Modern World 1952-1954 70" Source: Lamb [1977]: 264 from Bergthorsson [1962]. The First Climatic Optimum Around 9,000 to 5,000 years ago the earth was much warmer than today; perhaps 4°F hotter, about the average of the various predictions for global warming after a doubling of CO2.23 Although the climate cooled a bit after 3000 B.C., it stayed relatively warmer than the modern world until sometime after 1000 B.C., when chilly temperatures became more common. During this Climatic Optimum epoch, Europe enjoyed mild winters and warm summers with a storm belt far to the north. Not only was the country less subject to severe storms, but the skies were less cloudy and the days sunnier. Notwithstanding the less stormy weather, rainfall was more than adequate to produce widespread forests. Western Europe, including parts of Iceland and the Highlands of Scotland, was mantled by great woods.24 The timber, until average temperatures dipped temporarily for about 400 years between 3,500 B.C. and 3,000 B.C., consisted of warmth-demanding trees, such as elms and linden in North America and oak and hazel in Europe. Not only did Europe enjoy a benign climate with adequate rainfall, but the Mediterranean littoral, including the Middle East, apparently received considerably more moisture than it does today.25 The Indian subcontinent and China were also much wetter during this Optimal period.26 Compared to cooler periods in the last few thousand years, the Sahara was much wetter and more fertile during the Climatic Optimum.27 Cave paintings from the epoch depict hippopotamuses, elephants, crocodiles, antelopes and even canoes.28 The water level in Lake Chad about 14° north of the equator in central Africa was some 30 to 40 meters, that is, 90 to 125 feet higher, than it is today, indicating much greater 23 Lamb (1988): 22. precipitation. Ruins of ancient irrigation channels in Arabia, probably from the warmest millennia, derived their water from sources well above current water supplies, indicating a wetter climate.29 With the cooling that started after 3000 B.C., North Africa dried up and the abundance of life disappeared. As already mentioned, the invention of agriculture coincided with the end of the last Ice Age and the melting of the glaciers. Archaeologists have found the earliest evidence for husbandry and farming in Mesopotamia around 9000 B.C.30 The domestication of plants appears to have occurred around the world at about the same time: from 10,000 YBP to 7,500 YBP.31 Planting of wheat and barley began in southwest Asia between 8000 B.C. and 7000 B.C. Food production in China extends back at least into the sixth millennium B.C. In the Americas domestication of some grains and chili peppers dates from between 7000 B.C. and 6000 B.C.; anthropologists have documented maize in the Tehuacan Valley by 5700 B.C. and production may have started earlier. In South America the evidence suggests that domestication of two species of beans and chili pepper as well in the Andean highlands arose 8,500 years ago. Domestication of cattle occurred in the Sahara about 8,000 years before the present.32 The development of agriculture and the establishment of fixed communities led to a population explosion and the founding of cities. Agricultural societies produce enough surplus to support such urban developments, including the evolution of trades and new occupations. A large community could afford to have specialists who made farm tools, crafted pots, and traded within the village and between the locals and outsiders. The people in today's Palestine established the first known city, Jericho, and thus the first step towards specialization which lies at the heart of economic advancement 8000 B.C.33 around In Europe, the Optimum period produced an expansion of civilization with the construction of cities and a technological revolution. The Bronze Age replaced the New Stone Age.34 The more benign climate with less severe storms encouraged travel by sea. Trade flourished during this warm period. People from ancient Denmark shipped amber along the Atlantic coast to the Mediterranean. As early as 2000 B.C., the Celts apparently were sailing from Cornwall and Brittany to both Scandinavia and southern Italy. Astrological monuments built around this time, such as Stonehenge, indicate that the skies were less cloudy than now.35 With the glaciers in the Alps during the late Bronze Age being only about 20 percent of the size of the ice in the nineteenth century, merchants made their way through the Brenner Pass, the dominant link between northern and southern Europe. Northern Europeans exchanged tin for manufactured bronze from the south. Alpine people mined gold and traded it for goods crafted around the Mediterranean. Prior to around 2500 to 1750 B.C., northwestern India, which is now very dry, enjoyed greater rainfall than it does in the twentieth century.36 In the Indus Valley, the Harappas created a thriving civilization that reached its apogee during the warmest and wettest periods, when their farmers were growing cereals in what is now a desert.37 The area was well watered with many lakes. This civilization disappeared around 1500 B.C. at a time when the climate became distinctly drier,38 Virtually all change can make some worse off and the warming after the last Ice Age is no exception. As the ice sheets melted, the sea level rose sharply and probably peaked around 2000 B.C.39 Although as the population explosion indicates most humans benefited, the growing warmth harmed some people, especially those who lived near the coast or who had earned their living hunting large animals. During the many centuries in which the waters mounted, storms often led to ocean flooding of coastal communities. Cooler, More Varied, and Stormy Times From the end of the Optimum period of sustained warmth until around 800 A.D. to 900 A.D., what we know of the world's climate and, in particular, the European varied between periods of warmth and cold. Based on the height of the upper tree lines in middle latitudes' mountains, the temperature record following the peak warm period around 5000 B.C. demonstrates a more or less steady decline right up to the 20th century.40 Tree ring data for New Zealand indicate that after temperatures reached a maximum around 6000 to 8000 B.C., the climate subsequently cooled in that part of the world. After 1000 B.C. the climate in Europe and the Mediterranean cooled sharply and by 500 B.C. had reached modern average temperatures.41 The period from 500 B.C. to 600 A.D. was one of varied warmth, although cooler on average than the previous 4,500 years. However, the climate became more clement and somewhat more stable from 100 35Lamb [1977]: 254. 