mild to cool, and there is little sunlight, plenty of rain, and the air is relatively dry. The southern part, which includes the Sahara and the Arabian deserts, has cool winters, extremely hot summers, bright sunlight, and except for southern and eastern Arabia, dry air. What both the northern and southern Caucasoid regions have in common is a combination of at least one cool season and low humidity. Conditions in the deserts of North Africa and Arabia are very similar to conditions in Bushmen country in South Africa, and in much of Australia. Thus Mediterraneans, Bushmen, and Australian aborigines are faced with similar environments.
One the other hand, the home of the Pygmies and Negroes is warm the year round, has little sunlight, heavy rainfall, and the air is saturated with moisture. There is very little seasonal change. Much the same conditions prevail in coastal New Guinea, most of Melanesia, and parts of Indonesia. In Polynesia and Micronesia the air is warm and moist, there is a medium amount of sunlight, the rainfall is abundant, and offshore breezes cool the air on the windward sides of the islands, where most of the people live.
The Chinese and other northern Asiatic Mongoloids are faced with great seasonal changes in temperature, little sunlight and variable rainfall, and in China the air is very humid ins summer. Of all the major regions of the Old World, except for the deserts, theirs is the most subject to seasonal change. The Americas, which have all climates, were first settled by people already adapted to climatic differences; like other Mongoloids, the American Indians can tolerate much environmental variation.
We did not draw an eighth map, one of altitude, because the reader can find it on any atlas. Only two parts of the world have altitudes high enough to be of importance in racial differentiation, Tibet and the Andes, and both are inhabited by Mongoloids.
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I don't endorse this Carleton S. Coon piece. He is coming from the unpopular perspective of a Multi regional origin of mankind. I believe in the more mainstream Out of Africa model. But there are some interesting remarks on climate here.
Posts: 42935 | From: , | Registered: Jan 2010
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