36Lamb [1977]: 251. 37Lamb [1977]: 389. 38Claiborne [1970]: 295. 39Lamb [1977]: note 1, p. 257. 40Lamb [1982]: Fig. 43, p. 118. 41Lamb [1988]: 22. B.C. to 400 A.D., the period of the Roman Empire.42 The Italians grew grapes and olives farther north than they had prior to this period. During these centuries of varied weather, Classical Greece flourished and then declined; the Roman Empire spread its authority through much of what is now Europe, the Middle East and North Africa, only to be overrun by barbarians from central Asia whose eruption out of their homeland may have been brought on by a change in the climate. After 550 A.D. until around 800, Europe suffered through a colder, wetter, and more stormy period. As the weather became wetter, peat bogs formed in northern areas.43 The population abandoned many lakeside dwellings while mountain passes became choked with ice and snow, making transportation between northern Europe and the south difficult. The Mediterranean littoral and North Africa dried up, although they remained moister than now. Inhabitants of the British Isles between the seventh and the ninth centuries were often crippled with arthritis while their predecessors during the warmer Bronze Age period suffered little from such an affliction. Although some archaeologists have attributed the difficulties of the dark age people to harder work, the cold wet climate between 600 and 1000 A.D. probably fostered such ailments.4 44 The High Middle Ages and Medieval Warmth From around 800 A.D. to 1200 or 1300, the globe warmed considerably and civilization prospered. This Little Climate Optimum generally displays, although less distinctly, many of the same characteristics as the first climate optimum.45 Virtually all of northern Europe, the British Isles, Scandinavia, Greenland, and Iceland were considerably warmer than at present. The Mediterranean, the Near East, and North Africa, including the Sahara, received more rainfall than they do today.46 North America enjoyed better weather during most of this period. China during the early part of this epoch experienced higher temperatures and a more clement climate. From Western Europe to China, East Asia, India, and the Americas, mankind flourished as never before. The timing of the medieval warm spell, which lasted no more than 300 years, was not synchronous around the globe. For much of North America, for Greenland and in Russia, the climate was warmer between 950 and 1200.47 The warmest period in Europe appears to have been later, roughly between 1150 and 1300, although parts of the tenth 42Lamb [1988]: 23. 43Lamb [1968]: 63. 44Lamb [1977]: 261. 45 Lamb [1968]: 64. 46Lamb [1968]: 64-65. 47 Lamb [1977]: 435. century were quite warm. Evidence from New Zealand indicates peak temperatures from 1200 to 1400. Data on the Far East is meager but mixed. Judging from the number of severe winters reported by century in China, the climate was somewhat warmer than normal in the ninth, tenth, and eleventh centuries, cold in the twelfth and thirteenth and very cold in the fourteenth. Chinese scholar Chu Ko-chen reports that the eighth and ninth centuries were warmer and received more rainfall, but that the climate deteriorated significantly in the twelfth century.48 He found records, however, that show that the first half of the thirteenth century was quite clement and very cold weather returned in the fourteenth century. 49 The evidence for Japan is based on records of the average April day on which the cherry trees bloomed in the royal gardens in Kyoto. From this record, the tenth century springs were warmer than normal; in the eleventh century they were cooler, the twelfth century experienced the latest springs; the thirteenth century was average and then the fourteenth was again colder than normal.50 This record suggests that the Little Climate Optimum began in Asia in the eighth or ninth centuries and continued into the eleventh. The warm climate moved west, reaching Russia and central Asia in the tenth through the eleventh, and Europe from the twelfth to the fourteenth. Some climatologists have theorized that the Mini Ice Age also started in the Far East in the twelfth century and spread westward reaching Europe in the fourteenth.51 Europe The warm period coincided with an upsurge of population almost everywhere, but the best data are for Europe. For centuries during the cold damp “dark ages" the population of Europe had been relatively stagnant. Towns shrank to a few houses clustered behind city walls. Although we lack census figures, the numbers from Western Europe after the climate improved show that cities grew in size; new towns were founded; and colonists moved into relatively unpopulated areas. The change in the climate from a cold, wet one to a warm, drier climate - it had more rainfall, but more evaporation reduced bogs and marshy areas must have played a significant role. In the eighth through the eleventh centuries, most people spent considerable time in dank hovels avoiding the inclement weather. These conditions were ripe for the spread of disease. Tuberculosis, malaria, influenza, and pneumonia undoubtedly took many small children and the elderly — those over 30. 48Ko-chen [1973]: 235. 49Ko-chen [1973]: 237 & 238. 50Lamb [1977]: Tables 17.3 and 17.4, pp. 443 & 447. 51Ko-chen [1973]: 239-240. |